JPH08157566A - Photosetting and thermosetting undercoat material and production of multilayer printed wiring board - Google Patents

Abstract

PURPOSE: To obtain a multilayer printed wiring board at a low cost by laminating a copper foil having a thermosetting insulating adhesive layer on an inner layer circuit board coated with a photosetting and thermosetting undercoat material capable of turning tack-free when applied on the inner layer circuit board and then irradiated with an active energy radiation, and subsequently heating the coated board to effect integral cure thereof. CONSTITUTION: The spaces of an inner circuit board are filled with an undercoat material comprising (A) an epoxy resin having a solid state at ordinary temp. (e.g. a bisphenol epoxy resin), (B) an epoxy resin curing agent (e.g. 4,4'- diaminophenylmethane), (C) a photopolymerizable and heat-reactive monomer as a diluent (e.g. hydroxyethyl acrylate), and (D) a photopolymn. initiator (e.g. benzophenone) to smooth the surface of the board. Subsequently, the undercoat material is turned into a tack-free state, and a copper foil with a thermosetting insulating adhesive contg. a bisphenol A epoxy resin having a wt.-average mol.wt. of at least 10,000 is then laminated on the undercoat material, followed by heat curing.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention provides a new photo- and thermosetting undercoat material which is tack-free by irradiation with active energy rays and hardens by heat, which is suitable for the production of a low-cost and highly productive multilayer printed wiring board. Is provided,
Further, the present invention provides a method for manufacturing a multilayer printed wiring board using this 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-cured are laminated on an inner layer circuit board on which a circuit is formed, and further The process of stacking copper foil on top and forming integrally with heating with a hot plate press is performed. But,
In this process, the impregnated resin is reflowed by heat and cured under a constant pressure.
I need time. As described above, the manufacturing process is long, and the cost is high due to the cost of the multi-layer laminating press and the glass cloth prepreg. In addition, it is difficult to make the interlayer thickness extremely thin because the glass cloth is impregnated with the resin.

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 material, has attracted attention again. There is.

[0004]

SUMMARY OF THE INVENTION The present invention has completed a method for manufacturing a multilayer printed wiring board at a low cost by a simplified build-up method in a short time, which is different from the above-mentioned hot plate pressing method. It is a thing.

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 layer circuit board and the circuit, surface smoothness cannot be obtained, and soldering failure etc. may occur during component mounting, or resist There is a problem that peeling and a decrease in pattern development occur, and stable resist formation cannot be performed.

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]

SUMMARY OF THE INVENTION As will be described below, the present invention is a light / heat treatment applied to an inner layer circuit board for producing a multilayer printed wiring board, which is tack-free by irradiation with active energy rays. Curable undercoat material, and a copper foil having a thermosetting insulating adhesive layer is laminated on the inner layer circuit board coated with such an undercoat agent, and then,
The present invention relates to a method for manufacturing a multilayer printed wiring board by heating and integrally curing.

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, and U
It is tack-free by irradiation with active energy rays by an exposure device such as a V irradiation conveyor. 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 this time, if the thermosetting insulating adhesive coated on the copper foil is mixed with an epoxy resin component having a weight average molecular weight of 10,000 or more, the adhesive is adhered while maintaining the shape by this component, that is, maintaining the interlayer thickness. Therefore, a multilayer printed wiring board having excellent board thickness accuracy can be produced without depending on the inner layer copper foil remaining rate. Then, the laminate is heated to cause simultaneous curing reaction to integrally mold the optical / thermosetting undercoat material for a multilayer printed wiring board and the thermosetting 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) Epoxy resin in a solid state at room temperature, (b) epoxy resin curing agent, (c) diluent composed of photopolymerizable and heat-reactive monomer, and (d) photopolymerization initiator.

The epoxy resin (a) used in the present invention in a solid state at room temperature is a bisphenol type epoxy resin,
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 -100 ° C. As the bisphenol type epoxy resin, bisphenol A type or bisphenol F type is used. As the novolac type epoxy resin, a phenol novolac type, a cresol novolac type or the like is used, and a cresol novolac type is particularly preferable.

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'-diaminodiphenylsulfone, m-phenylenediamine, 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, 2-undecylimidazole,
Acid anhydrides such as phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic acid anhydride, amine complexes of boron trifluoride, dicyandiamide or its derivatives Examples thereof include epoxy adducts and microencapsulated products thereof.

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, 2,
Tertiary amines such as 4,6-tris (dimethylaminomethyl) phenol, imidazoles such as 2-ethyl-4-methylimidazole, N-benzylimidazole, ureas, phosphines, metal salts and the like, 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 with respect 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, Hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, butanediol monoacrylate glycerol methacrylate, phenoxyhydroxypropyl acrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, or glycerol dimethacrylate. Alternatively, a photopolymerizable monomer such as glycidyl acrylate or glycidyl methacrylate having one or more glycidyl groups in one molecule is used. Preferable monomers are 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 as the component (c) 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) Examples of the photopolymerization initiator include 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,
Examples thereof include thioxanthones such as 2,4-dimethylthioxanthone and alkylanthraquinones such as ethylanthraquinone and butylanthraquinone. These may be used alone or as a mixture of two or more kinds. The addition amount of this photopolymerization initiator is usually 0.1 to
Used in the range of 10% by weight.

In addition, for the storage stability, an ultraviolet ray inhibitor, a thermal polymerization inhibitor, a plasticizer, etc. may be added to the light / thermosetting type undercoat material for a multilayer printed wiring board of the present invention, 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 optical / thermosetting undercoat material for a multilayer printed wiring board of the present invention comprising these components is substantially solvent-free and fills the copper foil circuit gap of the inner layer circuit board,
Smooth the inner layer circuit surface. Further, solid tack-free can be easily achieved by irradiation with active energy rays. Especially, in the conventional method, the process of drying and tack-free by heat is
In the present invention, as to what is possible only by irradiation with active energy rays, the epoxy resin of component (a) in a solid state at room temperature and the diluent of photopolymerization and thermoreactive monomer of component (c) are used. This is due to the fact.

The component (c) in the prepared undercoat material of the present invention acts as a solvent to dissolve the component (a) and other components to fill the copper foil circuit gap of the inner layer circuit board, A varnish is used to smooth the circuit surface. When the component (c) acting as a solvent is polymerized by irradiating this with active energy rays, the component (c) becomes
Is a component (a) because it loses its effect as a solvent as it solidifies.
Is deposited. At this time, the polymerized component (C) and other components are dispersed in the solid component (A). Therefore,
If the component (a) that is in a suitable tack-free solid state at room temperature is selected, the undercoat material of the present invention is tack-free without undergoing a thermosetting reaction. Such a tack free mechanism is the greatest feature of the present invention. In addition, since the component (c) of the present invention polymerized by irradiation with active energy rays also has a thermoreactive functional group, it reacts integrally with the main epoxy resin or curing agent during the subsequent thermosetting reaction. Therefore, the cured product is also excellent in heat resistance, chemical resistance and the like.

Next, the thermosetting insulating adhesive coating the copper foil will be described. Generally, rubber compounds, polyvinyl butyral, phenoxy resin, polyester resin, etc. are compounded as a method for forming an adhesive film, which is an interlayer insulating layer, into a film or a roll, but these components are thermally mixed as a multilayer printed wiring board. Significantly reduces performance. Therefore, the adhesive used in the present invention is a bisphenol A having a weight average molecular weight of 10000 or more in order to keep the fluidity small to maintain the interlayer thickness and to have film formability when integrally curing with the undercoat agent. Type epoxy resin or bisphenol F type epoxy resin is compounded.
The compounding ratio of such epoxy resin is 30 in all epoxy resins.
˜90 wt%, preferably 50-90 wt%. As the curing agent, the one used for the undercoat agent described above can be used.

In order to achieve the object of the present invention, an undercoating agent is applied to an inner layer circuit board, a copper foil with a thermosetting insulating adhesive is laminated, and integrally cured to form a multilayer printed wiring board. The outline of the manufacturing method will be described with reference to FIG. (A): A liquid undercoat agent (3) is applied on the inner layer circuit board (1) to a thickness to completely cover the inner layer circuit (2) by using conventional coating equipment such as screen printing, roller coater and curtain coater. To apply. If the filling amount is insufficient, air will be trapped in the subsequent laminate. After that, it is tack-free by irradiating the active energy ray with an exposure device 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 hard rolls (6) to achieve surface smoothness.
The laminating condition varies 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.
~ 6 m / min. Under these conditions, the viscosity of the undercoating 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): Then, the undercoating agent (3) and the thermosetting insulating adhesive (4) coated on the copper foil are integrally molded to form a multilayer printed wiring board by heating and simultaneously performing a simultaneous curing reaction. can do.

[0020]

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

Example 1 Bisphenol A type epoxy resin (epoxy equivalent 6400, 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 while stirring, and 2-imidazole which was microencapsulated as a curing agent was dissolved therein. 120 parts and silane coupling agent (Nippon Unicar Co., Ltd.)
A-187) (10 parts) was added to prepare a thermosetting insulating adhesive varnish. This varnish was applied to the anchor surface of a copper foil having a thickness of 18 μm by a roller coater so that the thickness after drying was 40 μm, and dried to produce a copper foil with a thermosetting insulating adhesive.

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 and add 5 parts of dicyandiamide and 2-ethyl-4 as a curing agent therein.
-Methylimidazole (0.15 parts) and a photopolymerization initiator (Ciba-Geigy Irgacure 651) (1.2 parts) were added, and the mixture was sufficiently stirred with a homomixer to give an undercoating 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 processed by patterning to obtain an inner layer 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.
Applied to. After that, 80 W / cm on UV conveyor machine
Ultraviolet irradiation with two high-pressure mercury lamps under conditions of about 2 J / cm ² , and tack-free undercoating agent by activation energy ray irradiation, temperature 100 ° C, pressure 2 kg / cm
^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.

<Embodiment 2> The circuit copper thickness of the inner layer 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 undercoating agent was 80 μm.

<< Comparative Example 1 >> Coating on an 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 prepared 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 the following table. ──────────────────────────────── Surface smoothness Moisture absorption Solder heat resistance Implantability Interlayer insulation layer thickness ───── ─────────────────────────── Example 1 3 μm ○○ 35 μm Example 2 3 ○○ 35 Comparative Example 1 15 ○○ 40 Comparative Example 25 × × 30 ─────────────────────────────────

(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) 2. Moisture absorption solder heat resistance test Moisture absorption conditions: Pressure cooker treatment, 125 ° C, 2.
3. Atmospheric pressure, 30 minutes Test condition: n = 5, all of which did not swell at 280 ° C. for 120 seconds were evaluated as ◯. 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 insulating layer thickness: The multilayer printed wiring board was cut, the cross section was observed with an optical microscope, and the interlayer insulating layer thickness between the inner layer circuit and the surface copper foil was measured.

[0029]

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, an undercoat agent which is tack-free by being irradiated with light after being applied to an inner layer circuit board is regenerated. The surface is smoothed by melting and the thermosetting insulation adhesive coated on the copper foil maintains its thickness, so it is a multilayer printed wiring board with excellent board thickness control without depending on the residual rate of the inner copper foil. Can be produced. 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. 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]

 1 Inner Layer Circuit Board 2 Inner Layer Circuit 3 Undercoat Agent 4 Thermosetting Insulating Adhesive 5 Copper Foil 6 Hard Roll 7 Multilayer Printed Wiring Board

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H05K 3/46 T 6921-4E

Claims (10)

[Claims] 1. A light / thermosetting undercoat material comprising the following components (a), (b), (c) and (d): (A) Epoxy resin in a solid state at room temperature, (b) epoxy resin curing agent, (c) diluent composed of photopolymerization and heat-reactive monomer, and (d) photopolymerization initiator. 2. The light according to claim 1, wherein the component (a) is an epoxy resin having a molecular weight of 500 or more and which is in a solid state at room temperature.
Thermosetting undercoat material. 3. 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 as the component (c). Light / thermosetting undercoat material. 4. The photo / thermosetting undercoat material according to claim 1, wherein the component (c) is glycidyl methacrylate. 5. The component (a) is an epoxy resin having a molecular weight of 500 or more and which is in a solid state at room temperature, and the component (c) is one or more acryloyl group or methacryloyl group in one molecule, and one or more glycidyl. The photo- and thermosetting undercoat material according to claim 1, which is a diluent comprising a photopolymerizable and thermoreactive monomer having a group. 6. The light / thermosetting undercoat material according to claim 1, wherein the component (a) is an epoxy resin having a molecular weight of 500 or more and which is in a solid state at room temperature, and the component (c) is glycidyl methacrylate. 7. An inner layer circuit board is coated with the light / thermosetting undercoat material 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. 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 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. 9. The thermosetting insulating adhesive comprises an epoxy resin and its curing agent, and one component of the epoxy resin comprises a bisphenol A type epoxy resin or a bisphenol F type epoxy resin having a weight average molecular weight of 10,000 or more. 7. The method for manufacturing a multilayer printed wiring board according to 7. 10. The thermosetting insulating adhesive comprises an epoxy resin and its curing agent, and one component of the epoxy resin comprises a bisphenol A type epoxy resin or a bisphenol F type epoxy resin having a weight average molecular weight of 10,000 or more. 8. The method for manufacturing a multilayer printed wiring board according to item 8.