JPH07331217A - Adhesive for printed wiring board and production of printed wiring board using the adhesive - Google Patents

Abstract

PURPOSE:To obtain an adhesive capable of roughening the surface of an adherend without using chromic acid, good in the aspects of environments and safety, and enabling to give the printed wiring board free from the swelling of a plated part and from the lowering of peeling-resistant strength. CONSTITUTION:The adhesive comprising an epoxy resin composition and used for printed wiring boards is produced by dispersing 20-100 pts.wt. of a bisphenol A epoxy resin having an epoxy equivalent of >=2000 and 100 pts.wt. of a bisphenol A or F epoxy resin having an epoxy equivalent of <=8000 in the mixture solvent of cyclohexane with toluene in a micro particle state. The mixture ratio of the cyclohexane to the toluene is preferably 20/80 to 70/30. Fine powdery fused silica whose surfaces are modified with hydrophobic groups is preferably added to the epoxy resin in an amount of 5-20 pts.wt. per 100 pts.wt. of the solid content of the epoxy resin. The printed wiring board is obtained by printed or coated on a substrate for the printed wiring board, dried, thermally cured to form an adhesive layer, partially dissolving off the epoxy resin with an alkaline oxidizing agent to roughen the surface, and subsequently subjecting the roughened substrate to an electroless plating treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board adhesive and a method for manufacturing a printed wiring board using this adhesive.

[0002]

2. Description of the Related Art In the production of a double-sided printed circuit board by the additive method, when a film-like adhesive is used, it is formed with a uniform thickness on the surface of a laminated board made of an insulating base material by a laminator or the like. However, in the production of a multilayer printed wiring board, it is necessary to form an interlayer insulating layer on the patterned inner layer circuit. In that case, if the adhesive is in the form of a film, it becomes difficult to embed it in the gap between the circuits. Therefore, in order to prevent the inclusion of air bubbles, we are improving the device and equipment such as laminating under vacuum and changing the material of the roll, but there are air bubbles remaining between the inner layer circuits,
It was necessary to change the laminating conditions when the pattern design was different.

Further, in a method of manufacturing a printed wiring board in which an adhesive layer is formed on the surface of a laminated board made of an insulating base material and a circuit and a through hole or a via hole are formed by electroless plating in the method, a plated circuit and an adhesive are used. It is known that the adhesive layer is roughened with an oxidizing agent in order to enhance the adhesion with the layer, but it is known from Japanese Patent Publication No. 63-10752, Japanese Patent Publication No. 63-297571, and Japanese Patent Publication No. 64-47095. As disclosed in Japanese Patent Laid-Open No. 3-18096, etc., most of them contain a rubber component such as acrylonitrile butadiene rubber, and a chromium-sulfuric acid aqueous solution is used as an oxidizer, whereby the rubber component is eluted. The surface of the adhesive was roughened. However, since hexavalent chromium is used in these methods, it is strongly regarded as a problem in terms of work environment and safety and health.

Further, an adhesive containing a rubber component has low reliability such as heat resistance and electric insulation (migration resistance), and a printed wiring board and a high-density plated circuit which require high reliability are formed. There was a problem in using it for a printed wiring board.

Further, in a resin matrix excellent in heat resistance such as epoxy resin, phenol resin, melamine resin,
There is also a method of roughening the adhesive layer by dispersing inorganic fine powder such as silica or calcium carbonate as an adhesive, and selectively eluting the inorganic fine powder with a specific chemical, but roughening, Since the acid resistance, alkali resistance and plating solution resistance are insufficient in the plating process, there are problems such as plating swelling and abnormal deposition due to particles falling off, and insufficient peel strength.

[0006]

When forming an interlayer insulating layer on an inner layer circuit in the production of a four-layer printed wiring board, if the adhesive is in the form of a film, it becomes difficult to embed it in the gap between the circuits. , Must be laminated after applying or printing the embedding medium. Further, in a conventional printed wiring board adhesive and a method of manufacturing a printed wiring board using this adhesive, in the case of an adhesive containing a rubber component, the problem of reducing the reliability of the printed wiring board,
Since an aqueous solution of chromium-sulfuric acid is used as an oxidizing agent for roughening these adhesives, there are problems in working environment and safety and hygiene, and in the method of roughening by selectively dissolving inorganic fine powder, plating swelling and peel strength are not There are problems such as sufficient.

The present invention solves all of the above problems. That is, a printed wiring board is manufactured by a curtain coater, a roll coater, or the like, which is surely embedded without being affected by the copper foil remaining rate of the inner layer circuit, and is subjected to electroless plating with good thickness accuracy without voids. be able to. In addition, since it can be roughened without using chromic acid, there are no problems in terms of working environment and safety and hygiene, and there is no problem of plating swelling and peel strength reduction caused by the method of selectively dissolving inorganic fine powder.

[0008]

The present invention is directed to a resin matrix which is hardly soluble in an alkaline oxidant after curing, and an alkaline oxidizer after curing such as a bisphenol A type epoxy resin (A) having an epoxy equivalent of 2000 or more. A partially soluble resin with respect to an adhesive having a micro-dispersed structure obtained by dissolving it in a mixed solvent of cyclohexanone and toluene, and applying or printing this adhesive on a substrate, drying, heat After curing to form an adhesive layer, the surface of the adhesive layer is roughened by dissolving and removing the epoxy resin micro-dispersed in the adhesive layer with an alkaline oxidizing agent, and then electroless plating is performed. And a method for manufacturing a printed wiring board.

The present invention will be described in detail below. INDUSTRIAL APPLICABILITY The present invention makes it possible to roughen an adhesive layer formed on the surface of a substrate with an alkaline oxidizing agent such as an alkaline permanganate aqueous solution in a method for manufacturing a printed wiring board by the additive method. That is, in the present invention,
A specific resin component in the adhesive component is selectively dissolved with an alkaline oxidizing agent to form a roughened shape. In this case, the resin forming the matrix of the adhesive is a bisphenol A type or bisphenol F type epoxy resin (B) having an epoxy equivalent of 800 or less.
00 or more bisphenol A type epoxy resin (A) is micro-dispersed, and a linear polyhydroxypolyether portion (the following chemical formula) constituting this resin (A) is swollen by an alkali and oxidized and dissolved by permanganate. Therefore, a fine roughening can be performed.

[0010]

[Chemical 1]

A typical example of the resin component soluble in the alkaline oxidizing agent is a high molecular weight bisphenol A type epoxy resin (A) having an epoxy equivalent of 2000 or more.
A brominated product or a phenoxy resin having a larger molecular weight can also be used and is included in the present invention. The bisphenol A type epoxy resin needs to have an epoxy equivalent of 2000 or more, and when the epoxy equivalent is 2000 or less, the linear polyhydroxypolyether moiety represented by the chemical formula to be dissolved decreases. Roughening with an alkaline oxidizing agent becomes difficult. The bisphenol A type epoxy resin (A) having an epoxy equivalent of 2000 or more is excellent in uniform dispersibility of the adhesive in the resin matrix and is finely dispersed in the resin matrix, so that it is melted and removed by the alkaline oxidizing agent. The roughened part becomes uniform and fine.

The solvent for the adhesive of the present invention is preferably a mixed solvent of cyclohexanone and toluene. The mixing ratio can be determined at a ratio of 20:80 to 70:30 depending on the thickness of the coating thickness and the drying conditions. After the drying, if there is a large amount of residual solvent, plating swelling may occur or sufficient peel strength may not be obtained, so it is necessary to perform sufficient drying.

Finely powdered fused silica is usually blended in the adhesive of the present invention, and it is preferable that the silica has a surface modified with a hydrophobic group because the dispersibility in the adhesive is very high. . Mixing of this fine powder fused silica provides thixotropy, which is particularly effective when thickening the interlayer insulating layer, and also improves heat resistance. The compounding amount is preferably 2 to 20 parts by weight with respect to 100 parts by weight of the epoxy resin solid content. If the amount is 2 parts by weight or less, no effect is obtained, and if the amount is 20 parts by weight or more, it is difficult to obtain the target roughened shape.

Next, a method of manufacturing the multilayer printed wiring board according to the present invention will be described. FIG. 1 shows this manufacturing process. (A) is a patterned inner layer substrate 1.
The adhesive layers 2 are formed on both surfaces of the inner layer substrate 1 (b). In this case, the inner layer substrate may be a general one, and a glass epoxy resin laminated plate, a glass polyimide laminated plate, a glass polyester laminated plate, a paper phenol resin laminated plate, a ceramic substrate or the like can be used.

In forming the adhesive layer, an adhesive varnish prepared by dissolving an adhesive component in a predetermined solvent at a predetermined concentration is directly applied or screen-printed on the surface of the substrate 1, dried and then cured. The plate used for screen printing is preferably 80 to 150 mesh. In addition to the above components, the adhesive may contain additives such as a leveling agent, a defoaming agent, a coupling agent, and a stabilizer, if necessary. The thickness of the adhesive layer 2 is preferably 30 to 70 μm. Adhesive surface is plated via hole 3 (or through hole)
And then roughening (or forming holes after roughening), and the palladium catalyst 4 is applied (c). Next, patterning is performed with the plating resist 5 (d), and the circuit 6 and the plated via hole 7 (or through hole) are formed by electroless copper plating (e). Then, the plating resist is peeled off to obtain a four-layer printed wiring board.

[0016]

EXAMPLES The present invention will be described below with reference to examples. << Example 1 >> Bisphenol F type epoxy resin (epoxy equivalent 175, manufactured by Dainippon Ink and Chemicals, Inc., Epicron 8
30) 100 parts by weight (hereinafter, all added amounts represent parts by weight) and 50 parts of bisphenol A type epoxy resin (epoxy equivalent 6400, weight average molecular weight 30000) are mixed solvent 2 in which the ratio of cyclohexanone and toluene is 40:60.
It was dissolved in 100 parts with stirring. There, 15 parts of 2-methylimidazole microencapsulated as a curing agent and a silane coupling agent (manufactured by Nippon Unicar Co., Ltd. A
187) and 3 parts of an antifoaming agent were added to prepare an adhesive varnish. Next, both surfaces of the patterned inner layer circuit board were coated with a roller coater so that the thickness after drying was 50 μm, and dried. Next, after heat-curing at 140 ° C. for 30 minutes, a hole having a diameter of 0.4 mm for a plated via hole was formed in the multilayer substrate.

Subsequently, the adhesive layer was immersed in an alkaline aqueous solution at 80 ° C. for 5 minutes to degrease and swell the adhesive layer, and then 7
It was roughened with an alkaline aqueous solution of potassium permanganate at 0 ° C. for 10 minutes, washed thoroughly with water, and then immersed in an aqueous solution of hydroxylamine sulfate at 50 ° C. for 10 minutes to neutralize and remove the permanganate remaining in the adhesive layer. . Next, after being immersed in an alkaline degreasing treatment liquid at 75 ° C. for 5 minutes, it was thoroughly washed and immersed in a palladium-tin salt colloid catalyst solution for 1 minute. After washing with water, the catalyst was immersed in a catalyst activation bath at room temperature for 2 minutes to remove excess tin salt from excess palladium-tin salt colloidal particles.
Then, a desired plating circuit and a plating resist for forming a plated through hole were formed by a known method. Then, it was dipped in an electroless copper plating solution at 70 ° C. for 10 hours to form an electroless copper plating film of about 20 μm on the entire surface of the substrate for a multilayer printed wiring board, to produce an additive method multilayer printed wiring board.

Example 2 An additive type multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that the compounding amount of the bisphenol A type epoxy resin having an epoxy equivalent of 6400 was 20 parts.

Example 3 Example 1 was repeated except that the bisphenol A type epoxy resin having an epoxy equivalent of 6400 was changed to a bisphenol A type epoxy resin having an epoxy equivalent of 2200.
An additive method multilayer printed wiring board was produced in exactly the same manner as in.

Example 4 A bisphenol A novolac type epoxy resin (epoxy equivalent 205 manufactured by Dainippon Ink and Chemicals, Inc.) was used instead of the bisphenol F type epoxy resin.
An additive-type multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that 100 parts of Epiclon N-865) was blended.

Example 5 An additive-type multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that the compounding amount of the bisphenol F type epoxy resin having an epoxy equivalent of 175 was 50 parts.

Example 6 The ratio of cyclohexanone and toluene in the mixed solvent was 70:30, and both surfaces of the patterned inner layer circuit board were coated with a roller coater so that the thickness after drying was 70 μm and dried. An additive method multilayer printed wiring board was produced in exactly the same manner as in Example 1 except for the above.

Comparative Example 1 An additive-type multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that the compounding amount of bisphenol A type epoxy resin having an epoxy equivalent of 6400 was changed to 10 parts.

Comparative Example 2 An additive-type multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that the compounding amount of the bisphenol A type epoxy resin having an epoxy equivalent of 6400 was 100 parts.

Comparative Example 3 Example 1 was repeated except that the bisphenol A type epoxy resin having an epoxy equivalent of 6400 was changed to the bisphenol A type epoxy resin having an epoxy equivalent of 1200.
An additive method multilayer printed wiring board was produced in exactly the same manner as in.

The additive-type multilayer printed wiring board thus obtained has the characteristics shown in Table 1.

[Table 1]

(Measurement method) 1. Peel strength, insulation resistance: According to JIS C 6486 2. Conditions for boiling test: 100 ° C., boiling for 2 hours 3. Solder heat resistance test: When n = 5 and no swelling was observed at 260 ° C. for 20 seconds or more, there was no abnormality. 4. Void: After the multilayer printed wiring board was produced, it was arbitrarily cut at 10 locations per 1 m ² , and the cross section was observed with an optical microscope at a magnification of 100 times to confirm the presence or absence of voids.

[0028]

As described above, according to the present invention, an adhesive layer is formed on an inner layer circuit of a substrate for a multilayer printed wiring board, and a plated circuit and a plated via hole or a through hole are formed thereon by electroless plating. In the method for producing an additive method multilayer printed wiring board, the adhesive layer formed on the surface of the substrate can be roughened with an alkaline oxidizing agent such as an alkaline permanganate aqueous solution. Since it can be roughened with an alkaline oxidizing agent such as potassium permanganate, it can be improved in terms of working environment and safety and hygiene compared to a chromium-sulfuric acid aqueous solution. That is, in the present invention, a specific resin component in the adhesive component is selectively dissolved with an alkaline oxidizing agent to form a roughened shape. In this case, the resin constituting the matrix of the adhesive is a bisphenol A type or bisphenol F type epoxy resin (B) having an epoxy equivalent of 800 or less, and this resin (B) has the above epoxy equivalent of 2000 or more bisphenol A type epoxy resin. (A) is micro-dispersed,
The linear polyhydroxypolyether moiety of the following chemical formula that constitutes this resin (A) swells with alkali, oxidizes and dissolves with permanganic acid, so that a dense roughened shape can be formed.

[Chemical 2]

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a manufacturing process of an additive-type multilayer printed wiring board according to the present invention.

[Explanation of symbols]

 1 Inner layer substrate 2 Adhesive layer 3 Hole for via hole 4 Palladium catalyst 5 Plating resist 6 Plating circuit 7 Plating via hole

Claims (4)

[Claims] 1. An adhesive for a printed wiring board comprising an epoxy resin composition, comprising 20 to 100 parts by weight of a bisphenol A type epoxy resin (A) having an epoxy equivalent of 2000 or more and bisphenol A type or bisphenol F type having an epoxy equivalent of 800 or less. An adhesive for a printed wiring board having a micro-dispersed structure, which is obtained by dissolving 100 parts by weight of an epoxy resin (B) in a mixed solvent of cyclohexanone and toluene. 2. The adhesive for a printed wiring board according to claim 1, wherein the mixing ratio of the mixed solvent of cyclohexanone and toluene is 20:80 to 70:30. 3. A fine powder fused silica whose surface is modified with a hydrophobic group is used in an amount of 5 parts by weight per 100 parts by weight of an epoxy resin solid content.
The adhesive for printed wiring boards according to claim 1, wherein the adhesive is contained in an amount of 20 to 20 parts by weight. 4. An adhesive according to any one of claims 1, 2 and 3 is printed or applied on a printed wiring board substrate, dried and heat-cured to form an adhesive layer, and then an alkaline oxidant is added thereto. A method for manufacturing a printed wiring board, characterized in that the epoxy resin of the adhesive layer is partially dissolved and removed to roughen the surface of the adhesive layer, and then electroless plating is performed.