JP3084351B2 - Interlayer insulating adhesive for multilayer printed wiring boards - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interlayer insulating adhesive for a multilayer printed wiring board, and more particularly to an epoxy resin based interlayer insulating adhesive which has excellent storage stability and heat resistance and can be rapidly cured at a high temperature of 100 ° C. or more. Agent.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a multilayer printed wiring board, 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. Further, a process of laminating a copper foil thereon and integrally forming it by heating with a hot plate press is performed. However, in this step, since the impregnated resin in the prepreg is reflowed by heat and cured under a constant pressure, it takes 1 to 1.5 hours to uniformly cure and mold. As described above, the manufacturing process takes a long time, and the cost is high due to the costs of the multilayer laminating press and the glass cloth prepreg.
In addition, because of the method of impregnating the glass cloth with the resin, the thickness between circuit layers is regulated by the glass cloth, and it has been difficult to make the entire multilayer printed wiring board extremely thin.

In recent years, in order to solve these problems, the technique of a multilayer printed wiring board by a build-up method which does not perform hot press molding by a hot plate press and does not use a glass cloth as an interlayer insulating adhesive has been renewed. ing.

[0004]

The present inventor has studied various methods for manufacturing a multilayer printed wiring board at a low cost by a simplified build-up method, in contrast to the above-described method of forming by a hot plate press. I have.

[0005] In the case of using a film-like interlayer insulating resin layer in a multilayer printed wiring board of a build-up system, in order to eliminate the step between the insulating substrate and the circuit of the inner circuit board and to smooth the surface thereof, It has become common to apply an undercoat material to the surface. As a typical example, in a state where the undercoat material applied to the inner circuit board is uncured, semi-cured or cured, a copper foil coated with an interlayer insulating adhesive is laminated and integrally cured to form a multilayer printed wiring. Get the board. Such a method eliminates steps due to the circuit of the inner circuit board, so that the copper foil coated with the interlayer insulating adhesive can be easily laminated, and it is not necessary to consider the residual ratio of the copper foil of the inner circuit board.

In such a process, since a glass fiber base material is not used for the interlayer insulating adhesive, heat resistance,
In particular, there is a disadvantage that the solder heat resistance after the moisture absorption treatment is not sufficient, and furthermore, the interlayer insulating adhesive coated on the copper foil undergoes a curing reaction during its storage, causing the inner circuit board to which the undercoat material has been applied. There is a problem that integral curing is not performed well when laminated. The present invention has been studied and completed in order to improve such problems.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an interlayer insulating adhesive for a multilayer printed wiring board, comprising the following components as essential components. (1) a bisphenol type epoxy resin having a weight average molecular weight of 10,000 or more, (2) a bisphenol type epoxy resin having an epoxy equivalent of 500 or less, (3) an epoxy resin curing agent, (4) a titanate coupling agent, (5) an inorganic filler,

In the present invention, the weight average molecular weight is 1000
An epoxy resin of 0 or more is blended for the purpose of reducing resin flow during molding, maintaining the thickness of the insulating layer, and imparting flexibility to the composition. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenoxy resins, and the like.
For the above purpose, bisphenol A type is preferred. The proportion of this high molecular weight epoxy resin is 50 to 70% by weight based on the whole epoxy resin. If the amount is less than 50% by weight, the viscosity does not increase and the thickness as an interlayer insulating adhesive becomes insufficient, so that the smoothness of the outer layer circuit after lamination becomes poor. On the other hand, if it is more than 70% by weight, the viscosity will be high, and application to the copper foil will not be easy, and it may be difficult to maintain the predetermined thickness. The high-molecular-weight epoxy resin may be brominated for flame retardancy.

The high-molecular-weight epoxy resin alone has a low cross-linking density after curing and is too flexible, and has a high viscosity when dissolved in a solvent to form a varnish of a predetermined concentration for coating a copper foil. And workability during coating is not good. In order to improve such a defect, an epoxy equivalent of 50 is used.
0 or less bisphenol type epoxy resin is blended. This compounding ratio is 30 to 50% by weight based on the entire epoxy resin. Examples of such an epoxy resin include a bisphenol A type epoxy resin and a bisphenol F type epoxy resin, and brominated ones for flame retardancy can also be used. More specifically, an epoxy equivalent of 20
There are about 0 and about 450 epoxy equivalents, and these are used alone or in combination in consideration of the thickness as an insulating layer, workability when coating a copper foil, and the like.

Next, the epoxy resin curing agent is not particularly limited, such as an amine compound, an acid anhydride, and an imidazole compound. However, the imidazole compound has a small compounding amount with respect to the epoxy resin, so that the above-mentioned features of the epoxy resin are sufficiently exhibited. It is preferred for. The imidazole compound is preferably solid at room temperature with a melting point of 130 ° C. or higher, has low solubility in the epoxy resin, and reacts quickly with the epoxy resin at a high temperature of 150 ° C. or higher. Specifically, 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, bis (2-ethyl-4-methyl-imidazole),
Examples include 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and triazine-added imidazole. These imidazoles are uniformly dispersed as fine powder in the epoxy resin varnish. Since the compatibility with the epoxy resin is small, the reaction does not proceed at room temperature to 100 ° C., so that the storage stability can be kept good. When heated to 150 ° C. or higher during lamination curing, it reacts with the epoxy resin to obtain a uniform cured product.

[0011] In addition to the epoxy resin, a component that reacts with the epoxy resin or the imidazole compound can be blended. For example, epoxy-reactive diluents (such as phenylglycidyl ether as a monofunctional type, resorcin diglycidyl ether and ethylene glycol glycidyl ether as a bifunctional type, and glycerol triglycidyl ether as a trifunctional type), resol type or novolac phenol type Resins, isocyanate compounds and the like.

[0012] In addition to the above components, fused silica, crystalline silica, calcium carbonate, aluminum hydroxide, alumina, clay, barium sulfate, mica, talc, and the like are used to improve the coefficient of linear expansion, heat resistance, and flame resistance. An inorganic filler such as white carbon and E glass fine powder is blended. The amount of the inorganic filler is 15 to 40% by weight based on the resin.
It is. When 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. When the amount is less than 15 parts by weight, the effect of the compounding is not sufficiently exhibited.

In the present invention, a titanate-based coupling agent is used in order to increase the adhesion to a copper foil or an inner circuit board, or to improve heat resistance and moisture resistance. Any titanate-based coupling agent can be used, and in particular, improves the adhesion between the resin and the inorganic filler, and thus improves the heat resistance of the interlayer insulating adhesive, particularly the solder heat resistance after the moisture absorption treatment.

Furthermore, it is also possible to add an antifoaming agent for preventing voids or a liquid or fine powder type flame retardant. As a solvent, an adhesive is applied to copper foil,
After drying at 0 ° 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, cyclohexanone and the like are used.

The copper foil with the interlayer insulating adhesive is bonded by applying an adhesive varnish in which the adhesive component is dissolved in a predetermined solvent at a predetermined concentration to the anchor surface of the copper foil and then drying at 80 ° C. to 130 ° C. It is prepared so that no solvent remains in the agent. The thickness of the adhesive layer is preferably 15 μm to 120 μm. 1
If the thickness is less than 5 μm, the interlayer insulation may be insufficient. If the thickness is more than 120 μm, there is no problem with the interlayer insulation. 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. .

The copper foil with an interlayer insulating 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.

Next, an undercoat material used to eliminate a step due to a circuit of the inner circuit board will be described. The undercoat material is usually made of the same material as the undercoat material so as to be integrally cured with the interlayer insulating adhesive. Therefore, in the present invention, a resin containing an epoxy resin as a main component is used. However, it may be a varnish dissolved in a solvent or a varnish dissolved in a reactive diluent which reacts by heat or light. The undercoat material varnish is applied to the inner layer circuit board, and then heated to evaporate the solvent or react to make it tack-free or prepolymerized, or to irradiate light to make it tack-free or prepolymerized by reaction.

[0018]

EXAMPLES <Example 1> Bisphenol A type epoxy resin (epoxy equivalent 640)
0, weight average molecular weight 30,000) 150 parts by weight (hereinafter, referred to as
120 parts of a bisphenol F-type epoxy resin (epoxy equivalent: 175, Epicron 830 manufactured by Dainippon Ink and Chemicals, Inc.) was stirred and dissolved in MEK, and 2-methyl was used as a curing agent there. An adhesive varnish is prepared by adding 6 parts of imidazole, 0.3 part of a titanate coupling agent (KR TTS manufactured by Ajinomoto Co., Inc.), 30 parts of calcium carbonate, and 0.5 part of ultrafine silica (Aerosil R-805). did.

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).

Next, a bisphenol A type epoxy resin (epoxy equivalent: about 470, weight average molecular weight: about 900)
00 parts were dissolved in 40 parts of glycidyl methacrylate, and 3 parts of 2-phenylimidazole as a curing agent and a photopolymerization initiator (Irgacure 651 manufactured by Ciba-Geigy) were added.
Was added and stirred sufficiently with a homomixer to obtain an undercoat material.

Further, the base material thickness is 0.1 mm and the copper foil thickness is 35 μm.
The glass-epoxy double-sided copper-clad laminate was subjected to pattern processing to obtain an inner circuit board. After the copper foil surface is blackened, the undercoat material is about 40 μm thick using a curtain coater.
Coated. Then, 80W / cm by UV conveyor
Ultraviolet irradiation was performed with two high-pressure mercury lamps under the condition of about ² J / cm ² to make the undercoat material tack-free.

The copper foil with the interlayer insulating adhesive is placed on the inner circuit board having the undercoat material layer at a temperature of 100 ° C.
° C, pressure 4kg / cm ² , lamination speed 0.8m
The above-mentioned copper foil with a thermosetting insulating adhesive was laminated using a hard roll under the conditions of / min and heat-cured at 150 ° C. for 30 minutes to produce a multilayer printed wiring board.

<Examples 2 to 12> The titanate-based coupling agent used for the interlayer insulating adhesive was KR 46B, K
R 55, KR 41B, KR 38S, KR 138S,
KR 238S, 338X, KR 12, KR 44, K
R 9SA and KR 34S (all from Ajinomoto Co., Inc.)
Except for the above, a multilayer printed wiring board was obtained in the same manner as in Example 1.

[0024] <Comparative Example 1> coupling agent epoxy silane coupling agent used for the interlayer insulating adhesive (Nippon Unicar Co., Ltd., A-18
A multilayer printed wiring board was produced in the same manner as in Example 1 except that the method was changed to 7).

The shelf life of the obtained copper foil with an interlayer insulating adhesive and the multilayer printed wiring board were measured for surface smoothness, Hirata heat resistance and peel strength, and the results shown in Table 1 were obtained.

Table 1------------------------------------------------------------------------------------------------------------------------------- −−−−−−−−−−−−−−−−−−−−−−−−−− Example 1 5 μm ○ 1.3 ○ Example 2 5 ○ 1.2 ○ Example 3 3 ○ 1 0.3 ○ Example 4 3 ○ 1.2 ○ Example 5 5 ○ 1.1 ○ Example 6 5 ○ 1.2 ○ Example 7 5 ○ 1.3 ○ Example 8 3 ○ 1.2 ○ Example 9 3 ○ 1.3 ○ Example 10 5 ○ 1.2 ○ Example 115 5 ○ 1.3 ○ Example 12 3 ○ 1.2 ○ Comparative Example 15 × 1.0 ○ --------- −−−−−−−−−−−−−−−−−−−−−−−−−−

(Measurement method) Inner layer circuit board test piece: 150 μm pitch between lines, clearance hole 1.0 mmφ 1. Surface smoothness: JIS B 0601 R (max) 1. Moisture absorption solder heat resistance Moisture absorption conditions: pressure cooker treatment, 125 ° C,
3 atm, 60 minutes Test conditions: n = 5, all were 280 ° C., 120 seconds without swelling, were rated as ○. 3. Peel strength: according to JIS C 6486. 4. Storage: 3 under the conditions of a temperature of 25 ° C. and a relative humidity of 60%.
After leaving for a month, roll-pressing on the inner layer circuit board coated with the undercoat material and heating and curing, those that can be molded without swelling under the copper foil are marked with ○, and those that swell and cannot be molded are marked with x. did.

[0028]

The interlayer insulating adhesive for a multilayer printed wiring board of the present invention has excellent preservability in a varnish state or a state coated on a copper foil, and is laminated on an inner layer circuit board coated with an undercoat material. At the same time, since the integral curing is performed well, the obtained multilayer printed wiring board has excellent properties such as heat resistance and moisture resistance as well as electrical properties. Furthermore, the addition of the titanate-based coupling agent greatly improves the solder heat resistance especially after the moisture absorption treatment.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a step of manufacturing a multilayer printed wiring board (one example) of the present invention.

[Explanation of symbols]

 Reference Signs List 1 inner layer circuit board 2 inner layer circuit 3 undercoat material 4 thermosetting insulating adhesive 5 copper foil 6 hard roll 7 multilayer printed wiring board

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toyoaki Kishi 2-5-8 Higashishinagawa, Shinagawa-ku, Tokyo Sumitomo Bakelite Co., Ltd. Examiner Masahiro Yamamoto (56) References JP-A-7-202418 (JP, A) JP-A-5-267842 (JP, A) JP-A-60-124615 (JP, A) JP-A-59-108072 (JP, A) JP-A-2-60982 (JP, A) JP-A-3 JP-A-188185 (JP, A) JP-A-6-108015 (JP, A) JP-A-7-154069 (JP, A) JP-A-7-286155 (JP, A) JP-A-7-331217 (JP, A) JP-A-8-315884 (JP, A) JP-A-9-67554 (JP, A) JP-A-3-143980 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09J 163/00-163/10

Claims (3)

(57) [Claims] 1. An interlayer insulating adhesive for a multilayer printed wiring board, comprising the following components as essential components. (1) bisphenol type epoxy resin having a weight average molecular weight of 10,000 or more, (2) bisphenol type epoxy resin having an epoxy equivalent of 500 or less, (3) epoxy resin curing agent, (4) titanate coupling agent, (5) inorganic filler, 2. An epoxy resin curing agent comprising 2-methylimidazole, 2-phenylimidazole, 2-phenyl-
4-methylimidazole, bis (2-ethyl-4-methyl-imidazole), 2-phenyl-4-methyl-5-
Hydroxymethylimidazole, 2-phenyl-4,5
The interlayer insulating adhesive according to claim 1, wherein the adhesive is one or two or more kinds of imidazole compounds selected from dihydroxymethylimidazole and triazine addition type imidazole. 3. A copper foil with an interlayer insulating adhesive for a multilayer printed wiring board, wherein the copper foil is coated with the interlayer insulating adhesive according to claim 1.