JP3373058B2 - Manufacturing method of 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 producing a multilayer printed wiring board excellent in surface smoothness and board thickness accuracy by using an additive method without using a press.

[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 at a constant pressure, so 1 to 1.5 is required for uniform curing and molding.
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 addition, even in the case of a multi-layer circuit board for making an outer layer circuit by the additive method, an adhesive devised in the additive plating method is pressed in place of the outer layer circuit board in order to obtain adhesion between the conductor circuit and the insulating layer by electroless copper plating. It was molded.

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]

DISCLOSURE OF THE INVENTION The present invention is to manufacture a multilayer printed wiring board by a simplified method at a low cost and in a short time as compared with the method of molding by the hot plate press.
In the multilayer printed wiring board by build-up method,
When the film-shaped interlayer insulating resin layer is used, the working efficiency is significantly improved as compared with the method of forming the interlayer insulating resin layer with the prepreg. However, it is expected that air will be entrained in the stepped portion between the insulating substrate and the circuit in the inner layer circuit board, 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 are problems such as peeling and deterioration of pattern development, 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 remaining rate of the inner layer circuit pattern, the same film does not have the same plate thickness after molding. That is, when the copper foil residual rate is large and the portion to be embedded is small, the plate thickness becomes thick, and when the copper foil residual rate is small and the portion to be embedded is large, the plate thickness becomes thin. Unless changed, the same plate thickness cannot be achieved.
Further, there is a drawback in that the thickness of the obtained multilayer printed wiring board is not uniform even if the remaining copper foil rate varies depending on the location of even one inner layer circuit board.

[0006]

According to the present invention, an undercoat agent is printed on a patterned inner layer circuit board, and after semi-curing, a film-like additive adhesive is laminated, and then the undercoat agent is heated. And Adite
The present invention relates to a method for manufacturing a multilayer printed wiring board, which is characterized in that it is integrally cured with an adhesive . That is, a liquid undercoating agent is printed by a method such as screen printing to fill the copper foil circuit gap of the inner layer circuit board and to be semi-cured by heating. The semi-cured undercoating agent only temporarily retains its shape, and then, when the film-like additive adhesive is integrally cured by heating, the undercoating agent is remelted to obtain surface smoothness. be able to. At that time, since the film-like additive is adhered while maintaining the shape, that is, maintaining the interlayer thickness, a multilayer printed wiring board having excellent board thickness accuracy is produced without depending on the inner layer copper foil remaining rate. can do. Moreover, since no glass cloth is used and no press is used, it can be manufactured at a much lower cost than a conventional multilayer printed wiring board.

The undercoat agent is preferably made of an epoxy resin, for example, an epoxy resin resin.
And dicyandiamide as at least one component of the curing agent
And the curing accelerator is an imidazole compound. Specifically, epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, and other polyphenol phenolic epoxy resins are available. An epoxy compound of a polyhydric alcohol, an alicyclic epoxy resin or the like can be used. Furthermore, a brominated epoxy resin may be used to impart flame resistance.

The epoxy curing agent used is preferably finely pulverized to have a maximum particle size of 5 μm or less because of excellent dispersibility. Examples of the imidazole accelerator include 2-methylimidazole, 2-ethyl-4-methylimidazole and 2-methylimidazole.
Phenyl-4-methylimidazole, 1-butylimidazole, 2-allylimidazole, 2-phenyl-4-
Methyl-5-hydroxyimidazole, 2-phenyl-
4,5-Dihydroxymethylimidazole or cyanoethylated ones of these, and those in which the tertiary nitrogen in the imidazole ring is salted with trimellitic acid are used, and these are epoxyadducted or microencapsulated. Things are selected.

If necessary, fused silica, crystalline silica, calcium carbonate, aluminum hydroxide, alumina,
Mica, talc, white carbon, E glass powder and the like can be added. It is also possible to add an epoxysilane coupling agent for improving the adhesion and moisture resistance to the copper foil or the inner layer circuit board, a defoaming agent for preventing voids, and a liquid or powder flame retardant.

Next, the film-like additive adhesive will be described. This adhesive is preferably composed of an epoxy resin and its curing agent. As a specific example, the epoxy resin is bisphenol A having an epoxy equivalent of 2000 or more.
Type epoxy resin 20 to 50 parts by weight with an epoxy equivalent of 800
50 to 100 parts by weight of the following bisphenol A type epoxy resin or bisphenol F type epoxy resin is microdispersed. That is, a bisphenol A type epoxy resin having an epoxy equivalent of 800 or less, which is hardly soluble in an alkaline oxidizing agent after curing, is used as a matrix, and an epoxy equivalent of 20 which is partially soluble in the alkaline oxidizing agent after curing is used.
A bisphenol A type epoxy resin of 00 or more is micro-dispersed, and a linear polyhydroxypolyether portion (the following chemical formula 1) constituting this resin is swollen by an alkali and is oxidized and dissolved by permanganate to be dense. Roughness can be roughened.

[Chemical 1]

[0011]

EXAMPLES The present invention will be described below with reference to examples.

Example 1 Bisphenol A type epoxy resin (epoxy equivalent 6400, weight average molecular weight 3000)
0) 50 parts by weight (all compounding amounts below represent parts by weight) and bisphenol F type epoxy resin (epoxy equivalent 175;
Made by Dainippon Ink and Chemicals, Inc. Epicron 830) 10
0 part was dissolved in a mixed solvent of 150 parts of toluene and 50 parts of butyl acetate with stirring. 3 parts of epoxysilane coupling agent and 2 microcapsules as a curing agent
20 parts of imidazole are uniformly mixed to prepare a varnish of an additive adhesive, and this varnish is applied to a release-treated aluminum foil (carrier film) to have a thickness of 5 after drying.
Coating was performed so as to have a thickness of 0 μm to obtain a film-like additive adhesive. Next, bisphenol A type epoxy resin (Okaka Shell Epoxy product name: Epicoat 828) 10
0 parts by weight, 50 parts of bisphenol F type epoxy resin (Epiclon 830 manufactured by Dainippon Ink and Chemicals), 20 parts of finely ground dicyandiamide as an epoxy curing agent and 2P4MZ1
Part, talc (average particle diameter 10 μm) 40 parts, and defoaming agent 5 parts were kneaded with a three-roll mill to obtain the undercoat agent.

Next, as shown in FIG. 1, the substrate thickness is 1.6 m.
m, a copper foil thickness 35 μm glass epoxy double-sided copper clad laminate was patterned to obtain an inner layer circuit board (1) having an inner layer circuit (2), and after blackening the copper foil surface by a usual method,
The undercoat agent (3) was printed on both sides using a 100 mesh solid plate manufactured by Tetoron after drying with a screen printing machine so that the thickness on the copper foil would be about 20 μm (A). Then, it was semi-cured by heating at 100 ° C. for 15 minutes with a hot air dryer. The film-like additive adhesive (4) with the carrier film (5) was added thereto at a temperature of 100 ° C.
Lamination was carried out using a heated hard roll (6) under the conditions of a pressure of 2 kg / cm ² and a speed of 1.0 m / min (B), and heat-cured at 140 ° C. for 30 minutes. 0.4m diameter for through hole after removing carrier film
The hole of m was opened with an NC drill, and the via hole was opened with a laser.

Subsequently, the surface of the additive adhesive is roughened with an alkaline potassium permanganate aqueous solution at 80 ° C., a palladium-tin colloid catalyst is applied by a known method, and then a plating resist for forming a plated circuit and through holes is formed. did. Then, an electroless copper plating circuit (7) having a thickness of about 30 μm was formed in a 60 ° C. electroless copper plating bath. In this way, a multilayer printed wiring board was produced by the roll laminating method without using a glass cloth and without using a hot platen press (C).

Example 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 undercoat material was 30 μm on the copper foil.

Example 3 The inner layer circuit board is made of a base material having a thickness of 0.4 m.
A multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that a glass epoxy double-sided copper clad laminate having a copper foil thickness of 35 μm was used.

Example 4 50 parts of a bisphenol A type epoxy resin having an epoxy equivalent of 2200 and an epoxy equivalent of 20
100 parts of bisphenol A type epoxy resin of 0 is mixed solvent of toluene and cyclohexanone (mixing ratio is 7: 3) 2
Dissolve in 100 parts with stirring, uniformly mix 3 parts of epoxysilane coupling agent and 20 parts of microencapsulated imidazole as a curing agent therein to prepare a varnish of an additive adhesive, and subject this varnish to a mold release treatment. The resulting aluminum foil was coated so that the thickness after drying was 50 μm to obtain a film-like additive adhesive. Others are Example 1
A multilayer printed wiring board was produced in exactly the same manner as.

Example 5 A curing agent in which 200 parts by weight of a bisphenol A type epoxy resin having an epoxy equivalent of 200 and 30 parts by weight of a bifunctional reactive monomer are premixed with finely ground dicyandiamide and microencapsulated 2-imidazole. (Asahi Kasei Co., Ltd. HX-3612) 35 parts by weight, 30 parts by weight of fine fused silica, and 5 parts by weight of a leveling agent were kneaded with a three-roll mill to obtain an undercoating agent, and in the same manner as in Example 1. A multilayer printed wiring board was produced.

Comparative Example 1 The inner layer circuit board patterned with the undercoating agent has a thickness of 2 on the copper foil after being dried.
A multilayer printed wiring board was produced in exactly the same manner as in Example 1 except that printing was performed so as to have a thickness of 0 μm, and heating was performed at 180 ° C. for 60 minutes to completely cure the printed wiring board.

Comparative Example 2 A multilayer printed wiring board was prepared in the same manner as in Example 1 except that the undercoat material was not applied. The obtained multilayer 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 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.
Test conditions: 3 atm, 30 minutes: n = 5, all test pieces at 280 ° C., 120
The case where there was no blistering in a second was marked with ◯. 3. Embeddability: After the plated copper was removed, the embeddability in the inner layer circuit was visually judged using an optical microscope, and the embeddability was rated 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 plated copper was measured. 5. Peel strength: The peel strength between the plated copper and the insulating substrate was measured.

[0022]                               Table 1   ──────────────────────────────────            Surface smoothness Moisture absorption Solder heat resistance Embeddability Interlayer insulation layer Peel strength              (Μm) (μm) (kg / cm)   ──────────────────────────────────   Example 1 3 ○ ○ 35 1.5   Example 2 3 ○ ○ 35 1.6   Example 3 3 ○ ○ 35 1.5   Example 4 3 ○ ○ 35 1.3   Example 5 3 ○ ○ 35 1.7   Comparative Example 1 8 ○ ○ 50 1.5   Comparative Example 2 15 ×× 30 NG   ──────────────────────────────────

[0023]

According to the present invention, the semi-cured undercoating agent is remelted by a roll laminator or the like, and the film-like additive adhesive is integrated while maintaining its shape, that is, maintaining the interlayer thickness. Therefore, a multilayer printed wiring board excellent in plate thickness accuracy can be manufactured without depending on the inner layer copper foil remaining rate. In addition, the build-up method by the additive method enables the creation of fine pattern circuits, which was not possible with the conventional subtractive method, and the roughening of the adhesive to develop the circuit adhesion by electroless plating. It has become possible without using dichromic acid, which has been used conventionally. Moreover, since no glass cloth is used and no press is used, a thin substrate can be manufactured at a significantly lower cost than a conventional multilayer printed wiring board.

[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 Film-like additive adhesive 5 carrier film 6 heat rolls 7 Electroless copper plating circuit

Claims (3)

(57) [Claims] 1. An undercoat agent is printed on a patterned inner layer circuit board, semi-cured, laminated with a film-like additive adhesive, and then heated.
A method for manufacturing a multilayer printed wiring board, comprising integrally curing an undercoat agent and an additive adhesive . 2. The film-like additive adhesive ,
The epoxy resin is obtained by microdispersing 50 to 100 parts by weight of a bisphenol A type epoxy resin or an bisphenol F type epoxy resin having an epoxy equivalent of 800 or less in 20 to 50 parts by weight of a bisphenol A type epoxy resin having an epoxy equivalent of 2000 or more. 2. The method for producing a multilayer printed wiring board according to claim 1, which comprises microcapsulated imidazole and is soluble in an alkaline oxidizing agent after curing. 3. The undercoat agent is an epoxy resin resin
And dicyandiamide as at least one component of the curing agent
Hints, a method for manufacturing a multilayer printed circuit board according to claim 1 or 2, wherein the curing accelerator is an imidazole compound.