JP2003298230A - Substrate for flexible printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for flexible printed wiring board that can reveal a superior adhesive strength even when the substrate is constituted by bonding copper foil to a flexible film at low temperatures. <P>SOLUTION: This substrate for flexible printed wiring board has the copper foil laminated upon one surface or both surfaces of the flexible film through adhesive layers. The bonded surface of the copper foil is roughened to have surface roughtness (Rz) of 3-5.5 μm and the roughened surface is treated with an amino silane coupling agent. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for a flexible printed wiring board, and more particularly to a substrate for a flexible printed wiring board used in electronic equipment such as a digital video disc (DVD).

[0002]

2. Description of the Related Art In recent years, the demand for flexible printed wiring boards has increased with the miniaturization, high density and weight reduction of electronic equipment. This tendency of downsizing of electronic devices leads to an increase in the internal temperature of the electronic devices, and particularly in an electronic device that rotates at high speed such as a digital video disk (DVD), the internal temperature rises to around 80 ° C. Even under such a high temperature environment, the flexible printed wiring board is required to have sliding flexibility equivalent to that at room temperature, and this tendency is becoming severer year by year. In the flexible printed wiring board, generally, copper foil (rolled copper foil is mainly used for bending) is attached to the surface of a polyimide film (insulating layer) via an adhesive layer. A circuit is formed by etching or the like on the surface of the copper foil.
Therefore, the adhesive composition forming the adhesive layer is also required to have heat resistance to satisfy sufficient flexibility at high temperatures. Specifically, as a characteristic of the adhesive, the glass transition temperature (Tg) after curing has been around 40 to 50 ° C. in the past, but with the recent increase in the internal temperature of electronic devices, the glass transition after curing has occurred. The temperature (Tg) is also required to be 80 ° C. or higher, and there is a need for an adhesive composition that does not soften even at such a temperature or higher and retains a high elastic modulus.

[0003]

By the way, T after curing
An adhesive composition having a high g (Tg = 80 to 130 ° C.) tends to have a high Tg before curing (Tg = 70 to 120).
C.), when producing a flexible printed wiring board using such an adhesive composition having a high Tg, the Tg after curing is
It is necessary to bond the film and the copper foil together at a temperature of about + 30 ° C (about 110 ° C or higher). However, when the film and the copper foil are bonded together at such a high temperature (approximately 110 ° C. or higher), a difference in the coefficient of thermal expansion of both materials causes defective appearance such as wrinkles and folds during bonding, and the adhesive strength is increased. There is a tendency to be inferior. On the other hand, in order to suppress the appearance failure due to thermal expansion, the temperature at the time of bonding is lowered (approximately 1
If it is less than 10 ° C), sufficient adhesive strength cannot be obtained. In this case, when an adhesive composition having a low Tg after curing (40 to 50 ° C.) (low Tg adhesive composition) is used, a certain degree of adhesive strength can be secured even when the temperature at the time of laminating is lowered. However, since a low Tg adhesive composition is used, there arises a problem that sliding flexibility at a high temperature is poor.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a base material for a flexible printed wiring board which can exhibit excellent adhesive strength even when laminated at a low temperature.

[0005]

In order to achieve the above object, the substrate for a flexible printed wiring board of the present invention has a copper foil laminated on one or both sides of a flexible film via an adhesive layer. In the base material for a flexible printed wiring board, the adhesive surface of the copper foil has a surface roughness (Rz) of 3
It is formed on a rough surface in the range of up to 5.5 μm, and this rough surface is treated with an aminosilane coupling agent.

That is, the present invention provides a flexible film in order to obtain a substrate for a flexible printed wiring board which can exhibit excellent adhesive strength even when laminated at a low temperature (35 ° C. or more and less than 110 ° C.). We have conducted intensive research centering on the copper foil side that is attached to the. Then, first, as a result of continuing research by focusing on Rz (ten-point average roughness) of the copper foil surface, the surface roughness (Rz) of the conventional rolled copper foil is generally 2 μm or more and less than 3 μm. , Surface roughness of copper foil (R
When z) is made 3 μm or more rougher than the conventional one, the adhesive property with the flexible film is improved due to the physical anchoring effect, but when the surface roughness (Rz) of the copper foil becomes too large, the copper foil becomes too thick. It was found that residual copper was generated when a circuit pattern was formed by etching on. Therefore, when studies are repeated on the preferable range of the surface roughness (Rz) of the copper foil, when the surface roughness (Rz) of the copper foil is set within the range of 3 to 5.5 μm, the circuit formability is not impaired. It has been found that the adhesive strength with the flexible film is improved. However, as a result of further research and development, the surface roughness (Rz) of the copper foil was 3 to
Sufficient adhesive strength could not be obtained only by forming a rough surface within the range of 5.5 μm. Therefore, the adhesive surface of the copper foil is formed into a rough surface having a specific surface roughness (Rz),
Moreover, when this rough surface is treated with an aminosilane coupling agent, a chemical bond required for adhesiveness is formed on the copper foil surface, and a physical anchoring effect (physical bond) due to the specific surface roughness (Rz) is produced. The inventors have found that the synergistic effect of the treatment with the aminosilane coupling agent and the chemical bond improves the adhesiveness between the copper foil and the flexible film, and the intended purpose can be achieved.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail.

The substrate for flexible printed wiring board of the present invention is constructed by laminating copper foil on one or both sides of a flexible film with an adhesive layer interposed therebetween. The greatest feature of the present invention is that the adhesive surface of the copper foil is formed into a specific rough surface.

The copper foil has a surface roughness (R
z) It is formed on a rough surface in the range of 3 to 5.5 μm, and this rough surface is treated with an aminosilane coupling agent instead of the commonly used epoxysilane.

The adhesive surface of the copper foil must be formed to have a surface roughness (Rz: ten-point average roughness) within a range of 3 to 5.5 μm, preferably Rz = 3 to 4. It is within the range of 5 μm. That is, when Rz is less than 3 μm, the physical anchoring effect is low and the adhesive force with the flexible film is small. On the contrary, when Rz is more than 5.5 μm, residual copper is generated during circuit formation. .

The aminosilane coupling agent used for the surface roughening treatment of the copper foil is not particularly limited, but those represented by the following general formula (1) are preferably used.

[0012]

[Chemical 2]

Specific examples of the specific aminosilane coupling agent include N-β represented by the following formula (2).
(Aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane represented by the following formula (3), γ-amino represented by the following formula (4) Examples thereof include propyltrimethoxysilane and γ-aminopropyltriethoxysilane represented by the following formula (5).

[0014]

[Chemical 3]

[0015]

[Chemical 4]

[0016]

[Chemical 5]

[0017]

[Chemical 6]

The method for treating the aminosilane coupling agent is not particularly limited, and examples thereof include a method of applying the aminosilane coupling agent by spray coating, roll coating, dipping or the like.

As the flexible film, for example, an electrically insulating resin film is used. Examples of the material of the resin film include heat resistant resins such as polyimide, polyester, polyether ketone, polyphenylene sulfide, aramid, polycarbonate, and polyether sulfone.

The thickness of the flexible film is not particularly limited, but a thickness within the range of 10 to 75 μm is usually used. It should be noted that at least one surface of the flexible film may be subjected to surface treatment such as corona discharge treatment, low temperature plasma treatment, and sandblast treatment as appropriate.

The adhesive composition used for forming the adhesive layer is not particularly limited, but one having a glass transition temperature (Tg) after curing within the range of 80 to 130 ° C. is preferable. That is, when the glass transition temperature (Tg) is less than 80 ° C., sliding flexibility under high temperature conditions is insufficient,
On the contrary, if the glass transition temperature (Tg) exceeds 130 ° C., the adhesive strength to the flexible film or the copper foil may decrease.

Examples of the adhesive composition having a high Tg as described above include a thermoplastic resin (component A), a phosphorus-containing phenoxy resin (component B), a phosphorus-containing epoxy resin (component C), and a curing agent. Those having (D component) as an essential component are preferably used.

The thermoplastic resin (component A) is not particularly limited, and examples thereof include polyamide resin, polyester resin, polycarbonate resin, polyphenylene oxide resin, polyurethane resin, polyacetal resin, polyethylene. Examples of the resin include a polypropylene resin, a polyvinyl resin, and a polyvinyl resin. These may be used alone or in combination of two or more. Among these, a polyamide resin is preferably used because of its adhesiveness to a flexible film, and an alcohol-soluble polyamide resin which is solid at room temperature is more preferable.

Here, the above-mentioned "alcohol-soluble polyamide resin which is solid at room temperature" is a polyamide resin which is soluble in an alcohol solvent and is a copolymerized polyamide resin obtained by copolymerizing dibasic acid or diamine. Or a polyamide resin having an N-alkoxymethyl group introduced into a polyamide bond in the molecule.

The above copolymerized polyamide resin can be obtained by using two or more kinds of dibasic acids and two or more kinds of diamines as monomers. Specific examples of the dibasic acid include adipic acid, sebacic acid, azelaic acid, undecanoic acid, dodecanedioic acid, dimer acid, isophthalic acid, terephthalic acid and sodium 5-sulfoisophthalate. Moreover, as said diamine, specifically, hexamethylene diamine, heptamethylene diamine, p-
Examples thereof include diaminomethylcyclohexane, bis (p-aminocyclohexyl) methane, m-xylenediamine, piperazine and isophoronediamine. Then, the copolymerized polyamide resin, particularly when it is obtained by copolymerizing an aliphatic dibasic acid and an alicyclic diamine, excellent solubility in a solvent, viscosity even after long-term storage Is hardly increased, and good adhesion to a wide range of adherends is exhibited, which is preferable.

Further, the above-mentioned copolyamide resin is prepared by preparing 11-aminoundecanoic acid, 12-aminododecanoic acid, 4-aminomethylbenzoic acid, 4-aminomethylcyclohexanecarboxylic acid, ε-caprolactam, ω. -Laurolactam, α-pyrrolidone, α-piperidone and the like may be appropriately blended.

The copolyamide resin thus obtained is, for example, nylon 6 / nylon 66, nylon 6 / nylon 6-10, nylon 6 / nylon 66 / nylon 6-10, nylon 6 / nylon 66 / nylon 11 , Nylon 6 / nylon 66 / nylon 12, nylon 6 / nylon 6-10 / nylon 6-11, nylon 6 / nylon 11 / isophorone diamine, nylon 6
/ Nylon 66 / Nylon 6, Nylon 6 / Nylon 6
-10 / nylon 12 or the like.

The polyamide resin in which N-alkoxymethyl group is introduced into the polyamide bond in the molecule is an alcohol-soluble polyamide resin obtained by adding formaldehyde and alcohol to the polyamide bond and introducing N-alkoxymethyl group. It is what Specific examples thereof include those obtained by alkoxymethylating 6-nylon, 6,6-nylon and the like. Then, the introduction of the N-alkoxymethyl group contributes to a decrease in melting point, an increase in flexibility, and an improvement in solubility, and depending on the purpose,
The introduction rate is set appropriately.

The melting point of the thermoplastic resin (component A) is 5
It is preferably in the range of 0 to 220 ° C, more preferably in the range of 70 to 180 ° C. That is, when the melting point is less than 50 ° C., the cured product of the adhesive becomes inferior in heat resistance, and conversely, when it exceeds 220 ° C., the solubility in a solvent is insufficient, which is not preferable in the present invention.
The melting point is measured by, for example, a microscopic method.

Further, the thermoplastic resin (component A) is preferably solid at room temperature. That is, when it is liquid at room temperature, the reaction becomes too fast when blended with the epoxy compound, and gelation may occur, which may cause precipitation in the solution or significantly thickening.

Phosphorus-containing phenoxy resin (component B)
Is mainly composed of phenoxy resin,
Moreover, several (about 1 to 5) phosphorus elements are contained in, for example, 1 mol of the phosphorus-containing phenoxy resin. Here, the term “main body” is intended to include a case where the entire body excluding the phosphorus element is made of a phenoxy resin. Specific examples of the phosphorus-containing phenoxy resin include ERF-001-4AF30 manufactured by Tohto Kasei Co., Ltd.

The proportion of the phosphorus-containing phenoxy resin (component B) is preferably in the range of 50 to 500 parts with respect to 100 parts by weight of the thermoplastic resin (component A) (hereinafter abbreviated as "part"), and particularly, It is preferably in the range of 100 to 300 parts. That is, when the B component is less than 50 parts,
Since the phosphorus content of the entire adhesive composition is low, the flame retardancy tends to be poor. On the other hand, when it exceeds 500 parts, the adhesive cured product becomes inflexible and easily cracked, and has sufficient adhesive strength. This is because there is a tendency such as not being obtained.

The above phosphorus-containing epoxy resin (component C) is
The main molecular skeleton is made of epoxy resin and contains a phosphorus element. The above-mentioned phosphorus-containing epoxy resin can be obtained, for example, by reacting an epoxy resin with an organic phosphorus compound. Specifically, an epoxy resin containing 20% by weight or more of a novolac type epoxy resin (a curable epoxy resin), an organic phosphorus compound having one active hydrogen bonded to a phosphorus atom, and a quinone compound It can be obtained by preparing a compound obtained by reacting with a predetermined ratio (a ratio in which the molar ratio of the quinone compound to the organic phosphorus compound is more than 0 and less than 1) and reacting them. Here, as an example of the above-mentioned "organophosphorus compounds having one active hydrogen bonded to a phosphorus atom", HCA (9, 1
0-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, manufactured by Sanko Chemical Co., Ltd., and diphenylphosphine oxide.

The phosphorus-containing epoxy resin (component C) is preferably mixed in a proportion of 20 to 200 parts, and particularly preferably 300 to 150 parts, relative to 100 parts of the thermoplastic resin (component A). Is. That is, when the amount of the C component is less than 20 parts, the crosslinking density is insufficient,
This is because sufficient heat resistance and adhesive strength cannot be obtained, and on the other hand, when it exceeds 200 parts, the cured product tends to be too hard and adhesive strength tends to be insufficient.

The curing agent (component D) is not particularly limited, and examples thereof include amine curing agents and acid anhydride curing agents. Specific examples of the amine-based curing agent include methylated melamine resins, butylated melamine resins, melamine resins such as benzoguanamine resins, dicyandiamide, and 4,4′-diphenyldiaminosulfone. These may be used alone or Used in combination of two or more. Further, as the acid anhydride-based curing agent,
Examples thereof include aromatic acid anhydrides and aliphatic acid anhydrides, which may be used alone or in combination of two or more.

The mixing ratio of the curing agent (D component) is preferably in the range of 3 to 50 parts, particularly preferably in the range of 5 to 20 parts, relative to 100 parts of the thermoplastic resin (A component). . That is, if the amount of the component D is less than 3 parts, the crosslinking density tends to be insufficient and heat resistance and adhesive strength will not be sufficiently obtained. On the contrary, if it exceeds 50 parts, the stability of the adhesive will be deteriorated. This is because there is a tendency that the gel becomes thickened over time and the pot life becomes shorter.

It should be noted that the above adhesive composition contains the above A to D.
In addition to the components, additives such as a curing accelerator, a flame retardant, a silane coupling agent, a heat aging inhibitor, a leveling agent, a defoaming agent, and an inorganic filler can be appropriately added.

The curing accelerator is not particularly limited, and examples thereof include imidazole compounds, aromatic carboxylic acids, blocked isocyanate compounds, block sulfonic acid compounds, and the like. In particular, it is preferable to use the imidazole compound and the aromatic carboxylic acid in combination.

Specific examples of the imidazole compound include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 1-
Cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 2,4-diamino-6- (2-methyl-1-imidazolyl) -ethyl- 1,3,5-triazine, 2,4-diamino-6-
(2-undecyl-1-imidazolylethyl) -1,
3,5-triazine, 2,4-diamino-6- (2-ethyl-4-methyl-1-imidazolylethyl) -1,
Examples include 3,5-triazine and the like. These may be used alone or in combination of two or more.

Specific examples of the aromatic carboxylic acid include benzoic acid, 1,2-benzenedicarboxylic acid and 1,3.
-Benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid, 1,2,3-benzenetricarboxylic acid, 1,2,4
-Benzenetricarboxylic acid (trimellitic acid: TM
A), 1,3,5-benzenetricarboxylic acid and the like. These may be used alone or in combination of two or more. Among these, polyfunctional benzenedicarboxylic acids and benzenetricarboxylic acids are preferably used because the degree of crosslinking of the cured product can be increased and the resistance to moist heat can be further improved.

A phosphorus compound such as triphenyl phosphate is preferably used as the flame retardant. Specific examples thereof include PX-200 manufactured by Daihachi Chemical Co., Ltd.

The phosphorus content in the adhesive composition is preferably set to 2% by weight or more, more preferably 2.3 to 3.5% by weight. That is, by setting the phosphorus content to 2% by weight or more, it is possible to impart high flame retardancy of UL-94-VTM-0 class.

The above adhesive composition can be obtained by mixing and stirring the above-mentioned components. The adhesive composition is usually used by dissolving it in a solvent. As the solvent, those capable of dissolving the above-mentioned respective components are preferably used, and specifically, methanol, ethanol, i-propyl alcohol, n-propyl alcohol, i-butyl alcohol, n-butyl alcohol. , Alcohol solvents such as benzyl alcohol, ethylene glycol methyl ether, propylene glycol methyl ether, diethylene glycol monomethyl ether, diacetone alcohol, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, isophorone, toluene, Aromatic solvents such as xylene, ethylbenzene, mesitylene, methyl acetate, ethyl acetate, ethylene glycol monomethyl ether acetate, 3-methoxybutyl acetate, etc. Le solvents, chloroform, carbon tetrachloride, dichloromethane, and chlorinated solvents trichlorethylene and the like. These may be used alone or in combination of two or more.

As described above, when the adhesive composition is used by dissolving it in a solvent, its resin solid content concentration is 3
It is preferably set to 80% by weight, and more preferably 10 to 50% by weight. That is,
If the concentration exceeds 80% by weight, the viscosity of the solution becomes too high, which makes it difficult to apply it uniformly to the flexible film surface, and conversely, if it is less than 3% by weight, a coating film having a desired thickness is obtained. Is difficult to form.

The substrate for flexible printed wiring board of the present invention can be produced, for example, as follows.

(Preparation of Adhesive Solution) The above components A to D and, if necessary, components such as a curing accelerator are mixed and stirred, and the mixture is dissolved in a solvent such as toluene or methanol to prepare an adhesive solution. .

(Rough surface treatment of copper foil) First, a rolled copper foil having a predetermined thickness is prepared, and at least one surface of the rolled copper foil is subjected to 10
In a sulfuric acid aqueous solution bath having a sulfuric acid concentration of ˜200 g / l (bath temperature is preferably 10 to 50 ° C.), acid cleaning is performed for 2 to 60 seconds to remove surface oxides and stains. Then, in a sulfuric acid acidic bath containing chlorine ions of 1 to 1000 ppm (as a bath composition, sulfuric acid 100 g / l, sodium chloride 10 ppm is preferable, and a bath temperature is preferably 10 to 50 ° C.), positive and negative alternating pulse electrolysis (on-time). 0.1 to 100 ms, off time 0 to 100 ms and one cycle 0.2 to 200
ms, positive / negative ratio of pulse electricity quantity is preferably 0.7 to 1.3), or AC electrolysis (current density 5 to 100 A / dm)
² , an electric quantity of 20 to 100 coulombs / dm ² , and a positive / negative ratio of the pulse electric quantity of 0.7 to 1.3 are preferable). Next, the copper protrusions are roughened by performing cathodic electrolysis in a sulfuric acid bath or a copper sulfate bath at or near the limiting current density.
Further, if necessary, in order to impart heat resistance and chemical resistance, a barrier layer (covering layer) of Co—Mo · W or Cu—Zn is formed to roughen the copper foil. After the surface roughening, if necessary, at least one of chromate treatment and organic substance rustproofing treatment may be performed. In this way, a copper foil is produced in which the surface of the copper foil is a rough surface having a specific surface roughness (Rz). Next, an aminosilane coupling agent is applied to the rough surface of this copper foil by spray coating or the like to perform an aminosilane coupling agent treatment. In this way, a copper foil whose surface (adhesive surface) has been roughened is produced.

(Production of Base Material for Flexible Printed Wiring Board) A flexible film such as a polyimide film is prepared,
The thickness of the adhesive solution after drying is 5 to 2 on the surface.
After coating with a roll laminator or the like so as to have a thickness of 0 μm, the roughened copper foil is laminated on the coated surface. And, this, hot air drying, far infrared heating,
The solvent of the adhesive solution is dried by passing it through a furnace capable of performing high-frequency induction heating or the like and performing a drying treatment under predetermined conditions (for example, 40 to 250 ° C. for 2 to 10 minutes). In this way, a base material for a flexible printed wiring board (a single-sided copper-clad laminated board for a flexible printed wiring board), in which a copper foil is laminated on one surface of a flexible film via an adhesive layer, is produced.

The laminating temperature for laminating the flexible film and the copper foil is preferably set to a low temperature of 35 ° C. or higher and lower than 110 ° C., more preferably 100 ° C.
Before and after. That is, when the laminating is performed at such a low temperature, a poor appearance such as wrinkles does not occur and an excellent adhesive force is obtained.

Next, examples will be described together with comparative examples.

[0051]

Example 1 (Preparation of Adhesive Solution) 100 parts of thermoplastic resin (alcohol-soluble polyamide resin) and phosphorus-containing phenoxy resin (ERF001-4AF3 manufactured by Tohto Kasei Co., Ltd.)
0, phosphorus content: 4.6% by weight, and 250 parts of phosphorus-containing epoxy resin (Toto Kasei Co., Ltd., FX-289BEK7)
5, phosphorus content: 2.0% by weight) and 70 parts of melamine resin (manufactured by Sanwa Chemical Co., Ltd., MX-750) 3 which is a curing agent.
0 parts, 3 parts of 2-undecyl imidazole (manufactured by Shikoku Kasei, Curezol C11Z) which is a curing accelerator, and 1,2,4-benzenetricarboxylic acid (manufactured by Mitsubishi Gas Chemical Company, F- 3 parts of TMA) was added to a solvent consisting of toluene and methanol, dissolved and dispersed with stirring to obtain an adhesive solution having a solid content concentration of 30% by weight (T after curing).
g: 90 ° C.) was prepared. The phosphorus content in the adhesive composition was 2.8% by weight.

(Rough Surface Treatment of Copper Foil) First, a rolled copper foil (RCF-T5B, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) having a thickness of 18 μm was prepared, and at least one surface of the rolled copper foil was immersed in a sulfuric acid solution bath. It was washed with acid to remove surface oxides and dirt. Then, in a sulfuric acid acid bath, activation was performed by positive and negative alternating pulse electrolysis for fine roughening. Next, in a copper sulfate bath, cathodic electrolysis is performed near the limiting current density to roughen the copper protrusions, and then a barrier layer (coating layer) is formed by copper plating to form a rough surface of the copper foil. Was made. In this way, a rolled copper foil having a surface roughness (Rz) of 3.0 μm was obtained. Then,
An aminosilane coupling agent [N-β (aminoethyl) γ-represented by the above formula (2) was formed on the rough surface of this rolled copper foil.
Aminopropylmethyldimethoxysilane] was applied by spray coating to perform an aminosilane coupling agent treatment.

(Preparation of Base Material for Flexible Printed Wiring Board) A polyimide film (Kapton 50EN, manufactured by Toray DuPont) having a thickness of 12.5 μm is prepared, and its surface is
The adhesive solution was coated using a roll laminator so that the thickness after drying was 20 μm, and then the coated surface was laminated with the copper foil subjected to the surface roughening treatment. The maximum temperature of the roll laminator at the time of pasting is 100 ° C.
And Then, this is passed through a furnace capable of performing processing such as hot air drying, far-infrared heating, and high frequency induction heating, and dried at 160 ° C. for 4 minutes to dry the solvent of the adhesive solution. It was In this way, a base material for a flexible printed wiring board (a single-sided copper-clad laminated board for a flexible printed wiring board), in which a copper foil was laminated on one surface of a polyimide film via an adhesive layer, was produced.

[0054]

[Examples 2 to 5, Comparative Examples 1 to 7] Roughness of copper foil (R
z) and the type of silane coupling agent are shown in Table 1 below.
Then, the copper foil was roughened as shown in Table 2. Then, a substrate for a flexible printed wiring board (a single-sided copper-clad laminate for a flexible printed wiring board) was produced in the same manner as in Example 1 except that this roughened copper foil was used. In addition, in Comparative Examples 1 and 3, the silane coupling agent treatment was not performed.

Using the thus-obtained base materials for flexible printed wiring boards of Examples and Comparative Examples,
Each property was evaluated according to the following criteria. The results are also shown in Tables 1 and 2 below.

[Adhesive Strength] Each flexible printed wiring board base material (single-sided copper-clad laminate for flexible printed wiring board) is treated in a hot air circulation type constant temperature bath at a maximum temperature of 160 ° C. for 4 hours or more to cure the adhesive. After that, the adhesive strength was measured. Adhesive strength is based on JIS C 6481, 2
The adhesive strength when the polyimide film was peeled from the copper foil was measured at 3 ° C.

[Circuit Formability] The copper foil of each flexible printed wiring board substrate was etched with a 40% ferric chloride aqueous solution to form a predetermined circuit pattern. Then, when etching, some residual copper was generated, x, and when no residual copper was generated, it was evaluated as ◯.

[Comprehensive Evaluation] ◯: Adhesive strength of 8 N / cm or more and good circuit formability; Adhesive strength: 8
A comprehensive evaluation was performed by setting the value less than N / cm or the one having poor circuit formability as x.

[0059]

[Table 1]

[0060]

[Table 2]

From the above results, in each of the example products, the surface of the copper foil was formed into a rough surface having a surface roughness (Rz) within a specific range, and the rough surface was treated with an aminosilane coupling agent. Therefore, it can be seen that the adhesive strength is high and the circuit formability is excellent even when laminated at a low temperature (100 ° C.). In addition, it was confirmed that all of the example products were excellent in solder heat resistance and high-temperature sliding bendability since they used the high Tg adhesive composition.

On the other hand, in Comparative Example 1, since the surface roughness (Rz) of the copper foil was smaller than the predetermined value and the copper foil was not treated with the aminosilane coupling agent, the adhesive strength was remarkably low. . The product of Comparative Example 2 was treated with an aminosilane coupling agent, but the surface roughness (R
Since z) is smaller than the predetermined value, it can be seen that the adhesive strength is small. It can be seen that the product of Comparative Example 3 has a surface roughness (Rz) of the copper foil within a predetermined range, but the adhesive strength is small because it is not treated with the aminosilane coupling agent. Although the product of Comparative Example 4 was treated with the aminosilane coupling agent, it was found that the circuit formability was inferior because the surface roughness (Rz) of the copper foil was larger than the predetermined value. In Comparative Examples 5 and 6, the surface roughness (Rz) of the copper foil is within the predetermined range, but it is understood that the adhesive strength is low because the copper foil is treated with the epoxysilane coupling agent. It can be seen that the product of Comparative Example 7 has a surface roughness (Rz) of the copper foil smaller than a predetermined value and is treated with an epoxysilane coupling agent, so that the adhesive strength is low.

[0063]

As described above, in the substrate for flexible printed wiring board of the present invention, the adhesive surface of the copper foil is formed into a rough surface having a specific surface roughness (Rz), and this rough surface Is a copper foil treated with an aminosilane coupling agent and laminated with a flexible film. Therefore, a physical anchoring effect (physical bond) due to the surface roughness (Rz) of the copper foil surface occurs, and the aminosilane coupling agent treatment causes a chemical bond effective for adhesiveness. The adhesiveness between the copper foil and the flexible film becomes strong. As a result, sufficient adhesive strength can be obtained even when the copper foil and the flexible film are laminated at a lower temperature (35 ° C. or more and less than 110 ° C.) as compared with the conventional case. Therefore, unlike the conventional method, it is not necessary to bond them at a high temperature (approximately 110 ° C or higher), so that appearance defects such as wrinkles and folds due to thermal expansion are not seen, and the temperature is lower than the conventional method (35 ° C or higher and lower than 110 ° C). ), The residual strain due to thermal expansion at the time of lamination can be reduced, and the shrinkage of the product after copper foil etching can be reduced.

When an adhesive layer is formed using the above-mentioned specific adhesive composition, the obtained flexible printed wiring board base material has excellent solder heat resistance and high-temperature sliding flexibility, and is flame retardant. Will also be excellent.

When the surface of the copper foil is roughened using the above specific aminosilane coupling agent, a chemical bond necessary for adhesiveness is easily formed on the surface of the copper foil.
It is preferable because the adhesiveness with the flexible film is further improved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09J 171/10 C09J 171/10 H05K 1/03 650 H05K 1/03 650 (72) Inventor Hidei Hotta Aichi Aichi F-term in Tokai Rubber Industrial Co., Ltd., 1st Higashi 3-chome, Komaki-shi JB16G JK14B JK14C JK17A JL11 YY00B YY00C 4J040 DA021 DA101 EC181 ED001 EE061 EF001 EG001 EG011 EG021 EG031 EL021 GA26 JA09 KA16 LA02 MB03 NA20 5E343 CC17 BB24 EE32 CC56 BB67EE22 CC17

Claims (4)

[Claims] 1. A flexible film on one side or both sides,
A base material for a flexible printed wiring board, comprising a copper foil laminated via an adhesive layer, wherein an adhesive surface of the copper foil is formed into a rough surface having a surface roughness (Rz) of 3 to 5.5 μm. A substrate for a flexible printed wiring board, characterized in that the rough surface is treated with an aminosilane coupling agent. 2. The flexible printed wiring board according to claim 1, wherein the adhesive layer is formed using an adhesive composition having a glass transition temperature (Tg) after curing within the range of 80 to 130 ° C. Substrate. 3. The adhesive layer comprises the following (A) to (D):
The base material for a flexible printed wiring board according to claim 1 or 2, which is formed using an adhesive composition containing as an essential component. (A) Thermoplastic resin. (B) Phosphorus-containing phenoxy resin. (C) Phosphorus-containing epoxy resin. (D) Curing agent. 4. The substrate for a flexible printed wiring board according to claim 1, wherein the aminosilane coupling agent is represented by the following general formula (1). [Chemical 1]