JPH09135081A - Four layer printed-wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make feasible of high density mounting having thin and smoothed surface in less dispersion in thickness by using a specific brominated bisphenol type epoxy resin etc., a specific bisphenol type epoxy resin and a specific imidazol compound for an interlayer insulating adhesive layer. SOLUTION: The compound of the interlayer insulating adhesive layer 4 coated on a copper foil 5 is made from brominated bisphenol type epoxy resin or brominated phenoxy resin in brominating percentage exceeding 20% and mean molecular weight exceeding 10000, bisphenol type resin in epoxy equivalent not exceeding 500 and imidazol compound in the melting point exceeding 130 deg.C. This brominated bisphenol type epoxy resin or brominated phenoxy resin reduces the resin flow in the molding step while sustaining the thickness of this insulating layer and providing the composition with the flexibility as well as ataining to flame retardance. Furthermore, the bisphenol type epoxy resin facilitates the coating step on the copper foil 5 while the imidazol compound is applicable for the setting agent of components.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flame-retardant material using a copper foil having an undercoat layer and an interlayer insulating adhesive layer.
The present invention relates to a layer printed wiring board.

[0002]

2. Description of the Related Art In multilayer printed wiring boards, the miniaturization and multifunctionality of electronic devices have been progressing, and the direction of higher density has been shifted. That is, the circuit is becoming thinner, more multilayered, the diameter of the via hole smaller, thinner, and the like. 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-cured are stacked on an inner layer circuit board on which a circuit has been formed, and then a copper foil is further formed thereon. It goes through the process of integrally forming by heating with a lap hot plate press. However, in this step, since the impregnated resin is reflowed by heat and cured under a constant pressure, it takes 1 to 1.5 hours to uniformly cure and mold. As described above, the manufacturing process takes a long time, and the cost is high due to the costs of the multilayer laminating press and the glass cloth prepreg. In addition, 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. 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. In a multilayer printed wiring board by the build-up method, a copper-clad insulation sheet with an insulation resin layer formed on the roughened surface of a copper foil is used, or a prepreg sheet that is semi-cured by impregnating glass cloth base material with epoxy resin is used. When a film-shaped interlayer insulating resin layer is used instead, the work efficiency is significantly improved as compared with the method of forming the interlayer insulating resin layer with a prepreg. However, it is not possible to completely remove the air in the step portion between the insulating substrate of the inner layer circuit board and the circuit, air remains, bubbles are generated, insulation failure and solder heat resistance deteriorate, and delamination occurs. It can happen and is a problem. In order to prevent this, lamination must be performed under a reduced pressure environment, and special equipment is required. 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 the same copper-clad insulating sheet or film-like interlayer insulating resin layer is used because the amount of resin to be embedded changes depending on the copper foil remaining rate of the inner layer circuit pattern. However, the plate thickness after forming is not the same. 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. Further, even if one inner layer circuit board has a difference in the copper foil residual rate depending on the location, there is a problem that the obtained multilayer printed wiring board does not have a uniform plate thickness. In such a process, it is said that the interlayer insulating adhesive coated on the copper foil undergoes a curing reaction at the time of storage, and when it is laminated on the inner layer circuit board coated with the undercoat agent, the integral curing is not performed well. There is a problem. Further, since the glass fiber base material is not used for the interlayer insulating adhesive, there is a problem that flame retardation is difficult.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a flame-retardant four-layer printed wiring board which is thin, has a small variation in thickness, and has a smooth surface and suitable for high-density mounting.

[0006]

According to the present invention, an undercoat layer, an interlayer insulating adhesive layer, and a copper foil are sequentially laminated on both sides of an inner layer circuit board made of a flame-retardant epoxy resin-impregnated glass cloth substrate. In a printed wiring board, the light / thermosetting undercoat layer has (b) a bromination rate of 20%.
With the above, a novolac type epoxy resin having a molecular weight of 500 to 4000, (b) a bisphenol type epoxy resin having a molecular weight of 500 to 2000, (c) a bisphenol type epoxy resin having a molecular weight of 500 or less, (d) glycidyl acrylate or glycidyl methacrylate, (e) Hydroxyethyl acrylate or hydroxyethyl methacrylate,
(F) A photopolymerization initiator, (g) an imidazole compound having a melting point of 130 ° C. or higher, and (h) a low-temperature-curable imidazole compound, and the interlayer insulating adhesive layer has a (b) bromination rate of 2
Brominated bisphenol type epoxy resin or brominated phenoxy resin with 0% or more and weight average molecular weight of 10,000 or more, (nu) bisphenol type epoxy resin with an epoxy equivalent of 500 or less, and (l) an imidazole compound having a melting point of 130 ° C. or more Is a four-layer printed wiring board.

That is, the present invention relates to screen printing on an inner layer circuit board made of a glass cloth base material impregnated with a flame retardant epoxy resin,
A liquid undercoating agent is applied with a roller coater, curtain coater or the like to fill the copper foil circuit gap of the inner layer circuit board, and the undercoating agent is made tack-free by irradiation with active energy rays by a UV conveyor or the like. Thereafter, the uncured or semi-cured copper foil with an interlayer insulating adhesive is laminated on one side or both sides of the inner layer circuit board coated with the undercoat agent by a heated roll or the like at the same time and bonded. Then, after laminating, heating is performed to simultaneously integrally cure the light / thermosetting type undercoat layer and the copper foil with the interlayer insulating adhesive to form a four-layer printed wiring board. When laminating, the undercoat agent is also softened by being heated by a roll and the thickness is averaged by the roll pressure, so that the surface smoothness of the copper foil surface can be obtained. At that time, since the interlayer 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, the interlayer thickness is maintained, the inner layer copper foil residual rate is reduced. The four-layer printed wiring board is excellent in plate thickness accuracy and can be manufactured without depending on the thickness of the four-layer printed wiring board without variation.

In the present invention, the undercoating agent used for the undercoating layer is to fill the copper foil circuit gap of the inner layer circuit board and smooth the inner layer circuit surface, and comprises the following components (a) to (h). It is characterized by becoming. (A) Bromination rate of 20% or more, molecular weight of 500 to 4000
Novolac type epoxy resin, (b) molecular weight 500-2
000 bisphenol type epoxy resin, (c) bisphenol type epoxy resin having a molecular weight of 500 or less, (d) glycidyl acrylate or glycidyl methacrylate,
(E) hydroxyethyl acrylate or hydroxyethyl methacrylate, (F) a photopolymerization initiator, (G) an imidazole compound having a melting point of 130 ° C. or higher, and (H) a low temperature curable imidazole compound.

The epoxy resin having a bromination rate of 20% or more and a molecular weight of 500 to 4000 of the component (a) used in the present invention is used for improving heat resistance and flame retardancy. It is a novolac type epoxy resin of novolac type or cresol novolac type, which is solid at room temperature. The melting point is usually 50 ° C. or higher.
If the bromination rate is less than 20%, the obtained four-layer printed wiring board cannot achieve flame retardancy V-0 according to UL standard. Further, 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 the upper limit of the bromination is determined by this.

The (b) component bisphenol type epoxy resin having a molecular weight of 500 to 2000 is bisphenol A type,
Examples thereof include bisphenol F type and bisphenol S type, which are solid at room temperature and are mainly used for increasing the adhesion and flexibility with the inner layer circuit board and the interlayer insulating adhesive layer, and (a) component Alternatively, it interacts with the component (c) to affect heat resistance, moldability (voidlessness), and surface smoothness. When the molecular weight exceeds 2000, the viscosity of the undercoating agent increases, the fluidity and embedding property deteriorate, and the surface smoothness deteriorates, which is not preferable. Examples of the bisphenol type epoxy resin having a molecular weight of 500 or less as the component (c) include bisphenol A type, bisphenol F type, and bisphenol S type, and are particularly those which improve curability and improve voidlessness and surface smoothness. Molecular weight 5
When it exceeds 00, the hardening of these is weakened, which is not preferable.

As the photopolymerizable and heat-reactive monomers used in the photo / thermosetting undercoating agent, the component (e), hydroxyethyl acrylate and hydroxyethyl methacrylate, and the component (d), have excellent thermosetting properties. Glycidyl acrylate or glycidyl methacrylate. These components also function as a solvent for the epoxy resin and are used as so-called solventless undercoat agents. The components (d) and (e) react with each other by irradiation with active energy rays, and the undercoat layer becomes tack-free depending on the degree of curing. Each blending ratio is 20 ~
It is appropriately determined between 80% by weight. Further, since the component (d) is epoxy-cured by imidazole, it is melt-mixed with other epoxy resins and reacts, so that the heat resistance is increased and the generation of voids is suppressed. Generally, the total amount of the monomers (d) and (e) is 20 to 100 parts by weight, preferably 30 to 70 parts by weight, based on 100 parts by weight of the total epoxy resin used.

Examples of the (f) component photopolymerization initiator include benzophenone, benzoylbenzoic acid, 4-phenylbenzophenone, benzophenones such as hydroxybenzophenone, benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, benzoin isobutyl ether, etc. Benzoin alkyl ethers, 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 4-
Acetophenones such as t-butyl-trichloroacetophenone and diethoxyacetophenone, thioxanthones, thioxanthones such as 2-chlorothioxanthone, 2-methylthioxanthone and 2,4-dimethylthioxanthone, ethylanthraquinone, butylanthraquinone and the like. Examples thereof include alkyl anthraquinones. These may be used alone or as a mixture of two or more. The amount of the photopolymerization initiator added is usually 0.1 to 1 with respect to 100 parts by weight of the photopolymerization and thermoreactive monomer.
It is used in the range of 0 parts by weight.

The (E) component epoxy resin curing agent has a melting point of 130 ° C. or higher, is solid at room temperature, has low solubility in the epoxy resin, and reacts quickly with the epoxy resin at a high temperature of 150 ° C. or higher. However, it is added so that the epoxy resin is finally cured. Specifically, 2
-Methylimidazole, 2-phenylimidazole, 2
-Phenyl-4-methylimidazole, bis (2-ethyl-4-methyl-imidazole), 2-phenyl-4-
There are methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, triazine addition type imidazole and the like. An epoxy adduct or a microcapsule of these may be used. These may be used alone or in combination of two or more.

The epoxy resin curing agent of the component (h) is a low temperature curing type, and the epoxy resin starts the reaction at 60 to 120 ° C. This curing agent causes the epoxy resin to undergo the initial reaction. Used for. When integrally curing the undercoating agent and the interlayer insulating adhesive, it is important for moldability to start the curing reaction from the side of the undercoating agent. Specifically used are imidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-. Ethyl-4-methylimidazole, 1-aminoethyl-2-methylimidazole, 1- (cyanoethylaminoethyl) -2-methylimidazole, 1-cyanoethyl-2-phenyl-4,5
-Bis (cyanoethoxymethylimidazole) and the like can be mentioned, and those obtained by epoxyadducting these or by encapsulating them can also be used. 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 1 to 10 parts by weight of the total of the (T) component and the (H) component with respect to 100 parts by weight of the epoxy resin. The ratio is appropriately determined depending on the degree of tack-free undercoating agent.

By using an epoxy resin or a phenoxy resin having a weight average molecular weight of 10,000 or more for the interlayer insulating adhesive coated on the copper foil, the shape can be maintained while maintaining its shape.
That is, since the layers are adhered while maintaining the interlayer thickness, it is possible to produce a multilayer printed wiring board having excellent board thickness accuracy without depending on the remaining rate of the inner layer copper foil and without variation in the thickness of the multilayer printed wiring board. Becomes However, this means that when laminating a copper foil with an interlayer insulating adhesive, the undercoat agent coated on the inner layer circuit board is softened by heating with a hot roll and the thickness is not averaged by the roll pressure. Cannot be realized. Further, the softening of the undercoat agent also has a great effect on the improvement of the adhesiveness with the interlayer insulating adhesive, and the melt integration reaction is also possible at the polar interface.
It also contributes to the reliability between layers. However, the curing reaction of the undercoating agent during heat curing is delayed from the curing reaction of the interlayer insulating adhesive, and when the melt viscosity of the undercoating agent is reduced more than necessary, it is affected by the curing shrinkage of the interlayer insulating adhesive, wrinkles, Molding defects such as voids may occur. On the other hand, the undercoating agent used in the present invention promotes the reaction in the low temperature range by the component (H) and suppresses the decrease of the melt viscosity more than necessary, so that it can be used even in the thermosetting molding under no pressure. It is possible to achieve good smoothness and interlayer adhesion.

In addition to the above, a photo- and thermosetting undercoating agent for a four-layer printed wiring board according to the present invention may be added with an anti-UV agent, a thermal polymerization inhibitor, a plasticizer, etc. for storage stability, 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,
An epoxy silane coupling agent that can contain inorganic fillers such as barium sulfate, mica, talc, clay, white carbon, and E glass powder to improve adhesion and moisture resistance to copper foil and inner circuit boards. An antifoaming agent for preventing voids or a liquid or powdered flame retardant may be added.

The optical / thermosetting undercoating agent for a four-layer printed wiring board of the present invention comprising these components is a solvent-free system, and fills the copper foil circuit gap of the inner layer circuit board to form an inner layer. Smooth the circuit surface. Further, it can be easily solidified by irradiation with active energy rays and can be tack-free. Ingredient (d) in the prepared undercoat agent of the present invention
First, (e) acts as a solvent, and the components (a) to
(C) and other components are melted to fill the gaps in the copper foil circuit of the inner layer circuit board, and the surface of the inner layer circuit is made into a smooth varnish state. When components (d) and (e) that act as a solvent by irradiating with active energy rays are cured, the components (d) and (e) lose their effect as a solvent as they harden and solidify. Components (a) and (b) are deposited.
At this time, the cured components (d), (e) and other components are dispersed in the solid components (a) and (c). Therefore, if the components (a) and (b) that are in a suitable tack-free solid state at room temperature are selected, the undercoating agent 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. Further, since the component (d) of the present invention cured by irradiation with active energy rays also has a thermoreactive functional group, it undergoes a curing reaction with the epoxy resin or the curing agent as the main component during the subsequent heating reaction. The product has excellent heat resistance and chemical resistance.

Next, the interlayer insulating adhesive coated on the copper foil used in the present invention is (b) a brominated bisphenol epoxy resin or brominated phenoxy resin having a bromination rate of 20% or more and a weight average molecular weight of 10,000 or more, (G) An epoxy equivalent of 500 or less bisphenol type epoxy resin and (l) an imidazole compound having a melting point of 130 ° C. or more, which is an adhesive having heat resistance and flame retardancy. The brominated bisphenol type epoxy resin or brominated phenoxy resin having a bromination rate of 20% or more and a weight average molecular weight of 10,000 or more of the component (i) reduces the resin flow at the time of molding, maintains the thickness of the insulating layer, and has a composition. It is added for the purpose of imparting flexibility to the product and achieving flame retardancy of the obtained four-layer printed wiring board. Examples of the brominated bisphenol type epoxy resin include bisphenol A type, bisphenol F type and bisphenol S type. Further, the (i) component alone has a low crosslink density after curing and becomes too flexible, and has a high viscosity when dissolved in a solvent and used as a varnish of a predetermined concentration for coating a copper foil. Workability on the coat deteriorates.
In order to improve these drawbacks, a bisphenol type epoxy resin having an epoxy equivalent of 500 or less is blended as the (nu) component. These bisphenol type epoxy resins include bisphenol A type and bisphenol F type.
Type, bisphenol S type and the like. The mixing ratio of the epoxy resin is as follows: (i) component: (nu) component = 50 to 7
0% by weight: 50 to 30% by weight. (I) 50 ingredients
If it is less than 70% by weight, the viscosity is not high and the thickness as an interlayer insulating adhesive cannot be maintained, and the smoothness of the outer layer circuit after lamination becomes poor, while if it exceeds 70% by weight, the viscosity becomes high on the contrary. , Coating copper foil is not easy,
It is difficult to maintain a predetermined thickness, which is not preferable. If the brominated rate of the brominated bisphenol type epoxy resin or brominated phenoxy resin is less than 20%, the obtained four-layer printed wiring board cannot achieve flame retardancy V-0, so 20% or more is required. is there.

As the curing agent for the component (l), it is preferable to use the same kind as the component (g) used for the undercoating agent. That is, it has a melting point of 130 ° C or higher, is solid at room temperature, has low solubility in an epoxy resin, and is 150 ° C.
It is added in order to react with the epoxy resin rapidly at the above high temperature and finally to cure the epoxy resin. Specifically, 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, bis (2-ethyl-4-methyl-imidazole),
There are 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, triazine addition type imidazole and the like. An epoxy adduct or a microcapsule of these may be used. These may be used alone or in combination of two or more. These imidazoles are fine powders and are uniformly dispersed in the epoxy resin varnish. Since the compatibility with epoxy resin is small, 100 ℃
In the following, the reaction does not proceed, and therefore the storability of the varnish can be kept good. 1 for copper foil as interlayer insulation adhesive
If the coating is performed at 00 ° C. or lower, the epoxy resin remains uncured, so that the storage stability as the adhesive can be kept good. Then, when it is laminated with an inner layer circuit board provided with an undercoat layer and then heated to 150 ° C. or higher during curing, the undercoat agent and the undercoat agent are partially melt-mixed on the contact surface, so that the epoxy resins react with each other to form a uniform cured product. Is obtained.

In addition to the above epoxy resin and curing agent, the interlayer insulating adhesive may contain a component that reacts with the epoxy resin and curing agent. For example, other epoxy resins, epoxy-reactive diluents (phenyl functional phenyl glycidyl ether nad, functional bifunctional resorcing glycidyl ether, ethylene glycol glycidyl ether, etc.,
Trifunctional glycerol triglycidyl ether etc.), resole type or novolak type phenolic resin,
Isocyanate compounds and the like. In addition to the above components, in order to improve linear expansion coefficient, heat resistance, flame resistance, etc., fused silica, crystalline silica, calcium carbonate, aluminum hydroxide, alumina, barium sulfate, mica, talc, clay, white carbon, E An inorganic filler such as glass powder may be added to the epoxy resin in an amount of 40% by weight or less. If it is blended in an amount of more than 40% by weight, the viscosity of the adhesive increases and the adhesiveness decreases. Further, an epoxysilane coupling agent for improving the adhesion to the copper foil and the moisture resistance, a defoaming agent for preventing voids, a liquid or powder flame retardant, and the like can be added.

As a solvent, an adhesive is applied to a copper foil and then 80
After drying at ~ 130 [deg.] C, one must choose what does not remain in the adhesive. For example, there are acetone, methyl ethyl ketone, toluene, xylene, n-hexane, methanol, ethanol, methyl cellosolve, cyclohexanone and the like. The copper foil with the interlayer insulating adhesive is coated with an adhesive varnish prepared by dissolving an adhesive component in a predetermined solvent at a predetermined concentration on the anchor surface of the copper foil, and then 80 to 130.
It is prepared by drying at ℃ so that no solvent remains in the adhesive. The thickness of the adhesive layer is preferably 15 to 120 μm. If it is thinner than 15 μm, the interlayer insulating property may be insufficient, and if it is thicker than 120 μm, the interlayer insulating property is not a problem, but it is difficult to prepare, and the thickness of the four-layer board is not suitable for the purpose of the present invention. .

Thus, as a photopolymerizable and thermoreactive monomer, a compound having at least one acryloyl group or methacryloyl group and at least one glycidyl group in one molecule, and at least one compound in one molecule By using a compound having an acryloyl group or a methacryloyl group and one or more hydroxyl groups in combination, the undercoat agent is made tack-free by irradiation with active energy rays, and integrally cured after lamination with a copper foil with an interlayer insulating adhesive. Is performed well, and a good four-layer printed wiring board can be manufactured.

An outline of a method of applying an undercoating agent and laminating and curing a copper foil with an interlayer insulating adhesive to achieve the object of the present invention will be described with reference to FIG. (A) Completely coat one side of the inner layer circuit (2) on the inner layer circuit board (1) using conventional coating equipment such as screen printing, roller coater, curtain coater, etc. Apply to cover thickness. If the embedding amount is insufficient, air will be entrained in the subsequent laminate. After that, it is tack-free by irradiation with active energy rays from a UV irradiation conveyor or the like. Then, the other surface of the inner layer circuit board (2) is coated with the undercoat agent (3) in the same manner. (B) A copper foil (5) with an interlayer insulating adhesive (4) is laminated on the surface. The laminator uses a pair of rolls (6) coated with silicon rubber or the like to achieve surface smoothness, and is laminated on both sides of the inner layer circuit board (2). 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 0.1 to 6 m.
/ Min. Under such conditions, the photo-curing undercoat agent can achieve surface smoothness 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 interlayer insulating adhesive. (C) Next, by heating and performing simultaneous integral curing reaction, a four-layer printed wiring board integrally formed with the undercoat agent (3) and the interlayer insulating adhesive (4) coated on the copper foil is formed. You can

[0024]

The present invention will be described below with reference to examples.
"Parts" represents parts by weight. Example 1 100 parts of brominated phenoxy resin (bromination 25%, weight average molecular weight 30,000) and bisphenol F
40 parts of type epoxy resin (epoxy equivalent 175, Epicron 830 manufactured by Dainippon Ink and Chemicals, Inc.) is MEK150
Parts with stirring, and 2 parts of 2-phenyl-4-methyl-5-hydroxymethylimidazole as a curing agent and a silane coupling agent (manufactured by Nippon Unicar Co., Ltd. A-
187) 1 part was added to prepare an interlayer insulating adhesive varnish. This varnish was applied to an 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 an interlayer insulating adhesive. Next, brominated cresol novolac epoxy resin (bromination 35%, epoxy equivalent 280, weight average molecular weight 140
0) 100 parts, bisphenol A type epoxy resin (epoxy equivalent 950, weight average molecular weight 1600) 100 parts and bisphenol F type epoxy resin (epoxy equivalent 17
5, Dainippon Ink and Chemicals, Inc. Epicron 830) 4
0 part was dissolved in 80 parts of glycidyl methacrylate and 90 parts of hydroxyethyl methacrylate, and 4 parts of 2-phenyl-4-methyl-5-hydroxymethylimidazole and 1-cyanoethyl-2-ethyl- were added thereto as a curing agent.
8 parts of 4-methylimidazole and 10 parts of a photopolymerization initiator (Irgacure 651 manufactured by Ciba-Geigy) were added and sufficiently stirred with a homomixer to obtain an undercoat agent. Furthermore,
A flame-retardant glass epoxy double-sided copper-clad laminate having a substrate thickness of 0.2 mm and a copper foil thickness of 35 μm was patterned to obtain an inner layer circuit board. After blackening the surface of the copper foil, the undercoat agent was applied to one surface of the inner circuit board by a curtain coater to a thickness of about 40 μm. After that, 8 on the UV conveyor machine
UV-irradiate with two 0 W / cm high-pressure mercury lamps under the condition of about 2 J / cm ² to create a tack-free undercoat layer by irradiation with active energy rays, and then undercoat the other surface of the inner circuit board in the same manner. A coat layer was created. After that, the temperature is 100 ℃ on the undercoat layer and the pressure is 2kg / cm.
² , Laminating speed: 0.8m / min, 2
The copper foil with the interlayer insulating adhesive was laminated using this roll and heat-cured at 180 ° C. for 30 minutes to prepare a four-layer printed wiring board.

Example 2 In an undercoating agent and an interlayer insulating adhesive, as an epoxy resin curing agent, 2
A 4-layer printed wiring board was prepared in the same manner as in Example 1 except that 2-phenyl-4-methylimidazole was used instead of -phenyl-4-methyl-5-hydroxymethylimidazole.

Comparative Example 1 In the undercoat agent,
A 4-layer printed wiring board was produced in exactly the same manner as in Example 1 except that 160 parts of glycidyl methacrylate was used instead of glycidyl methacrylate and hydroxyethyl methacrylate. << Comparative Example 2 >> A four-layer printed wiring board was produced in exactly the same manner as in Example 1 except that 180 parts of hydroxyethyl methacrylate was used in place of glycidyl methacrylate and hydroxyethyl methacrylate in the undercoat agent. <Comparative Example 3> As a curing agent for an epoxy resin as an undercoat agent, 1-cyanoethyl-2-ethyl-4-methylimidazole was not used, and only 12 parts of 2-phenyl-4-methylimidazole was used. A 4-layer printed wiring board was produced in exactly the same manner as in 1.

Comparative Example 4 As a curing agent for the epoxy resin of the interlayer insulating adhesive, 2-phenyl-4-methyl-5-
A 4-layer printed wiring board was produced in exactly the same manner as in Example 1 except that 12 parts of 1-cyanoethyl-2-ethyl-4-methylimidazole was used without using hydroxymethylimidazole. << Comparative Example 5 >> 100 parts of a brominated cresol novolac epoxy resin (epoxy equivalent: 280, weight average molecular weight: 1400) was not used as an epoxy resin in an undercoating agent, and a bisphenol A type epoxy resin (epoxy equivalent: 950, weight average molecular weight: 1600) was used. A four-layer printed wiring board was prepared in the same manner as in Example 1 except that 200 parts and 40 parts of a bisphenol F type epoxy resin (epoxy equivalent: 175, Epichron 830 manufactured by Dainippon Ink and Chemicals, Inc.) were used. <Comparative Example 6> Four layers were prepared in the same manner as in Example 1 except that a bisphenol A type epoxy resin (epoxy equivalent 6400, weight average molecular weight 30,000) was used instead of the brominated phenoxy resin of the interlayer insulating adhesive. A printed wiring board was produced. The obtained 4-layer printed wiring board has the characteristics shown in Table 1.

(Test method) Inner layer circuit board test piece: 150 μm pitch between lines, clearance hole 2.54 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 without swelling at 280 ° C. for 120 seconds were evaluated as ◯, and swelling was evaluated as x. 3. Interlayer insulating layer thickness: A four-layer 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. 4. Flame retardance: According to UL standard 94

Table 1 ─────────────────────────────────── Example Comparative Example 1 2 1 2 3 4 5 6 ─────────────────────────────────── Surface smoothness (μm) 3 3 8 3 5 20 15 35 Moisture absorption solder heat resistance ○ ○ ○ × × ○ ○ × Interlayer insulation layer thickness (μm) 50 50 55 50 50 55 55 60 40 Flame retardant V-0 V-0 V-0 V-0 V-0 V-0 V-1 V-1 ────────────────────────────────────

[0030]

According to the present invention, since the surface is smooth and the thermosetting insulating adhesive coated on the copper foil maintains the thickness,
Excellent in plate thickness control without depending on the residual rate of the inner layer copper foil 4
A layer printed wiring board could be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a layer structure of a four-layer printed wiring board of the present invention.

FIG. 2 is a schematic cross-sectional view showing a process for producing a four-layer printed wiring board (one example) of the present invention.

[Explanation of symbols]

 1 Inner Layer Circuit Board 2 Inner Layer Circuit 3 Undercoat Layer 4 Interlayer Insulation Adhesive Layer 5 Copper Foil 6 Hard Roll 7 4 Layer Printed Wiring Board

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C09J 163/00 JFL C09J 163/00 JFL H05K 1/03 630 7511-4E H05K 1/03 630D 3 / 38 6921-4E 3/38 E

Claims (1)

[Claims] 1. A four-layer printed wiring board in which an undercoat layer, an interlayer insulating adhesive layer, and a copper foil are sequentially laminated on both surfaces of an inner layer circuit board made of a flame-retardant epoxy resin-impregnated glass cloth substrate. -The thermosetting undercoat layer has a (b) bromination rate of 20% or more and a molecular weight of 500 to 4
000 novolak type epoxy resin, (b) molecular weight 50
0-2000 bisphenol type epoxy resin, (C)
Bisphenol type epoxy resin having a molecular weight of 500 or less,
(D) Glycidyl acrylate or glycidyl methacrylate, (v) hydroxyethyl acrylate or hydroxyethyl methacrylate, (f) photopolymerization initiator,
(G) A brominated bisphenol having an imidazole compound having a melting point of 130 ° C. or higher and (H) a low temperature curable imidazole compound, and an interlayer insulating adhesive layer having a (b) bromination rate of 20% or more and a weight average molecular weight of 10,000 or more. Type epoxy resin or brominated phenoxy resin, (nu) bisphenol type epoxy resin having an epoxy equivalent of 500 or less, and (l) an imidazole compound having a melting point of 130 ° C. or more, a four-layer printed wiring board.