HK1022448A - Resin-coated composite foil, production thereof, and productions of multilayer copper-clad laminate and multilayer printed wiring board using the resin-coated composite foil - Google Patents

Description

Resin-coated composite foil, production thereof, and production of multilayer copper-clad laminate and multilayer printed wiring board using the same

The present invention relates generally to resin coated composite foils. In particular, the present invention relates to a resin-coated composite foil suitable for producing a high-density printed wiring board, a method for producing the resin-coated composite foil, and a method for producing a multilayer copper-clad laminate and a multilayer printed wiring board using the resin-coated composite foil.

A laminated board for a printed wiring board used for electronic materials is generally produced by impregnating a material such as glass cloth, kraft paper, or a non-woven glass fiber fabric with a thermosetting resin such as a phenol resin or an epoxy resin, semi-curing the thermosetting resin to obtain an impregnated precast sheet, and finally laminating a copper foil on one surface or both surfaces of the impregnated precast sheet. The multilayer printed wiring board is generally manufactured by forming a wiring on both sides of a copper clad laminate to obtain a core material and laminating another copper foil on both sides of the core material by impregnating a prefabricated board as an intermediate.

In recent years, in order to meet the demand for an increase in density of printed wiring boards, it is common to provide printed wiring boards having interlayer small holes, i.e., through holes. Such through holes may be formed by, for example, laser beam or plasma cutting. When an impregnated preformed sheet containing inorganic components such as glass fibers is used as an insulating layer, the cutting result with a laser beam or plasma is poor. Therefore, resins containing no inorganic component alone have been increasingly used as insulating layers. Therefore, a resin film of a semi-cured thermosetting resin or a coated resin composite foil obtained by applying a resin on one side of a copper foil and then semi-curing the resin can be used for the insulating layer.

A printed wiring board can be manufactured by laminating such a resin film or resin-coated composite foil on a printed wiring board (core material) having a wiring, and then forming the wiring and a through-hole. The heat resistance, the electrical property and the chemical resistance of the obtained laminated board can fully meet the requirements of the printed circuit board in practical use.

Although the copper foil currently used for coating the resin copper foil is generally electrolytic copper of 12 to 35 μm thickness, the use of a thinner copper foil is required as the need to provide miniaturized wiring, i.e., smaller wiring (thinner lines and spaces) is required. However, a resin-coated copper foil obtained by applying a resin varnish on an ultra-thin copper foil 12 μm thick or less and then heating and drying the resin varnish has many disadvantages.

For example, the copper foil is likely to be broken during coating, heating or drying, which brings difficulty in stable production. Another problem is that the applied resin layer shrinks during the drying step, increasing the possibility of deformation (i.e., warpage) of the resin-coated copper foil, and thus the processing of the resin-coated copper foil is very difficult. There is also a problem that the resin composition for coating the resin copper foil must be a resin composition of the type proposed by the present inventors (japanese patent application laid-open No. 9-176565) to prevent the cracking of the resin layer, thereby limiting the formulation of the resin mixture. Another problem is that when the ultra-thin copper foil and the inner layer wire are combined to constitute a multi-layered board, the ultra-thin copper foil may be cracked or wrinkled due to the uneven surface of the inner layer wire.

One known solution to the above problem is to insert a thick copper foil or plastic film between a hot press plate and the resin-coated copper foil. Further, as described in Japanese patent application laid-open (unexamined) No. Hei 9-36550, a method for producing a resin-coated composite foil using an ultra-thin copper foil provided with a supporting metal foil (carrier) has been proposed. The ultra-thin copper foil generally used as the copper foil having a supporting metal foil has an etchable type in which the supporting metal foil is selectively removed using a liquid chemical; the release type is a type in which the supporting metal foil is released and removed by a mechanical release method.

However, the above-described method of inserting a thick copper foil or plastic film between a hot press plate and a resin-coated copper foil in the laminating step encounters problems in cost of the copper foil and the plastic film and in deterioration of working efficiency. Moreover, when the plastic film is inserted, the plastic film is electrostatically charged, and it is likely that dust in the working environment is deposited on the surface of the plastic film. Therefore, dust is transferred to the product, and etching failure or other problems occur. The production of resin-coated composite foils, which are usually produced from ultra-thin copper foils provided with a supporting metal foil, also has drawbacks. In particular, the use of etchable supports presents problems due to the need to etch and dispose of the spent etching solution, adding to the process steps. On the other hand, the use of the peelable type carrier poses a problem that it is difficult to obtain an optimum adhesive strength between the supporting metal foil and the ultra-thin copper foil. That is, when the adhesive strength is too low, although peeling of the supporting metal foil laminated on the substrate is facilitated, when the organic insulating layer is applied after the resin varnish is applied, and heating and drying are performed, peeling between the supporting metal foil and the ultra-thin copper foil is likely to occur. Therefore, blistering of the ultra-thin copper foil and separation of the supporting metal foil and the ultra-thin copper foil from each other are likely to occur, causing difficulty in actual production. In contrast, when the adhesive strength between the supporting metal foil and the ultra-thin copper foil is improved, although no problem occurs in the application of varnish and the heating/drying step, it is found that in the peeling step after the supporting metal foil is laminated to the base material, peeling thereof is difficult, and the base material is deformed due to stress generated by peeling, so that residual stress on the base material increases, cracks occur, and the inner wiring is broken.

When a laser is used to create through holes in a copper clad material sheet, a sodium hydroxide solution is used as a cleaning solution to remove dust and other materials that are created when the layer is perforated. The sodium hydroxide solution corrodes the insulating resin, with the result that the diameter of the through-hole formed in the insulating resin layer becomes excessively large. On the other hand, a resin composition comprising an epoxy resin mixture composed of an epoxy resin and a curing agent, and a thermoplastic resin which is soluble in a solvent and has a functional group other than one alcoholic hydroxyl group capable of polymerizing with the epoxy resin can be used as the alkali-resistant resin. However, such resin compositions have a disadvantage in that cracks are likely to occur in the resin compositions at the time of B-stage (semi-curing), and the deformation of the resin-coated copper foil during the processing thereof is likely to cause cracks in the insulating resin layer. Under these circumstances, the present inventors have made extensive and intensive studies with a view toward solving the above-mentioned problems. It has been found that the above-mentioned technical problems and the drawbacks of the prior art are solved by an organic release layer, which is placed on an ultra-thin copper foil on top of a supporting metal foil. The present invention has been completed based on this finding.

The object of the present invention is to solve the above-mentioned problems in the prior art. An object of the present invention is to provide a resin-coated composite foil which does not cause mutual separation between a supporting metal foil and an ultra-thin copper foil even in the steps of varnish coating and heating/drying, and which can be easily peeled off and removed after being laminated on a substrate. It is another object of the present invention to provide a printed wiring board which has excellent laser processability and plasma cutting processability and thus has fine wiring and through holes thereon. It is still another object of the present invention to provide a method for producing a multilayer copper-clad laminate and a multilayer printed wiring board using the coated resin composite foil having high alkali resistance.

The resin-coated composite foil of the present invention comprises:

a layer of a support metal is provided,

an organic peeling layer disposed on the surface of the support metal layer,

an ultra-thin copper foil placed on the organic peeling layer,

an organic insulating layer disposed on the ultra-thin copper foil.

The organic insulating layer is preferably formed of a resin composition comprising:

an epoxy resin mixture comprising an epoxy resin and a curing agent,

(ii) a thermoplastic resin which is soluble in the solvent and has functional groups other than alcoholic hydroxyl groups capable of polymerizing with the epoxy resin. Such thermoplastic resins are preferably selected from the group consisting of polyvinyl acetal resins, phenoxy resins or polyether sulfone resins.

Preferred organic release layers comprise a compound selected from the group consisting of nitrogen-containing compounds, sulfur-containing compounds, or carboxylic acids.

Preferred nitrogen-containing compounds are substituted triazole compounds, such as carboxybenzotriazole, N' -bis (benzotriazolylmethyl) urea or 3-amino-1H-1, 2, 4-triazole.

Examples of the sulfur-containing compound include mercaptobenzothiazole, thiocyanic acid, and 2-benzimidazolethiol (2-benzimidazolethiol).

Preferred carboxylic acids are monocarboxylic acids such as oleic acid, linoleic acid and linolenic acid.

The method of manufacturing the resin-coated composite foil of the present invention comprises the steps of:

forming an organic peeling layer uniformly on the support metal layer;

electrodepositing a layer of ultrathin copper foil on the organic stripping layer;

an organic insulating layer is formed on the ultra-thin copper foil layer.

The method for manufacturing the multilayer copper-clad laminate of the present invention comprises the steps of:

laminating a resin-coated composite foil (A) comprising a supporting metal layer, an organic peeling layer disposed on the surface of the supporting metal layer, an ultra-thin copper foil disposed on the organic peeling layer, and an organic insulating layer disposed on the ultra-thin copper foil, and a copper-clad laminate (B) comprising an insulating base layer having an inner wiring on one or both sides, the organic insulating layer of the resin-coated composite foil (A) being in contact with the wiring-coated side of the copper-clad laminate (B) when laminated,

subsequently providing heat and applying pressure to obtain a laminate; and

the support metal layer is peeled off from the laminate.

The method of manufacturing the multilayer printed wiring board of the present invention comprises the following steps of forming an outer wiring on the ultra-thin copper foil layer of the multilayer copper clad laminate obtained by the above method.

The external wiring may be formed by the steps of forming a through hole with a UV-YAG laser or a carbon dioxide laser, performing panel plating, and etching.

Fig. 1 is a schematic cross-sectional view of a resin-coated composite foil according to an embodiment of the present invention.

The resin-coated composite foil of the present invention will be described in detail below.

The resin-coated composite foil of the present invention comprises:

a layer of a support metal is provided,

an organic peeling layer disposed on the surface of the support metal layer,

an ultra-thin copper foil placed on the organic peeling layer,

an organic insulating layer disposed on the ultra-thin copper foil.

Fig. 1 is a schematic cross-sectional view of a resin-coated composite foil according to an embodiment of the present invention. In fig. 1, in a resin-coated composite foil 1 of this embodiment, an organic peeling layer 3 and an ultra-thin copper foil 4 are sequentially placed on a supporting metal layer 2. An organic insulating layer 5 is disposed on the ultra-thin copper foil 4.

Copper or copper alloy is preferably used as the supporting metal because the organic peeling layer 3 used in the present invention forms a chemical bond with copper. The use of copper or copper alloys is also advantageous in that the stripped support metal layer can also be used as a raw material for the production of copper foil. The support metal layer 2 may also be made of a material other than copper and copper alloys, such as copper-plated aluminum. The thickness of the support metal layer 2 is not particularly limited, and it may be, for example, a foil 10 to 18 μm thick. When the support metal layer 2 is relatively thin, it may be referred to as a foil. However, the thickness of the supporting metal layer 2 may be larger than that of a general foil, and a thicker supporting sheet having a thickness of, for example, about 5 mm or less may be used.

In the present invention, the organic peeling layer is composed of an organic compound selected from a nitrogen-containing compound, a sulfur-containing compound, or a carboxylic acid.

Preferably, the nitrogen-containing compound is a nitrogen-containing compound having a substituent (functional group). Of these, particularly preferable are triazole compounds having one substituent (functional group), such as Carboxybenzotriazole (CBTA), N' -bis (benzotriazolylmethyl) urea (BTD-U), and 3-amino-1H-1, 2, 4-triazole (ATA).

Examples of the sulfur-containing compound include Mercaptobenzothiazole (MBT), thiocyanic acid (TCA), and 2-Benzimidazolethiol (BIT).

The carboxylic acid is, for example, a high molecular weight carboxylic acid. Of these, monocarboxylic acids such as fatty acids derived from animal and vegetable fats and oils or unsaturated fatty acids such as oleic acid, linoleic acid and linolenic acid are preferable.

The organic release layer 3 composed of the organic compound prevents the support metal layer 2 and the ultra-thin copper foil 4 from being separated from each other, and the support metal layer 2 is very easily peeled and removed after being laminated on a substrate.

The ultra-thin copper foil 4 used for the resin-coated composite foil 1 of the present invention has a thickness of 12 μm or less, preferably 5 μm or less. When the copper foil is thicker than 12 μm, it can be processed without the aid of a supporting metal layer.

The material for the organic insulating layer 5 of the resin-coated composite foil 1 of the present invention is not particularly limited as long as it is a commercially available insulating resin for electrical or electronic use. However, it is preferable to use an insulating resin excellent in alkali resistance because the punched through-hole needs to be cleaned with an alkali solution after the laser drilling operation.

The insulating resin composition used comprises:

an epoxy resin mixture comprising an epoxy resin and a curing agent,

(ii) a thermoplastic resin which is soluble in the solvent and has a functional group other than an alcoholic hydroxyl group capable of polymerizing with the epoxy resin, and it is preferable to use such a thermoplastic resin for the above-mentioned insulating resin.

The epoxy resin mixture (i) may contain a curing accelerator.

The above-mentioned insulating resin composition can be used in the form of a resin varnish by dissolving it in a solvent such as methyl ethyl ketone.

The above-mentioned insulating resin composition has a disadvantage that cracks are easily generated at the B stage, and thus, it is difficult to use the resin composition as a resin layer of an unsupported resin-coated copper foil. The present inventors have found that when it is used as an organic insulating layer of a supported composite foil, deformation of the copper foil at the time of processing can be reduced, and all of the insulating resin composition can be used.

The epoxy resin used in the epoxy resin mixture is not particularly limited as long as it is those resins that can be used for electrical and electronic purposes. Examples of suitable epoxy resins include bisphenol a epoxy resins, bisphenol F epoxy resins, novolac epoxy resins, cresol novolac epoxy resins, tetrabromobisphenol resins, and glycidyl amine epoxy resins. From the viewpoint of the coated resin composite foil usable in the present invention, a curing agent which is less active at room temperature but causes curing upon heating, i.e., a latent curing agent, is suitable for curing these epoxy resins. For example, dicyandiamide, imidazole, aromatic amines, phenol novolac resins or cresol novolac epoxy resins may be used as the latent curing agent. The epoxy resin mixture (i) may contain a curing accelerator for accelerating the reaction between the epoxy resin and the curing agent. For example, tertiary amines or imidazoles may be used as curing accelerators.

The amount of the epoxy resin mixture (i) is preferably 95 to 50 parts by weight per 100 parts by weight of the total amount of the insulating resin used in the present invention. When the amount of the epoxy resin mixture (i) added to the insulating resin composition is less than 50 parts by weight, the adhesion to a substrate such as FR-4 may be reduced. On the other hand, when the amount is more than 95 parts by weight, the resin layer is highly likely to be broken even if the resin-coated copper foil has the support metal layer bonded thereto, and thus the workability thereof is very poor.

The thermoplastic resin (ii) which is soluble in the solvent and has a functional group other than one alcoholic hydroxyl group capable of polymerizing with the epoxy resin is preferably selected from the group consisting of polyvinyl acetal resin, phenoxy resin or polyether sulfone resin. These thermoplastic resins may be used in combination.

The above thermoplastic resin (ii) is used in the form of a varnish by dissolving it in a solvent such as methyl ethyl ketone and mixing it with a solution of the epoxy resin mixture.

In general, the reactivity of epoxy resins with alcoholic hydroxyl groups is low, and it is difficult to crosslink a thermoplastic resin having only alcoholic hydroxyl groups as reactive functional groups with epoxy resins. Therefore, mixing a thermoplastic resin having only alcoholic hydroxyl groups as reactive functional groups with an epoxy resin may result in a decrease in water-resistant and heat-resistant properties, and the mixture is not suitable for use as a material for printed wiring boards. The reactive functional group other than the alcoholic hydroxyl group may be, for example, a phenolic hydroxyl group, a carboxyl group and an amino group. When a thermoplastic resin containing any of these functional groups is used, the thermoplastic resin and the epoxy resin are easily cross-linked with each other upon curing, thereby avoiding the above-mentioned problems (lowering of heat-resistant and water-resistant properties). The thermoplastic resin having a functional group other than one alcoholic hydroxyl group capable of polymerizing with the epoxy resin is preferably used in an amount of 5 to 50 parts by weight per 100 parts by weight of the total amount of the insulating resin composition. When the amount of the thermoplastic resin having a functional group polymerizable with an epoxy resin other than one alcoholic hydroxyl group is less than 5 parts by weight, the fluidity of the resin composition is too high, and it is likely that the thickness of the insulating resin layer in the laminate after press molding is not uniform. And when the amount is more than 50 parts by weight, the degree of shrinkage of the insulating resin layer during cooling after drying is large, and deformation (warpage) of the coated resin composite foil is highly likely to occur, so that the support metal layer and the ultra-thin copper foil are separated from each other. Therefore, it is harmful to stable production.

Such an organic insulating layer may further contain other resin components such as a thermosetting polyimide resin, a polyurethane resin, a phenol resin or a phenoxy resin, as long as the amount thereof is within a range not deviating from the gist of the present invention. The addition of these resin components can enhance, for example, flame retardancy and resin flow properties.

The organic insulating layer is in a partially cured state or a semi-cured state (B stage). When the organic insulating layer is in the above state, the fluidity of the resin at the time of lamination and the ease of encapsulating the inner wiring therein can be controlled. Although the thickness of the organic insulating layer is not particularly limited, it is preferably about 30 to 100 μm in order to ensure easy encapsulation of the inner wiring and sufficient insulation.

The method of manufacturing the resin-coated composite foil of the present invention will be described below.

The method of manufacturing the resin-coated composite foil of the present invention comprises the steps of:

forming an organic peeling layer uniformly on the support metal layer;

electrodepositing a layer of ultrathin copper foil on the organic stripping layer;

an organic insulating layer is formed on the ultra-thin copper foil layer.

In the present invention, an organic peeling layer is first formed on a support metal layer. Before the organic peeling layer is formed, the oxide film formed on the surface of the support metal layer is removed by acid washing and water washing.

The organic release layer may be formed by a dipping method, a coating method, or any other method that can form a uniform layer on the support. For example, in the immersion method, a support metal layer is immersed in an aqueous solution of an organic compound such as triazole, thereby forming an organic peeling layer on the support metal layer. The concentration of the aqueous solution is preferably in the range of 0.01 to 10 g/l. The dipping time is preferably 5 to 60 seconds. Although increasing the concentration and extending the immersion time do not impair the effect of the organic release layer formed, this is not desirable from an economic and production standpoint. After removing the support from the solution, the excess adherent is preferably washed away with water, leaving only a thin layer of the organic release layer on the surface of the support. The thickness of the organic release layer after cleaning is preferably in the range of 30 to 100 , more preferably 30 to 60 .

And then an ultra-thin copper foil layer is formed on the formed organic peeling layer. An ultra-thin copper foil layer is deposited on an organic release layer disposed on a support metal layer using an electroplating solution. Electrodeposition of copper can be carried out using, for example, a copper pyrophosphate plating solution, an acidic copper sulfate plating solution, or a copper cyanide plating solution. Although any plating solution can be used, it should be selected according to the specific purpose.

In order to improve adhesion of the ultra-thin copper foil layer and the organic insulation layer formed thereon, the outer surface of the ultra-thin copper foil may be subjected to an adhesion promoting treatment such as a roughening treatment (nodular treatment) method in which a plurality of conductive fine particles are electrodeposited on the foil surface by adjusting electrodeposition conditions, using a known method. An example of roughening treatment is disclosed, for example, in us patent 3,674,656. The roughened surface of the ultra-thin copper foil can be passivated to prevent the oxidation of the ultra-thin copper foil. Passivation may be performed alone or after the roughening treatment. Passivation is typically the electrodeposition of zinc, zinc chromate, nickel, tin, cobalt or chromium on ultra-thin copper foil. An example of passivation is disclosed in us patent 3,625,844.

Then, an organic insulating layer is formed on the surface of the ultra-thin copper foil.

The method of forming the organic insulating layer is not particularly limited. For example, the organic insulating layer can be formed by coating a resin varnish obtained by mixing the above epoxy resin mixture (i) and the above thermoplastic resin (ii) in a solvent.

There is also no particular limitation in the solvent used for the dissolution. For example, methyl ethyl ketone can be used as a solvent for dissolution. The amount of the thermoplastic resin (ii) added to the solvent is also not particularly limited as long as the resin varnish prepared has a viscosity suitable for coating.

After the organic insulating layer is formed, heating and drying are performed, and a resin-coated composite foil is generally obtained. The conditions for heating and drying are not particularly limited and may be determined according to the resin formulation of the insulating resin composition to be used and the type of solvent to be used, but it is preferable to heat at 130-200 ℃ for 1-10 minutes from the viewpoint of productivity and solvent recovery efficiency.

After the above-described heating and drying conditions are applied, the organic insulating layer is in a partially cured, i.e., semi-cured state (B stage), so that the resin flowability and encapsulation of the inner layer wiring at the time of lamination can be controlled.

The method of manufacturing the multilayer copper clad laminate comprises the steps of:

stacking the resin-coated composite foil (a) obtained above and a copper-clad laminate (B) comprising an insulating base layer having an inner wiring on one or both sides thereof, the organic insulating layer of the resin-coated composite foil (a) being in contact with the wired side of the copper-clad laminate (B) at the time of stacking, followed by supplying heat and applying pressure to obtain a laminate;

the support metal layer is peeled off so that the support metal layer is separated and removed from the laminate due to the presence of the organic peeling layer.

Any resin base material generally used for electronic equipment applications may be used as the insulating base material layer without particular limitation, and the resin base material layer includes base materials such as FR-4 (glass fiber reinforced epoxy resin), paper/phenol resin, and paper/epoxy resin.

The lamination of the copper clad laminate and the resin-coated composite foil is performed by a method of heating under pressure according to a press molding or roll lamination technique. Thereby, the semi-cured organic insulating layer is completely cured.

A method for manufacturing a multilayer printed wiring board includes the steps of peeling off a support metal layer to expose an ultra-thin copper foil on the surface of a multilayer copper-clad laminate, drilling a hole in the multilayer copper-clad laminate to form a through hole, irradiating the ultra-thin copper foil with laser such as UV-YAG laser, carbon dioxide laser or plasma to form a through hole, and then forming a wiring by panel plating and etching.

These steps of manufacturing a multilayer printed wiring board are repeated, and a printed wiring board of more layers can be manufactured.

The resin-coated composite foil of the present invention can prevent the occurrence of blistering and separation between the support metal layer and the ultra-thin copper foil when producing a copper-clad laminate. Although the resin-coated composite foil is a composite foil including an ultra-thin copper foil, it is excellent in processability. Moreover, a copper-clad laminate produced from such a resin-coated composite foil has excellent laser processability and can easily form a fine wiring.

In the present invention, by using a composite foil comprising an ultra-thin copper foil and a specific resin composition, a printed wiring board which is excellent in forming a fine wiring and forming a via hole by laser or plasma can be manufactured.

Examples

The present invention is described in more detail with reference to the following examples, which, however, are not to be construed as limiting the scope of the present invention.

Example 1

Electrolytic copper foil 35 μm thick was used as a support metal layer. This electrolytic copper foil has one surface rough (matte) and the other surface smooth (glossy). An organic peeling layer is formed on the shiny surface of a copper foil, and then first copper plating, second copper plating, roughening treatment and passivation treatment are performed in this order.

(A) Forming an organic release layer

The electrolytic copper foil used as a support metal layer was immersed in a 2 g/l Carboxybenzotriazole (CBTA) solution, heated at 30 ℃ for 30 seconds, taken out of the solution, and washed with water. An organic release layer of CBTA was formed on the shiny side of the copper foil.

(B) First copper plating

The cathodic electrolysis was carried out in a copper pyrophosphate bath heated to 50 ℃ and having a pH of 8.5, containing 17 g/l copper and 500 g/l potassium pyrophosphate, at a current density of 3A/dm²As a result, a layer of copper having a thickness of 1 μm was deposited on the surface of the organic release layer formed on the shiny side of the electrolytic copper foil.

(C) Second copper plating

Washing the surface of the formed ultra-thin copper foil with water, and performing cathodic electrolysis in a copper sulfate bath solution containing 80 g/L copper and 150 g/L sulfuric acid heated to 50 deg.C at a current density of 60A/dm²A 2 micron thick copper layer was deposited. Thereby obtaining an ultra-thin copper foil layer having a total thickness of 3 μm.

(D) Roughening treatment

The surface of the prepared ultra-thin copper foil is subjected to conventional roughening treatment.

(E) Passivation treatment

And passivating the surface of the obtained ultrathin copper foil layer by zinc chromate by a conventional method. Thereby obtaining a composite copper foil.

On the surface of the ultra-thin copper foil of the obtained composite copper foil, a layer of an insulating resin composition of the following formulation was coated in a thickness of 80 μm (in terms of solid content), followed by heating in an oven at 150 ℃ for 4 minutes, removal of the solvent and drying. And semi-curing the resin to obtain the resin-coated composite foil. No blistering and delamination occurred between the supporting copper foil and the ultra-thin copper foil layer.

1) Epoxy resin mixture

1- (1) epoxy resin:

bisphenol A epoxy resin (trade name: Epomic R-140, manufactured by Mitsui Chemical, Inc.) and m-cresol novolac epoxy resin (trade name: Epo Tohto YDCN-704, manufactured by Tohto Kasei K.K.) were mixed together in a weight ratio of 100: 100.

1- (2) epoxy resin curing agent:

to the epoxy resin mixture was added 1 equivalent of an epoxy resin curing agent.

1- (3) epoxy resin curing accelerator:

to the above epoxy resin mixture was added 1 part by weight of an epoxy resin curing accelerator (trade name: Curezol2PZ, manufactured by Shikoku Chemicals corporation).

The above epoxy resin mixture, epoxy resin curing agent and epoxy resin curing accelerator were dissolved in dimethylformamide to obtain a 50% solution as an epoxy resin mixture.

2) Thermoplastic resin soluble in solvent and having functional group capable of polymerizing with epoxy resin other than alcoholic hydroxyl group

A carboxyl group-modified polyvinyl acetal resin (polymerization degree of the starting polyvinyl alcohol: 2400, acetal ratio: 80, acetaldehyde/butylaldehyde: 50/50 (molar ratio), hydroxyl group concentration: 17% by weight, carboxyl group concentration: 1% by weight) was used.

These components and methyl ethyl ketone were mixed together in the proportions shown in Table 1 to obtain a resin composition.

TABLE 1

	Component ratio
		1 epoxy resin mixture	80 parts by weight (based on solid content)
2 thermoplastic resin soluble in solvent and having functional group capable of polymerizing with epoxy resin other than alcoholic hydroxyl group	20 parts by weight of
		3 methyl ethyl ketone	The total solids content was adjusted to 30% by weight

The resin-coated composite foils described above were covered on both sides of an FR-4 copper-clad laminate (core thickness: 0.6 mm, copper foil thickness: 35 μm) having wiring on both sides thereof, respectively, while the resin layers of the resin-coated composite foils were in contact with the FR-4 copper-clad laminate. The resin layer was cured by heating at 175 ℃ for 60 minutes under a pressure of 25 kg/cm 2.

The laminate was cooled, and the supporting copper foil was peeled off to obtain a multilayer copper-clad laminate having four conductive layers (copper foil layers). The peel strength between the supporting copper foil and the ultra-thin copper foil (measured according to japanese industrial standard C-6481) is low, 0.01 kgf/cm, which ensures that they can be easily peeled from each other. A multilayer printed wiring board is produced by providing via holes and wiring on a multilayer copper-clad laminate according to the following method comprising:

1) the via holes were formed using a UV-YAG laser (hole diameter: 100 microns);

2) cleaning the base material by using 10% NaOH solution;

3) panel plating (thickness: 12 microns);

4) the lines were etched (line width/line spacing =60 microns/60 microns).

The multilayer printed wiring board thus obtained does not cause resin cracks when laid. Due to the use of ultra-thin copper foil, through holes can be easily formed with UV-YAG. The resin layer of the multilayer printed wiring board is not dissolved by the alkaline cleaning liquid, a through hole of a desired diameter can be obtained, and a wiring of a line width/line interval of 60 μm/60 μm can be formed.

Examples 2 to 4

In the same manner as in example 1, a supporting composite foil was produced. Specifically, three electrolytic copper foils each 35 μm thick were provided as supporting metal layers, and an organic peeling layer was formed on each of these supporting electrolytic copper foils. A layer of 1 micron thick copper was deposited on the organic release layer by first copper plating. In examples 2, 3 and 4, copper layers of 4 microns, 8 microns and 11 microns thickness were deposited by a second copper plating, respectively. Thus, ultra-thin copper foil layers having total thicknesses of 5 micrometers, 9 micrometers, and 12 micrometers were formed on the supporting composite foils of examples 2, 3, and 4, respectively.

From these three-layer-supported composite foils, a multilayer copper-clad laminate and a multilayer printed wiring board were obtained in the same manner as in example 1.

In these examples, no blistering or peeling occurred between the supporting copper foil and the ultra-thin copper foil layer. The peel strength between the supporting copper foil and the ultra-thin copper foil is as low as 0.01 kgf/cm in example 2, as low as 0.01 kgf/cm in example 3, and as low as 0.02 kgf/cm in example 4, which ensures that the supporting copper foil and the ultra-thin copper foil can be easily peeled from each other. In addition, in examples 2 to 4, no resin cracks occurred during the lamination, and the through-hole was easily formed. Lines with a line width/line spacing of 60 microns/60 microns can also be formed.

Comparative example 1

Resin-coated copper foils (resin layer thickness: 80 μm), multilayer copper-clad laminates and multilayer printed wiring boards were produced in the same manner as in example 1 except that 7 μm-thick electrolytic copper foils without supporting copper foils were used and the matte side thereof was subjected to roughening treatment and passivation treatment in the same manner as in example 1. The resulting resin-coated copper foil warped very sharply, was difficult to lay, and exhibited cracks and resin peeling due to the warping. The surface of the resulting multilayer copper-clad laminate was wrinkled, and it was therefore difficult to form through-holes having a diameter of 100 μm and wirings having a line width/line spacing of 60 μm/60. mu.m.

Claims (20)

1. A resin-coated composite foil comprising:

a layer of a support metal is provided,

an organic release layer disposed on a surface of the support metal layer,

an ultra-thin copper foil placed on the organic peeling layer,

an organic insulating layer disposed on the ultra-thin copper foil.

2. The resin-coated composite foil according to claim 1, wherein the organic insulating layer is formed of a resin composition comprising:

an epoxy resin mixture comprising an epoxy resin and a curing agent,

(ii) a thermoplastic resin which is soluble in the solvent and has a functional group other than alcoholic hydroxyl groups capable of polymerizing with the epoxy resin.

3. The resin-coated composite foil according to claim 2, wherein the thermoplastic resin is selected from the group consisting of a polyvinyl acetal resin, a phenoxy resin, and a polyether sulfone resin.

4. The resin-coated composite foil according to claim 1 wherein the organic release layer comprises a compound selected from the group consisting of nitrogen-containing compounds, sulfur-containing compounds, and carboxylic acids.

5. The resin-coated composite foil according to claim 4, wherein the organic release layer comprises a nitrogen-containing compound.

6. The resin-coated composite foil of claim 5 wherein the organic release layer comprises a substituted nitrogen-containing compound.

7. The resin-coated composite foil according to claim 6 wherein the substituted nitrogen-containing compound is a substituted triazole compound.

8. The coated resin composite foil of claim 7 wherein the substituted triazole compound is selected from the group consisting of carboxybenzotriazole, N' -bis (benzotriazolylmethyl) urea, and 3-amino-1H-1, 2, 4-triazole.

9. The resin-coated composite foil according to claim 4, wherein the organic release layer comprises a sulfur-containing compound.

10. The coated resin composite foil of claim 9 wherein the sulfur-containing compound is selected from the group consisting of mercaptobenzothiazole, thiocyanic acid, and 2-benzimidazole thiol.

11. The resin-coated composite foil of claim 4, wherein the organic release layer comprises carboxylic acids.

12. The resin-coated composite foil according to claim 11, wherein the carboxylic acids include monocarboxylic acids.

13. The resin-coated composite foil according to claim 12 wherein the monocarboxylic acid is selected from the group consisting of oleic acid, linoleic acid and linolenic acid.

14. The resin-coated composite foil according to claim, wherein the ultra-thin copper foil has a thickness of 12 μm or less.

15. The resin-coated composite foil according to claim, wherein the ultra-thin copper foil has a thickness of 5 μm or less.

16. The resin-coated composite foil according to claim, wherein the support metal layer comprises a metal selected from the group consisting of copper, copper alloy, and copper-coated aluminum.

17. A method of making a resin coated composite foil comprising the steps of:

forming an organic peeling layer uniformly on the support metal layer;

electrodepositing an ultrathin copper foil layer on the organic stripping layer;

an organic insulating layer is formed on the ultra-thin copper foil layer.

18. A method of making a multilayer copper clad laminate comprising the steps of:

laminating a resin-coated composite foil (A) comprising a supporting metal layer, an organic peeling layer disposed on the surface of the supporting metal layer, an ultra-thin copper foil disposed on the organic peeling layer, and an organic insulating layer disposed on the ultra-thin copper foil, and a copper-clad laminate (B) comprising an insulating base layer having an inner wiring on one or both sides, the organic insulating layer of the resin-coated composite foil (A) being in contact with the wired side of the copper-clad laminate (B) when laminated,

subsequently providing heat and applying pressure to obtain a laminate;

the support metal layer is peeled off from the laminate.

19. A method for producing a multilayer printed wiring board, which comprises forming an outer wiring on the ultra-thin copper foil layer of the multilayer copper-clad laminate produced by the method of claim 18.

20. The method of claim 19, wherein the outer trace is formed by using UV-YAG laser or carbon dioxide laser to form the via, panel plating, and etching steps.