JP3056678B2 - 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 which has excellent adhesion between an inner layer circuit copper foil and an undercoat agent and can eliminate the need for black processing.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a multilayer printed wiring board, in general, both sides of a circuit-processed core material laminated on an inner layer are subjected to an oxidation treatment called a so-called black treatment, whereby a circuit is formed. After roughening the surface, one or more prepregs obtained by applying, impregnating, and drying a thermosetting resin on a substrate were stacked, and a metal foil was further stacked on the upper surface thereof, followed by heating and pressing. The purpose of the black treatment is to obtain good adhesion with the prepreg, and since the inner layer circuit and the prepreg that have not been subjected to the black treatment have almost no adhesion at all, the black treatment is indispensable. Technology.
However, this technology applies the oxidation phenomenon of the outer copper foil of the inner circuit board by chemical treatment.
It is very difficult to manage the process, and furthermore, a great deal of equipment investment and running costs are required. Further, it has been pointed out that copper oxide has a low acid resistance and a low physical strength, so that problems are likely to occur during multilayer forming, drilling, and through-hole plating.

Japanese Patent Application Laid-Open No. Sho 53-132772 discloses a method for manufacturing a multilayer printed wiring board in which a resin layer is formed on the circuit surface of an inner-layer copper-clad laminate processed by a circuit as disclosed in the present invention.
JP-A-60-62194, JP-A-63-10879
In any of the techniques, the goal is to improve the withstand voltage, the halo resistance, the heat dissipation, and the thickness of the insulating layer by reducing the voids during molding. This is for a purpose different from that of the present invention.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a multilayer printed wiring board capable of improving the adhesion between an inner layer circuit copper foil and an undercoat agent, thereby eliminating the need for black processing. Yes, in multi-layer printed wiring boards, undercoat agent to solve the problems of adhesion with inner layer copper foil, especially inner layer copper foil not subjected to black treatment, moisture absorption heat resistance, plating solution resistance and delamination As a result of diligent studies on the composition of the present invention, the present invention has been achieved.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a multilayer printed wiring in which a prepreg impregnated with a thermosetting resin on a substrate and dried is laminated on a circuit-processed single-sided or double-sided copper-clad laminate and laminated and pressed. In the board manufacturing method, (1) a bifunctional terminal linear epoxy resin having an average epoxy equivalent of 450 to 6000, and (2) 2-undecyl on a circuit surface of the copper-clad laminate processed by the circuit. Imidazole,
An undercoat agent containing at least one of 1-cyanoethyl-2-undecylimidazole and 2,4-diamino-6 {2'-undecylimidazole (1 ')} ethyl-s-triazine as an essential component was applied and dried. Thereafter, a prepreg obtained by impregnating and drying an epoxy resin on a base material is overlapped and laminated and pressed to produce a multilayer printed wiring board.

Hereinafter, the present invention will be described in detail. An object of the present invention is to eliminate the need for black treatment of the inner layer circuit copper foil by improving the adhesion between the inner layer circuit copper foil surface and the undercoat agent as described in the section of the problem to be solved by the invention. It is an object of the present invention to provide a method for manufacturing a multilayer printed wiring board which can be performed as follows. The present inventors have conducted intensive studies on the composition of the undercoat agent. As a result, not only when the black treatment was performed, but also when the black treatment was not performed, the terminal bifunctional linear epoxy resin having a constant molecular weight, It has been found that the combination of the imidazole compound described above can secure sufficient adhesion and heat resistance to the inner layer circuit copper foil.

As the epoxy resin, a terminal bifunctional linear epoxy resin having an average epoxy equivalent of 450 to 6000, that is, a bifunctional linear epoxy resin obtained by reacting a bifunctional phenol with epihalohydrin, Use is made of, for example, a terminal bifunctional linear epoxy resin obtained by an alternating copolymerization reaction of a functional epoxy resin and a bifunctional phenol. These can be used in combination of several types. For example, bisphenol A epoxy resin, bisphenol F epoxy resin, tetrabromobisphenol A epoxy resin, propylene oxide bisphenol A epoxy resin, bisphenol S epoxy resin, biphenyl epoxy resin, 2,6-naphthol diglycidyl ether Examples thereof include a polymer, a bisphenol A type epoxy resin and a tetrabromobisphenol A copolymer, a bisphenol F type epoxy resin and a tetrabromobisphenol A copolymer, and a bisphenol S type epoxy resin and a tetrabromobisphenol A copolymer. If the average epoxy equivalent falls within the above range,
An epoxy resin having a low epoxy equivalent (low molecular weight) such as diglycidyl ether of bisphenol A can be blended. Further, a brominated epoxy resin can be used for flame retardation.

Reference will be made to the molecular weight of the epoxy resin.
In consideration of the adhesion to copper that has not been subjected to black treatment, it has been found that the higher the molecular weight, the higher the adhesion, but the solder heat resistance after moisture absorption tends to deteriorate. Although there are some differences in the absolute value depending on the base skeleton of the epoxy resin and the base skeleton of the aromatic polyamine,
This trend remained almost the same. The inner circuit peel strength required for practical use of epoxy-based multilayer printed wiring boards (FR-4 grade etc.) is generally 0.5 kN /
m, and the peel strength of the inner copper foil not subjected to the black treatment was at a practically minimum level by using an epoxy resin having an average epoxy equivalent of 450. On the other hand, if the weight average epoxy equivalent exceeds 6000, the necessary moisture absorption heat resistance is not exhibited even though the inner layer peel strength not subjected to the black treatment is a sufficient level of 1.1 kN / m. It is considered that this is because the epoxy groups, which are crosslinking sites, are too far apart.

As a curing agent or a curing accelerator for improving the curability of the undercoat agent, an imidazole-based curing accelerator, which is a general curing accelerator for epoxy resins, is used. And 2-undecylimidazole, 1-cyanoethyl-2-undecylimidazole or 2,4-diamino-6 {2′-undecylimidazole (1 ′)} ethyl-s-triazine for improving interlayer adhesion. Use alone or in combination. The amount of these curing accelerators is preferably from 0.4 to 1.8 parts by weight based on 100 parts by weight of the epoxy resin. If the addition amount exceeds 1.8 parts by weight, the curing speed is too fast to deteriorate the moldability, and the solder heat resistance after moisture absorption and the interlayer adhesion are not compatible, or both properties are deteriorated. On the other hand, if the addition amount is less than 0.4 parts by weight, heat resistance becomes particularly insufficient due to insufficient curing, and the adhesiveness also decreases.

When the above composition is applied to the inner layer circuit board, it is possible to adjust the viscosity with a solvent. Solvent species include acetone, methyl ethyl ketin, toluene, xylene, ethylene glycol monoethyl ether and its acetate compound, propylene glycol monoethyl ether and its acetate, dimethylformamide, methyldiglycol, ethyldiglycol, methanol, ethanol, etc. Is mentioned.

In addition, depending on the method of application, an inorganic filler may be added to impart thixotropy and heat resistance. For example, aluminum hydroxide, hydrated silica, alumina, antimony oxide, barium titanate,
Colloidal silica, calcium carbonate, calcium sulfate,
Examples include mica, silica, silicon carbide, talc, titanium oxide, quartz, zirconium oxide, zirconium silicate, boron nitride, carbon, graphite, and the like.

A coupling agent can be added to improve the adhesion to copper or the adhesion to the inorganic filler. As the coupling agent, a silane coupling agent,
Titanate-based coupling agents, aluminum chelate-based coupling agents, and the like can be used. For example, chloropropyltrimethoxysilane, vinyltrichlorosilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, N -Β (aminoethyl) γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, isopropyl triisostearoyl titanate, isopropyl trimethacryl titanate, isopropyl tri (dioctyl phyllophosphate) titanate, isopropyl isostearoyl di (4- Aminobenzoyl) titanate and the like.

Further, in order to have a defoaming function and a foam breaking function, it is also possible to add a silicone-based defoaming agent, an acrylic-based defoaming agent, a fluorine-based surfactant and the like. Furthermore, it is generally known that toughness is very effective for improving the peel strength of copper foil. For example, carboxy terminated butadiene acrylonitrile rubber (CTBN manufactured by Ube Industries, Ltd.), epoxy-modified polybutadiene rubber and the like can be added.

As a method for applying the undercoat agent, a roll coater, a curtain coater, a casting method,
There are methods such as spinner coater and screen printing,
Coating is possible by either method. Further, the method is not limited to the above-described coating method as long as the method can apply the inner circuit surface without leakage. In any method, since the undercoat agent has an optimum viscosity required, depending on the application method, it is necessary to adjust the reactive diluent, the type of solvent, the type of inorganic filler, the particle size, and the amount of compounding. .

The cured state of the undercoat agent will be described. The cured state is generally A, which is a completely uncured state.
It can be divided into a stage state, a B-stage state which is a semi-cured state, a gel state which has been further cured, and a C-stage state which is a completely cured state. Although any state can be used for this purpose, handling is facilitated by proceeding the reaction in a tack-free state or higher.

By using the undercoating agent of the present invention, the black processing conventionally required for a multilayer printed wiring board becomes unnecessary. Therefore, it is expected that the number of man-hours spent for quality control in the black processing step and the production cost are reduced, and the absence of black processing does not cause a halo phenomenon, so that high-density wiring can be easily achieved. Furthermore, since an undercoat layer is formed on the upper surface of the copper-clad laminate that has been subjected to the circuit processing, the circuit pattern gap can be filled in advance with a resin.
Molding can be performed without leaving air bubbles. Accordingly, the amount of resin of the prepreg and the fluidity during heating have been changed depending on the residual ratio of the copper foil in the inner layer circuit, but this is no longer necessary. That is, since the thickness accuracy does not depend on the residual ratio of the copper foil in the inner layer circuit, it is possible to use only a small number of types of prepregs, so that the prepregs can be stored and managed in a small variety. Further, the time required for filling the etched portion of the inner layer copper foil of the prepreg becomes unnecessary. Conventionally, the heating rate was set to 2 to 5 ° C./min because it was necessary to secure time for defoaming, so that one press time was 140 minutes or more. The press time can be reduced to about 80 minutes or less because the temperature can be increased to about 15 ° C./min, the manufacturing cost is greatly reduced, and the man-hours spent on quality control and inventory control are also significantly reduced. Become so.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments.

Example 1 100 parts by weight of diglycidyl ether bisphenol A (weight average molecular weight: 1600) was dissolved in 120 parts by weight of butyl cellosolve acetate.
0.8 parts by weight of 2,4-diamino-6 {2'-undecylimidazole (1 ')} ethyl-s-triazine was added and dissolved therein. Further, 80 parts by weight of hydrophobically treated calcium carbonate having an average particle size of 1 to 2 μm, ultrafine silica 2
After adding 0 parts by weight and 1 part by weight of γ-glycidoxypropyltrimethoxysilane, the mixture was kneaded with a three-roll mill.
Defoaming was performed with a vacuum defoamer at a degree of vacuum of 3 mmHg for 5 minutes to obtain an undercoat agent. Next, base material thickness 0.1m
The glass-epoxy double-sided copper-clad laminate having a thickness of 35 μm and a copper foil thickness of 35 μm was subjected to surface processing and soft etching to remove rust prevention treatment, and then circuit processing was performed by etching. Normally, black processing is performed after circuit processing, but the black coating is not applied, the above-mentioned undercoat agent is screen-printed on one side of the inner layer material, and then heated at 120 ° C. for 5 minutes in a drier to obtain a tack-free state. After that, an undercoat agent was applied to the opposite surface in the same manner and dried.

Further, a 100 μm thick FR-4 prepreg (EI-6765, manufactured by Sumitomo Bakelite Co., Ltd.) obtained by impregnating and drying an epoxy resin on a base material is laminated one by one on both sides of the dried undercoat agent. Then, a copper foil having a thickness of 18 μm was laminated one by one on the upper surface, and the material was heated and cured by a vacuum press at a maximum temperature of 170 ° C. for 80 minutes including temperature rise and cooling to obtain a multilayer printed circuit board. . The properties were evaluated and the results are shown in Table 1. Since no oxidation treatment was applied to the inner circuit board, no halo phenomenon occurred when through-hole plating was performed.

(Examples 2 to 10) A multilayer printed wiring board was produced in the same manner as in Example 1 except that the resin composition of the undercoat agent was changed as shown in Table 1, and the characteristics were evaluated. . Table 1 shows each resin composition and evaluation results.
Shown in As in the first embodiment, no halo phenomenon occurs.

[0021]

[Table 1]

C11Z: 2-undecylimidazole C11ZA: 2,4-diamino-6 {2′-undecylimidazole (1 ′)} ethyl-s-triazine C11Z · CN: 1-cyanoethyl-2 -Undecylimidazole 2E4MZ: 2-ethyl-4-methylimidazole 2P4MZ: 2-phenyl-4-methylimidazole

Comparative Example 1 An undercoat agent was obtained in the same manner as in Example 1 except that 2-ethyl-4-methylimidazole was used as an imidazole compound as a curing accelerator. Hereinafter, a multilayer printed wiring board was manufactured in the same manner as in the example. Table 2 shows the evaluation results of the characteristics. No halo phenomenon occurred as in the example.

(Comparative Examples 2 to 8) A multilayer printed wiring board was prepared in the same manner as in Example 1 except that the resin composition of the undercoat agent was changed as shown in Table 2, and the characteristics were evaluated. . Table 2 shows the respective resin compositions and evaluation results. No halo phenomenon occurred as in the example.

(Comparative Example 9) An inner layer circuit board was produced in the same manner as in the Examples and Comparative Examples except that no undercoat agent was applied and oxidation treatment was carried out, thereby producing a multilayer printed wiring board. . Table 2 shows the evaluation results of the characteristics. The halo phenomenon occurs due to the oxidation treatment.

Comparative Example 10 A multilayer printed wiring board was produced in the same manner as in Comparative Example 1, except that the inner surface circuit board was subjected to an oxidation treatment (black treatment) on the circuit surface. Table 2 shows the evaluation results of the characteristics.
Shown in The halo phenomenon occurs due to the oxidation treatment.

[0027]

[Table 2]

(Measurement method) Formability: circular etched part with a diameter of 20 mm (A)
After preparing a multilayer printed wiring board using an inner circuit board having 100 pieces, etching the surface copper foil, observing the presence or absence of voids in A, and determining the void generation rate (%) from the number of voided A. I asked. 2. Interlayer adhesion: A multilayer printed wiring board was prepared by the method described in the Examples or Comparative Examples except that an inner layer circuit board having a circuit only on one side was used, and the inner layer circuit board and the prepreg were peeled off. The peel strength was determined, and the result was defined as interlayer adhesion. 3. Moisture absorption solder heat resistance: PCT treatment of multilayer printed wiring board (125 ° C, 0.5 hours) and solder bath at 260 ° C
After immersion for 2 seconds, the presence or absence of blisters was observed.

(Evaluation Criteria) Evaluation was made according to the evaluation criteria shown in Table 3.

[Table 3]

[0030]

The method for producing a multilayer printed wiring board of the present invention has excellent adhesion between a copper foil and an undercoat agent.
Therefore, the black processing, which has been required for manufacturing a conventional multilayer printed wiring board, becomes unnecessary. Therefore, since the halo phenomenon does not occur, high density wiring can be easily achieved,
Further, reductions in man-hours spent on quality control in the black processing step and reductions in production costs are expected. In addition, since an undercoat agent is applied in advance to bury the steps in the inner circuit, there are no air bubbles in the gaps between the circuits, and voids are generated even without long-time pressurization by a conventional vacuum press. Without doing so, good moldability can be obtained. At the same time, it is not necessary to change the type of prepreg according to the residual copper foil ratio of the inner circuit, so that the manufacturing time of the multilayer printed wiring board can be significantly reduced. In addition, it is expected that the road to the automation of the prepreg set, which requires a huge amount of man-hours at present and is performed manually, will be opened.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-154096 (JP, A) JP-A-6-279569 (JP, A) JP-A-7-245480 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H05K 3/46 B32B 15/08

Claims (2)

(57) [Claims] 1. A method for manufacturing a multilayer printed wiring board, comprising laminating and pressing a prepreg obtained by impregnating a thermosetting resin on a substrate and drying the substrate on a circuit-processed single-sided or double-sided copper-clad laminate. On the circuit surface of the processed copper-clad laminate, (1) a terminal bifunctional linear epoxy resin having an average epoxy equivalent of 450 to 6000, and (2) 2
-Undecylimidazole, 1-cyanoethyl-2-undecylimidazole and 2,4-diamino-6 @ 2 '
-Undecyl imidazole (1 ') @-Ethyl-s-triazine is coated with an undercoat agent as an essential component, dried and then impregnated with an epoxy resin on a substrate, and dried and prepreg are laminated and laminated. A method for manufacturing a multilayer printed wiring board. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the circuit-processed copper-clad laminate is not subjected to oxidation treatment.