JPH0974278A - Light and heat curing undercoat material for multilayer printed wiring board and manufacture of multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To turn a light and heat curing undercoat material tack-free well by irradiation with an active energy beam by a method wherein the undercoat material is composed of epoxy resin which is prescribed in a bromination rate, molecular weight, and solid at normal temperatures, epoxy resin curing resin, diluent formed of photopolymerizing and heat-reactive monomer, and photopolymerization initiator. SOLUTION: Epoxy resin which is of bromination rate 20% or above, of molecular weight 5000 to 4000, and solid at normal temperatures, epoxy resin curing resin such as 4,4-diaminophenylmethane, diluent formed of photopolymerizing and heat-reactive monomer such as hydroxyethyl acrylate, and photopolymerization initiator such as benzophenone are mixed together for the formation of undercoating agent. When the diluent is polymerized by irradiation with active energy, epoxy resin separates with solidification of diluent because diluent does not functions as solvent any more. At this point, solidified diluent agent and other components are dispersed into solid component epoxy resin. Epoxy resin properly solid and tack-free at normal temperatures can be selected and turned tack-free well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel light for multi-layer printed wiring board comprising low cost and high productivity tack-free irradiation by active energy ray irradiation and main curing by heat.
The present invention provides a thermosetting undercoat agent, and further relates to a method for producing a multilayer printed wiring board using this undercoat agent.

[0002]

2. Description of the Related Art Conventionally, in the case of manufacturing a multilayer printed wiring board, one or more prepreg sheets obtained by impregnating a glass cloth base material with epoxy resin and semi-cured are stacked on an inner layer circuit board on which a circuit is formed. A copper foil is laminated on it and is integrally molded by heating with a hot plate press. However, in this process, the impregnated resin is reflowed by heat and cured under a constant pressure.
1.5 hours is required. 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, it is difficult to make the circuit layer 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]

DISCLOSURE OF THE INVENTION The present invention is to complete a multilayer printed wiring board by a simplified method at a low cost and in a short time, as compared with the above-mentioned hot plate pressing method.

When a film-shaped interlayer insulating resin layer is used in a multilayer printed wiring board by a build-up method, work efficiency is remarkably improved as compared with the method of forming the interlayer insulating resin layer with a prepreg. However, it is expected that air will be entrained in the stepped portion between the insulating substrate of the inner layer circuit board and the circuit, and in order to prevent this, lamination must be performed under a reduced pressure environment, and special equipment is required. Come on. 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 pattern development degree, which makes it impossible to form a stable resist.

Further, the same applies to the case of using a prepreg, but since the amount of resin to be embedded changes depending on the copper foil residual rate of the inner layer circuit pattern, the same film does not have the same plate thickness after molding. In other words, if the copper foil residual rate is large and the portion to be embedded is small, the plate thickness will be thick, and if the copper foil residual rate is small and the portion to be embedded is large, the plate thickness will be thin. Unless changed, the same plate thickness cannot be achieved.
In addition, even if one inner layer circuit board has a different copper foil residual rate depending on the location, the resulting multilayer printed wiring board may have a non-uniform thickness.

[0007]

According to the present invention, an inner layer circuit board is coated with a light / thermosetting undercoating agent for a multilayer printed wiring board, which is made tack-free by irradiation with active energy rays, and then a thermosetting type. The present invention relates to a photo / thermosetting undercoat agent for use in a multilayer printed wiring board in which a copper foil having an insulating adhesive layer is laminated and then integrally cured by heating, and a method for producing the multilayer printed wiring board.

That is, a liquid undercoating agent is applied by screen printing, a roller coater, a curtain coater, etc. to fill the copper foil circuit gap of the inner layer circuit board, and the active energy ray is irradiated by an exposure machine such as a UV irradiation conveyor. To make it tack free. After that, the undercoat agent can be remelted by laminating with a hard roll heated when the copper foil with a thermosetting insulating adhesive is adhered to obtain surface smoothness. At that time, since the thermosetting insulating adhesive coated on the copper foil is bonded by the epoxy resin component having a weight average molecular weight of 10,000 or more while maintaining its shape, that is, while maintaining the interlayer thickness, the inner layer copper foil residual rate It is possible to produce a multilayer printed wiring board having excellent board thickness accuracy without depending on Then, after laminating, heating and simultaneous monolithic curing reaction are performed to integrally form the optical / thermosetting undercoat agent for a multilayer printed wiring board and the thermosetting type copper foil with an insulating adhesive.

In the present invention, the undercoat agent fills the copper foil circuit gap of the inner layer circuit board and smoothes the inner layer circuit surface. The following components (a), (b), (c) and (d) ) Consists of. (A) Bromination rate of 20% or more, molecular weight of 500 to 4000
, An epoxy resin in a solid state at room temperature, (b) an epoxy resin curing agent, (c) a diluent comprising a photopolymerizable and heat-reactive monomer, and (d) a photopolymerization initiator.

The epoxy resin (a) used in the present invention in a solid state at room temperature has a bromination rate of 20% or more and a molecular weight of 5%.
A bisphenol type epoxy resin of from 0 to 4000,
It is a novolac type epoxy resin or a mixture thereof, which is solid at room temperature. The melting point is usually 50
It may be in the range of 150 ° C. As the bisphenol type epoxy resin, bisphenol A type or bisphenol F type is used, and bisphenol A type is particularly preferable. Further, as the novolac type epoxy resin, phenol novolac type, cresol novolac type, etc. can be used.

The bromination rate of the brominated epoxy resin is 20.
% Or more. When the bromination rate is less than 20%, the obtained multilayer printed wiring board cannot achieve the flame retardancy v-0 according to the UL standard. It should be noted that the upper limit of the bromination rate is the case where all the brominated portions of the benzene nucleus of the epoxy resin are brominated, and this upper limit value is determined.

As the (b) epoxy resin curing agent, various commonly used curing agents can be used. For example, 4,
Aromatic diamines such as 4'-diaminophenylmethane, 4,4'-diaminodiphenyl sulfone, m-phenylenediamine, p-phenylenediamine; diethylenetriamine, triethylenetetramine, tetraethylenepentamine, hexamethylenetriamine, mensendiamine,
Aliphatic polyamines such as isophoronediamine; imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, bis (2 -Ethyl-4-methyl-imidazole), 2-undecylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole,
Imidazoles such as 2-phenyl-4,5-dihydroxymethylimidazole and triazine addition type imidazole, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, and benzophenone tetracarboxylic anhydride An acid anhydride such as an acid, an amine complex of boron trifluoride, dicyandiamide or a derivative thereof and the like can be mentioned, and an epoxy adduct thereof or a microcapsule thereof can also be used. Further, in the present invention, a curing accelerator for the epoxy resin may be added if necessary.

As the curing accelerator, various commonly used curing accelerators can be used. For example, tributylamine,
Benzylmethylamine, tertiary amines such as 2,4,6-tris (dimethylaminomethyl) phenol, 2-ethyl-4-methylimidazole, imidazoles such as N-benzylimidazole, ureas, phosphines, metals Examples thereof include salts, and these may be used alone or in combination of two or more kinds. 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 with respect to the glycidyl group.

(C) As a diluent comprising a photopolymerizable and thermoreactive monomer, (a) an acrylate or methacrylate compound having at least one hydroxyl group in one molecule, for example, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxy. Propyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, butanediol monoacrylate glycerol methacrylate, phenoxy hydroxypropyl acrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, or glycerol dimethacrylate. Further, (b) a photopolymerizable monomer such as glycidyl acrylate or glycidyl methacrylate having one or more glycidyl groups in one molecule is also preferably used. The compound (a) and the compound (b) can be used alone or in combination. Especially,
Preferred monomers are glycidyl acrylate and glycidyl methacrylate, which have excellent thermosetting properties after solid tack-free by irradiation with active energy rays, and these are used alone or in combination with the compound (a) for easy handling. It is practically preferable to do so. Usually (C)
The amount of the diluent as a component is 20 to 100 parts by weight, preferably 30 to 70 parts by weight, relative to 100 parts by weight of the epoxy resin as the component (a).

(D) As the photopolymerization initiator, benzophenone, benzoylbenzoic acid, 4-phenylbenzophenone, benzophenones such as 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, for the storage stability of the photocurable / thermosetting undercoating agent for a multilayer printed wiring board of the present invention, an ultraviolet inhibitor, a thermal polymerization inhibitor, a plasticizer, etc. may be added, if necessary. Further, an acrylate monomer, a methacrylate monomer, a vinyl monomer or the like may be added to adjust 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 added to prevent epoxy silane coupling agents and voids for improving adhesion and moisture resistance to copper foil and inner circuit boards. An antifoaming agent, a liquid or powder flame retardant, or the like may be added.

The light / thermosetting undercoating agent for multilayer printed wiring boards of the present invention comprising these components is substantially solvent-free and has a low viscosity, so that the copper foil circuit gap of the inner layer circuit board is To smooth the inner circuit surface.
Also, it becomes solid easily by irradiation with active energy rays,
Can be tack free.

In particular, in place of the conventional process of drying and tack-free by heat, tack-free is achieved only by irradiation with active energy rays. Therefore, in the present invention, the component (a) is in a solid state at room temperature. It is characterized by using an epoxy resin and a diluent comprising a photopolymerization and a heat-reactive monomer of component (C).

The prepared undercoating agent of the present invention is in the form of a varnish, and the component (c) is first used as a solvent to dissolve the component (a) and other components to fill the copper foil circuit gaps of the inner layer circuit board. , Smooth the inner layer circuit surface. When the component (C) is polymerized by irradiating the active energy ray in this normal state, the component (C) loses its effect as a solvent as it solidifies upon curing, so that the component (B) is deposited. At this time, the cured component (C) and other components are dispersed in the solid component (A). Therefore, if the component (a) that is in a suitable solid tack-free state at room temperature is selected, the undercoating agent of the present invention becomes tack-free without undergoing a thermosetting reaction. Such a tack free mechanism is the greatest feature of the present invention.

Further, since the component (c) of the present invention which is cured by irradiation with active energy rays also has a thermoreactive functional group, it reacts with the epoxy resin or the curing agent as the main component during the subsequent thermosetting reaction. The cured product also has excellent heat resistance and chemical resistance.

Next, the thermosetting insulating adhesive coating the copper foil will be described. Generally, as a method of forming a film or winding an adhesive which is an interlayer insulating layer, a rubber-based compound or polyvinyl butyral, a phenoxy resin, or a thermoplastic resin such as a polyester resin is mixed as a main component,
These components significantly deteriorate the thermal performance as a multilayer printed wiring board. For this reason, the adhesive used in the present invention further suppresses the fluidity when it is integrally cured with the undercoating agent, maintains the interlayer thickness, and imparts film moldability, and further imparts flame retardancy. Therefore, it is preferable that the bromination rate is 20% or more and the weight average molecular weight is 1000.
0 or more bisphenol A type epoxy resin or bisphenol F type epoxy resin and its curing agent are blended.
The mixing ratio of the epoxy resin is 30 to 30 in all epoxy resins.
90% by weight, preferably 50 to 90% by weight. As the curing agent, those used for the undercoat agent described above can be used.

An outline of a method of applying an undercoating agent and laminating and hardening a copper foil with a thermosetting insulating adhesive to achieve the object of the present invention will be described with reference to FIG.

(A) The inner layer circuit (2) is completely covered with the liquid undercoat agent (3) on the inner layer circuit board (1) by using a conventional coating equipment such as screen printing, roller coater, curtain coater and the like. Apply to thickness.
If the embedding amount is insufficient, air will be entrained in the subsequent laminate. After that, it is tack-free by irradiating active energy rays with an exposure machine such as a UV irradiation conveyor.

(B) Thermosetting insulating adhesive (4) on the surface
Laminate the attached copper foil (5). The laminator preferably uses hard rolls (6) to achieve surface smoothness. The laminating condition depends 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 about 0.1 to 6 m / min. 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) Then, by heating, the undercoat agent (3) and the thermosetting insulating adhesive (4) coated on the copper foil are simultaneously and integrally cured to form a multilayer printed wiring board. You can

[0026]

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

Example 1 Brominated bisphenol A type epoxy resin (bromination rate 25%, weight average molecular weight 3000)
0) 150 parts and 30 parts of bisphenol F type epoxy resin (epoxy equivalent 175, Epicron 830 manufactured by Dainippon Ink and Chemicals, Inc.) were dissolved in MEK with stirring, and 2-methyl which was microencapsulated as a curing agent therein. A thermosetting insulating adhesive varnish was prepared by adding 120 parts of imidazole and 10 parts of a silane coupling agent (A-187 manufactured by Nippon Unicar Co., Ltd.). 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, 100 parts of brominated bisphenol A type epoxy resin (bromination rate of 50%, epoxy equivalent of about 800, molecular weight of about 1600) was added to glycidyl methacrylate 60.
1.0 part of 2-phenyl-4-methyl-5-hydroxymethylimidazole as a curing agent, and a photopolymerization initiator (Irgacure 651 manufactured by Ciba-Geigy)
2.0 parts was added and sufficiently stirred with a homomixer to obtain an undercoat 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
Of 2 high pressure mercury lamps at about 2 J / cm ² on the undercoating agent, which was made tack-free by irradiation with active energy rays, at a temperature of 100 ° C and a pressure of 2 kg / cm 2.
^2. Lamination speed: The above-mentioned thermosetting type copper foil with insulating adhesive was laminated using a hard roll under the conditions of 0.8 m / min, and heat-cured at 180 ° C. for 20 minutes to prepare a multilayer printed wiring board.

Example 2 As Example 1, except that the epoxy resin used for the undercoat agent was a novolac type epoxy resin (bromination rate 35%, epoxy equivalent about 280, molecular weight 1400). A multilayer printed wiring board was manufactured in the same manner.

Example 3 The same procedure as in Example 1 was repeated except that 30 parts of glycidyl methacrylate and 30 parts of hydroxyethyl methacrylate were used instead of 60 parts of glycidyl methacrylate used in the undercoat agent. A printed wiring board was produced.

<< Comparative Example 1 >> Coating on the inner layer circuit board,
A multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that it was heated at 80 ° C. for 60 minutes to completely cure it.

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

The resulting multilayer printed wiring board has the characteristics shown in Table 1. Table 1 ─────────────────────────────────── Surface smoothness Moisture absorption Solder heat resistance Embedding Interlayer insulation layer thickness Flame retardance ─────────────────────────────────── Example 1 3 μm ○ ○ 35 μm V-0 Example 25 ○○ 40 V-0 Example 3 3 ○○ 35 V-0 Comparative Example 1 15 ○○ 40 V-0 Comparative Example 2 5 × × 30 V-0 ──────────── ───────────────────────

(Test 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 heat resistance test Moisture absorption conditions: pressure cooker treatment, 125 ° C,
3 atmospheres, 30 minutes Test condition: n = 5, all were swelling at 280 ° C. for 120 seconds, and were rated as ◯. 3. Embedding property: After the outer layer copper foil was peeled off, the embedding property in the inner layer circuit was visually judged using an optical microscope, and the embedding property was marked 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. 5. Flame retardance: measured according to UL-94.

[0036]

According to the method of the present invention, by laminating a copper foil with a thermosetting insulating adhesive on a hard roll or the like, the undercoat agent which has been photo-cured after being applied to the inner layer circuit is remelted to form a surface Since the thermosetting insulating adhesive that is smoothed and coated on the copper foil maintains its thickness, it is possible to produce a multilayer printed wiring board with excellent board thickness control without depending on the residual rate of the inner copper foil. it can. Furthermore, the undercoating agent and the thermosetting insulating adhesive coated on the copper foil can be integrally molded by heating after laminating and simultaneously performing an integral curing reaction. A multilayer obtained by using a brominated epoxy resin as an epoxy resin which is a main component of an undercoat agent, and more preferably using a brominated epoxy resin also as a thermosetting insulating adhesive coated on a copper foil. The printed wiring board can be made flame-retardant to UL standard V-0. In addition, since it is possible to manufacture a multilayer printed wiring board having an outer copper foil by a laminating method without using a prepreg and a hot plate press as in the past and without plating as in an additive method, insulation can be obtained. The time required for layer formation and outer conductive layer formation is greatly shortened, which can contribute to simplification of the process and cost reduction. Furthermore, since no glass cloth is used, the interlayer insulating layer can be made extremely thin.

[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) Masahiro Mitsui, 2-5-8 Higashi-Shinagawa, Shinagawa-ku, Tokyo Sumitomo Bakelite Co., Ltd. (72) Toyoaki Kishi 2--5-8, Higashi-Shinagawa, Shinagawa-ku, Tokyo Sumitomo Bakelite Co., Ltd.

Claims (9)

[Claims] 1. A photo-thermosetting undercoat agent for a multilayer printed wiring board, comprising the following components (a), (b), (c) and (d): (A) Bromination rate of 20% or more, molecular weight of 500 to 4000
Epoxy resin in room temperature solid state, (b) Epoxy resin curing agent, (c) Diluent consisting of photopolymerization and thermoreactive monomer, (d) Photopolymerization initiator 2. The component (c) is a diluent comprising a photopolymerizable and thermoreactive monomer having at least one acryloyl group or methacryloyl group and at least one glycidyl group in one molecule. Light for multi-layer printed wiring board
Thermosetting undercoat agent. 3. The light / thermosetting undercoat agent for a multilayer printed wiring board according to claim 1, wherein the component (c) is glycidyl methacrylate. 4. The component (c) is a diluent comprising a photopolymerizable and thermoreactive monomer having at least one acryloyl group or methacryloyl group and at least one active hydroxyl group in one molecule. An optical / thermosetting undercoat agent for a multilayer printed wiring board as described above. 5. A mixture of glycidyl methacrylate as a component (c) and a diluent comprising a photopolymerizable and thermoreactive monomer having at least one acryloyl group or methacryloyl group in one molecule, and at least one active hydroxyl group. The light / thermosetting undercoat agent for a multilayer printed wiring board according to claim 1. 6. An inner circuit board is coated with the photocurable / thermosetting undercoat agent for a multilayer printed wiring board according to claim 1 to be tack-free by irradiation with active energy rays, and then thermosetting insulating adhesive. A method for manufacturing a multilayer printed wiring board, comprising laminating a copper foil having an agent layer, and then integrally curing the copper foil by heating. 7. An inner-layer circuit board is coated with the light / thermosetting undercoat agent for a multilayer printed wiring board according to claim 5, and is made tack-free by irradiation with active energy rays, and then thermosetting insulating adhesive. A method for manufacturing a multilayer printed wiring board, comprising laminating a copper foil having an agent layer, and then integrally curing the copper foil by heating. 8. The thermosetting insulating adhesive is composed of an epoxy resin and a curing agent thereof, and the main component of the epoxy resin is
The method for producing a multilayer printed wiring board according to claim 6, comprising a bisphenol epoxy resin having a bromination rate of 20% or more and a weight average molecular weight of 10,000 or more, and a bisphenol epoxy resin having an epoxy equivalent of 500 or less. 9. The thermosetting insulating adhesive is composed of an epoxy resin and a curing agent thereof, and the main component of the epoxy resin is
The method for producing a multilayer printed wiring board according to claim 7, comprising a bisphenol type epoxy resin having a bromination rate of 20% or more and a weight average molecular weight of 10,000 or more, and a bisphenol type epoxy resin having an epoxy equivalent of 500 or less.