JP2908258B2 - Light / thermosetting undercoat material and method for manufacturing multilayer printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a low-cost, high-productivity light / thermosetting undercoat material for multilayer printed wiring boards which is tack-free by irradiation with active energy rays and is cured by heat. Another object of the present invention is to provide a method for manufacturing a multilayer printed wiring board using the undercoat 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-curing are laminated on an inner circuit board on which a circuit is formed. The process of laminating a copper foil on top and performing heat integral molding by a hot plate press is performed. But,
In this step, the impregnated resin is reflowed by heat and cured under a constant pressure.
Time is needed. 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, the method of impregnating the glass cloth with a resin has made it difficult 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 system which does not perform hot press molding by a hot plate press and does not use a glass cloth as an interlayer insulating material has been renewed. I have.

[0004]

An object of the present invention is to provide a method of manufacturing a multilayer printed wiring board at a low cost by using a simplified build-up method in a short time, compared with the above-mentioned method of forming by a hot plate press. It is a thing.

When a film-like interlayer insulating resin layer is used in a multilayer printed wiring board of a build-up system, the work efficiency is remarkably improved as compared with a method of forming an interlayer insulating resin layer by prepreg. However, it is expected that air at the step between the insulating board of the inner circuit board and the circuit will be entrained.To prevent this, lamination must be performed under reduced pressure and special equipment is required. Come. In addition, since the laminated insulating layer follows the step between the insulating substrate of the inner circuit board and the circuit, surface smoothness cannot be obtained, soldering failure or the like may occur at the time of component mounting, or the resist may not be formed in the etching resist forming step. There are problems such as peeling and a decrease in the degree of pattern development, making it impossible to form a stable resist.

The same applies to the case where a prepreg is used. However, since the amount of resin to be embedded varies depending on the residual ratio of the copper foil in the inner circuit pattern, even if the same film is used, the thickness after molding does not become the same. In other words, when the copper foil residual ratio is large and the portion to be embedded is small, the plate thickness is large, and when the copper foil residual ratio is small and the portion to be embedded is large, the plate thickness is small. If you do not change, you cannot achieve the same thickness.
In addition, if there is a difference in the residual ratio of copper foil depending on the location even in one inner layer circuit board, there is a disadvantage that the thickness of the obtained multilayer printed wiring board is not uniform.

[0007]

SUMMARY OF THE INVENTION As described below, the present invention provides a method for producing a multilayer printed wiring board, which is applied to an inner layer circuit board, is made tack-free by irradiating active energy rays , and is heated. Curing multilayer printed wiring
Light and thermosetting undercoat material for boards , and a copper foil having a thermosetting insulating adhesive layer laminated on the inner layer circuit board coated with such undercoat agent, and then integrally cured by heating to form a multilayer The present invention relates to a method for manufacturing a printed wiring board.

That is, the liquid undercoat agent is applied by screen printing, a roller coater, a curtain coater, or the like to fill the copper foil circuit gap of the inner layer circuit board.
Tack-free by irradiation with active energy rays by an exposure machine such as a V irradiation conveyor. Thereafter, the undercoat agent is re-melted by laminating with a heated hard roll or the like when bonding the copper foil with the thermosetting insulating adhesive, whereby the surface smoothness can be obtained. At this time, if the epoxy resin component having a weight average molecular weight of 10,000 or more is blended in the thermosetting insulating adhesive coated on the copper foil, the adhesive is maintained while maintaining the shape by this component, that is, maintaining the interlayer thickness. Therefore, a multilayer printed wiring board having excellent thickness accuracy can be manufactured without depending on the residual ratio of the inner layer copper foil. Then, after lamination, heating and simultaneous simultaneous curing reaction are performed to integrally form the light / thermosetting undercoat material for the multilayer printed wiring board and the copper foil with thermosetting insulating adhesive.

The undercoating agent for a multilayer printed wiring board of the present invention fills a gap between copper foil circuits of an inner layer circuit board and smoothes the surface of the inner layer circuit. The following components (a), (b),
(C) and (d). (A) an epoxy resin in a solid state at room temperature; (b) an epoxy resin curing agent; (c) a diluent comprising a photopolymerizable and thermally reactive monomer; and (d) a photopolymerization initiator.

The epoxy resin (a) in a solid state at room temperature used in the present invention is a bisphenol type epoxy resin,
It is a novolak type epoxy resin or a mixture thereof and is a solid at room temperature. The melting point is usually 50
The temperature may be in the range of 100 to 100 ° C. As the bisphenol type epoxy resin, a bisphenol A type or a bisphenol F type is used. As the novolak type epoxy resin, a phenol novolak type, a cresol novolak type, or the like is used, and a cresol novolak type is particularly preferable.

(B) As the epoxy resin curing agent, various curing agents generally used can be used. For example, 4,
4'-diaminophenylmethane, 4,4'-diaminodiphenylsulfone, m-phenylenediamine, aromatic diamines such as p-phenylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, hexamethylenetriamine, mensendiamine,
Aliphatic polyamines such as isophoronediamine, imidazoles such as imidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, and 2-undecylimidazole;
Acid anhydrides such as phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, an amine complex of boron trifluoride, dicyandiamide or a derivative thereof. Epoxy adducts and microencapsulated ones of these can also be used.

In the present invention, a curing accelerator for the epoxy resin may be added as required. As the curing accelerator, various commonly used curing accelerators can be used. For example, tributylamine, benzylmethylamine, 2,2
Tertiary amines such as 4,6-tris (dimethylaminomethyl) phenol; imidazoles such as 2-ethyl-4-methylimidazole and N-benzylimidazole; ureas; phosphines; metal salts; These may be used alone or in combination of two or more. The amount of the epoxy resin curing agent varies depending on the type of the curing agent, but is usually 0.1 to 1.0 equivalent relative to the glycidyl group.

(C) As a diluent comprising a photopolymerizable and heat-reactive monomer, an acrylate or methacrylate compound having at least one hydroxyl group in one molecule, for example, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, Examples include hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, butanediol monoacrylate glycerol methacrylate, phenoxyhydroxypropyl acrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, and glycerol dimethacrylate. Alternatively, a photopolymerizable monomer such as glycidyl acrylate or glycidyl methacrylate having one or more glycidyl groups in one molecule is used. Preferred monomers include glycidyl acrylate and glycidyl methacrylate, which are heat-curable after solid tack-free by irradiation with active energy rays. Usually, the amount of the diluent (C) is 20 to 100 parts by weight, preferably 30 to 70 parts by weight, per 100 parts by weight of the epoxy resin (A).

(D) Examples of the photopolymerization initiator 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, 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 4-t
-Butyl-trichloroacetophenone, acetophenones such as diethoxyacetophenone, thioxanthone,
2-chlorothioxanthone, 2-methylthioxanthone,
Thioxansones such as 2,4-dimethylthioxanthone and alkylanthraquinones such as ethylanthraquinone and butylanthraquinone can be mentioned. These may be used alone or as a mixture of two or more. The addition amount of the photopolymerization initiator is usually 0.1 to 0.1.
It is used in the range of 10% by weight.

In addition, if necessary, an ultraviolet inhibitor, a thermal polymerization inhibitor, a plasticizer, and the like can be added to the light / thermosetting undercoat material for a multilayer printed wiring board of the present invention for storage stability. Further, an acrylate monomer, a methacrylate monomer, a vinyl monomer, or the like may be added for adjusting the viscosity. Furthermore, fused silica, crystalline silica, calcium carbonate, aluminum hydroxide, alumina,
Inorganic fillers such as mica, talc, white carbon, and E-glass powder can be blended to prevent epoxy silane coupling agents and voids to improve adhesion and moisture resistance with copper foil and inner circuit boards. , A liquid or powdered flame retardant, and the like.

The light / thermosetting undercoat material for a multilayer printed wiring board of the present invention comprising these components is substantially solvent-free, and fills the gaps between the copper foil circuits of the inner circuit board.
Smooths inner circuit surface. In addition, solid tack-free can be easily achieved by irradiation with active energy rays. In particular, in the conventional method, the step of drying and tack-free by heat,
In the present invention, the fact that it is possible only by irradiation with active energy rays is that the epoxy resin in the solid state at room temperature of the component (a) and the diluent composed of the photopolymerizable and heat-reactive monomer of the component (c) are used. It is because of that.

The component (c) in the prepared undercoat material of the present invention first acts as a solvent, dissolves the component (a) and other components, fills the copper foil circuit gap of the inner circuit board, and It is in a varnish state to smooth the circuit surface. When the component (c) acting as a solvent is irradiated with an active energy ray and polymerized, the component (c)
Is a component (a) because it loses its effect as a solvent with solidification
Precipitates. At this time, the polymerized component (c) and other components are dispersed in the solid component (a). Therefore,
If the component (A) which is in an appropriate tack-free solid state at room temperature is selected, the undercoat material of the present invention is tack-free without a thermosetting reaction. Such a tack-free mechanism is the greatest feature of the present invention. The component (c) of the present invention, which has been polymerized by irradiation with active energy rays, also has a heat-reactive functional group. Therefore, the cured product is excellent in heat resistance, chemical resistance and the like.

Next, the thermosetting insulating adhesive to be coated on the copper foil will be described. Generally, rubber-based compounds, polyvinyl butyral, phenoxy resin, polyester resin, etc. are compounded as a method of forming a film or a roll of the adhesive which is an interlayer insulating layer, but these components are used for thermal processing as a multilayer printed wiring board. Significantly degrade performance. For this reason, the adhesive used in the present invention is a bisphenol A having a weight average molecular weight of 10,000 or more in order to keep the fluidity small and maintain the interlayer thickness when integrally curing with the undercoat agent, and to impart film formability. Type epoxy resin or bisphenol F type epoxy resin.
The mixing ratio of the epoxy resin is 30% of the total epoxy resin.
９０90% by weight, preferably 50-90% by weight. As the curing agent, those used for the undercoat agent described above can be used.

In order to achieve the object of the present invention, an undercoat agent is applied to the inner layer circuit board, a copper foil with a thermosetting insulating adhesive is laminated, and integrally cured to form a multilayer printed wiring board. An outline of the manufacturing method will be described with reference to FIG. (A): Screen printing of liquid undercoating agent (3) on inner circuit board (1), using conventional coating equipment such as roller coater, curtain coater, etc., to a thickness that completely covers inner circuit (2). Apply. If the embedding amount is insufficient, air will be entrained in the subsequent laminate. After that, it is tack-free by irradiating an active energy ray with an exposure machine such as a UV irradiation conveyor. (B): A copper foil (5) with a thermosetting insulating adhesive (4) is laminated on the surface. The laminator preferably uses a hard roll (6) to achieve surface smoothness.
The laminating conditions vary depending on the pattern of the inner layer circuit, but the pressure is about 0.5 to ⁶ kgf / cm ² , the surface temperature is from room temperature to about 100 ° C., and the laminating speed is 0.1.
Perform at about 6 m / min. Under such conditions, the viscosity of the undercoat agent is 1 to 300 poise, and the surface smoothness can be achieved by using a hard roll. At this time, the interlayer thickness between the inner layer circuit (2) and the copper foil (5) can be achieved by the thickness of the thermosetting insulating adhesive. (C): Next, a simultaneous integrated curing reaction is performed by heating to form a multilayer printed wiring board integrally molded with the undercoat agent (3) and the thermosetting insulating adhesive (4) coated on the copper foil. can do.

[0020]

The present invention will be described below with reference to examples.
"Parts" represents parts by weight.

Example 1 Bisphenol A type epoxy resin (epoxy equivalent weight 6400, weight average molecular weight 3000)
0) 150 parts of bisphenol F type epoxy resin (epoxy equivalent: 175, Epicron 830 manufactured by Dainippon Ink and Chemicals, Incorporated) were dissolved in MEK with stirring, and microencapsulated 2-imidazole was added thereto as a curing agent. 120 parts and silane coupling agent (Nihon Unicar Co., Ltd.)
A-187) 10 parts were added to prepare a thermosetting insulating adhesive varnish. The varnish was applied to an anchor surface of a copper foil having a thickness of 18 μm with a roller coater so that the thickness after drying became 40 μm, and dried to prepare a copper foil with a thermosetting insulating adhesive.

Next, a bisphenol A type epoxy resin (epoxy equivalent: about 470, weight average molecular weight: about 900) 1
Was dissolved in 40 parts of glycidyl methacrylate, and 5 parts of dicyandiamide and 2-ethyl-4 as a curing agent were dissolved therein.
0.15 parts of -methylimidazole and 1.2 parts of a photopolymerization initiator (Irgacure 651 manufactured by Ciba Geigy) were added, and sufficiently stirred with a homomixer to obtain an undercoat agent.

Further, the thickness of the base material is 0.1 mm, and the thickness of the copper foil 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 above undercoat agent is applied with a curtain coater to a thickness of about 40 μm.
Coated. Then, 80W / cm by UV conveyor
Irradiation with UV light from two high-pressure mercury lamps under the condition of about 2 J / cm ² was carried out.
^2. Lamination speed The above-mentioned copper foil with a thermosetting insulating adhesive was laminated using a hard roll under the condition of 0.8 m / min and heat-cured at 180 ° C. for 20 minutes to produce a multilayer printed wiring board.

<< Embodiment 2 >> The circuit copper thickness of the inner circuit board is 70
A multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that the thickness of the undercoat agent was set to 80 μm.

<< Comparative Example 1 >>
A multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that the coating was completely cured by heating at 80 ° C. for 60 minutes.

Comparative Example 2 A multilayer printed wiring board was produced in the same manner as in Example 1 except that the undercoat agent was not applied.

The obtained multilayer printed wiring board has characteristics as shown in the following table. ──────────────────────────────── Surface smoothness Moisture-absorbing solder heat resistance Embedding property Interlayer insulation layer thickness ───── ─────────────────────────── Example 1 3 μm ○ ○ 35 μm Example 2 3 ○ ○ 35 Comparative Example 1 15 ○ ○ 40 Comparative Example 25 × × 30 mm

(Test 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 heat resistance test Moisture absorption conditions: pressure cooker treatment, 125 ° C,
Test conditions: 3 atm, 30 minutes Test conditions: n = 5, all were 280 ° C., no swelling for 120 seconds, rated as ○. Embedding property: After peeling the outer layer copper foil, the embedding property in the inner layer circuit was visually judged using an optical microscope, and the embedded one was evaluated as ○. 4. Interlayer insulation layer thickness: The multilayer printed wiring board was cut, and its cross section was observed with an optical microscope to measure the thickness of the interlayer insulation layer between the inner layer circuit and the surface copper foil.

[0029]

According to the method of the present invention, by laminating a copper foil with a thermosetting insulating adhesive with a hard roll or the like, the undercoat agent which has been tack-free by light irradiation after coating on the inner circuit board is re-used. Multi-layer printed wiring board with excellent thickness control without depending on the inner layer copper foil residual rate because the thermosetting insulating adhesive coated on the copper foil maintains its thickness by melting and smoothing the surface Can be produced. Furthermore, by performing a simultaneous integral curing reaction by heating after lamination, the undercoat agent and the thermosetting insulating adhesive coated on the copper foil can be integrally molded. In addition, without using a prepreg and a hot plate press as in the past, and without plating as in the additive method, a multilayer printed wiring board having an outer layer copper foil can be manufactured by a laminating method, so that insulation can be achieved. The time required for forming the layer and forming the outer conductive layer is greatly reduced, which can contribute to simplification of the process and cost reduction. Further, since no glass cloth is used, the thickness of the interlayer insulating layer can be made extremely thin.

[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 undercoating agent 4 thermosetting insulating adhesive 5 copper foil 6 hard roll 7 multilayer printed wiring board

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H05K 3/46 H05K 3/46 B GT (56) References JP-A-60-206823 (JP, A) JP-A-61- 185525 (JP, A) JP-A-8-73565 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08G 59/40-59/66 C09J 163/00-163/10 C09J 4/06 B32B 15/08 H05K 3/38 H05K 3/46

Claims (10)

(57) [Claims] 1. A light / thermosetting undercoat material for a multilayer printed wiring board comprising the following components (a), (b), (c) and (d). (A) an epoxy resin which is in a solid state at normal temperature; (b) an epoxy resin curing agent; (c) a diluent comprising a photopolymerizable and thermally reactive monomer; and (d) a photopolymerization initiator. Wherein component (b) is a multilayer of claim 1, wherein a molecular weight of 500 or more at room temperature is an epoxy resin which is in solid state
Light and thermosetting undercoat material for printed wiring boards . 3. The diluent according to claim 1, wherein the component (c) is a photopolymerizable and heat-reactive monomer having at least one acryloyl or methacryloyl group and at least one glycidyl group in one molecule. Light for multilayer printed wiring boards
Thermosetting undercoat material. 4. The photo-thermosetting undercoat material for a multilayer printed wiring board according to claim 1, wherein the component (c) is glycidyl methacrylate. 5. An epoxy resin which has a molecular weight of 500 or more and is in a solid state at room temperature, wherein the component (c) has one or more acryloyl or methacryloyl groups and one or more glycidyl in one molecule. a diluent comprising a photopolymerization and thermal reactive monomer having a group claim 1 multi according
Light and thermosetting undercoat material for multilayer printed wiring boards . 6. The multilayer print according to claim 1, wherein the component (a) is an epoxy resin having a molecular weight of 500 or more and in a solid state at room temperature, and the component (c) is glycidyl methacrylate.
Light and thermosetting undercoat material for wiring boards . 7. An inner layer circuit board is coated with the light / thermosetting undercoat material for a multilayer printed wiring board according to claim 1 and is made tack-free by irradiating with active energy rays. A method for producing a multilayer printed wiring board, comprising laminating a copper foil having an agent layer, and then curing the laminate by heating. 8. An inner layer circuit board is coated with the light / thermosetting undercoat material for a multilayer printed wiring board according to claim 5 and is made tack-free by irradiating with active energy rays. A method for producing a multilayer printed wiring board, comprising laminating a copper foil having an agent layer, and then curing the laminate by heating. 9. The thermosetting insulating adhesive comprises an epoxy resin and a curing agent thereof, and one component of the epoxy resin is a bisphenol A epoxy resin or a bisphenol F epoxy resin having a weight average molecular weight of 10,000 or more. 8. The method for producing a multilayer printed wiring board according to 7. 10. The thermosetting insulating adhesive comprises an epoxy resin and a curing agent thereof, and one component of the epoxy resin is a bisphenol A epoxy resin or a bisphenol F epoxy resin having a weight average molecular weight of 10,000 or more. 9. The method for producing a multilayer printed wiring board according to item 8.