JPH0967554A - Interlayer insulation adhesive for multilayer printed wiring boards - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To obtain an interlayer insulating adhesive for a multilayer printed wiring board which is excellent in storage stability. An interlayer insulating adhesive for a multilayer printed wiring board, which contains 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) Melting point of 130 ° C. or more, and insoluble or hardly soluble in epoxy resin at room temperature. Imidazole compound.

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, which has excellent storage stability,
In addition, the present invention relates to an epoxy resin-based interlayer insulating adhesive that can be rapidly cured at a high temperature of 100 ° C. or higher.

[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 the layers are stacked on an inner layer circuit board on which a circuit is formed. Further, a step of stacking a copper foil on it and heating and integrally molding it with a hot plate press is performed. However, in this step, the impregnated resin in the prepreg is reflowed by heat and cured under a constant pressure, so that 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, since the glass cloth is impregnated with the resin, the thickness between the circuit layers is regulated by the glass cloth, and it is difficult to make the entire multilayer printed wiring board extremely thin.

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

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention have studied various methods for manufacturing a multilayer printed wiring board at low cost by a simplified build-up method with respect to the above-mentioned hot plate pressing method. There is.

When a film-shaped interlayer insulating resin layer is used in a build-up type multilayer printed wiring board, in order to eliminate the step between the insulating substrate and the circuit of the inner layer circuit board and smooth the surface, the inner layer circuit board It has become common to apply an undercoat material to the. As a typical example of this, in a state where the undercoat material applied to the inner layer 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, the interlayer insulating adhesive coated on the copper foil undergoes a curing reaction during storage, and when it is laminated on the inner layer circuit board coated with the undercoat material, integral curing is well performed. There is a problem of not being denied. 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, which contains 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) melting point of 130 ° C.
As described above, an imidazole compound which is insoluble or hardly soluble in an epoxy resin at room temperature,

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 the resin flow during molding, maintaining the thickness of the insulating layer, and imparting flexibility to the composition. Examples of such epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, and phenoxy resin.
For the above purpose, the bisphenol A type is preferable. The proportion of the high molecular weight epoxy resin is 50 to 70% by weight based on the whole epoxy resin. If it is less than 50% by weight, the viscosity will not be high and the thickness as an interlayer insulating adhesive will be insufficiently maintained, so that the smoothness of the outer layer circuit after lamination will be poor. On the other hand, if the amount is more than 70% by weight, the viscosity is increased, which may make it difficult to apply the copper foil and it may be difficult to maintain a predetermined thickness. The high molecular weight epoxy resin may be brominated for flame retardancy.

The above high molecular weight epoxy resin alone has a low crosslink density after curing and is too flexible, and has a viscosity when dissolved in a solvent to form a varnish having a predetermined concentration for coating a copper foil. Is high and the workability during coating is poor. An epoxy equivalent of 50 is used to improve such a defect.
A bisphenol type epoxy resin of 0 or less is blended. This compounding ratio is 30 to 50% by weight based on the whole epoxy resin.

Examples of such an epoxy resin include a bisphenol A type epoxy resin and a bisphenol F type epoxy resin, and brominated resins can also be used. More specifically, epoxy equivalent of about 200,
There are epoxy equivalents of about 450, 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 imidazole compound has a melting point of 130 ° C.
It is a solid at room temperature as described above, has a low solubility in an epoxy resin, and has a high temperature of 150 ° C. or higher and reacts quickly with an epoxy resin. Specifically, 2-methylimidazole, 2-phenylimidazole, 2-phenyl-
4-methylimidazole, bis (2-ethyl-4-methyl-imidazole), 2-phenyl-4-methyl-5-
Hydroxymethylimidazole, 2-phenyl-4,5
-Dihydroxymethylimidazole, triazine addition type imidazole and the like. These imidazoles are uniformly dispersed in the epoxy resin varnish as a fine powder. Since it has low compatibility with epoxy resin, it is at room temperature to 1
At 00 ° C., the reaction does not proceed, and therefore the storage stability can be kept good. When the laminate is cured and heated to 150 ° C. or higher, it reacts with the epoxy resin to obtain a uniform cured product.

In addition to the above-mentioned epoxy resin, a component which 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, resorcinic diglycidyl ether as a bifunctional type, ethylene glycol glycidyl ether, a glycerol triglycidyl ether as a trifunctional type), resole type or novolak type phenol Examples include resins and isocyanate compounds.

In addition to the above components, in order to improve the coefficient of linear expansion, heat resistance, flame resistance, etc., fused silica, crystalline silica, calcium carbonate, aluminum hydroxide, alumina, clay, barium sulfate, mica, talc, You may mix white carbon, E glass fine powder, etc. with 40 weight% or less with respect to 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.

Further, a silane coupling agent such as epoxysilane or a titanate-based coupling agent for enhancing the adhesion with a copper foil or an inner layer circuit board or improving moisture resistance, a defoaming agent for preventing voids, Alternatively, a liquid or fine powder type flame retardant may be added.

As a solvent, an adhesive is applied to a copper foil and then 80
After drying at <RTIgt; C-130 C, </ RTI> those that do not remain in the adhesive must be selected. 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 adhered 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 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 it is thinner than 5 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 it does not meet the object of the present invention to reduce the thickness of the multilayer board. .

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

Next, the undercoat agent used for eliminating the step due to the circuit of the inner layer circuit board will be described. Since the undercoating agent is usually integrally cured with the interlayer insulating adhesive, the same kind of material is used. Therefore, in the present invention, 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 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.

[0019]

【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) Made by Epikron 830) 120 parts and MEK
The mixture is stirred and dissolved in 6 parts by weight of 2-methylimidazole as a curing agent, 0.3 parts of a silane coupling agent (trade name: A-187 manufactured by Nippon Unicar Co., Ltd.), 30 parts of calcium carbonate and ultrafine silica (Aerosil). R-805)
An adhesive varnish was prepared by adding 0.5 part.

Hereinafter, a multilayer printed wiring board was manufactured in the process shown in FIG. The adhesive varnish was applied to the 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).

Next, a bisphenol A type epoxy resin (epoxy equivalent of about 470, weight average molecular weight of about 900) 1
Dissolve 00 parts in 40 parts of glycidyl methacrylate, add 3 parts of 2-methylimidazole and 1.2 parts of a photopolymerization initiator (Irgacure 651 manufactured by Ciba-Geigy) as a curing agent, and sufficiently stir with a homomixer to under It was used as a coating agent.

Further, the substrate 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 blackening the copper foil surface, the above undercoat agent is applied to a curtain coater to a thickness of about 40 μm.
Coated. After that, 80 W / cm on UV conveyor machine
The undercoating agent was made tack-free by irradiating it with ultraviolet rays under the condition of about ² J / cm ² with two high pressure mercury lamps.

On the inner layer circuit board having the undercoat agent layer, the copper foil with the interlayer insulating adhesive was applied at a temperature of 100.
℃, pressure 4kg / cm ² , laminating speed 0.8m
The above-mentioned thermosetting insulating adhesive-attached copper foil was laminated using a hard roll under the condition of / min, and heat-cured at 150 ° C. for 30 minutes to prepare a multilayer printed wiring board.

<Examples 2 to 4> The imidazole used for the interlayer insulating adhesive and the undercoat agent was changed from 2-methylimidazole to 2-phenyl-4-methylimidazole.
A multilayer printed wiring board was produced in the same manner as in Example 1 except that 2-phenyl-4-methyl-5-hydroxymethylimidazole or 2-methylimidazoleazine was used instead.

<Comparative Example 1> A multilayer printed wiring board was prepared in the same manner as in Example 1 except that 2-methylimidazole was used as the imidazole used for the interlayer insulating adhesive and the undercoat agent instead of 2-ethyl-4-methylimidazole. Was produced.

The storability of the obtained copper foil with an interlayer insulating adhesive and the multi-layer printed wiring board were measured for peel strength, surface smoothness, and moisture absorption Hirata heat resistance, and the results shown in the following table were obtained.

------------------------------------------ Smooth surface moisture absorption Solder heat resistance Peel strength Storage stability --- −−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Example 1 5 μm ○ 1.3 kg / cm ○ Example 2 5 ○ 1.2 ○ Example 3 3 ○ 1.2 ○ Example 4 3 ○ 1.0 ○ Comparative Example 1 10 × 1.0 × × −−−−−−−−−−−−−−−−−−−−−−− −−−−−−−−−−

(Measuring method) Inner layer circuit board test piece: 150 μm pitch between lines, clearance hole 1.0 mmφ 1. 1. Surface smoothness: JIS B 0601 R (max) 1. Moisture absorption solder heat resistance Moisture absorption conditions: pressure cooker treatment, 125 ° C,
3. Atmospheric pressure, 30 minutes Test condition: n = 5, all of which did not swell at 280 ° C. for 120 seconds were evaluated as ◯. 3. Peel strength: according to JIS C 6486 Storability: 3 under conditions of temperature 25 ° C and relative humidity 60%
After leaving it to stand for a month, it is roll-pressed onto the inner layer circuit board coated with an undercoating agent, and when it is heat-cured, the ones that can be molded without swelling under the copper foil are marked with ◯, and those that cannot be molded due to swelling are marked with x. did.

[0029]

INDUSTRIAL APPLICABILITY The interlayer insulating adhesive for a multilayer printed wiring board of the present invention has excellent storability in a varnish state or a state coated with a copper foil, and is laminated on an inner layer circuit board coated with an undercoat agent. At this time, integral curing is favorably performed, so that the obtained multilayer printed wiring board has excellent characteristics in heat resistance, humidity resistance, etc. as well as electric characteristics.

[Brief description of drawings]

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

[Explanation of symbols]

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

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kyomi Honjoya 2-5-8 Higashishinagawa, Shinagawa-ku, Tokyo Sumitomo Bakelite Co., Ltd. (72) Masahiro Mitsui 2-5-8 Higashishinagawa, Shinagawa-ku, Tokyo No. Sumitomo Bakelite Co., Ltd.

Claims (3)

[Claims] 1. An interlayer insulating adhesive for a multilayer printed wiring board, which comprises 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) Melting point of 130 ° C. or more, and insoluble or hardly soluble in epoxy resin at room temperature. Imidazole compound. 2. The imidazole compound is 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, which is one kind or two or more kinds selected from dihydroxymethylimidazole and triazine addition type imidazole. 3. A copper foil with an interlayer insulating adhesive for a multilayer printed wiring board, which is obtained by coating the interlayer insulating adhesive according to claim 1 or 2 on a copper foil.