JP3329922B2 - Interlayer adhesive for multilayer printed wiring board, copper foil with the adhesive, and method for manufacturing multilayer printed wiring board using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is excellent in adhesion to an inner circuit board, excellent in embedding between inner circuit circuits, and excellent in smoothness of a laminated outer circuit circuit. The present invention relates to a material for a multilayer printed wiring board that can be manufactured at a low cost and a method for manufacturing a multilayer printed wiring board using the same.

[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-curing are laminated on an inner circuit board on which a circuit is formed. A process of laminating a copper foil thereon and integrally forming it by heating with a lamination press is performed. But,
In this step, since heating and pressure molding is performed with a lamination press,
It requires a huge amount of equipment and a long time. Further, since a glass cloth is used for the prepreg sheet, it is difficult and extremely 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 that does not perform integrated heating and forming by a lamination press and does not use a glass cloth as an interlayer insulating material has attracted attention.

[0003]

In a multilayer printed wiring board of a build-up type, a method of forming an outer layer circuit by an additive method is generally used. However, the process of electroless plating involves abnormal deposition, swelling and adhesion of plated copper. In addition, there are problems such as decomposition of the plating solution, and it is difficult to control the conditions. In addition to the need for roughening the adhesive surface as a pre-process, the use of chromic acid etc. has recently caused environmental, health and safety problems. Is coming.

[0004] The present invention provides a multilayer printed wiring board using a copper foil coated with a thermosetting insulating interlayer adhesive, thereby reducing the number of processes and solving the problems of work environment and health and safety. It is intended to stably produce a multilayer printed wiring board having an outer copper foil circuit.

[0005]

In order to achieve the above-mentioned object, the present invention relates to a method for producing an adhesive having a molecular weight of 10,000.
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
Weight percent of thermosetting insulating interlayer adhesive applied to copper foil
The adhesive-backed copper foil formed by the cloth roll laminator to <br/> over preparative an inner layer circuit board, be cured by heating without using a laminating press a method of manufacturing a multilayer printed wiring board, wherein is there.

[0006] The interlayer adhesive constituting the multilayer printed wiring board in the present invention must satisfy various properties such as heat resistance, insulation properties, and flame resistance equivalent to those of a glass epoxy circuit board. Specifically, polyphenolic epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolak type epoxy resin, cresol novolak 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 epoxy resin brominated to provide flame resistance is used.

[0007] In order to provide good embedding between the inner layer circuits, a liquid epoxy resin or an epoxy reactive diluent is blended as one of the main components of the epoxy resin. As the liquid epoxy resin, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin and a bisphenol A novolak type epoxy resin having an epoxy equivalent of about 200 are preferable. Epoxy-reactive diluents include monofunctional phenyl glycidyl ether, alkylphenyl glycidyl ether, allyl glycidyl ether, etc., bifunctional resorcin diglycidyl ether, ethylene glycol diglycidyl ether, butanediol diglycidyl ether, hexanediol Diglycidyl ether and the like, or trifunctional glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether and the like are used.

The content of these liquid epoxy resins or epoxy-based reactive diluents is preferably 20 to 70% by weight based on the entire adhesive (resin, curing agent and other components). If the amount is less than 20% by weight, the embedding property between the inner layer circuits tends to be insufficient. If 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.

Further, 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 resins include bisphenol A type epoxy resins and phenol novolak type epoxy resins. This mixing ratio is preferably from 10 to 50% by weight based on the whole adhesive. If the amount is less than 10% by weight, the viscosity is low, so the smoothness of the outer layer circuit is poor, and it is difficult to maintain the thickness as an interlayer insulating material. If it is more than 50% by weight, on the contrary, the viscosity becomes high and the embedding property between the inner layer circuits becomes worse.

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

The epoxy resin curing agent used in the present invention is selected from amine curing agents, amide curing agents, imidazole curing agents, and those obtained by epoxy adducting or microencapsulating these. For example, aliphatic polyamines such as diethylenetriamine, alicyclic polyamines such as isophoronediamine, dicyandiamide or derivatives thereof, 2-methylimidazole, 2-ethyl-4-
Methylimidazole, 2-phenyl-4-methylimidazole, 1-butylimidazole, 2-allylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole and these A cyanoethylated product, and a tertiary nitrogen in an imidazole ring formed with an organic acid such as trimellitic acid are used.

As a solvent, an adhesive is applied and the temperature is 80.degree.
After drying at 20 ° C., one must choose what does not remain in the adhesive. For example, acetone, methyl ethyl ketone, toluene, xylene, n-hexane, methanol, ethanol, methyl cellosolve, ethyl cellosolve and the like are used. Copper foil with an interlayer adhesive is obtained by applying an adhesive varnish in which an adhesive component is dissolved in a predetermined solvent at a predetermined concentration to an anchor surface of the copper foil, and then drying the coating at 80 ° C to 120 ° C to obtain a solvent in the adhesive. It is prepared so that no residue remains. The thickness of the adhesive layer is preferably 15 μm to 120 μm. If the thickness is less than 15 μm, the interlayer insulating property may be insufficient. If the thickness is more than 120 μm, there is no problem with the interlayer insulating property. However, it is not easy to manufacture and does not meet the purpose of the present invention of reducing the thickness of the multilayer board. .

This copper foil with an interlayer adhesive is usually laminated on an inner layer circuit board by a dry film laminator and cured, so that a multilayer printed wiring board having an outer layer copper foil can be easily formed.

[0014]

EXAMPLES Example 1 Bisphenol A type epoxy resin (epoxy equivalent 640)
0, weight average molecular weight 30,000) 100 parts by weight (hereinafter, referred to as
The amounts are all parts by weight) and bisphenol F type epoxy resin (epoxy equivalent: 175, Dainippon Ink and Chemicals, Inc.)
80 parts of Epiclon 830) was dissolved in MEK with stirring, and dicyandiamide 15 was added thereto as a curing agent.
And 10 parts by weight of microencapsulated 2-methylimidazole as a curing accelerator and 5 parts of a silane coupling agent (trade name: A-187, manufactured by Nippon Unicar Co., Ltd.) were added to prepare an adhesive varnish.

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

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

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 amount of 0) was changed to 20 parts.

Comparative Example 2 Bisphenol F type epoxy resin (epoxy equivalent: 175, manufactured by Dainippon Ink Co., Ltd.)
A multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that the amount of Epicron 830) was changed to 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): 150 μm pitch between lines, clearance hole φ1.0 mm, black treated copper foil peel strength, insulation resistance, surface roughness: JIS C 6486
Of Surface Roughness: Surface Roughness of Outer Copper Foil, JIS B 06
Measuring the R _MAX of 01. Conditions of boiling test: 100 ° C., boiling for 2 hours Solder heat resistance test: n = 5, all samples were 260 ° C., and no swelling occurred for 20 seconds or more. Flame resistance: Embedding property according to UL method 94 V-0: After peeling off the outer layer copper foil, the embedding property between the inner layer circuits was visually judged. The embedded one was marked with a circle.

[0022]

According to the method of the present invention, a multilayer printed wiring board having a copper foil on the outer layer can be produced by laminating and thermosetting without using a prepreg and a laminating press, and without plating. Therefore, the time required for forming the insulating layer and forming the outer conductive layer is greatly reduced, which contributes to simplification of the process and cost reduction. Further, the insulating layer can be made extremely thin because no glass cloth is used. is there. In addition, liquid epoxy resin or epoxy-based reactive diluent is added, so that it is excellent in embedding into the inner layer circuit, and high-molecular-weight epoxy resin, which suppresses resin flow during molding, is added to improve flexibility. It is possible to form a multilayer printed wiring board having a predetermined insulating layer thickness.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copper foil 2 Adhesive layer 3 Copper foil with adhesive 4 Inner layer circuit 5 Inner layer circuit board 6 Four layer printed circuit board

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 3/46 C09J 7/02 C09J 163/00 H05K 3/38

Claims (1)

(57) [Claims] (1) a molecular weight of 10,000 based on the whole 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
Weight percent of thermosetting insulating interlayer adhesive applied to copper foil
The adhesive-backed copper foil formed by the cloth roll laminator to <br/> over preparative an inner layer circuit board, a method for manufacturing a multilayer printed circuit board, characterized in that heating and curing without the use of a lamination press.