JPH07202418A - Interlayer adhesive for multilayer printed wiring board, copper foil applied with adhesive and production of multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To simplify the production process while solving the problems of work environment, safety and health by employing a thermosetting and insulating interlayer adhesive containing specified wt.% of-epoxy resin having molecular weight higher than a specified value or specified wt.% of epoxy based reactive diluent. CONSTITUTION:The content of liquid epoxy resin or epoxy based reactive diluent is preferably set in the range of 10-50-wt.%. In order to sustain the thickness of insulation layer by decreasing the fluidity of resin at the time of molding while providing flexibility, 20-70wt.% of epoxy resin having molecular weight of 10000 or above is admixed as one more principle component. The thermosetting and insulating interlayer adhesive is then applied to the anchor face of a copper foil 1 and dried to produce a copper foil 3 applied with adhesive 2. An inner layer circuit board 5 having an inner layer circuit 4 is produced from a glass epoxy copper clad laminate and laminated. on the opposite sides thereof, with the copper foil 3 applied with adhesive and then it is thermally set to produce a four layer printed board 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent adhesion to inner circuit boards, excellent embedding between inner layer circuits, and smoothness of outer layer circuits formed by laminating. The present invention relates to a material for a multilayer printed wiring board that can be manufactured at low cost and a method for manufacturing a multilayer printed wiring board using the material.

[0002]

2. Description of the Related Art Conventionally, when a multilayer printed wiring board is manufactured, one or more prepreg sheets obtained by impregnating a glass cloth base material with an epoxy resin and semi-cured are laminated on an inner layer circuit board on which a circuit is formed, and further The process of stacking copper foil on top and heating and integrally molding with a laminating press is performed. But,
In this process, since heat and pressure molding is performed with a laminating press,
A huge amount of equipment and a long time are required. In addition, since glass cloth is used for the prepreg sheet, it is difficult and expensive to make the interlayer thickness extremely thin. In recent years, in order to solve these problems, a technique of a multilayer printed wiring board by a build-up method, in which heat integral molding is not performed by a laminating press and glass cloth is not used as an interlayer insulating material, has been attracting attention.

[0003]

In the build-up type multilayer printed wiring board, a method of forming an outer layer circuit by an additive method is generally used. However, in the electroless plating step, abnormal deposition, swelling or adhesion of plated copper is performed. However, there are problems such as decomposition of the plating solution, it is difficult to control the conditions, and not only the surface of the adhesive needs to be roughened as a pre-process but also chromic acid is used, which has recently become a problem in terms of environment and safety and health. Is coming.

According to the present invention, a multilayer printed wiring board is manufactured by using a copper foil coated with a thermosetting insulating interlayer adhesive, thereby reducing the number of steps and solving the problems of working environment and safety and health. It is intended to stably manufacture a multilayer printed wiring board having an outer layer copper foil circuit.

[0005]

In order to achieve the above object, the present invention has a molecular weight of 10,000 with respect to the entire adhesive.
20 to 70% by weight of the above high molecular weight epoxy resin, and liquid epoxy resin or epoxy-based reactive diluent 10 to 50
A thermosetting insulating interlayer adhesive containing wt%, and a copper foil with an adhesive in which the interlayer adhesive is applied to a copper foil, and further, the copper foil with the adhesive is heat-cured after being laminated on an inner layer circuit board. The present invention relates to a multilayer printed wiring board which is integrated by.

The interlayer adhesive constituting the multilayer printed wiring board of the present invention must satisfy various characteristics such as heat resistance, insulation and flame resistance equivalent to those of the glass epoxy circuit board. Specifically, in addition to polyphenolic epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin and cresol novolac type epoxy resin, polyhydric alcohols, An epoxy resin such as an alicyclic epoxy resin can be used as a main component. Further, the above-mentioned brominated epoxy resin is used for imparting flame resistance.

A liquid epoxy resin or an epoxy-based reactive diluent is blended as one of the main components of the epoxy resin in order to impart a good embedding property between the inner layer circuits. The liquid epoxy resin is preferably a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, or a bisphenol A novolac type epoxy resin having an epoxy equivalent of about 200. Epoxy reactive diluents include monofunctional phenylglycidyl ether, alkylphenylglycidyl ether, allyl glycidyl ether, etc., difunctional resorcin diglycidyl ether, ethylene glycol diglycidyl ether, butanediol diglycidyl ether, hexanediol. Diglycidyl ether or the like, or trifunctional glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether or the like is used.

The liquid epoxy resin or the epoxy-based reactive diluent is preferably contained in an amount of 20 to 70% by weight based on the whole adhesive (resin, curing agent and other compounding agents). When the amount is less than 20% by weight, the embeddability between the inner layer circuits tends to be insufficient, and when the amount is more than 70% by weight, the viscosity becomes too low and it becomes difficult to maintain the thickness as an interlayer insulating material.

A high molecular weight epoxy resin having a molecular weight of 10,000 or more is blended as another main component for the purpose of reducing the resin flow during molding, maintaining the thickness of the insulating layer, and providing flexibility. Examples of such high molecular weight epoxy resin include bisphenol A type epoxy resin and phenol novolac type epoxy resin. The mixing ratio is preferably 10 to 50% by weight based on the whole adhesive. If the amount is less than 10% by weight, the outer layer circuit is inferior in smoothness because of low viscosity, and it becomes difficult to maintain the thickness as an interlayer insulating material. On the other hand, if the amount is more than 50% by weight, the viscosity is increased and the embedding property between the inner layer circuits is deteriorated.

In the adhesive of the present invention, as the resin component, in addition to the liquid epoxy resin or the epoxy-based reactive diluent and the high molecular weight epoxy resin, another epoxy resin or a resin component which reacts with the epoxy resin is blended. You can also For example, it is a solid epoxy resin having a molecular weight of about 400 or more, a phenol resin, an isocyanate compound, or the like. Further, in addition to the above components, in order to improve linear expansion coefficient, heat resistance, flame resistance, etc., fused silica, crystalline silica,
Calcium carbonate, aluminum hydroxide, alumina, mica, talc, white carbon, E glass fine powder and the like may be added in an amount of 40% by weight or less based on the resin content. If it is blended in an amount of more than 40% by weight, the viscosity of the adhesive becomes high and the embedding property between the inner layer circuits is deteriorated. Furthermore, it is possible to add epoxy silane coupling agent to improve adhesion with copper foil or inner circuit board and to improve moisture resistance, antifoaming agent to prevent voids and liquid or fine powder type flame retardant. Is.

The epoxy resin curing agent used in the present invention is selected from amine type curing agents, amide type curing agents, imidazole type curing agents, or epoxy adducts or microencapsulated types thereof. For example, aliphatic polyamines such as diethylenetriamine, alicyclic polyamines such as isophoronediamine, dicyandiamide or its derivatives, 2-methylimidazole, 2-ethyl-4-
Methyl imidazole, 2-phenyl-4-methyl imidazole, 1-butyl imidazole, 2-allyl imidazole, 2-phenyl-4-methyl-5-hydroxymethyl imidazole, 2-phenyl-4,5-dihydroxymethyl imidazole and these Those which are cyanoethylated, and those in which the tertiary nitrogen in the imidazole ring is salted with an organic acid such as trimellitic acid are used.

As a solvent, an adhesive is applied and the temperature is 80 ° C to 1
One must choose one that does not remain in the adhesive after drying at 20 ° C. For example, acetone, methyl ethyl ketone, toluene, xylene, n-hexane, methanol, ethanol, methyl cellosolve, ethyl cellosolve, etc. are used. The copper foil with the interlayer adhesive is prepared by applying an adhesive varnish prepared by dissolving an adhesive component in a predetermined solvent at a predetermined concentration on the anchor surface of the copper foil and then drying at 80 ° C. to 120 ° C. to remove the solvent in the adhesive. It is made so that there is no residue. The thickness of the adhesive layer is preferably 15 μm to 120 μm. If it is thinner than 15 μm, the interlayer insulating property may be insufficient, and if it is thicker than 120 μm, the interlayer insulating property is not a problem, but it is not easy to manufacture, and the purpose of the present invention to reduce the thickness of the multilayer board is not met. .

This copper foil with interlayer adhesive is usually laminated on an inner circuit board by a dry film laminator and cured to easily form a multilayer printed wiring board having an outer copper foil.

[0014]

【Example】

Example 1 150 parts by weight of a bisphenol A type epoxy resin (epoxy equivalent: 6400, weight average molecular weight: 30,000) (hereinafter, all compounding amounts are parts by weight) and a bisphenol F type epoxy resin (epoxy equivalent: 175, Dainippon Ink and Chemicals) 120 parts of Epicron 830 manufactured by ME Co., Ltd.
It is dissolved in K with stirring, and 120 parts by weight of microencapsulated 2-methylimidazole as a curing agent and a silane coupling agent (manufactured by Nippon Unicar Co., Ltd., trade name: A-
187) 10 parts was added to prepare an adhesive varnish.

Hereinafter, a multilayer printed wiring board was produced in the process shown in FIG. The adhesive varnish was applied to an anchor surface of a copper foil (1) having a thickness of 18 μm by a roller coater so that the thickness after drying was 50 μm, and dried to obtain a copper foil (3) with an adhesive (2). (A). On the other hand, an inner layer circuit board (5) having an inner layer circuit (4) is prepared from a glass epoxy double-sided copper clad laminate (b), and then a copper foil (3) with an adhesive is applied to both sides of the inner layer circuit board (5). (C), and cured by heating at 180 ° C. for 20 minutes to obtain a 4-layer printed wiring board (6) (d).

Example 2 The adhesive varnish having a thickness of 18 is used.
A multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that coating was performed on the anchor surface of a copper foil having a thickness of 80 μm with a roller coater so that the thickness after drying was 80 μm, and drying.

Example 3 A multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that a copper foil having a thickness of 35 μm was used.

Comparative Example 1 Bisphenol A type epoxy resin (epoxy equivalent 6400, weight average molecular weight 3000)
A multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that the compounding amount of 0) was 20 parts.

Comparative Example 2 Bisphenol F type epoxy resin (epoxy equivalent 175, manufactured by Dainippon Ink and Chemicals, Inc.
A multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that the amount of Epiclon 830) was 30 parts.

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

[Table 1]

(Test method) Test piece (inner layer circuit): pitch between wires 150 μm, clearance hole φ1.0 mm, black treated copper foil peel strength, insulation resistance, surface roughness: JIS C 6486
Measurement of surface roughness: Surface roughness of outer layer copper foil, JIS B 06
Measure R _MAX of 01. Conditions of boiling test: boiling at 100 ° C. for 2 hours Soldering heat resistance test: n = 5, all of which did not swell at 260 ° C. for 20 seconds or more were evaluated as ◯. Flame resistance: UL method 94 V-0 Embeddability: After the outer layer copper foil was peeled off, the embeddability between the inner layer circuits was visually evaluated. The embedded ones were marked with a circle.

[0022]

According to the method of the present invention, a multilayer printed wiring board having a copper foil as an outer layer can be produced by using a prepreg and a laminating press without using plating, and by carrying out thermosetting after laminating without laminating. Therefore, the time required for forming the insulating layer and the outer conductive layer is significantly shortened, which can contribute to the simplification of the process and cost reduction. Furthermore, since the glass cloth is not used, the insulating layer can be made extremely thin. is there. In addition, since liquid epoxy resin or epoxy-based reactive diluent is added, it has excellent embeddability in the inner layer circuit, and high molecular weight epoxy resin that suppresses resin flow during molding is added, thus providing flexibility. It is possible to form a multilayer printed wiring board having a predetermined insulating layer thickness.

[Brief description of drawings]

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

[Explanation of symbols]

 1 Copper Foil 2 Adhesive Layer 3 Copper Foil with Adhesive 4 Inner Layer Circuit 5 Inner Layer Circuit Board 6 4 Layer Printed Circuit Board

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[Procedure amendment]

[Submission date] March 23, 1995

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be amended] Title of invention

[Correction method] Change

[Correction content]

[Title of Invention] Interlayer adhesive for multilayer printed wiring board,
Copper foil with adhesive and method for producing multilayer printed wiring board using the same

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

[0014]

Examples << Example 1 >> 100 parts by weight of a bisphenol A type epoxy resin (epoxy equivalent 6400, weight average molecular weight 30,000) (hereinafter, all compounding amounts represent parts by weight) and a bisphenol F type epoxy resin (epoxy equivalent 175, MEK with 80 parts of Epicron 830 manufactured by Dainippon Ink and Chemicals, Inc.
Dissolve with stirring into 15 parts of dicyandiamide as a curing agent and microencapsulation as a curing accelerator.
An adhesive varnish was prepared by adding 10 parts by weight of methylimidazole and 5 parts of a silane coupling agent (manufactured by Nippon Unicar Co., Ltd., trade name: A-187).

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Claims (3)

[Claims] 1. A molecular weight of 10,000 with respect to the entire adhesive.
20 to 70% by weight of the above high molecular weight epoxy resin, and liquid epoxy resin or epoxy-based reactive diluent 10 to 50
A thermosetting insulating interlayer adhesive containing wt%. 2. A copper foil with an interlayer adhesive for a multilayer printed wiring board, which is obtained by applying the adhesive according to claim 1 to a copper foil. 3. A method for producing a multilayer printed wiring board, which comprises laminating the copper foil with an adhesive according to claim 2 on an inner layer circuit board and curing the same.