JP3046201B2 - 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 relates to a method for manufacturing a multilayer printed wiring board using a new photo-thermosetting type interlayer insulating resin material capable of two-step curing of light and heat.

[0002]

2. Description of the Related Art As a conventional method of manufacturing a multilayer printed wiring board, a circuit is first formed on a double-sided copper-clad board by etching, the circuit surface is roughened, and a glass cloth base material is impregnated with epoxy resin. This was a process in which one or more prepreg sheets that had been semi-cured were stacked, and a copper foil or a single-sided copper-clad board was further laminated thereon, followed by heat integration by a hot press. In this process, a glass cloth base material must be impregnated with epoxy resin and semi-cured once to make a prepreg sheet. there were. In addition, since the residual copper foil ratio of the patterned inner layer material differs, it is necessary to prepare various types of prepregs with different amounts of resin and melting behavior in order to adjust the interlayer thickness. Since the base material is used, it is difficult and extremely costly to reduce the thickness of the interlayer, and there is a problem in terms of electric characteristics that the dielectric constant is increased due to the glass cloth.

[0003] In order to solve these problems, in recent years, various techniques have been reported in which a glass cloth substrate is not used for an interlayer insulating layer. For example, there is a method using a thermosetting epoxy resin coating or film, a polyimide resin coating or film, a thermoplastic heat-resistant resin film, or a photocurable epoxy interlayer insulating film.

[0004]

First, in the above method, when a film type is used as the interlayer insulating material, the inner layer circuit board has irregularities of the patterned circuit, so that no bubbles remain. In order to do so, the film lamination must be performed in a reduced pressure environment, which requires extensive equipment. Further, since the film follows the unevenness of the circuit, surface smoothness cannot be obtained, which causes peeling of the etching dry film at the time of pattern processing and poor soldering at the time of component mounting.

[0005] Next, when a thermosetting resin coating agent is used as an interlayer insulating material, since screen printing and the like are performed on one side at a time, the substrate is warped due to curing shrinkage of the resin, and processing of an extremely thin plate or the like is performed. Will be difficult. Further, in simultaneous double-sided processing such as a dipping method, it is possible to suppress warpage to some extent, but in any case, a long time is required for heat curing.

In the present invention, since a liquid photo-thermosetting type interlayer insulating resin material is used, it can be easily filled without leaving air bubbles in the copper foil circuit gap of the core material. Then, the additive adhesive sheet can be laminated or pressed with a heated roll or hot plate to re-melt the interlayer insulating resin material, thereby smoothing the surface. In addition, by subsequently heating and curing, it becomes possible to increase the adhesion between the temporarily cured interlayer insulating resin material and the additive adhesive.

[0007] In particular, when laminating or pressing an additive adhesive sheet, if the temporarily cured interlayer insulating resin material is fluidized and filled only in the recesses of the circuit, the thickness accuracy of the additive adhesive sheet is reduced. It can be easily and precisely controlled only by the thickness of the adhesive layer, and therefore, the interlayer thickness can be made extremely thin.

[0008]

According to the present invention, as an interlayer insulating resin material, 100 parts by weight of an epoxy resin, 1 to 30 parts by weight of an epoxy resin curing agent, 1 to 100 parts by weight of a photocurable resin, and a photocurable resin After applying a photo-thermosetting type interlayer insulating resin material comprising 1 to 10 parts by weight of a photopolymerization initiator to 100 parts by weight on an inner circuit board, it is cured by light irradiation,
The present invention relates to a method for manufacturing a multilayer printed wiring board, which comprises laminating or pressing an additive adhesive sheet on this interlayer insulating resin material under heating, and heat-curing to integrate it. In the interlayer insulating material, those in which the photocurable resin is an epoxy resin have excellent compatibility with the epoxy resin, and when the epoxy resin and the photocurable resin are both liquid, do not require a solvent. It can be easily mixed in a short time, and has high reliability as a printed wiring board. Further, by using a solvent-free system, the amount of curing shrinkage after heating is suppressed, and it becomes extremely easy to maintain the surface smoothness without depending on the copper foil circuit pattern of the core material.

Therefore, the epoxy resin to be used is preferably a bisphenol A type epoxy resin having an average molecular weight of 300 to 500. If the average molecular weight is more than 500, the viscosity increases or the solidification occurs, which is not preferable in terms of handling.
The photocurable resin is preferably a liquid acrylate resin, and among them, bisphenol A epoxy acrylate, bisphenol F epoxy acrylate, novolak epoxy acrylate, or urethane acrylate is more preferable.
It is composed of 1 to 100 parts by weight per 0 parts by weight. The average molecular weight of the acrylate resin is preferably from 500 to 1500, and if the molecular weight is higher than that, the acrylate resin becomes high in viscosity and solidified, similarly to the epoxy resin. The tackiness, hardness, and the like of the resin surface after photocuring are adjusted by the amount of the acrylate. If the amount of the acrylate resin exceeds 100 parts by weight, the mechanical properties, heat resistance, and chemical resistance deteriorate, which is not preferable.

[0010] The epoxy resin curing agent is preferably an imidazole-based compound having excellent heat-curing properties.
Ethyl-4-methylimidazole and microencapsulated 2-methylimidazole can be used. The amount of the epoxy resin curing agent used is 1 to 30 parts by weight based on 100 parts by weight of the epoxy resin. If the amount is less than 1 part by weight, there is almost no compounding effect. If the amount is more than 30 parts by weight, the preservability of the resin material is reduced, and the properties after curing are undesirably reduced. Photopolymerization initiator is a radical polymerization initiator, benzoin ether type, benzophenone type, ketal type,
Acetophenone type, thioxanthone type, etc. can be used,
In particular, 1-hydroxycyclohexyl acetophenone and 2,2-dimethoxy-1,2 which are excellent in moldability and cured product characteristics.
-Diphenylethan-1-one is preferred. The amount of the photopolymerization initiator is 1 to 100 parts by weight of the photocurable resin.
To 10 parts by weight. When the amount is less than 1 part by weight, the effect of the compounding is small, and when the amount is more than 10 parts by weight, the curing is too fast and uniform curing is hindered, resulting in a deterioration in curing characteristics.

The above epoxy resin, acrylate resin,
When applying photo- and thermosetting interlayer insulating resin consisting of epoxy resin curing agent and photo-initiator to the roughened inner layer circuit surface, use screen printing, roller coater, curtain coater, etc. to coat one or both sides After doing
Light curing is performed once with an exposure machine such as a UV irradiation conveyor. After that, an additive adhesive sheet is adhered to the surface. By laminating with a hard roll or the like heated at this time, the resin can be re-melted and surface smoothness can be obtained. The light-cured resin is completely cured by subsequent thermal curing, and firmly adheres to the additive adhesive. Subsequently, electroless plating is performed by a normal process to form a surface circuit layer. The additive adhesive sheet is generally formed by coating a plastic resin film or a metal foil with an adhesive obtained by mixing an organic or inorganic component soluble in an alkaline oxidizing agent with a thermosetting resin such as an epoxy resin or a phenol resin. It is a film.

[0012]

According to the present invention, by using the above-mentioned photo-thermosetting type interlayer insulating resin material, it is possible to laminate or heat under heating without leaving bubbles by using a conventional coating equipment. By pressing, an interlayer insulating layer with improved surface smoothness can be formed. This is because by using liquid epoxy resin and acrylate resin without solvent, the filling property between circuits is enhanced, and at the same time, the amount of shrinkage after thermosetting is minimized. The reason why the additive adhesive can be firmly bonded is that photo-curing is a semi-curing treatment, and the two layers can be completely integrated by subsequent heat curing.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. (Example 1) 100 parts by weight of bisphenol A type epoxy resin (manufactured by Yuka Shell Epoxy: Epicoat 828), 10 parts by weight of bisphenol A type epoxy acrylate resin (manufactured by Showa Polymer: Lipoxy SP-1507), epoxy resin curing agent ( Yuka Shell Epoxy: EMI-24-C
N) A composition comprising 10 parts by weight and 0.5 part by weight of a photopolymerization initiator (manufactured by Ciba-Geigy: Irgacure 184) was thoroughly stirred with a homomixer, and vacuum degassed at 50 ° C.

An inner-layer circuit board was prepared by patterning a glass-epoxy double-sided copper-clad laminate having a substrate thickness of 0.1 mm and a copper foil thickness of 35 μm. Then, sodium chlorite 31 g / l,
Sodium hydroxide 15g / l, sodium phosphate 12g
/ L of an alkaline aqueous solution at 95 ° C for 2 minutes to roughen the circuit surface, apply the above mixed resin to a thickness of about 50 µm using a curtain coater, and apply 80 µm using a UV conveyor.
Ultraviolet irradiation was performed with two W / cm high-pressure mercury lamps under the condition of about 2 J / cm, and photocuring was performed. Next, an epoxy resin-based additive adhesive sheet containing fine powdered silica is roll-laminated at 100 ° C. on the above-mentioned photocured resin on the surface of the inner circuit board, and is heated and cured at 140 ° C. for 20 minutes to form a multilayer printed wiring. A substrate was prepared.

(Example 2) A double-sided roughening using a 35-μm-thick copper foil previously roughened on both sides as a glass-epoxy double-sided copper-clad laminate having a substrate thickness of 0.1 mm for forming an inner circuit board. An interlayer insulating resin was applied and light-cured in the same manner as in Example 1 except that a copper-clad laminate was used, and an additive adhesive sheet was laminated thereon and heat-cured.

COMPARATIVE EXAMPLE A solvent-based polyimide resin for undercoat (resin content: 70%) was applied on the inner circuit board in the same manner as in Example 1, and cured by heating at 180 ° C. for 60 minutes. The same additive adhesive sheet as in Example 1 was laminated and further heated and cured at 180 ° C. for 20 minutes.

Each multilayer printed wiring board thus obtained has the characteristics shown in Table 1.

Table 1 Example 1 Example 2 Comparative Example ───────────────── Surface smoothness (μm) 3.0 3.0 25.0 Heat resistance to moisture absorption solder ○ ○ ○ ─────────── ────────────────

(Measurement method) 1. Surface smoothness: JIS B 0601 R (max) Hygroscopic solder heat resistance test Hygroscopic conditions Pressure cooker treatment 125 ℃, 30
Min Test conditions n = 5, all without swelling at 280 ° C for 120 seconds ○

[0020]

As described above, a multilayer printed wiring board in which an insulating resin layer is formed on both sides of a double-sided copper-clad board whose circuit surface has been roughened, and an additive adhesive sheet is laminated thereon. In the manufacturing method of (1), the two-step curing type of light and heat is used for the interlayer insulating resin, so that it can be quickly cured by light immediately after application, and there is no thermal stress. Can laminate the additive adhesive sheet. Also,
When laminating an additive adhesive sheet, the surface can be smoothed with a heated hard roll or press and completely cured by heating, so the adhesion between the interlayer insulating resin and the additive adhesive can be increased Becomes

Claims (4)

(57) [Claims] 1. A method of manufacturing a multilayer printed wiring board, comprising the following steps (A) to (D). (A) a step of etching the double-sided copper-clad board to form an inner layer circuit, (B) a step of roughening the surface of the inner layer circuit, (C) 100 parts by weight of epoxy resin on both or one side of the obtained inner layer circuit board 1 to 30 parts by weight of an epoxy resin curing agent, 1 to 100 parts by weight of a photocurable resin, and 1 to 10 parts by weight of a photopolymerization initiator with respect to 100 parts by weight of a photocurable resin. (D) laminating or pressing the additive adhesive sheet on the interlayer insulating resin material under heating, and heating and curing to integrate the resin onto the interlayer insulating resin material; 2. A method for manufacturing a multilayer printed wiring board, comprising the following steps (A) to (C). (A) a step of forming an inner layer circuit by etching a double-sided roughened copper clad board obtained by laminating and molding using a copper foil previously roughened on both sides, and (B) a double-sided or single-sided obtained inner-layer circuit board. 100 parts by weight of an epoxy resin, 1 to 30 parts by weight of an epoxy resin curing agent, 1 to 100 parts by weight of a photocurable resin, and 1 to 10 parts by weight of a photopolymerization initiator based on 100 parts by weight of the photocurable resin. (C) laminating or pressing an additive adhesive sheet under heating on the interlayer insulating resin material after applying a light / thermosetting type interlayer insulating resin material, and curing by heating; Process of integrating, 3. The epoxy resin has an average molecular weight of 300 to 300.
3. The method for manufacturing a multilayer printed wiring board according to claim 1, comprising 500 liquid bisphenol A epoxy resins. 4. The photocurable resin has an average molecular weight of 500 to 500.
The method for producing a multilayer printed wiring board according to claim 1, comprising a acrylate resin of 1500.