TWI859161B - Metal-clad laminates, circuit substrates and multi-layer circuit substrates - Google Patents

Abstract

The present invention provides a metal-clad laminate, a circuit substrate, a multi-layer circuit substrate and a manufacturing method thereof. A multi-layer circuit substrate having excellent dimensional stability of a conductor circuit and including an adhesive layer that can reduce transmission loss even in the transmission of high-frequency signals is provided. The circuit substrate 101 includes: an insulating resin layer 10; a conductive circuit layer 50, which is laminated on one side of the insulating resin layer 10; and an adhesive layer 30, which is laminated on the other side of the insulating resin layer 10. The multi-layer circuit board 200 is manufactured by overlapping the adhesive layer 30 of the first circuit board 101 so as to face the conductive circuit layer 50 of the second circuit board 101, and overlapping the adhesive layer 30 of the second circuit board 101 so as to face the conductive circuit layer 50 of any circuit board 110 that does not have the adhesive layer 30, and pressing them together.

Description

Metal-clad laminates, circuit substrates and multi-layer circuit substrates

The present invention relates to a metal-clad laminate and a circuit substrate, as well as a multi-layer circuit substrate having a multi-layered conductive circuit layer and a manufacturing method thereof.

In recent years, with the progress of high density and high functionality of electronic equipment, circuit substrate materials with further dimensional stability or excellent high-frequency characteristics are required. In particular, low dielectric constant and low dielectric loss are important for the characteristics of organic interlayer insulation materials required for high-speed signal processing. In order to cope with high frequencies, it has been proposed to make a multi-layer wiring board with a dielectric layer made of liquid crystal polymer (LCP) characterized by low dielectric constant and low dielectric loss tangent (for example, Patent Document 1). Multilayer wiring boards with liquid crystal polymer as the insulating layer are manufactured by heating and pressing while heating to near the melting point of the liquid crystal polymer substrate as a thermoplastic resin. Therefore, the position of the circuit conductor is easily shifted due to the thermal deformation of the liquid crystal polymer substrate, and there are concerns that the impedance mismatch will have an adverse effect on the electrical characteristics. In addition, when the multilayer bonding interface of the liquid crystal polymer is smooth, the multilayer wiring board does not show an anchoring effect and the interlayer bonding force is insufficient. Therefore, the surfaces of the circuit conductor and the liquid crystal polymer substrate need to be roughened, and there is also a problem of complicated manufacturing steps.

As a technique related to an adhesive layer having polyimide as a main component, a crosslinked polyimide resin is proposed to be applied to an adhesive layer of a coverlay film. The crosslinked polyimide resin is obtained by reacting a polyimide having a diamine compound derived from an aliphatic diamine such as dimer acid as a raw material with an amino compound having at least two primary amino groups as functional groups (for example, Patent Document 2). The crosslinked polyimide resin of Patent Document 2 has the following advantages: it does not generate volatile components including cyclic siloxane compounds, has excellent solder heat resistance, and does not reduce the adhesion between the wiring layer and the coverlay film even in a use environment repeatedly exposed to high temperatures. However, Patent Document 2 does not study the possibility of application in high-frequency signal transmission.

[Prior art literature]

[Patent Literature]

[Patent document 1] Japanese Patent Publication No. 2005-317953

[Patent Document 2] Japanese Patent Publication No. 2013-1730

In the future, as a direction to achieve high-frequency signal transmission in multi-layer circuit boards, it is considered to increase the total thickness of the insulating resin layer or adhesive layer while maintaining the dimensional stability of the conductor circuit, thereby achieving improvement in dielectric properties. For this reason, in the metal-clad laminate or circuit board that becomes the material of the multi-layer circuit board, not only the material but also the structure of these materials are required to have a different design concept from the previous multi-layer circuit board.

Therefore, the object of the present invention is to provide a multi-layer circuit substrate having excellent dimensional stability of a conductor circuit and a novel structure that can reduce transmission loss even in the transmission of high-frequency signals.

The inventors of the present invention have conducted diligent research and found that by using a metal-clad laminate with a specific structure as the material for a multi-layer circuit substrate, they can maintain excellent adhesion while maintaining the dimensional stability of the conductor circuit and can also handle the transmission of high-frequency signals, thus completing the present invention.

That is, the metal-clad laminate of the present invention includes: an insulating resin layer; a metal layer laminated on one side of the insulating resin layer; and an adhesive layer laminated on the other side of the insulating resin layer.

In addition, the circuit substrate of the present invention includes: an insulating resin layer; a conductive circuit layer formed on one side of the insulating resin layer; and an adhesive layer laminated on the other side of the insulating resin layer.

Moreover, in the metal-clad laminate or circuit board of the present invention, the resin constituting the adhesive layer is a thermoplastic resin or a thermosetting resin and satisfies the following conditions (i) to (iii): (i) the storage elastic modulus at 50°C is less than 1800 MPa; (ii) the maximum value of the storage elastic modulus in the temperature range from 180°C to 260°C is less than 800 MPa; (iii) the glass transition temperature (Tg) is less than 180°C.

In the metal-clad laminate or circuit substrate of the present invention, the thermoplastic resin may be an adhesive polyimide containing tetracarboxylic acid residues and diamine residues. In the case, the adhesive polyimide may contain 50 mol or more of diamine residues derived from dimer acid type diamine relative to 100 mol of the total amount of the diamine residues, wherein the dimer acid type diamine is obtained by replacing the two terminal carboxylic acid groups of the dimer acid with primary aminomethyl or amino groups.

The metal-clad laminate of the present invention can be a material for a circuit substrate in which the metal layer is processed into wiring.

In the metal-clad laminate or circuit board of the present invention, the adhesive polyimide may contain a total of 90 mol parts or more of tetracarboxylic acid residues derived from tetracarboxylic anhydride represented by the following general formula (1) and/or general formula (2) relative to 100 mol parts of the total amount of the tetracarboxylic acid residues.

In the general formula (1), X represents a single bond or a divalent group selected from the following formulas. In the general formula (2), the cyclic part represented by Y represents a cyclic saturated hydrocarbon group selected from a 4-membered ring, a 5-membered ring, a 6-membered ring, a 7-membered ring or an 8-membered ring.

In the formula, Z represents -C ₆ H ₄ -, -(CH ₂ )n- or -CH ₂ -CH(-OC(=O)-CH ₃ )-CH ₂ -, and n represents an integer of 1-20.

In the metal-clad laminate or circuit board of the present invention, the adhesive polyimide may contain diamine residues derived from the dimer acid type diamine in a range of 50 mol parts to 99 mol parts relative to the total amount of 100 mol parts of the diamine residues, and may contain diamine residues derived from at least one diamine compound selected from the diamine compounds represented by the following general formula (B1) to (B7) in a range of 1 mol parts to 50 mol parts.

[Chemistry 3]

In formula (B1) to formula (B7), R ₁ independently represents a monovalent alkyl group or alkoxy group having 1 to 6 carbon atoms, the linking group A independently represents a divalent group selected from -O-, -S-, -CO-, -SO-, -SO ₂ -, -COO-, -CH ₂ -, -C(CH ₃ ) ₂ -, -NH- or -CONH-, and n ₁ independently represents an integer of 0 to 4; wherein, from formula (B3), the portion repeating with formula (B2) is removed, and from formula (B5), the portion repeating with formula (B4) is removed.

The multi-layer circuit substrate of the present invention is formed by stacking multiple circuit substrates, and is characterized in that it includes at least one of the above-mentioned circuit substrates as the circuit substrate.

The manufacturing method of a multi-layer circuit substrate of the first aspect of the present invention may include: a step of preparing a plurality of circuit substrates, wherein the circuit substrates include an insulating resin layer, a conductive circuit layer formed on one side of the insulating resin layer, and an adhesive layer laminated on the other side of the insulating resin layer; and a step of overlapping and pressing the conductive circuit layer of one circuit substrate and the adhesive layer of another circuit substrate in a facing manner.

The manufacturing method of the multi-layer circuit substrate of the second aspect of the present invention may include: the step of preparing a plurality of circuit substrates, wherein the circuit substrates include an insulating resin layer, a conductive circuit layer formed on one side of the insulating resin layer, and an adhesive layer laminated on the other side of the insulating resin layer; and the step of overlapping and pressing the adhesive layer of one circuit substrate with the adhesive layer of another circuit substrate in a facing manner.

The metal-clad laminate of the present invention has a metal layer on one side of an insulating resin layer and an adhesive layer on the other side of the insulating resin layer. Therefore, a multi-layer circuit substrate can be easily manufactured by lamination, and is useful as a material for a multi-layer circuit substrate. In addition, when a multi-layer circuit substrate is manufactured using a metal-clad laminate, the dimensional stability of the conductor circuit can be maintained while ensuring the coating and adhesion of the conductor circuit layer, thereby ensuring the thickness of the entire resin layer. Therefore, by using the metal-clad laminate of the present invention, a multi-layer circuit substrate with good inter-layer connection and high reliability can be obtained.

In addition, the multi-layer circuit substrate of the present invention can reduce transmission loss even in the transmission of high-frequency signals, and can realize high-density integration or high-density mounting of electronic components. In addition, the multi-layer circuit substrate of the present invention has excellent heat resistance, so it can also carry semiconductor chips with high heat generation.

10: Insulating resin layer

20: Metal layer

30: Adhesive layer

40: Single-sided metal laminate

50: Conductor circuit layer

100: Metal-clad laminate

101: Circuit board

102: Circuit board unit

110: Any circuit board

200, 201: Multi-layer circuit substrate

T1: Total thickness

T2, T3: thickness

FIG1 is a cross-sectional view showing the structure of a metal-clad laminate according to an embodiment of the present invention.

FIG2 is a cross-sectional view showing the structure of a circuit substrate in an embodiment of the present invention.

FIG3 is a cross-sectional view showing the structure of a multi-layer circuit substrate according to the first embodiment of the present invention.

FIG4 is an explanatory diagram showing the manufacturing steps of the multi-layer circuit substrate of the first embodiment of the present invention.

FIG5 is a cross-sectional view showing the structure of a multi-layer circuit substrate according to the second embodiment of the present invention.

FIG6 is an explanatory diagram showing the manufacturing steps of a multi-layer circuit substrate according to the second embodiment of the present invention.

The implementation form of the present invention is described in detail.

[Metal-clad laminate]

FIG1 is a cross-sectional view showing the structure of a metal-clad laminate of an embodiment of the present invention. The metal-clad laminate 100 of the present embodiment includes: an insulating resin layer 10; a metal layer 20 laminated on one side of the insulating resin layer 10; and an adhesive layer 30 laminated on the other side of the insulating resin layer 10. That is, the metal-clad laminate 100 has a structure in which the metal layer 20/insulating resin layer 10/adhesive layer 30 are laminated in this order. If another expression is used, the metal-clad laminate 100 has a structure in which an adhesive layer 30 is further added to the back side (insulating resin layer 10 side) of a single-sided metal-clad laminate 40 formed by laminating an insulating resin layer 10 and a metal layer 20. Furthermore, the adhesive layer 30 may be formed on the entire surface of a single side of the insulating resin layer 10 or may be formed on only a portion.

<Single-sided metal laminate>

The structure of the single-sided metal-clad laminate 40 is not particularly limited, and a common material used as a flexible printed circuit (FPC) material can be used, for example, a commercially available copper-clad laminate. For example, as a commercially available copper-clad laminate, R-F705T (trade name) manufactured by Panasonic, Espanex (trade name) manufactured by Nippon Steel Chemical & Materials Co., Ltd., etc. can be used.

(Metal layer)

The material of the metal layer 20 is not particularly limited, and examples thereof include: copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among these, copper or copper alloys are particularly preferred. Furthermore, the material of the wiring layer in the circuit substrate of the present embodiment described later is also the same as that of the metal layer 20.

The thickness of the metal layer 20 is not particularly limited. For example, when using a metal foil such as copper foil, it is preferably less than 35 μm, and more preferably in the range of 5 μm to 25 μm. From the perspective of production stability and handling, the lower limit of the thickness of the metal layer is preferably set to 5 μm. Furthermore, when using copper foil, it can be either a rolled copper foil or an electrolytic copper foil. In addition, as the copper foil, a commercially available copper foil can be used.

In addition, the metal foil may be subjected to rust-proof treatment or surface treatment such as siding, aluminum alcoholate, aluminum chelate, silane coupling agent, etc. for the purpose of improving adhesion.

(Insulating resin layer)

As the insulating resin layer 10, if it contains a resin with electrical insulation, there is no particular limitation, for example, polyimide, liquid crystal polymer, epoxy resin, phenolic resin, polyethylene, polypropylene, polytetrafluoroethylene, silicone, ethylene tetrafluoroethylene (ETFE), bismaleimide triazine (BT) resin, etc., preferably containing polyimide. Furthermore, the case of polyimide in the present invention refers to polymers having an imide group in the molecular structure, such as polyamide imide, polyether imide, polyester imide, polysiloxane imide, polybenzimidazole imide, etc., in addition to polyimide.

In addition, the insulating resin layer 10 is not limited to a single layer, and a plurality of resin layers may be laminated. In addition, the insulating resin layer 10 preferably includes a non-thermoplastic polyimide layer formed of a non-thermoplastic polyimide. Furthermore, the so-called "non-thermoplastic polyimide" is generally a polyimide that does not show adhesiveness even when softened by heat. In the present invention, it refers to a polyimide having a storage elastic modulus of 1.0×10 ⁹ Pa or more at 30°C and a storage elastic modulus of 3.0×10 ⁸ Pa or more at 300°C measured using a dynamic viscoelasticity measuring device (Dynamic Mechanical Analyzer (DMA)).

The insulating resin layer 10 can be selected and used from, for example, a commercially available polyimide film, a commercially available liquid crystal polymer film, or a resin used as an insulating substrate in a commercially available metal-clad laminate. As the polyimide film, Upilex (trade name) manufactured by Ube Industries, Kapton (trade name) manufactured by Toray Dupont, Apical (trade name) manufactured by Kaneka, and Pixeo (trade name) manufactured by Kaneka can be used. As the liquid crystal polymer film, Vecstar (trade name) manufactured by Kuraray, BIAC Film (trade name) manufactured by Primatech, etc. can be used.

The coefficient of thermal expansion (CTE) of the insulating resin layer 10 is not particularly limited, and may be greater than 10ppm/K, preferably within the range of greater than 10ppm/K and less than 30ppm/K, and more preferably within the range of greater than 15ppm/K and less than 25ppm/K. If the CTE is less than 10ppm/K or exceeds 30ppm/K, warping may occur or dimensional stability may decrease. The desired CTE may be controlled by appropriately changing the combination of raw materials used, thickness, and drying/hardening conditions.

Furthermore, the overall thermal expansion coefficient (CTE) of the resin layer including the insulating resin layer 10 and the adhesive layer 30 is not particularly limited, but is preferably within the range of 10ppm/K or more and 30ppm/K or less, and more preferably within the range of 15ppm/K or more and 25ppm/K or less. If the overall CTE of these resin layers is less than 10ppm/K or exceeds 30ppm/K, warping occurs or dimensional stability is reduced.

When the insulating resin layer 10 is used in a multi-layer circuit board, for example, in order to suppress the deterioration of dielectric loss, the dielectric loss tangent (Tanδ) at 10 GHz is preferably 0.02 or less, more preferably in the range of 0.0005 or more and 0.01 or less, and further preferably in the range of 0.001 or more and 0.008 or less. If the dielectric loss tangent of the insulating resin layer 10 at 10 GHz exceeds 0.02, when it is used in a multi-layer circuit board, it is easy to cause disadvantages such as loss of electrical signals in the transmission path of high-frequency signals. On the other hand, there is no particular restriction on the lower limit of the dielectric loss tangent of the insulating resin layer 10 at 10 GHz, and physical property control of the insulating resin layer of a multi-layer circuit substrate can be considered.

When the insulating resin layer 10 is used as an insulating resin layer of a multi-layer circuit substrate, for example, the dielectric constant (ε) at 10 GHz is preferably 4.0 or less in order to ensure impedance matching. If the dielectric constant of the insulating resin layer 10 at 10 GHz exceeds 4.0, when applied to a multi-layer circuit substrate, the dielectric loss of the insulating resin layer 10 deteriorates, and it is easy to cause disadvantages such as loss of electrical signals in the transmission path of high-frequency signals.

<Adhesive layer>

The adhesive layer 30 includes a thermoplastic resin or a thermosetting resin and meets the following conditions: (i) the storage elastic modulus at 50°C is less than 1800 MPa; (ii) the maximum value of the storage elastic modulus from 180°C to 260°C is less than 800 MPa; and (iii) the glass transition temperature (Tg) is less than 180°C.

Examples of such resins include polyimide resins, polyamide resins, epoxy resins, phenoxy resins, acrylic resins, polyurethane resins, styrene resins, polyester resins, phenol resins, polysulfone resins, polyethersulfone resins, polyphenylene sulfide resins, polyethylene resins, polypropylene resins, silicone resins, polyetherketone resins, polyethylene alcohol resins, and polyvinyl butyral resins. , styrene-maleimide copolymer, maleimide-vinyl compound copolymer, or (meth) acrylic acid copolymer, benzoxazine resin, dimaleimide resin and cyanate resin, etc. Resins satisfying conditions (i) to (iii) can be selected from these, or they can be designed to satisfy conditions (i) to (iii) and used in the adhesive layer 30.

When the adhesive layer 30 is a thermosetting resin, it may contain organic peroxides, hardeners, hardening accelerators, etc., and hardeners and hardening accelerators, or catalysts and co-catalysts may be used together as needed. As long as the amount of hardener, hardening accelerator, catalyst, co-catalyst, and organic peroxide added and the presence or absence of addition are determined within the range of the above conditions (i) to (iii).

As shown in conditions (i) and (ii), the storage modulus of the adhesive layer 30 at 50°C is less than 1800 MPa, and the maximum value of the storage modulus in the temperature range from 180°C to 260°C is less than 800 MPa. It is believed that this characteristic of the adhesive layer 30 is the main reason for relieving the internal stress during hot pressing and maintaining the dimensional stability after circuit processing. In addition, the storage modulus of the adhesive layer 30 at the upper limit temperature (260°C) of the temperature range is preferably less than 800 MPa, and more preferably less than 500 MPa. By setting it to such a storage modulus, warping is difficult to occur even after the solder reflow step after circuit processing.

As shown in condition (iii), the glass transition temperature (Tg) of the adhesive layer 30 can be below 180°C, preferably below 160°C. By setting the glass transition temperature of the adhesive layer 30 below 180°C, heat pressing can be performed at a low temperature, thereby relieving the internal stress generated during lamination and suppressing dimensional changes. If the Tg of the adhesive layer 30 exceeds 180°C, the temperature during bonding becomes high due to the presence of a spacer between the insulating resin layer 10 and any circuit board, and there is a concern that dimensional stability may be impaired.

(CTE of adhesive layer)

The thermoplastic resin or thermosetting resin constituting the adhesive layer 30 has high thermal expansion but low elasticity and a low glass transition temperature, so even if the CTE exceeds 30ppm/K, it can alleviate the internal stress generated during lamination. Therefore, the CTE of the adhesive layer 30 is preferably 35ppm/K or more, more preferably 35ppm/K or more and 200ppm/K or less, and further preferably 35ppm/K or more and 150ppm/K or less. By appropriately changing the combination of raw materials used, thickness, and drying/hardening conditions, an adhesive layer 30 having a desired CTE can be produced.

(Dielectric loss tangent of the adhesive layer)

For example, when the adhesive layer 30 is applied to a multi-layer circuit substrate, in order to suppress the deterioration of dielectric loss, the dielectric loss tangent (Tanδ) at 10GHz may be preferably less than 0.004, more preferably less than 0.003, and further preferably less than 0.002. If the dielectric loss tangent of the adhesive layer 30 at 10GHz exceeds 0.004, it is easy to cause undesirable conditions such as loss of electrical signals in the transmission path of high-frequency signals when applied to a multi-layer circuit substrate. On the other hand, there is no particular limit on the lower limit of the dielectric loss tangent of the adhesive layer 30 at 10GHz.

(Dielectric constant of adhesive layer)

For example, when the adhesive layer 30 is applied to a multi-layer circuit board, in order to ensure impedance matching, the dielectric constant at 10 GHz is preferably less than 4.0. If the dielectric constant of the adhesive layer 30 at 10 GHz exceeds 4.0, when applied to a multi-layer circuit board, the dielectric loss of the adhesive layer 30 deteriorates, which easily causes the loss of electrical signals in the transmission path of high-frequency signals and other undesirable conditions.

(Padding)

If necessary, the adhesive layer 30 may also contain fillers. Examples of fillers include silicon dioxide, aluminum oxide, magnesium oxide, curium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, metal salts of organic phosphinates, etc. These may be used alone or in combination of two or more.

(Adhesive polyimide)

Next, a specific configuration example of the adhesive layer 30 is described by taking as an example a case where the resin constituting the adhesive layer 30 is an adhesive thermoplastic polyimide containing tetracarboxylic acid residues and diamine residues (hereinafter, sometimes described as "adhesive polyimide"). The adhesive polyimide is produced by imidizing a polyamic acid precursor obtained by reacting a specific acid anhydride with a diamine compound. Therefore, the specific example of the adhesive polyimide is understood by describing the acid anhydride and the diamine compound. Furthermore, in the present invention, the so-called tetracarboxylic acid residue refers to a tetravalent group derived from tetracarboxylic dianhydride, and the so-called diamine residue refers to a divalent group derived from a diamine compound. The so-called "thermoplastic polyimide" is generally a polyimide having a clearly identifiable glass transition temperature (Tg), and in the present invention, refers to a polyimide having a storage elastic modulus of 1.0×10 ⁸ Pa or more at 30°C and less than 3.0×10 ⁷ Pa at 300°C as measured using DMA.

(Tetracarboxylic acid residue)

The adhesive polyimide preferably contains 90 mol parts or more of tetracarboxylic acid residues derived from tetracarboxylic anhydride represented by the following general formula (1) and/or general formula (2) (hereinafter sometimes described as "tetracarboxylic acid residue (1)", "tetracarboxylic acid residue (2)") in total relative to 100 mol parts of all tetracarboxylic acid residues. In the present invention, by containing 90 mol parts or more of tetracarboxylic acid residues (1) and/or tetracarboxylic acid residues (2) in total relative to 100 mol parts of all tetracarboxylic acid residues, solvent solubility is imparted to the adhesive polyimide, and it is easy to achieve both flexibility and heat resistance of the adhesive polyimide, which is more preferred. If the total amount of tetracarboxylic acid residues (1) and/or tetracarboxylic acid residues (2) is less than 90 mol parts, the solvent solubility of the adhesive polyimide tends to decrease.

In the general formula (1), X represents a single bond or a divalent group selected from the following formulas. In the general formula (2), the cyclic part represented by Y represents a cyclic saturated hydrocarbon group selected from a 4-membered ring, a 5-membered ring, a 6-membered ring, a 7-membered ring or an 8-membered ring.

[Chemistry 5]

In the formula, Z represents -C ₆ H ₄ -, -(CH ₂ )n- or -CH ₂ -CH(-OC(=O)-CH ₃ )-CH ₂ -, and n represents an integer of 1-20.

Examples of tetracarboxylic dianhydrides used to derive tetracarboxylic acid residues (1) include 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenylsulfonate tetracarboxylic dianhydride (DSDA), 4,4'-oxydiphthalic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), p-phenylene bis(trimellitic acid monoester anhydride) (TAHQ), ethylene glycol bis(trimellitic acid monoester anhydride) (TMEG), etc.

In addition, examples of tetracarboxylic dianhydrides used to derive tetracarboxylic acid residues (2) include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,4,5-cycloheptanetetracarboxylic dianhydride, and 1,2,5,6-cyclooctanetetracarboxylic dianhydride.

The adhesive polyimide may contain tetracarboxylic acid residues derived from an acid anhydride other than the tetracarboxylic acid anhydride represented by the general formula (1) or (2) within a range that does not impair the effect of the invention.

(Diamine residue)

The adhesive polyimide contains dimer acid diamine residues derived from dimer acid diamine in an amount of 50 mol parts or more, for example, in a range of 50 mol parts or more and 99 mol parts or less, preferably in a range of 80 mol parts or more, for example, in a range of 80 mol parts or more and 99 mol parts or less, relative to 100 mol parts of all diamine residues. By containing the dimer acid diamine residues in such an amount, the dielectric properties of the adhesive layer 30 can be improved, the glass transition temperature of the adhesive layer 30 can be lowered to improve the heat pressing properties, and the internal stress can be relieved by lowering the elastic modulus. In addition, by setting the dimer acid type diamine residue to more than 50 mol parts, solvent solubility and thermoplasticity can be imparted, so that the water absorption of the adhesive layer 30 is reduced, for example, reducing the dimensional change caused by etching. If the dimer acid type diamine residue is less than 50 mol parts relative to 100 mol parts of all diamine residues, the solvent solubility of the adhesive polyimide is reduced.

Here, the dimer acid type diamine refers to a diamine in which the two terminal carboxylic acid groups (-COOH) of the dimer acid are substituted with primary aminomethyl groups (-CH ₂ -NH ₂ ) or amino groups (-NH ₂ ). Dimer acid is a known dibasic acid obtained by the intermolecular polymerization reaction of unsaturated fatty acids. Its industrial production process has been largely standardized in the industry, and it can be obtained by dimerizing unsaturated fatty acids with carbon numbers of 11 to 22 using clay catalysts and the like. Industrially obtained dimer acid is mainly composed of a dibasic acid with carbon number 36 obtained by dimerizing unsaturated fatty acids with carbon number 18 such as oleic acid or linoleic acid, and contains any amount of monomeric acid (with carbon number 18), trimer acid (with carbon number 54), and other polymerized fatty acids with carbon number 20 to 54, depending on the degree of purification. In the present invention, the dimer acid is preferably a compound whose dimer acid content is increased to 90% by weight or more by molecular distillation. In addition, after the dimerization reaction, double bonds remain, but in the present invention, the dimer acid also includes compounds that further undergo hydrogenation reaction to reduce unsaturation.

As a characteristic of dimer acid type diamine, it can impart characteristics derived from the dimer acid skeleton to polyimide. That is, dimer acid type diamine is a giant aliphatic molecule with a molecular weight of about 560 to 620, so the molecular molar volume can be increased and the polar groups of polyimide can be relatively reduced. It is believed that such characteristics of dimer acid type diamine contribute to suppressing the decrease in heat resistance of polyimide and reducing the dielectric constant and dielectric loss tangent to improve dielectric properties. In addition, it contains two freely movable hydrophobic chains with carbon numbers of 7 to 9 and two chain-like aliphatic amino groups with a length close to carbon numbers of 18, which not only imparts flexibility to polyimide, but also allows the polyimide to have an asymmetric chemical structure or a non-planar chemical structure, so it is believed that the dielectric constant and dielectric loss tangent of polyimide can be reduced.

Dimer acid type diamines are commercially available, for example: PRIAMINE 1073 (trade name) manufactured by CRODA Japan, PRIAMINE 1074 (trade name) manufactured by CRODA Japan, PRIAMINE 1075 (trade name) manufactured by CRODA Japan, Versamine 551 (trade name) manufactured by BASF Japan, Versamine 552 (trade name) manufactured by BASF Japan, etc.

In addition, the adhesive polyimide preferably contains diamine residues derived from at least one diamine compound selected from the diamine compounds represented by the following general formula (B1) to (B7) in a total range of 1 mol or more and 50 mol or less relative to 100 mol of all diamine residues, and more preferably contains diamine residues in a range of 1 mol or more and 20 mol or less. The diamine compounds represented by the general formula (B1) to (B7) have a molecular structure having flexibility. Therefore, by using at least one diamine compound selected from these in an amount within the above range, the flexibility of the polyimide molecular chain can be improved to impart solvent solubility and thermoplasticity. In addition, by using the diamine compounds represented by general formula (B1) to general formula (B7), for example, even when a via hole is formed in the adhesive layer 30 by laser processing, the ratio of the aromatic ring in the polyimide molecular structure becomes higher, and the absorption in the ultraviolet region, for example, can be improved. In addition, the glass transition temperature of the adhesive layer 30 can be increased, thereby improving the heat resistance to the temperature increase of the bottom metal caused by the incidence of laser light, thereby further improving the laser processability. If the total amount of diamine residues derived from at least one diamine compound selected from the diamine compounds represented by the following general formula (B1) to general formula (B7) exceeds 50 mol parts relative to 100 mol parts of all diamine residues, the softness of the adhesive polyimide is insufficient, and the glass transition temperature rises, so the residual stress caused by heat pressing increases and there is a tendency for the dimensional change rate after etching to deteriorate.

[Chemistry 6]

In formula (B1) to formula (B7), _R1 independently represents a monovalent alkyl group or alkoxy group having 1 to 6 carbon atoms, the linking group A independently represents a divalent group selected from -O-, -S-, -CO-, -SO-, _-SO2- , -COO-, _-CH2- , -C( _CH3 ) _2- , -NH- or -CONH-, and _n1 independently represents an integer of 0 to 4. In formula (B3), the part repeated with formula (B2) is removed, and the part repeated with formula (B4) is removed from formula (B5).

Furthermore, the term "independently" means that in one or more of the formulas (B1) to (B7), multiple linking groups A, multiple _R1 or multiple _n1 may be the same or different. In the formulas (B1) to (B7), the hydrogen atoms in the two terminal amino groups may be substituted _, for example, _-NR2R3 (herein, _R2 and _R3 independently refer to any substituent such as an alkyl group).

The diamine represented by formula (B1) (hereinafter, sometimes described as "diamine (B1)") is an aromatic diamine having two benzene rings. The diamine (B1) is directly bonded to the amino group on at least one benzene ring and the divalent linking group A is located at the meta position, so that the degree of freedom of the polyimide molecular chain increases and the flexibility is high, which contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B1), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -O-, _-CH2- , -C( _CH3 ) _2- , -CO-, _-SO2- , -S-, -COO- are preferred.

Examples of diamine (B1) include 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenylsulfone, 3,3-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, (3,3'-bisamino)diphenylamine, etc.

The diamine represented by formula (B2) (hereinafter, sometimes described as "diamine (B2)") is an aromatic diamine having three benzene rings. The diamine (B2) is directly bonded to the amino group on at least one benzene ring and the divalent linking group A is located at the meta position, and the degree of freedom of the polyimide molecular chain is increased and has high flexibility, thereby contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B2), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -O- is preferred.

Examples of diamines (B2) include 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]aniline, and 3-[3-(4-aminophenoxy)phenoxy]aniline.

The diamine represented by formula (B3) (hereinafter, sometimes described as "diamine (B3)") is an aromatic diamine having three benzene rings. The diamine (B3) is believed to increase the degree of freedom of the polyimide molecular chain and have high flexibility by directly bonding two divalent linking groups A on one benzene ring to each other at the meta position, thereby contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B3), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -O- is preferred.

Examples of diamine (B3) include 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), 4,4'-[2-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[4-methyl-(1,3-phenylene)bisoxy]bisaniline, and 4,4'-[5-methyl-(1,3-phenylene)bisoxy]bisaniline.

The diamine represented by formula (B4) (hereinafter, sometimes described as "diamine (B4)") is an aromatic diamine having four benzene rings. The diamine (B4) is considered to have high flexibility due to the amino group directly bonded to at least one benzene ring and the divalent linking group A being located at the meta position, thereby contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B4), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -O-, _-CH2- , -C( _CH3 ) _2- , _-SO2- , -CO-, and -CONH- are preferred.

Examples of diamines (B4) include bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)benzophenone, and bis[4,4'-(3-aminophenoxy)]benzanilide.

The diamine represented by formula (B5) (hereinafter, sometimes described as "diamine (B5)") is an aromatic diamine having four benzene rings. It is believed that the two divalent linking groups A of the diamine (B5) are directly bonded to at least one benzene ring and are located at the meta position, and the degree of freedom of the polyimide molecular chain is increased and has high flexibility, which helps to improve the flexibility of the polyimide molecular chain. Therefore, by using diamine (B5), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -O- is preferred.

Examples of diamine (B5) include 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline and 4,4'-[oxybis(3,1-phenyleneoxy)]bisaniline.

The diamine represented by formula (B6) (hereinafter, sometimes described as "diamine (B6)") is an aromatic diamine having four benzene rings. It is believed that the diamine (B6) has high flexibility due to having at least two ether bonds, thereby contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, the thermoplasticity of the polyimide is improved by using the diamine (B6). Here, the linking group A is preferably -C( _CH3 ) _2- , -O-, _-SO2- , or -CO-.

Examples of diamines (B6) include 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), bis[4-(4-aminophenoxy)phenyl]ether (BAPE), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), and bis[4-(4-aminophenoxy)phenyl]ketone (BAPK).

The diamine represented by formula (B7) (hereinafter, sometimes described as "diamine (B7)") is an aromatic diamine having four benzene rings. It is believed that the diamine (B7) has a highly flexible divalent linking group A on both sides of the diphenyl skeleton, and thus contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B7), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -O- is preferred.

Examples of diamine (B7) include bis[4-(3-aminophenoxy)]biphenyl and bis[4-(4-aminophenoxy)]biphenyl.

The adhesive polyimide may contain diamine residues derived from the dimer acid type diamine and diamine compounds other than diamines (B1) to (B7) within a range that does not impair the effect of the invention.

In addition, regarding the adhesive polyimide, by selecting the types of the tetracarboxylic acid residues and diamine residues, or the respective molar ratios when containing two or more tetracarboxylic acid residues or diamine residues, the thermal expansion coefficient, tensile elastic modulus, glass transition temperature, etc. can be controlled. In addition, in the case of a plurality of structural units of polyimide, they can exist in the form of blocks or randomly, preferably randomly.

The imide group concentration of the adhesive polyimide is preferably 20 wt% or less. Here, "imide group concentration" refers to the value obtained by dividing the molecular weight of the imide group (-(CO) ₂ -N-) in the polyimide by the molecular weight of the entire structure of the polyimide. If the imide group concentration exceeds 20 wt%, the molecular weight of the resin itself becomes small, and the low hygroscopicity also deteriorates due to the increase in polar groups, and the elastic modulus increases.

The weight average molecular weight of the adhesive polyimide is preferably in the range of 10,000 to 400,000, and more preferably in the range of 20,000 to 350,000. If the weight average molecular weight is less than 10,000, the strength of the adhesive layer 30 decreases and tends to be brittle. On the other hand, if the weight average molecular weight exceeds 400,000, the viscosity increases excessively and tends to cause defects such as uneven thickness and streaks in the adhesive layer 30 during the coating operation.

When forming a multi-layer circuit board, the adhesive polyimide covers any conductive circuit layer of the circuit board, so in order to suppress the diffusion of copper, it is most preferably a completely imidized structure. Among them, a part of the polyimide can also be amide. The imidization rate can be measured by using a Fourier conversion infrared spectrophotometer (commercial product: FT/IR620 manufactured by JASCO Corporation) and using the single reflection ATR (Attenuated Total Reflectance) method to measure the infrared absorption spectrum of the polyimide film, and calculate it based on the absorbance of the C=O stretching derived from the imide group at 1780cm ^-1 with the benzene ring absorber near 1015cm ^-1 as the reference.

(Cross-linking formation)

When the adhesive polyimide has a ketone group, the ketone group is reacted with an amino group of an amino compound having at least two primary amino groups as functional groups to form a C=N bond, thereby forming a cross-linked structure. By forming a cross-linked structure, the heat resistance of the adhesive polyimide can be improved. Preferred tetracarboxylic anhydrides for forming polyimide having a ketone group include, for example, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), and preferred diamine compounds include, for example, aromatic diamines such as 4,4'-bis(3-aminophenoxy)benzophenone (BABP) and 1,3-bis[4-(3-aminophenoxy)benzyl]benzene (BABB).

As amino compounds that can be used in the crosslinking formation of adhesive polyimide, dihydrazide compounds, aromatic diamines, aliphatic amines, etc. can be exemplified. Among these, dihydrazide compounds are preferred. Aliphatic amines other than dihydrazide compounds easily form a crosslinking structure even at room temperature, and there is a concern about the storage stability of the varnish. On the other hand, aromatic diamines need to be set to a high temperature in order to form a crosslinking structure. When a dihydrazide compound is used, the storage stability of the varnish can be improved and the curing time can be shortened. As the dihydrazide compound, for example, dihydrazide oxalate, dihydrazide malonate, dihydrazide succinate, dihydrazide glutarate, dihydrazide adipic acid, dihydrazide pimelic acid, dihydrazide suberate, dihydrazide azelaic acid, dihydrazide sebacic acid, dihydrazide dodecanedioic acid, dihydrazide maleic acid, dihydrazide fumaric acid, diethylene glycol Acid dihydrazide, tartaric acid dihydrazide, apple acid dihydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthoic acid dihydrazide, 4,4-diphenyl dihydrazide, 1,4-naphthoic acid dihydrazide, 2,6-pyridine dihydrazide, itaconic acid dihydrazide and other dihydrazide compounds. The above dihydrazide compounds can be used alone or in combination of two or more.

The adhesive polyimide can be produced by reacting the tetracarboxylic dianhydride and the diamine compound in a solvent to generate polyamide, and then heating and ring closing. For example, the tetracarboxylic dianhydride and the diamine compound are dissolved in an organic solvent in approximately equimolar amounts, and the polymerization reaction is carried out by stirring for 30 minutes to 24 hours at a temperature in the range of 0°C to 100°C, thereby obtaining polyamide as a precursor of the adhesive polyimide. During the reaction, the reaction components are dissolved in a manner such that the generated precursor is in the range of 5% by weight to 50% by weight, preferably in the range of 10% by weight to 40% by weight in the organic solvent. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphatamide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), cresol, etc. These solvents may be used in combination of two or more, and aromatic hydrocarbons such as xylene and toluene may also be used in combination. In addition, the amount of such an organic solvent used is not particularly limited, but it is preferably used in an amount adjusted so that the concentration of the polyamide solution obtained by the polymerization reaction is about 5% by weight to 50% by weight.

The synthesized polyamine is usually advantageously used as a reaction solvent solution, and can be concentrated, diluted or replaced with other organic solvents as needed. In addition, polyamine is usually advantageously used due to its excellent solvent solubility. The viscosity of the polyamine solution is preferably in the range of 500cps~100,000cps. If it deviates from the above range, it is easy to produce defects such as uneven thickness and streaks in the film during the coating operation using a coating machine.

There is no particular limitation on the method of imidizing polyamine to form polyimide. For example, a heat treatment such as heating in the solvent at a temperature range of 80°C to 400°C for 1 hour to 24 hours can be appropriately adopted.

When the adhesive polyimide obtained as above is crosslinked, the amino compound is added to a resin solution containing a polyimide having a ketone group, and the ketone group in the adhesive polyimide is subjected to a condensation reaction with the primary amino group of the amino compound. The resin solution is cured by the condensation reaction to form a cured product. In the above case, the amount of the amino compound added may be 0.004 mol to 1.5 mol, preferably 0.005 mol to 1.2 mol, more preferably 0.03 mol to 0.9 mol, and most preferably 0.04 mol to 0.5 mol of the primary amino group relative to 1 mol of the ketone group. Regarding the addition amount of the amino compound such as less than 0.004 mol of primary amino group relative to 1 mol of keto group, the crosslinking of the polyimide chain using the amino compound is insufficient, so there is a tendency that the heat resistance of the adhesive layer 30 after hardening is difficult to show. If the addition amount of the amino compound exceeds 1.5 mol, the unreacted amino compound acts as a thermoplastic agent, and there is a tendency that the heat resistance of the adhesive layer 30 is reduced.

The conditions for the crosslinking condensation reaction are not particularly limited as long as the ketone group in the adhesive polyimide reacts with the primary amino group of the amino compound to form an imine bond (C=N bond). The temperature of the heat condensation is preferably in the range of 120°C to 220°C, more preferably in the range of 140°C to 200°C, for the reasons of releasing water generated by the condensation to the outside of the system or simplifying the condensation step when the heat condensation reaction is performed after the synthesis of the adhesive polyimide. The reaction time is preferably about 30 minutes to 24 hours. The endpoint of the reaction can be confirmed, for example, by measuring the infrared absorption spectrum using a Fourier transform infrared spectrophotometer (commercially available product: FT/IR620 manufactured by JASCO Corporation) and by using the decrease or disappearance of the absorption peak derived from the ketone group in the polyimide resin near 1670 cm ^-1 and the appearance of the absorption peak derived from the imine group near 1635 cm ^-1 .

The heat condensation of the ketone group of the adhesive polyimide and the primary amino group of the amino compound can be performed, for example, by the following methods: (a) a method of adding the amino compound and heating immediately after the synthesis (imidization) of the adhesive polyimide; (b) a method of pre-adding an excess amount of the amino compound as a diamine component, and heating the adhesive polyimide together with the residual amino compound that does not participate in the imidization or amidation; or (c) a method of heating the adhesive polyimide composition after processing the amino compound-added adhesive polyimide into a predetermined shape (for example, after coating on an arbitrary substrate or forming into a film).

In order to impart heat resistance to the adhesive layer 30, the formation of imide bonds is described in the formation of the cross-linked structure in the adhesive polyimide, but the present invention is not limited thereto. As a method for hardening the adhesive layer 30, for example, epoxy resin, epoxy resin hardener, etc. may be prepared for hardening.

<Thickness of resin layer>

Regarding the metal-clad laminate 100, when the total thickness of the insulating resin layer 10 thickness T3 and the adhesive layer 30 thickness T2 is set to T1, the total thickness T1 is in the range of 50μm to 250μm, preferably in the range of 70μm to 150μm. If the total thickness T1 is less than 50μm, the effect of reducing transmission loss when using the metal-clad laminate 100 to manufacture a multi-layer circuit substrate is insufficient, and if it exceeds 250μm, there is a concern about reduced productivity.

In addition, the thickness T2 of the adhesive layer 30 is preferably in the range of 20μm to 200μm, and more preferably in the range of 20μm to 100μm. If the thickness T2 of the adhesive layer 30 is less than the lower limit, the transmission loss may increase for high-frequency substrates. On the other hand, if the thickness T2 of the adhesive layer 30 exceeds the upper limit, it may cause undesirable conditions such as reduced dimensional stability.

In addition, the ratio (T2/T1) of the thickness T2 of the adhesive layer 30 to the total thickness T1 is in the range of 0.5 to 0.8, preferably in the range of 0.5 to 0.7. If the ratio (T2/T1) is less than 0.5, it is difficult to set the total thickness T1 to more than 50μm, and if it exceeds 0.8, it will cause problems such as reduced dimensional stability.

The thickness T3 of the insulating resin layer 10 is preferably in the range of 12μm to 100μm, and more preferably in the range of 12μm to 50μm. If the thickness T3 of the insulating resin layer 10 is less than the lower limit, problems such as warping of the metal-clad laminate 100 may occur. If the thickness T3 of the insulating resin layer 10 exceeds the upper limit, problems such as reduced productivity may occur.

In the metal-clad laminate 100 of this embodiment, in order to achieve low dielectric loss tangent of the resin layer as a whole and cope with high-frequency transmission, the thickness T2 of the adhesive layer 30 itself is increased. However, generally, materials with low elastic modulus show high thermal expansion coefficients, so increasing the layer thickness may lead to reduced dimensional stability. Here, it is considered that the dimensional change caused by circuit processing and multi-layer circuitization of the metal-clad laminate 100 is mainly caused by the following a) to c) mechanisms, and the total amount of b) and c) becomes the dimensional change after etching and appears.

a) When manufacturing the metal-clad laminate 100, internal stress is accumulated in the resin layer.

b) During circuit processing, the internal stress accumulated in a) is released by etching the metal layer 20, and the resin layer expands or contracts.

c) During circuit processing, the exposed resin absorbs moisture and expands due to etching of the metal layer 20.

The main causes of the internal stress in a) are: 1) the difference in thermal expansion coefficient between the metal layer 20 and the resin layer; 2) the internal strain of the resin generated by film formation. Here, the magnitude of the internal stress caused by 1) is not only affected by the difference in thermal expansion coefficient, but also by the temperature difference ΔT from the temperature during bonding (heating temperature) to the temperature of cooling and solidification during multi-layer circuit formation. That is, the internal stress increases in proportion to the temperature difference ΔT, so even if the difference in thermal expansion coefficient between the metal layer 20 and the resin layer is small, the higher the temperature of the resin required for bonding, the greater the internal stress. In the metal-clad laminate 100 of this embodiment, by using a material satisfying the above conditions (i) to (iii) as the adhesive layer 30, internal stress is reduced and dimensional stability is ensured. In addition, the adhesive layer 30 is laminated on the insulating resin layer 10, so when a multi-layer circuit board is formed, it functions as an intermediate layer and suppresses warping and dimensional changes.

[Method for manufacturing metal-clad laminate]

The metal-clad laminate 100 can be manufactured, for example, using the following method 1 or method 2.

[Method 1]

A method of forming a resin composition to be an adhesive layer 30 into a film shape to make an adhesive film, arranging and laminating the adhesive film in a manner facing the insulating resin layer 10 of the single-sided metal-clad laminate 40, and performing heat-pressing.

[Method 2]

A method of applying a solution of a resin composition that becomes an adhesive layer 30 to a predetermined thickness on an insulating resin layer 10 of a single-sided metal-clad laminate 40 and drying the coating. In the above case, heating or other treatments for hardening reaction or crosslinking reaction may be performed as needed.

The adhesive film used in method 1 can be produced, for example, by applying a solution of a resin composition to be the adhesive layer 30 to an arbitrary supporting substrate, drying the solution, and then peeling the solution from the supporting substrate. As the adhesive film, an adhesive polyimide film formed by forming the adhesive polyimide into a film can also be used. As forms of the method for producing an adhesive polyimide film, for example, the following methods can be cited: [1] a method of coating a support substrate with a solution of polyimide, drying the solution, heat-treating the solution to imidize the solution, and then peeling the solution off the support substrate to produce an adhesive film; [2] a method of coating a support substrate with a solution of polyimide, drying the solution, peeling the gel film of polyimide off the support substrate, heat-treating the solution to imidize the solution, and then producing an adhesive film; [3] a method of coating a support substrate with a solution of adhesive polyimide, drying the solution, and then peeling the solution off the support substrate to produce an adhesive film. Among the above-mentioned [1] to [3], it is preferred to form the adhesive film by coating a solution of an adhesive polyimide that has been imidized in a polyamic acid solution on a supporting substrate and drying the solution. Since the adhesive polyimide is solvent-soluble, it is advantageous to imidize the polyamic acid in a solution state so that the adhesive polyimide can be directly used as a coating liquid for the adhesive polyimide. Furthermore, the adhesive polyimide constituting the adhesive film can also be cross-linked by the above-mentioned method.

In the above-mentioned method 1 and method 2, there is no particular limitation on the method of applying the solution of the resin composition that becomes the adhesive layer 30 on the supporting substrate or the insulating resin layer 10. For example, the application can be performed using an applicator such as a notched wheel, a die, a scraper, or a die lip. In the step of forming the adhesive layer 30, it is preferred to form the surface of the formed adhesive layer 30 to be flat. In addition, it is preferred to also form the thickness of the adhesive layer 30 uniformly. By forming the surface of the adhesive layer 30 to be flat and making the thickness uniform, the adhesion in the manufacturing step of the multi-layer circuit board is improved.

The metal-clad laminate 100 of the present embodiment obtained as described above can manufacture a single-sided FPC or a double-sided FPC by performing wiring circuit processing on the metal layer 20. In addition, multiple single-sided FPCs or double-sided FPCs can be laminated using the adhesiveness of the adhesive layer 30 or using any bonding sheet, thereby manufacturing a multi-layer circuit board.

[Circuit board]

FIG2 is a cross-sectional view showing the structure of a circuit substrate of an embodiment of the present invention. The circuit substrate 101 includes: an insulating resin layer 10; a conductive circuit layer 50, which is laminated on one side of the insulating resin layer 10; and an adhesive layer 30, which is laminated on the other side of the insulating resin layer 10. That is, the circuit substrate 101 is a structure in which the conductive circuit layer 50/insulating resin layer 10/adhesive layer 30 are laminated in sequence. The circuit substrate 101 of this embodiment is obtained by performing wiring circuit processing on the metal layer 20 of the metal-clad laminate 100.

(Conductive circuit layer)

The conductive circuit layer 50 is a layer formed by forming a conductive circuit in a predetermined pattern on one side of the insulating resin layer 10. For example, a photosensitive resist is applied on the metal layer 20 of the metal-clad laminate 100, and exposure and development are performed to form a predetermined mask pattern. After etching the metal layer 20 through the mask pattern, the mask pattern is removed, thereby forming a conductive circuit layer 50 with a predetermined pattern. Furthermore, the so-called "conductive circuit layer" refers to the in-plane connecting electrode (land electrode) formed in the surface direction of the insulating resin layer 10, and is distinguished from the inter-layer connecting electrode (via electrode).

Regarding the conductive circuit layer 50, from the perspective of reducing transmission loss in high-frequency transmission, the maximum height roughness (Rz) of the surface in contact with the insulating resin layer 10 is preferably 1.0 μm or less. Transmission loss includes the sum of conductor loss and dielectric loss. If the Rz of the conductive circuit layer 50 is large, the conductor loss increases and has an adverse effect on the transmission loss. Therefore, it is preferred to control Rz.

The structures of the insulating resin layer 10 and the adhesive layer 30 in the circuit substrate 101 of this embodiment are as described in the metal-clad laminate 100.

[Multi-layer circuit board]

Next, a multilayer circuit substrate of an embodiment of the present invention is described with reference to FIGS. 3 to 6. Generally, a multilayer circuit substrate has a laminate including a plurality of insulating resin layers and two or more conductive circuit layers embedded in the laminate, and preferably has at least two or more insulating resin layers and at least two or more conductive circuit layers. Here, two preferred embodiments of the multilayer circuit substrate are listed for description. The multilayer circuit substrate 200 and the multilayer circuit substrate 201 of the present embodiment include at least one of the circuit substrates 101. In addition, the multi-layer circuit substrate 200 and the multi-layer circuit substrate 201 of the present embodiment may include one or more arbitrary circuit substrates other than the circuit substrate 101 that are stacked on the circuit substrate 101.

<First implementation form>

FIG3 is a cross-sectional view in the stacking direction showing the structure of the multi-layer circuit substrate 200 of the first embodiment of the present invention. The multi-layer circuit substrate 200 of the first embodiment is a structure in which a plurality of circuit substrates 101 and arbitrary circuit substrates 110 are stacked in the same direction.

That is, from the top to the bottom in FIG. 3 , the adhesive layer 30 of the first circuit substrate 101 is connected and stacked in a manner to cover the conductive circuit layer 50 of the second circuit substrate 101, and further, the adhesive layer 30 of the second circuit substrate 101 is connected and stacked in a manner to cover the conductive circuit layer 50 of any circuit substrate 110 that does not have the adhesive layer 30. Here, the structure or material of the arbitrary circuit substrate 110 is not limited, for example, the conductive circuit layer 50 may be formed by a patterned metal layer 20, or may have a damascene structure. In addition, the conductive circuit layer 50 of any circuit substrate 110 can be formed on the insulating resin layer 10 by inkjet, sputtering, plating, etc. Furthermore, the thickness, material, physical properties, etc. of the conductive circuit layer 50 or the insulating resin layer 10 of any circuit substrate 110 are not particularly limited.

FIG3 shows a stacked structure of two circuit substrates 101 and one arbitrary circuit substrate 110, but three or more circuit substrates 101 may be stacked. In addition, the adhesive layer 30 may cover the entire conductive circuit layer 50 of the adjacent circuit substrate 101 or the arbitrary circuit substrate 110, or may cover a part of the conductive circuit layer 50. Furthermore, in the multi-layer circuit substrate 200, the conductive circuit layer 50 is exposed on the surface of the uppermost circuit substrate 101, and an arbitrary protective film covering the uppermost conductive circuit layer 50 may be provided. In addition, FIG. 3 shows an example of a case where a conductive circuit layer 50 is formed on one side of an insulating resin layer 10 as an arbitrary circuit substrate 110, but a conductive circuit layer 50 may be formed on both sides of the insulating resin layer 10.

FIG4 is a diagram showing the manufacturing steps of the multi-layer circuit substrate 200 according to the first embodiment. First, a plurality of circuit substrates 101 and arbitrary circuit substrates 110 are prepared. Then, the adhesive layer 30 of the first circuit substrate 101 is arranged to overlap with the conductive circuit layer 50 of the second circuit substrate 101, and the adhesive layer 30 of the second circuit substrate 101 is arranged to overlap with the conductive circuit layer 50 of an arbitrary circuit substrate 110 that does not have the adhesive layer 30, and these are pressed together to manufacture (pressing step). In addition, FIG4 shows an example of laminating two circuit substrates 101, but three or more circuit substrates 101 may be laminated at one time. In addition, any circuit substrate 110 is not limited to one, and multiple circuit substrates can be stacked.

Since the adhesive layer 30 of the circuit substrate 101 is flattened on its surface, voids will not be generated in the adhesive layer 30 during the press-bonding step, and the adhesive resin can be filled between the conductive circuits of the conductive circuit layer 50 for lamination. In addition, if necessary, the multi-layer circuit substrate 200 obtained by lamination can be pressed from both sides using a press roller or a press device, thereby adjusting the thickness of the adhesive layer 30. Through the thickness adjustment step, the thickness accuracy of the adhesive layer 30 and the multi-layer circuit substrate 200 as a whole can be improved. Furthermore, during the press-bonding, a heat treatment can be performed at a temperature of 60°C to 220°C, for example. Thus, a multi-layer circuit substrate 200 in which multiple circuit substrates are integrally stacked can be manufactured. During the heat treatment, a cross-linked structure of imide bonds can be formed in the adhesive layer 30, for example, by heat condensation of the adhesive polyimide.

In this embodiment, the adhesive layer 30 of each circuit substrate 101 has the function of a bonding sheet for bonding the circuit substrates to each other, and the function of a protective film for protecting the conductive circuit. Therefore, there is no need to prepare an adhesive sheet or a protective layer for the conductive circuit and have it exist between the circuit substrates, which can simplify the process and equipment for forming a multi-layer circuit, simplify materials, and reduce costs.

The multi-layer circuit board 200 obtained as described above includes the following structure: an adhesive layer 30 having a sufficient thickness is provided between the conductive circuit layer 50 and the insulating resin layer 10 to ensure insulation, flexibility and low dielectric properties. Furthermore, in the multi-layer circuit board 200 of the present embodiment, a layer such as a cover film or a solder resist may be provided as a protective layer as needed. In addition, although it is omitted in the figure, chip-type electronic parts such as a chip or a chip capacitor, a chip coil, a chip resistor, etc. may also be built into the multi-layer circuit board 200 of the present embodiment. In addition, in the multi-layer circuit board 200 of the present embodiment, inter-layer connection electrodes (through-hole electrodes) not shown in the figure may also be formed. The interlayer connection electrode can be formed by forming a via hole in the insulating resin layer 10 by laser processing or drilling, and then filling the via hole with a conductive paste by printing or the like. The conductive paste can be, for example, a conductive paste obtained by mixing an organic solvent or an epoxy resin with a conductive powder having tin as the main component. In addition, the interlayer connection electrode can be formed by forming a coating portion on the inner surface of the via hole and a portion of the surface of the conductive circuit layer 50 after the via hole is formed.

<Second implementation form>

FIG5 is a cross-sectional view in the stacking direction showing the structure of the multi-layer circuit substrate 201 of the second embodiment of the present invention. In the multi-layer circuit substrate 201 of the second embodiment, a structure in which a pair of circuit substrates 101 are bonded together with their adhesive layers 30 facing each other is set as a circuit substrate unit 102, and includes at least one or more of the circuit substrate units 102.

That is, from the top to the bottom in FIG. 5 , the first metal clad laminate 100, the circuit substrate unit 102, and the second metal clad laminate 100 are sequentially arranged (in the opposite direction to the first metal clad laminate 100), and the circuit substrate unit 102 is sandwiched between the adhesive layers 30 of the two metal clad laminates 100 for lamination. The adhesive layer 30 of the first metal-clad laminate 100 is laminated in contact with the conductive circuit layer 50 on one side (the upper side in the figure) of the circuit substrate unit 102, and further, the adhesive layer 30 of the second metal-clad laminate 100 is laminated in contact with the conductive circuit layer 50 on the other side (the lower side in the figure) of the circuit substrate unit 102. In addition, FIG. 5 shows a laminate structure including only one circuit substrate unit 102, but a laminate structure including a plurality of circuit substrate units 102 may be produced by further interposing an adhesive sheet or a circuit substrate 101 or an arbitrary circuit substrate 110. In addition, the circuit substrate 101 may also be used as one or both of the upper and lower metal-clad laminates 100.

FIG6 is a manufacturing step diagram of the multi-layer circuit substrate 201 of the second embodiment. First, a circuit substrate unit 102 and two metal-clad laminates 100 are prepared. Here, the circuit substrate unit 102 can be manufactured in the following manner: a pair of circuit substrates 101 are prepared, and the adhesive layer 30 of one circuit substrate 101 is bonded to the adhesive layer 30 of the other circuit substrate 101. Furthermore, the multilayer circuit board 201 can be manufactured as follows: the adhesive layer 30 of the first metal clad laminate 100 is arranged to face the conductive circuit layer 50 on the upper surface side of the circuit board unit 102, and then, the adhesive layer 30 of the second metal clad laminate 100 is arranged to face the conductive circuit layer 50 on the lower surface side of the circuit board unit 102, and these are pressed together (pressing step).

Furthermore, instead of manufacturing the circuit substrate unit 102, the adhesive layer 30 of the first metal clad laminate 100 is arranged to face the conductive circuit layer 50 of the upper circuit substrate 101, the adhesive layer 30 of the upper circuit substrate 101 is arranged to face the adhesive layer 30 of the lower circuit substrate 101, and further, the adhesive layer 30 of the second metal clad laminate 100 is arranged to face the conductive circuit layer 50 of the lower circuit substrate 101, and these are pressed together.

If necessary, the multilayer circuit substrate 201 obtained by lamination can be pressurized from both sides using a press roller or a pressing device, thereby adjusting the thickness of the adhesive layer 30. Through the thickness adjustment step, the thickness accuracy of the adhesive layer 30 and the multilayer circuit substrate 201 as a whole can be improved. Furthermore, during the pressing, a heat treatment can be performed at a temperature of 60°C to 220°C. In this way, a multilayer circuit substrate 201 in which multiple circuit substrates are laminated integrally can be manufactured. During the heat treatment, in the adhesive layer 30, for example, a cross-linked structure of imide bonds can be formed by heating and condensing the adhesive polyimide.

In this embodiment, the adhesive layer 30 of each circuit substrate 101 also has the function of serving as an adhesive sheet for bonding the circuit substrates to each other. Therefore, there is no need to prepare an adhesive sheet separately and place it between the circuit substrates, which can simplify the process and equipment for forming a multi-layer circuit, simplify materials, and reduce costs.

The other structures and effects of the multi-layer circuit substrate 201 of this embodiment are the same as those of the multi-layer circuit substrate 200 of the first embodiment.

[Implementation example]

The following examples are shown to explain the features of the present invention in more detail. However, the scope of the present invention is not limited to the examples. Furthermore, in the following examples, unless otherwise specified, various measurements and evaluations are based on the following contents.

[Measurement of dimensional change rate]

The dimensional change rate is measured in the following order. First, a 150 mm square test piece is exposed and developed with a dry film resist at intervals of 100 mm to form a target for position measurement. The size before etching (normal state) is measured in an environment of temperature 23±2°C and relative humidity 50±5%, and then the copper other than the target of the test piece is removed by etching (liquid temperature below 40°C and time within 10 minutes). After standing for 24±4 hours in an environment of temperature 23±2°C and relative humidity 50±5%, the size after etching is measured. The dimensional change rate relative to normal state is calculated for each of three locations in the MD direction (long side direction) and the TD direction (width direction), and the average value of each is taken as the dimensional change rate after etching. The dimensional change rate after etching is calculated using the following formula.

Dimension change rate after etching (%) = (B-A)/A×100

A: Target distance before etching

B: Target distance after etching

Next, the test piece was heated in an oven at 250°C for 1 hour, and the distance between the position targets was measured. The dimensional change rate after etching was calculated for each of the three locations in the MD direction (longitudinal direction) and the TD direction (width direction), and the average value of each was taken as the dimensional change rate after heating. The heating dimensional change rate was calculated using the following formula.

Dimensional change rate after heating (%) = (C-B)/B×100

B: Target distance after etching

C: Target distance after heating

[Viscosity measurement]

Use an E-type viscometer (Brookfield, trade name: DV-II+Pro) to measure the viscosity at 25°C. Set the speed so that the torque is 10% to 90%, and read the value when the viscosity stabilizes 2 minutes after the start of the measurement.

[Determination of coefficient of thermal expansion (CTE)]

A thermomechanical analyzer (Bruker, trade name: 4000SA) was used to analyze a 3mm×20mm polyimide membrane. A load of 5.0g was applied while the temperature was raised from 30°C to 300°C at a certain rate. The membrane was then kept at the temperature for 10 minutes and then cooled at a rate of 5°C/min. The average thermal expansion coefficient (thermal expansion coefficient) from 250°C to 100°C was obtained.

[Determination of storage elastic modulus and glass transition temperature (Tg)]

A dynamic viscoelasticity measuring device (DMA: manufactured by UBM, trade name: E4000F) was used to measure the resin sheet of 5mm×20mm size at a heating rate of 4℃/min and a frequency of 11Hz from 30℃ to 400℃. In addition, the temperature at which the elastic modulus change (tanδ) is the largest is set as the glass transition temperature.

[Determination of dielectric constant and dielectric loss tangent]

The dielectric constant and dielectric loss tangent of the resin sheet at 10 GHz were measured using a Vector Network Analyzer (manufactured by Agilent, trade name E8363C) and a Split Post Dielectric Resonator (SPDR). The material used in the measurement was placed at a temperature of 24°C to 26°C and a humidity of 45% to 55%RH for 24 hours.

[Measurement of surface roughness of copper foil]

Using an atomic force microscope (AFM) (manufactured by Bruker AXS, trade name: Dimension Icon Scanning Probe Microscope (SPM)) and a probe (manufactured by Bruker AXS, trade name: TESPA (NCHV), top curvature radius 10nm, spring constant 42N/m), the copper foil surface was measured in a range of 80μm×80μm in tapping mode, and the ten-point average roughness (Rzjis) was calculated.

The abbreviations used in the synthesis examples represent the following compounds.

○BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride

○BPADA: 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride

○PMDA: Pyromellitic dianhydride

○BTDA: 3,3',4,4'-benzophenone tetracarboxylic dianhydride

○m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl

○TPE-R: 1,3-bis(4-aminophenoxy)benzene

○Bisaniline-M: 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene

○BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane

○DDA: Aliphatic diamine with 36 carbon atoms (manufactured by CRODA Japan Co., Ltd., trade name: PRIAMINE 1074, amine value: 205 mgKOH/g, mixture of dimer diamines with ring structure and chain structure, content of dimer component: 95% by weight or more)

○DMAc: N,N-dimethylacetamide

○NMP: N-methyl-2-pyrrolidone

○N-12: Dodecanedioic acid dihydrazine

○OP935: Aluminum organic phosphinate (manufactured by Clariant Japan, trade name: Exolit OP935)

○R710: (trade name, manufactured by Printec Co., Ltd., bisphenol-type epoxy resin, epoxy equivalent 170, liquid at room temperature, weight average molecular weight: about 340)

○VG3101L: (trade name, manufactured by Printec Co., Ltd., multifunctional epoxy resin, epoxy equivalent: 210, softening point 39℃~46℃)

○SR35K: (trade name, manufactured by Printec Co., Ltd., epoxy resin, epoxy equivalent: 930~940, softening point: 86℃~98℃)

○YDCN-700-10: (trade name, manufactured by Nippon Steel Chemicals & Materials Co., Ltd., cresol novolac type epoxy resin, epoxy equivalent 210, softening point 75℃~85℃)

○ Milex XLC-LL: (trade name, manufactured by Mitsui Chemicals Co., Ltd., phenolic resin, hydroxyl equivalent: 175, softening point: 77°C, water absorption: 1% by mass, heating mass loss rate: 4% by mass)

○HE200C-10: (Trade name, manufactured by AIR WATER (co., Ltd.), phenolic resin, hydroxyl equivalent: 200, softening point: 65℃~76℃, water absorption: 1% by mass, heating mass reduction rate: 4% by mass)

○HE910-10: (Trade name, manufactured by AIR WATER (co., Ltd.), phenolic resin, hydroxyl equivalent: 101, softening point: 83°C, water absorption: 1% by mass, heating mass reduction rate: 3% by mass%)

○SC1030-HJA: (trade name, manufactured by Admatechs, silica filler dispersion, average particle size: 0.25μm)

○Aerosil R972: (trade name, manufactured by Aerosil Japan Co., Ltd., silicon dioxide, average particle size: 0.016μm)

○Acrylic rubber (acryl gum) HTR-860P-30B-CHN: (sample name, manufactured by Teikoku Chemical Industry Co., Ltd., weight average molecular weight: 230,000, glycidyl functional monomer ratio: 8%, Tg: -7℃)

○Acrylic rubber (acryl gum) HTR-860P-3CSP: (sample name, manufactured by Teikoku Chemical Industry Co., Ltd., weight average molecular weight: 800,000, glycidyl functional monomer ratio: 3%, Tg: -7℃)

○A-1160: (trade name, manufactured by GE Toshiba, γ-ureidopropyltriethoxysilane)

○A-189: (trade name, manufactured by GE Toshiba Corporation, γ-butylpropyltrimethoxysilane)

○Curezol 2PZ-CN: (trade name, manufactured by Shikoku Chemical Industries, Ltd., 1-cyanoethyl-2-phenylimidazole)

○RE-810NM: (trade name, manufactured by Nippon Kayaku Co., Ltd., diallyl bisphenol A diglycidyl ether (properties: liquid))

○ Phoret SCS: (Trade name: manufactured by Soken Chemical Co., Ltd., styrene-containing acrylic polymer (Tg: 70°C, weight average molecular weight: 15,000))

○BMI-1: (trade name, manufactured by Tokyo Chemical Industry Co., Ltd., 4,4'-bismaleimide diphenylmethane)

○TPPK: (Trade name: manufactured by Tokyo Chemical Industry Co., Ltd., tetraphenylphosphonium tetraphenylborate)

○HP-P1: (trade name, manufactured by Mizushima Alloy Steel Co., Ltd., boron nitride filler)

(Synthesis Example 1)

<Preparation of resin solution A for adhesive layer>

Cyclohexanone is added to a composition containing (a) an epoxy resin and a phenol resin as a thermosetting resin and (c) an inorganic filler having the product name and composition ratio (unit: mass parts) shown in Table 1, and the mixture is stirred and mixed. Acrylic rubber as a high molecular weight component (b) shown in Table 1 is added thereto and stirred, and further, (e) a coupling agent and (d) a hardening accelerator shown in Table 1 are added and stirred until the components become uniform, thereby obtaining a resin solution A for an adhesive layer.

(Synthesis Example 2)

<Synthesis of polyimide resin (PI-1) and preparation of resin solution B for adhesive layer>

In a 300 mL flask equipped with a thermometer, a stirrer, a cooling tube, and a nitrogen inlet tube, 15.53 g of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: LP-7100), 28.13 g of polyoxypropylenediamine (manufactured by BASF, trade name: D400, molecular weight: 450), and 100.0 g of NMP were added and stirred to prepare a reaction solution. After the diamine was dissolved, 32.30 g of 4,4'-oxydiphthalic dianhydride, which had been purified by recrystallization from anhydrous acetic acid in advance, was added to the reaction solution in small portions while cooling the flask in an ice bath. After reacting at room temperature (25°C) for 8 hours, 67.0 g of xylene was added, and the mixture was heated at 180°C while blowing nitrogen, thereby removing xylene and water together by azeotropy. The reaction solution was injected into a large amount of water, and the precipitated resin was collected by filtration and dried to obtain a polyimide resin (PI-1). The molecular weight of the obtained polyimide resin (PI-1) was measured by gel permeation chromatography (GPC). As a result, the number average molecular weight Mn = 22400 and the weight average molecular weight Mw = 70200 in terms of polystyrene conversion.

The obtained polyimide resin (PI-1) was used to prepare the components in the composition ratio (unit: mass parts) shown in Table 2 to obtain a resin solution B for the adhesive layer.

(Synthesis Example 3)

<Preparation of resin solution C for adhesive layer>

In a 500 mL four-necked flask equipped with a nitrogen inlet tube, a stirrer, a thermocouple, a Dean-Stark trap, and a cooling tube, 44.92 g of BTDA (0.139 mol), 75.08 g of DDA (0.141 mol), 168 g of NMP, and 112 g of xylene were placed and mixed at 40° C. for 30 minutes to prepare a polyamine solution. The polyamine solution was heated to 190° C., heated and stirred for 4 hours, and the distilled water and xylene were removed from the system. Afterwards, the mixture was cooled to 100°C, 112 g of xylene was added and stirred, and then cooled to 30°C to complete the imidization, thereby obtaining a resin solution C for the adhesive layer (solid content: 29.5% by weight, weight average molecular weight: 75,700).

(Synthesis Example 4)

<Preparation of resin solution D for adhesive layer>

A polyamide solution was prepared in the same manner as in Synthesis Example 3 except that 42.51 g of BPADA (0.082 mol), 34.30 g of DDA (0.066 mol), 6.56 g of BAPP (0.016 mol), 208 g of NMP and 112 g of xylene were used as the raw material composition. The polyamide solution was treated in the same manner as in Synthesis Example 3 to obtain a resin solution D for the adhesive layer (solid content: 30.0% by weight, weight average molecular weight: 65,000).

(Synthesis Example 5)

<Preparation of polyamide solution 1 for insulating resin layer>

Under nitrogen flow, 64.20 g of m-TB (0.302 mol) and 5.48 g of dianiline-M (0.016 mol) and DMAc in an amount of 15 wt% solid content after polymerization were added to the reaction tank, and stirred and dissolved at room temperature. Next, 34.20 g of PMDA (0.157 mol) and 46.13 g of BPDA (0.157 mol) were added, and then the polymerization reaction was continued at room temperature for 3 hours to prepare polyamide solution 1 (viscosity: 26,500 cps).

(Synthesis Example 6)

<Preparation of polyamide solution 2 for insulating resin layer>

69.56 g of m-TB (0.328 mol), 542.75 g of TPE-R (1.857 mol), DMAc in an amount of 12 wt% solid content concentration after polymerization, 194.39 g of PMDA (0.891 mol) and 393.31 g of BPDA (1.337 mol) were used as the raw material composition. Polyamide solution 2 (viscosity: 2,650 cps) was prepared in the same manner as in Synthesis Example 3 except that the above-mentioned ingredients were used.

(Production Example 1)

<Preparation of resin sheet A for adhesive layer>

The resin solution A for the adhesive layer was applied to the silicone treated surface of a release substrate (length × width × thickness = 320 mm × 240 mm × 25 μm) to a thickness of 50 μm after drying, and then dried at 80°C for 15 minutes, and then dried at 120°C for 15 minutes, and then peeled from the release substrate to prepare a resin sheet A. In addition, the resin sheet A was heated in an oven at 120°C for 2 hours and at 170°C for 3 hours in order to evaluate the physical properties after curing. At this time, regarding the cured resin sheet A, Tg is 95°C, the storage elastic modulus at 50°C is 960MPa, and the maximum value of the storage elastic modulus in the range of 180°C to 260°C is 7MPa.

(Production Example 2)

<Preparation of resin sheet B for adhesive layer>

The resin solution B for the adhesive layer was applied to the silicone treated surface of a release substrate (length × width × thickness = 320 mm × 240 mm × 25 μm) to a thickness of 50 μm after drying, and then dried at 80°C for 15 minutes, and then dried at 120°C for 15 minutes, and then peeled off from the release substrate to prepare a resin sheet B. In addition, the resin sheet B was heated in an oven at 120°C for 2 hours and at 170°C for 3 hours in order to evaluate the physical properties after curing. At this time, for the cured resin sheet B, Tg is below 100°C, the storage elastic modulus at 50°C is below 1800 MPa, and the maximum value of the storage elastic modulus in the range of 180°C to 260°C is 70 MPa.

(Production Example 3)

<Preparation of resin sheet C for adhesive layer>

1.8 g of N-12 (0.0036 mol) and 12.5 g of OP935 were mixed into 169.49 g of resin solution C for the adhesive layer (50 g in terms of solid content), and 6.485 g of NMP and 19.345 g of xylene were added for dilution to prepare polyimide varnish 1.

Polyimide varnish 1 was applied to the silicone treated surface of a release substrate (length × width × thickness = 320 mm × 240 mm × 25 μm) in a manner to a thickness of 50 μm after drying, and then heat dried at 80°C for 15 minutes and peeled off from the release substrate to prepare a resin sheet C. The Tg of the resin sheet C was 78°C, the storage elastic modulus at 50°C was 800 MPa, and the maximum storage elastic modulus in the range of 180°C to 260°C was 10 MPa. In addition, the dielectric constant (Dk) and dielectric loss tangent (Df) were 2.68 and 0.0028, respectively.

(Production Example 4)

<Preparation of resin sheet D for adhesive layer>

The resin solution D for the adhesive layer was applied to the silicone treated surface of the release substrate (length × width × thickness = 320mm × 240mm × 25μm) in a manner to a thickness of 50μm after drying, and then dried at 80°C for 15 minutes and peeled off from the release substrate to prepare a resin sheet D. The Tg of the resin sheet D was 82°C, the storage elastic modulus at 50°C was 1800MPa or less, and the maximum value of the storage elastic modulus in the range of 180°C to 260°C was 2MPa or less. In addition, the dielectric constant (Dk) and dielectric loss tangent (Df) were 2.80 and 0.0026, respectively.

(Production Example 5)

<Preparation of single-sided metal-clad laminates>

On copper foil 1 (electrolytic copper foil, thickness: 12 μm, surface roughness Rz of the resin layer side: 0.6 μm), polyamide solution 2 is uniformly applied to a thickness of about 2 μm to 3 μm after curing, and then heat-dried at 120°C to remove the solvent. Secondly, polyamide solution 1 is uniformly applied thereon to a thickness of about 21 μm after curing, and heat-dried at 120°C to remove the solvent. Furthermore, polyamide solution 2 is uniformly applied thereon to a thickness of about 2 μm to 3 μm after curing, and then heat-dried at 120°C to remove the solvent. Furthermore, a stepwise heat treatment is performed from 120°C to 360°C to complete the imidization and prepare a single-sided metal-clad laminate 1. The dimensional change rate of the single-sided metal-clad laminate 1 is as follows.

Dimensional change rate after etching in MD direction (long side direction): 0.01%

Dimension change rate after etching in TD direction (width direction): -0.04%

Dimensional change rate after heating in MD direction (long side direction): -0.03%

Dimensional change rate after heating in TD direction (width direction): -0.01%

In addition, the polyimide film 1 (thickness: 25 μm) prepared by etching away the copper foil 1 of the single-sided metal-clad laminate 1 using an aqueous solution of ferric chloride has a CTE of 20.0 ppm/K, and a dielectric constant (Dk) and a dielectric loss tangent (Df) of 3.40 and 0.0029, respectively.

[Implementation Example 1]

The resin solution A for the adhesive layer was applied to the resin surface of the single-sided metal-clad laminate 1 in such a manner that the thickness after drying was 50 μm, and then dried at 80°C for 15 minutes and further dried at 120°C for 15 minutes to prepare the single-sided metal-clad laminate 1 with an adhesive layer. In addition, the single-sided metal-clad laminate 1 with an adhesive layer was heated in an oven at 120°C for 2 hours and at 170°C for 3 hours in order to evaluate the physical properties of the adhesive layer after curing. The evaluation results of the single-sided metal-clad laminate 1 with an adhesive layer after heating are as follows.

Dimension change rate after etching in MD direction: -0.05%

Dimension change rate after etching in TD direction: -0.02%

Dimensional change rate after heating in MD direction: -0.01%

Dimensional change rate after heating in TD direction: -0.03%

There is no problem with the dimensional change of the single-sided metal-clad laminate 1 with an adhesive layer after heating. In addition, the CTE of the resin laminate 1 (thickness: 75μm) prepared by etching away the copper foil 1 of the single-sided metal-clad laminate 1 with an adhesive layer after heating is 36.2ppm/K.

[Example 2]

The resin solution B for the adhesive layer was applied to the resin surface of the single-sided metal-clad laminate 1 in such a manner that the thickness after drying was 50 μm, and then dried at 80°C for 15 minutes and further dried at 120°C for 15 minutes to prepare a single-sided metal-clad laminate 2 with an adhesive layer. In addition, the single-sided metal-clad laminate 2 with an adhesive layer was heated in an oven at 120°C for 2 hours and at 170°C for 3 hours in order to evaluate the physical properties of the adhesive layer after curing. The evaluation results of the single-sided metal-clad laminate 2 with an adhesive layer after heating are as follows.

Dimension change rate after etching in MD direction: -0.08%

Dimension change rate after etching in TD direction: -0.06%

Dimensional change rate after heating in MD direction: -0.03%

Dimensional change rate after heating in TD direction: -0.06%

There is no problem with the dimensional change of the single-sided metal-clad laminate 2 with an adhesive layer after heating. In addition, the CTE of the resin laminate 2 (thickness: 75μm) prepared by etching away the copper foil 1 of the single-sided metal-clad laminate 2 with an adhesive layer after heating is 25.0ppm/K.

[Implementation Example 3]

The polyimide varnish 1 was applied to the resin surface of the single-sided metal-clad laminate 1 in a manner to have a thickness of 50 μm after drying, and then heated and dried at 80°C for 15 minutes, thereby preparing a single-sided metal-clad laminate 3 with an adhesive layer. In addition, the single-sided metal-clad laminate 3 with an adhesive layer was heated in an oven at 180°C for 1 minute and at 150°C for 30 minutes, and then evaluated. The results are as follows.

Dimension change rate after etching in MD direction: -0.05%

Dimension change rate after etching in TD direction: -0.04%

Dimensional change rate after heating in MD direction: 0.05%

Dimensional change rate after heating in TD direction: 0.01%

There is no problem with the dimensional change of the single-sided metal-clad laminate 3 with an adhesive layer after heating. In addition, the CTE of the resin laminate 3 (thickness: 75μm) prepared by etching away the copper foil 1 of the single-sided metal-clad laminate 3 with an adhesive layer after heating is 25.6ppm/K, and the dielectric constant (Dk) and dielectric loss tangent (Df) are 2.92 and 0.0028 respectively.

[Implementation Example 4]

The resin solution D for the adhesive layer was applied to the resin surface of the single-sided metal-clad laminate 1 in a manner to a thickness of 50 μm after drying, and then heated and dried at 80°C for 15 minutes to prepare a single-sided metal-clad laminate 4 with an adhesive layer. In addition, the single-sided metal-clad laminate 4 with an adhesive layer was heated in an oven at 180°C for 1 minute and at 150°C for 30 minutes, and then evaluated. As a result, there was no problem with dimensional change, and the dielectric constant (Dk) and dielectric loss tangent (Df) were 3.00 and 0.0027, respectively.

[Implementation Example 5]

A liquid crystal polymer film (manufactured by Kuraray, trade name: CT-Z, thickness: 25 μm, CTE: 18 ppm/K, thermal deformation temperature: 300°C, Dk: 3.40, Df: 0.0022) is used as an insulating substrate, and a double-sided metal-clad laminate 1 having copper foil 1 on both sides thereof is prepared. The copper foil 1 on one side of the double-sided metal-clad laminate 1 is etched away to prepare a single-sided metal-clad laminate 2.

The polyimide varnish 1 was applied to the resin surface of the single-sided metal-clad laminate 2 in a manner to a thickness of 50 μm after drying, and then heated and dried at 80°C for 15 minutes to prepare a single-sided metal-clad laminate 5 with an adhesive layer. In addition, the single-sided metal-clad laminate 5 with an adhesive layer was heated in an oven at 180°C for 1 minute and at 150°C for 30 minutes, and then evaluated. As a result, there was no problem with dimensional change, and the dielectric constant (Dk) and dielectric loss tangent (Df) were 2.92 and 0.0026, respectively.

[Implementation Example 6]

The resin solution D for the adhesive layer was applied to the resin surface of the single-sided metal-clad laminate 2 in a manner to a thickness of 50 μm after drying, and then heated and dried at 80°C for 15 minutes to prepare a single-sided metal-clad laminate 6 with an adhesive layer. In addition, the single-sided metal-clad laminate 6 with an adhesive layer was heated in an oven at 180°C for 1 minute and at 150°C for 30 minutes, and then evaluated. As a result, there was no problem with dimensional change, and the dielectric constant (Dk) and dielectric loss tangent (Df) were 3.00 and 0.0025, respectively.

[Implementation Example 7]

A single-sided wiring board 1 with a conductive circuit layer formed thereon is prepared by performing circuit processing using a subtractive method on a copper foil 1 of a single-sided metal-clad laminate 1. A single-sided wiring board 1 with a conductive circuit layer formed thereon is prepared by performing circuit processing using a subtractive method on two single-sided metal-clad laminates 3 with adhesive layers, and two single-sided wiring boards 1 with adhesive layers formed thereon are prepared.

The conductive circuit layer of the single-sided wiring substrate 1 and the adhesive layer of a single-sided wiring substrate 1 with an adhesive layer, and the conductive circuit layer of a single-sided wiring substrate 1 with an adhesive layer and the adhesive layer of another single-sided wiring substrate 1 with an adhesive layer are overlapped in a manner facing each other, and then heat-pressed for 60 minutes at 160°C and 4MPa to prepare a multi-layer circuit substrate 1. In the press-bonded surface of the multi-layer circuit substrate 1, the adhesive is fully filled into the conductive circuit layer, and there is no disorder of the conductive circuit caused by the heat-pressing step.

[Implementation Example 8]

Two single-sided wiring substrates 1 with adhesive layers are prepared, and the adhesive layer of one single-sided wiring substrate 1 with adhesive layers is overlapped with the adhesive layer of the other single-sided wiring substrate 1 with adhesive layers in a facing manner, and then hot-pressed for 60 minutes at 160°C and 4MPa to prepare a double-sided circuit substrate 1. In the press-bonded surfaces of the double-sided circuit substrates 1, the adhesive layers are fully bonded to each other, and no disturbance of the conductor circuit caused by the hot-pressing step occurs.

[Implementation Example 9]

The copper foil 1 of two single-sided metal-clad laminates 4 with adhesive layers is subjected to circuit processing using a subtractive method to prepare two single-sided wiring substrates 2 with adhesive layers formed with conductive circuit layers.

The conductive circuit layer of the single-sided wiring board 1 and the adhesive layer of a single-sided wiring board 2 with an adhesive layer, and the conductive circuit layer of a single-sided wiring board 2 with an adhesive layer and the adhesive layer of another single-sided wiring board 2 with an adhesive layer are overlapped in a manner facing each other, and then heat-pressed for 60 minutes at 160°C and 4MPa to prepare a multi-layer circuit board 2. In the press-bonded surface of the multi-layer circuit board 2, the adhesive is fully filled into the conductive circuit layer, and no disturbance of the conductive circuit caused by the heat-pressing step occurs.

[Example 10]

Two single-sided wiring substrates 2 with adhesive layers were prepared, and the adhesive layer of one single-sided wiring substrate 2 with adhesive layer was overlapped with the adhesive layer of the other single-sided wiring substrate 2 with adhesive layer in a facing manner, and then heat-pressed for 60 minutes at 160°C and 4MPa to prepare a double-sided circuit substrate 2. In the press-bonded surfaces of the double-sided circuit substrates 2, the adhesive layers were fully bonded to each other, and no disturbance of the conductor circuit caused by the heat-pressing step occurred.

[Implementation Example 11]

The copper foil 1 of the single-sided metal laminate 2 is subjected to circuit processing using a subtractive method to prepare a single-sided wiring board 2 with a conductive circuit layer formed thereon. The copper foil 1 of two single-sided metal laminates 5 with adhesive layers is subjected to circuit processing using a subtractive method to prepare two single-sided wiring boards 3 with adhesive layers with conductive circuit layers formed thereon.

The conductive circuit layer of the single-sided wiring board 2 and the adhesive layer of a single-sided wiring board 3 with an adhesive layer, and the conductive circuit layer of a single-sided wiring board 3 with an adhesive layer and the adhesive layer of another single-sided wiring board 3 with an adhesive layer are overlapped in a manner facing each other, and then heat-pressed for 60 minutes at 160°C and 4MPa to prepare a multi-layer circuit board 3. In the press-bonded surface of the multi-layer circuit board 3, the adhesive is fully filled into the conductive circuit layer, and there is no disorder of the conductive circuit caused by the heat-pressing step.

[Implementation Example 12]

Two single-sided wiring substrates 3 with adhesive layers are prepared, and the adhesive layer of one single-sided wiring substrate 3 with adhesive layers is overlapped with the adhesive layer of another single-sided wiring substrate 3 with adhesive layers in a facing manner, and then hot-pressed for 60 minutes at 160°C and 4MPa to prepare a double-sided circuit substrate 3. In the press-bonded surfaces of the double-sided circuit substrates 3, the adhesive layers are fully bonded to each other, and no disturbance of the conductor circuit caused by the hot-pressing step occurs.

[Implementation Example 13]

The copper foil 1 of two single-sided metal-clad laminates 6 with adhesive layers is subjected to circuit processing using a subtractive method to prepare two single-sided wiring substrates 4 with adhesive layers formed with conductive circuit layers.

The conductive circuit layer of the single-sided wiring substrate 2 and the adhesive layer of a single-sided wiring substrate 4 with an adhesive layer, and the conductive circuit layer of a single-sided wiring substrate 4 with an adhesive layer and the adhesive layer of another single-sided wiring substrate 4 with an adhesive layer are overlapped in a manner facing each other, and then heat-pressed for 60 minutes at 160°C and 4MPa to prepare a multi-layer circuit substrate 4. In the press-bonded surface of the multi-layer circuit substrate 4, the adhesive is fully filled into the conductive circuit layer, and there is no disorder of the conductive circuit caused by the heat-pressing step.

[Example 14]

Two single-sided wiring substrates 4 with adhesive layers were prepared, and the adhesive layer of one single-sided wiring substrate 4 with adhesive layer was overlapped with the adhesive layer of the other single-sided wiring substrate 4 with adhesive layer in a facing manner, and then heat-pressed for 60 minutes at 160°C and 4MPa to prepare a double-sided circuit substrate 4. In the press-bonded surfaces of the double-sided circuit substrates 4, the adhesive layers were fully bonded to each other, and no confusion of the conductor circuit was caused by the heat-pressing step.

The above is a detailed description of the implementation form of the present invention for the purpose of illustration, but the present invention is not limited to the above implementation form and can be modified in various ways.

10: Insulating resin layer

30: Adhesive layer

50: Conductor circuit layer

101: Circuit board

110: Any circuit board

200:Multi-layer circuit board

Claims (10)

A metal-clad laminate comprises: an insulating resin layer; a metal layer laminated on one side of the insulating resin layer; and an adhesive layer laminated on the other side of the insulating resin layer, wherein the thickness T2 of the adhesive layer is in the range of 20 μm to 200 μm, the thickness T3 of the insulating resin layer is in the range of 12 μm to 100 μm, and the total thickness T1 of the thickness T2 of the adhesive layer and the thickness T3 of the insulating resin layer is in the range of 50 μm to 250 μm, and the thickness T2 of the adhesive layer is in the range of 12 μm to 100 μm. The ratio (T2/T1) of the thickness T2 to the total thickness T1 is within the range of 0.5 to 0.8, the resin constituting the adhesive layer is a thermoplastic resin or a thermosetting resin, and satisfies the following conditions (i) to (iii): (i) the storage elastic modulus at 50°C is less than 1800MPa; (ii) the maximum value of the storage elastic modulus in the temperature range from 180°C to 260°C is less than 800MPa; (iii) the glass transition temperature (Tg) is less than 180°C. The metal-clad laminate as described in item 1 of the patent application, wherein the thermoplastic resin is an adhesive polyimide containing tetracarboxylic acid residues and diamine residues, and the adhesive polyimide contains 50 mol parts or more of diamine residues derived from dimer acid type diamine relative to 100 mol parts of the total amount of the diamine residues, wherein the dimer acid type diamine is obtained by replacing the two terminal carboxylic acid groups of the dimer acid with primary aminomethyl or amino groups. A metal-clad laminate as described in item 1 of the patent application, wherein the metal-clad laminate is a material for a circuit substrate in which the metal layer is processed into wiring. The metal-clad laminate as claimed in claim 2, wherein the adhesive polyimide contains 90 mol parts or more of tetracarboxylic acid residues derived from tetracarboxylic anhydride represented by the following general formula (1) and/or general formula (2) relative to 100 mol parts of the total amount of the tetracarboxylic acid residues:

In the general formula (1), X represents a single bond or a divalent group selected from the following formulas; in the general formula (2), the cyclic moiety represented by Y represents a cyclic saturated hydrocarbon group selected from a 4-membered ring, a 5-membered ring, a 6-membered ring, a 7-membered ring or an 8-membered ring, -CO-, -SO ₂ -, -O-, -C(CF ₃ ) ₂ -,

, -COO- or -COO-Z-OCO- In the formula, Z represents -C ₆ H ₄ -, -(CH ₂ )n- or -CH ₂ -CH(-OC(=O)-CH ₃ )-CH ₂ -, and n represents an integer of 1-20. The metal-clad laminate as described in claim 2, wherein the adhesive polyimide contains diamine residues derived from the dimer acid type diamine in an amount of 50 to 99 mol parts relative to 100 mol parts of the total amount of the diamine residues, and contains diamine residues derived from at least one diamine compound selected from the diamine compounds represented by the following general formulae (B1) to (B7) in an amount of 1 to 50 mol parts:

In formula (B1) to formula (B7), R ₁ independently represents a monovalent alkyl group or alkoxy group having 1 to 6 carbon atoms, the linking group A independently represents a divalent group selected from -O-, -S-, -CO-, -SO-, -SO ₂ -, -COO-, -CH ₂ -, -C(CH ₃ ) ₂ -, -NH- or -CONH-, and n ₁ independently represents an integer of 0 to 4; wherein, from formula (B3), the portion repeating with formula (B2) is removed, and from formula (B5), the portion repeating with formula (B4) is removed. A circuit substrate comprises: an insulating resin layer; a conductive circuit layer formed on one side of the insulating resin layer; and an adhesive layer laminated on the other side of the insulating resin layer, wherein the thickness T2 of the adhesive layer is in the range of 20 μm to 200 μm, the thickness T3 of the insulating resin layer is in the range of 12 μm to 100 μm, and the total thickness T1 of the thickness T2 of the adhesive layer and the thickness T3 of the insulating resin layer is in the range of 50 μm to 250 μm. The ratio (T2/T1) of the thickness T2 of the adhesive layer to the total thickness T1 is in the range of 0.5 to 0.8, and the resin constituting the adhesive layer is a thermoplastic resin or a thermosetting resin and meets the following conditions (i) to (iii): (i) the storage elastic modulus at 50°C is less than 1800MPa; (ii) the maximum value of the storage elastic modulus in the temperature range from 180°C to 260°C is less than 800MPa; (iii) the glass transition temperature (Tg) is less than 180°C. As described in item 6 of the patent application, the thermoplastic resin is an adhesive polyimide containing tetracarboxylic acid residues and diamine residues, and the adhesive polyimide contains 50 moles or more of diamine residues derived from dimer acid type diamine relative to 100 moles of the total amount of the diamine residues, wherein the dimer acid type diamine is formed by replacing the two terminal carboxylic acid groups of the dimer acid with primary aminomethyl or amino groups. The circuit substrate as described in claim 7 is characterized in that the adhesive polyimide contains 90 mol parts or more of tetracarboxylic acid residues derived from tetracarboxylic anhydride represented by the following general formula (1) and/or general formula (2) relative to 100 mol parts of the total amount of the tetracarboxylic acid residues:

In the general formula (1), X represents a single bond or a divalent group selected from the following formulas; in the general formula (2), the cyclic moiety represented by Y represents a cyclic saturated hydrocarbon group selected from a 4-membered ring, a 5-membered ring, a 6-membered ring, a 7-membered ring or an 8-membered ring; -CO-, -SO ₂ -, -O-, -C(CF ₃ ) ₂ -,

, -COO- or -COO-Z-OCO- wherein Z represents -C ₆ H ₄ -, -(CH ₂ )n- or -CH ₂ -CH(-OC(=O)-CH ₃ )-CH ₂ -, and n represents an integer of 1-20. The circuit substrate as described in claim 7, wherein the adhesive polyimide contains diamine residues derived from the dimer acid type diamine in an amount of 50 to 99 mol parts relative to 100 mol parts of the total amount of the diamine residues, and contains diamine residues derived from at least one diamine compound selected from the diamine compounds represented by the following general formulae (B1) to (B7) in an amount of 1 to 50 mol parts:

In formula (B1) to formula (B7), R ₁ independently represents a monovalent alkyl group or alkoxy group having 1 to 6 carbon atoms, the linking group A independently represents a divalent group selected from -O-, -S-, -CO-, -SO-, -SO ₂ -, -COO-, -CH ₂ -, -C(CH ₃ ) ₂ -, -NH- or -CONH-, and n ₁ independently represents an integer of 0 to 4; wherein, from formula (B3), the portion repeating with formula (B2) is removed, and from formula (B5), the portion repeating with formula (B4) is removed. A multi-layer circuit substrate, which is a multi-layer circuit substrate having multiple circuit substrates stacked, and is characterized in that: it includes at least one circuit substrate as described in any one of items 6 to 9 of the patent application scope as the circuit substrate.