JP2000104033A - Inter layer insulation adhesive for multi-layer printed wiring board and preparation of multi-layer printed- wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preparing multi-layer printed wiring boards excellent in heat resistance, formability and surface smoothness without using an undercoating agent and with high productivity as well. SOLUTION: An inter layer insulation adhesive for a multi-layer printed wiring board comprises, as essential components, (a) an epoxy resin having an epoxy equivalent weight of not more than 500, (b) an epoxy resin curing agent, (c) a diluent composed of a monomer having a plurality of photo- functional groups and/or a polyfunctional monomer having a photo-functional group and a heat-functional group, (d) a photopolymerization initiator, and (e) an inorganic filler. An insulation adhesive film is obtained by coating this insulation adhesive on a carrier film. A method for preparing a multi-layer printed wiring board comprises the steps of laminating this insulation adhesive film on an inner circuit substrate; irradiating the laminated adhesive film with activation energy rays; and heat-curing the resulting film.

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 a method for manufacturing a multilayer printed board using the same, and to provide heat resistance, moldability and surface smoothness without using an undercoat agent. An object of the present invention is to provide a method for producing a multilayer printed board which is excellent and has high productivity.

[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 press-molding the same 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. In addition to the long manufacturing process, the cost of the press and glass cloth prepreg for multi-layer molding, etc.
Multilayer printed wiring boards are expensive. In addition, due to the method of impregnating the glass cloth with the resin, the thickness between the circuit layers is limited 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, without performing hot press molding by hot plate press,
The technique of a multilayer printed wiring board by a build-up method that does not use glass cloth as an interlayer insulating material has been attracting attention again.

[0003]

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. When using a film-shaped interlayer insulating resin in a multilayer printed wiring board by the build-up method, in order to eliminate the step between the insulating substrate and the circuit of the inner circuit board and improve smoothness and moldability, It has become common to apply an undercoat agent.
According to this method, a multilayer printed wiring board is obtained by laminating a film coated with an interlayer insulating adhesive in an uncured or semi-cured state of the undercoat agent applied to the inner circuit board and integrally curing the film. In such a process, the step of applying the undercoat agent to the inner circuit board is rate-limiting. Also, the undercoat agent cannot be applied uniformly, and if the curing reaction of the undercoat agent progresses, the film-like interlayer insulating adhesive is laminated on the applied inner circuit board, and then the integral curing is not performed well. Has occurred. Also, a technique relating to a conventional interlayer insulating adhesive, for example, Japanese Unexamined Patent Publication No. 7-245480.
In JP-A-8-111585 and the like, the heat resistance required for the interlayer insulating adhesive accompanying the densification of the multilayer printed wiring board is not sufficiently satisfied. The present invention
Various studies have been made to improve such a problem, and the invention has been completed.

[0004]

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. (A) an epoxy resin having an epoxy equivalent of 500 or less, (b)
Epoxy resin curing agent, (c) a diluent comprising a monomer having a plurality of photofunctional groups and / or a polyfunctional monomer having a photofunctional group and a thermal functional group, (d) a photopolymerization initiator, and (e)
Inorganic filler.

In the present invention, the epoxy resin having an epoxy equivalent of 500 or less as the component (a) includes bisphenol epoxy resin, novolak epoxy resin, dicyclopentadiene epoxy resin, aminophenol epoxy resin, and alicyclic epoxy resin. There are resins and the like. If the epoxy resin has an epoxy equivalent of more than 500, the molecular weight between the cross-linking points becomes large, and sufficient thermal properties, particularly, glass transition temperature cannot be obtained.

Next, the epoxy resin curing agent (b) is a resol type or novolak type phenolic resin, an amine compound, an imidazole compound, an acid anhydride and the like, and is not particularly limited. Specifically, in the imidazole compound, 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole,
Bis (2-ethyl-4-methyl-imidazole), 2-
Examples include phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and triazine-added imidazole. Examples of the acid anhydride include phthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylendomethylenetetrahydrophthalic anhydride, methylbutenyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, Examples include hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, and benzophenonetetracarboxylic anhydride.
Other examples include an amine complex of boron trifluoride, dicyandiamide or a derivative thereof, and epoxy adduct or microencapsulated of these can also be used.

[0007] In addition to the epoxy resin and the curing agent, a component that reacts with the epoxy resin and the curing agent 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), isocyanate compounds, and the like.

(C) As a diluent composed of a monomer having a plurality of photofunctional groups and / or a polyfunctional monomer having a photofunctional group and a thermal functional group, typically at least two or more acryloyl per molecule. And a compound having a methacryloyl group. For example, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, diethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,3
-Butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, glycerol diacrylate, neopentyl glycol diacrylate, bisphenol A diacrylate, etc. . Preferred monomers include trimethylolpropane triacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate, which have good heat resistance after photocuring. Furthermore, glycidyl acrylate or glycidyl methacrylate that can react with a carboxyl group or a phenolic hydroxyl group can be used to improve the chemical resistance after heat curing.

The role of the monomer having a photofunctional group is to prevent the resin from flowing and softening at the time of heat curing in a later step. The flow and softening of these resins cause a change in the thickness of the insulating layer and impair the surface smoothness. In order to achieve the above object, the component (c) is (a), (b) and (c)
Is preferably 5% to 50% of the total weight of 5
%, The effect of preventing the resin from flowing and softening during thermosetting becomes small. On the other hand, if it is 50% or more, stickiness after application of the adhesive is large, and it is difficult to apply it to a carrier film to form a film.

(D) Examples of photopolymerization initiators include benzophenones such as benzophenone, benzoylbenzoic acid, 4-phenylbenzophenone and hydroxybenzophenone, benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether,
Benzoin alkyl ethers such as benzoin isobutyl ether and benzyl dimethyl ketal, acetophenones such as 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 4-t-butyl-trichloroacetophenone, and diethoxyacetophenone; thioxanthone; Chlorthioxanthone, 2
Thioxanthones such as -methylthioxanthone, 2,4-dimethylthioxanthone, ethylanthraquinone,
Alkyl anthraquinones such as butyl anthraquinone and the like can be mentioned. These can be used alone or 2
Used as a mixture of more than one species. The addition amount of this photopolymerization initiator is usually the sum of (a), (b) and (c).
It is used in the range of 0.1 to 10% by weight.

In addition to the above components, (e) an inorganic filler is blended for improving the coefficient of linear expansion, heat resistance, flame resistance and the like. As the inorganic filler, fused silica, crystalline silica, calcium carbonate, aluminum hydroxide, alumina,
Clay, barium sulfate, mica, talc, white carbon, metal oxide, E-glass fine powder, and the like. An organic filler can be blended in addition to the inorganic filler. Examples of the organic filler include a cured product of an epoxy resin and a phenol resin, and acrylonitrile butadiene rubber in a powder form. These fillers may be blended in an amount of 40% by weight or less based on the resin component. If the content is more than 40% by weight, the viscosity of the adhesive becomes high, and the embedding property between the circuits of the inner circuit board is reduced.

Further, a silane coupling agent such as epoxysilane or a titanate coupling agent for improving adhesion to an inner copper circuit or an inner circuit board or improving moisture resistance, and a defoaming agent for preventing voids. It is also possible to add a flame retardant of the liquid or fine powder type. As the solvent, one that does not substantially remain in the adhesive after the adhesive is applied to the carrier film and dried must be selected. For example, acetone, methyl ethyl ketone, toluene, xylene, n-hexane, methanol,
Ethanol, methyl cellosolve, ethyl cellosolve, cyclohexanone, dimethylformamide and the like are used.

Next, the film with an interlayer insulating adhesive is coated with an adhesive varnish obtained by dissolving an adhesive composition in a solvent onto a carrier film, and then coated with a solvent so that no solvent remains in the adhesive.
It is manufactured by drying at a temperature of 130 ° C. The thickness of the adhesive layer is preferably from 15 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 the object of the present invention is to reduce the thickness of the multilayer printed wiring board. Will not fit. The film with the interlayer insulating adhesive is laminated on the inner circuit board by a laminator such as a dry film laminator or a vacuum laminator. Recently, the number of stages of build-up has been increased due to high-density wiring, and it is necessary to fill blind via holes. Therefore, it is desirable to use a vacuum laminator for very high-density multilayer printed wiring boards and multi-stage multilayer printed wiring boards.

Further, in order to embed an inner layer circuit without using an undercoat agent, the viscosity of the adhesive during lamination is 1, 1,
It is necessary to be between 10,000 and 10,000 poise. If the viscosity is lower than 1,000 poise, the resin flow during lamination is large and it is difficult to secure the thickness of the insulating layer.
In addition, there is a possibility that the equipment may be stained by the resin that has flowed out. 1
If the viscosity is higher than 000 poise, the resin flow at the time of lamination is too small and molding failure occurs, which also causes a decrease in insulation, solder heat resistance and a decrease in yield.

Since the film with an interlayer insulating adhesive is adhered to the inner circuit board without using an undercoat agent, the surface of the film as it is is affected by the difference in height between the circuit of the inner circuit board and the insulating substrate. Lack of sex. Therefore, after laminating the interlayer insulating adhesive film on the inner circuit board,
By heating before light irradiation and thermal curing, the surface can be smoothed and the thickness of the insulating layer can be made uniform. That is, the viscosity of the interlayer insulating adhesive on the carrier film is 1,
By heating to a temperature at which the tension of the carrier film is not impaired, the tension of the carrier film and the softening of the adhesive from the time of coating and laminating the adhesive are utilized. As a result, surface smoothness and uniform thickness of the insulating layer can be ensured. The heating temperature is preferably not lower than the temperature at which the interlayer insulating adhesive becomes 10,000 poise and not higher than the glass transition temperature of the carrier film + 20 ° C.

Next, the laminated interlayer insulating adhesive is irradiated with active energy rays, and then thermally cured. When heat curing is performed without irradiation with active energy rays after lamination, the resin becomes low in viscosity and fluidized by heating, and the surface smoothness and the uniform thickness of the insulating layer are impaired. Therefore, the monomer having a photofunctional group is polymerized by irradiating active energy rays such as ultraviolet rays before thermal curing, so that fluidization and softening of the resin during thermal curing can be suppressed.

As a method for forming a surface conductor circuit of a multilayer printed wiring board, photopolymerization is performed by irradiating active energy rays, a copper foil with a resin is further laminated on an insulating adhesive, heat curing is performed, and then the conductor circuit is etched. A method of forming a conductive circuit by laminating and thermally curing the above, removing all of the copper foil, and using the resin surface onto which the roughened shape of the copper foil has been transferred, in the same manner as described below to form a conductive circuit how to;
After curing of the insulating adhesive, the surface of the resin is roughened by permanganic acid, and after applying a catalyst such as palladium, only by chemical copper plating, or electrolytic copper plating after chemical copper plating, and a conductor circuit is formed by etching. There is a method to do. In the case of plating, a via hole is formed by a laser or the like, and a conductor can be formed with a lower layer. Regardless of which method is used, the printed circuit board prepared using the interlayer insulating adhesive of the present invention has excellent surface smoothness. Therefore, the surface is obtained by repeating the build-up process (lamination / integral curing process and circuit forming process). A smooth and extremely thin multilayer printed wiring board can be obtained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

Example 1 20% by weight of solid novolak type epoxy resin (epoxy equivalent 190), 15% by weight of liquid bisphenol A type epoxy resin (epoxy equivalent 190), solid novolak type phenol resin (hydroxyl equivalent 11
0) 20% by weight, 2-phenyl-4- as a curing accelerator
An interlayer insulating adhesive containing 1% by weight of methyl-5-hydroxymethylimidazole, 20% by weight of pentaerythritol tetraacrylate, 4% by weight of benzyldimethyl ketal as a photopolymerization initiator, and 20% by weight of aluminum hydroxide was prepared. . PET carrier film
A film (glass transition temperature: 80 ° C.), the adhesive was applied to the film by a roller coater so that the thickness after drying was 70 μm, and dried at 80 ° C. for 10 minutes to produce a film with an interlayer insulating adhesive. did. The viscosity at 80 ° C. of this interlayer insulating adhesive film was 2,300 poise.

Hereinafter, a multilayer printed wiring board was manufactured by the steps shown in FIG. An inner circuit board having a 35 μm thick circuit copper foil (2) on an insulating substrate (1) was used (a). The film (4) with the interlayer insulating adhesive (3) is laminated on the inner circuit board with a vacuum roll using a hard roll at a temperature of 60 ° C., a pressure of 4 kg / cm ² , and a laminating speed of 2 m / min. (B). This insulating resin film was heated at 80 ° C. for 5 minutes to smooth the surface (c). After irradiating with ultraviolet rays at 1 J / cm ² ,
The carrier film was peeled off and cured by heating at 150 ° C. for 1 hour. Next, a copper foil circuit was formed by an additive plating method by a standard method, and a multilayer printed wiring board was manufactured (d).

<Example 2> The composition of the interlayer insulating adhesive was changed to a solid novolak type epoxy resin (epoxy equivalent: 19).
0) 20% by weight, 15% by weight of liquid bisphenol A type epoxy resin (epoxy equivalent 190), 20% by weight of solid novolak type phenol resin (hydroxyl equivalent 110), 2-phenyl-4-methyl-5-hydroxy as a curing accelerator 1% by weight of methyl imidazole, 10% by weight of pentaerythritol tetraacrylate, 4% by weight of benzyl dimethyl ketal as a photopolymerization initiator, and 30% by weight of aluminum hydroxide. Was prepared. The viscosity at 80 ° C. of the interlayer insulating adhesive film was 4,500 poise. Hereinafter, a multilayer printed wiring board was produced in the same manner as in Example 1.

Example 3 The composition of the interlayer insulating adhesive was changed to a solid novolak type epoxy resin (epoxy equivalent: 19).
0) 30% by weight, liquid bisphenol A type epoxy resin (epoxy equivalent 190) 5% by weight, methyl endmethylene tetrahydrophthalic anhydride (carboxylic acid group equivalent 90)
15% by weight, 1% by weight of 2-phenyl-4-methyl-5-hydroxymethylimidazole as a curing accelerator, 24% by weight of pentaerythritol tetraacrylate, 5% by weight of benzyldimethyl ketal as a photopolymerization initiator,
A film with an interlayer insulating adhesive was prepared in the same manner as in Example 1 except that the amount was changed to 20% by weight of aluminum hydroxide. The viscosity at 80 ° C. of this interlayer insulating adhesive film is 1800 po.
ise. Hereinafter, a multilayer printed wiring board was produced in the same manner as in Example 1.

Example 4 The composition of the interlayer insulating adhesive was changed to a solid novolak type epoxy resin (epoxy equivalent: 19).
0) 25% by weight, 5% by weight of an aminophenol type epoxy resin (epoxy equivalent: 107), 15 methylendmethylenetetrahydrophthalic anhydride (carboxylic acid group equivalent: 90) 15
% By weight, 2-phenyl-4-methyl- as a curing accelerator
5% by weight of 5-hydroxymethylimidazole, 24% by weight of pentaerythritol tetraacrylate, 5% by weight of benzyl dimethyl ketal as a photopolymerization initiator, and 25% by weight of aluminum hydroxide. A film with an agent was prepared. The viscosity at 80 ° C. of this interlayer insulating adhesive film is 1200 poise
Met. Hereinafter, a multilayer printed wiring board was produced in the same manner as in Example 1.

Comparative Example 1 A solid novolak-type epoxy resin (epoxy equivalent 19
0) 30% by weight, liquid bisphenol A type epoxy resin (epoxy equivalent 190) 15% by weight, solid novolak type phenol resin (hydroxyl equivalent 110) 30% by weight, 2-phenyl-4-methyl-5-hydroxy as a curing accelerator A film with an interlayer insulating adhesive was prepared in the same manner as in Example 1 except that the amount of methyl imidazole was changed to 1% by weight and aluminum hydroxide was changed to 19%. The viscosity at 80 ° C. of this interlayer insulating adhesive film was 2500 poise. Hereinafter, a multilayer printed wiring board was produced in the same manner as in Example 1 except that ultraviolet irradiation was not performed.

Comparative Example 2 The composition of the interlayer insulating adhesive was 50% by weight of a solid long-chain bisphenol A type epoxy resin (epoxy equivalent: 15000) and liquid bisphenol A
Type epoxy resin (epoxy equivalent 190) 5% by weight, solid novolak type phenol resin (hydroxyl equivalent 110) 4% by weight, 2-phenyl-4-methyl-5 as a curing accelerator
1% by weight of hydroxymethylimidazole, 15% by weight of pentaerythritol tetraacrylate, 5% by weight of benzyldimethyl ketal as a photopolymerization initiator, 20% by weight of aluminum hydroxide and a solvent (cyclohexanone)
And a film with an interlayer insulating adhesive was produced in the same manner as in Example 1. 80 of this interlayer insulating adhesive film
C. The viscosity at 2.degree. C. was 28,000 poise. Hereinafter, a multilayer printed wiring board was produced in the same manner as in Example 1.

The surface smoothness and glass transition temperature of the obtained multilayer printed wiring board were measured, and the results shown in Table 1 were obtained.

[0027]

(Measurement method) Inner layer circuit board test piece: 1.5 mm between lines, inner layer copper thickness 35 μm 1. Surface smoothness: JIS B 0601 R (max) Based on the loss tangent of the dynamic viscoelasticity measurement.

[0029]

The interlayer insulating adhesive for multilayer printed wiring boards of the present invention is polymerized by irradiation with active energy rays to reduce or almost eliminate the fluidity during the next heat curing, so that the surface smoothness after heat curing is obtained. Is better. Furthermore, when manufacturing a multilayer printed wiring board by laminating on an inner circuit board as a film with an interlayer insulating adhesive applied to a carrier film, without using an undercoat agent on the inner circuit board,
After laminating the film with the insulating adhesive, a heating treatment is performed with the carrier film covering the surface, so that a multilayer printed wiring board having a smooth surface can be efficiently obtained, and furthermore, a plurality of build-up steps ( Even if the laminating / integral curing step and the circuit forming step are performed, the smoothness is maintained, and a multilayer printed wiring board by build-up can be efficiently obtained. Further, since the surface is smooth and a uniform thickness of the insulating layer can be ensured, there is no need to polish the surface when forming the surface circuit, and the impedance between the circuit layers can be controlled. Further, the surface mounting can be reliably performed by smoothing the surface.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a step of manufacturing a multilayer printed wiring board using a film with an interlayer insulating adhesive of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating board 2 Inner layer circuit copper foil 3 Interlayer insulating adhesive layer 4 Carrier film 5 Surface circuit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takeshi August Shuto 2-5-8 Higashishinagawa, Shinagawa-ku, Tokyo Sumitomo Bakelite Co., Ltd. F-term (reference) 4J036 AD01 AE07 AF01 AH07 AJ08 DB15 DB18 DB21 DB22 DC19 DC31 DC41 FA01 FA05 FA10 FA11 FB07 HA02 HA12 JA08 4J040 CA072 EB042 EC041 EC061 EC071 EC081 HA116 HA136 HA196 HA306 HA326 HB16 HB19 HB21 HB27 HB31 HB47 HC01 HC16 HC24 HD19 HD43 JA09 JB02 JB08 KA02 PA30 LA05 PA12 LA10 AA12 AA16 BB01 CC09 CC41 CC43 DD02 DD12 DD31 DD32 EE31 EE35 GG01 GG02 GG28 HH11

Claims (6)

[Claims] 1. An interlayer insulating adhesive for a multilayer printed wiring board, comprising the following components as essential components. (A) an epoxy resin having an epoxy equivalent of 500 or less, (b)
Epoxy resin curing agent, (c) a diluent comprising a monomer having a plurality of photofunctional groups and / or a polyfunctional monomer having a photofunctional group and a thermal functional group, (d) a photopolymerization initiator, and (e)
Inorganic filler. 2. The component (c) is composed of (a), (b) and (c).
The insulating adhesive according to claim 1, which is 5 to 50% of the total weight of the insulating adhesive. 3. An insulating adhesive film obtained by applying the interlayer insulating adhesive for multilayer printed wiring boards according to claim 1 to a carrier film. 4. A melt viscosity at 80 ° C. of 1,000 to
4. The insulating adhesive film according to claim 3, which is in a range of 10,000 poise. 5. A step of laminating the insulating adhesive film according to claim 3 on an inner circuit board, a step of irradiating the laminated adhesive film with active energy rays, and a step of heat curing. A method for producing a multilayer printed wiring board, which is characterized by the following. 6. A method of laminating an interlayer insulating adhesive film on an inner circuit board and then heating the film before light irradiation and heat curing to smooth the surface and make the thickness of the insulating layer uniform. A method for manufacturing a multilayer printed wiring board according to claim 5.