JPH09139572A - Manufacture of multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To strengthen the adhesion of undercoat agent and copper foil even if a black processing is not executed on an inner layer circuit and to produce a sufficient laminate characteristic. SOLUTION: A multilayer printed wiring board obtained by stacking, and pressing prepregs where a base is impregnated with thermosetting resin, is dried, is stacked on a copper-clad laminate which is circuit-worked. In such a case, (1) terminal two functional normal chain-like high molecular epoxy resin whose average epoxy equivalent is more than 450 and less than 600, (2) aromatic polyamine and (3) undercoat agent where calcium carbonate whose surface is hydrophobic-processed with saturated fatty acid and coupling agent is set to be essential components as inorganic filler are applied to the copper- clad laminate which is circuit-worked. The copper foil step of the inner layer circuits is eliminated or reduced, and they are dried. Furthermore, the prepregs where the base is impregnated with epoxy resin and is dried, are laminated and stacked/pressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent adhesion between an inner layer circuit copper foil and an undercoat agent, and has a black treatment (oxidation treatment).
The present invention relates to a method for manufacturing a multilayer printed wiring board, which can eliminate the need for.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a multilayer printed wiring board, generally, a so-called black treatment is performed on a circuit surface of an inner circuit board on which circuit processing is performed on both surfaces or one surface, After roughening the circuit surface, one or more prepregs obtained by applying, impregnating, and drying a thermosetting resin on a base material are laminated, and a metal foil is further laminated 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 an essential technology. there were. However, this technology is based on the oxidization phenomenon caused by the chemical treatment of the outer copper foil of the inner circuit board. Basically, it is very difficult to control the process, and furthermore, a great deal of equipment investment and running costs are required. Is done. 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 completely different purpose from 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]

DISCLOSURE OF THE INVENTION The present invention is a multilayer print in which a prepreg obtained by impregnating a base material with a thermosetting resin and drying is superposed on one or both sides of a circuit-processed copper-clad laminate, and laminated and pressed. In the method for producing a wiring board, the circuit surface of the circuit-processed copper-clad laminate is (1) epoxy resin, (2) aromatic polyamine, and (3) inorganic filler, the surface of which is saturated fatty acid, cup A method for manufacturing a multilayer printed wiring board, which comprises applying an undercoat agent containing calcium carbonate subjected to hydrophobic treatment with a ring agent or the like as an essential component, further impregnating an epoxy resin into a base material, and laminating and pressing a dried prepreg. It is a thing.

Hereinafter, the present invention will be described in detail. An object of the present invention is, as described above, to improve the adhesion between the inner layer circuit copper foil surface and the undercoat agent, thereby making it possible to eliminate the need for black processing of the inner layer circuit copper foil. It is to provide a method. The present inventor has 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,
It has been found that a combination of an epoxy resin, in particular, a bifunctional linear epoxy resin having a certain molecular weight at the end, an aromatic polyamine and a hydrophobically treated calcium carbonate can ensure sufficient adhesion and heat resistance to the inner layer copper foil. It was

As the epoxy resin, any epoxy resin can be used as long as it is used for ordinary laminated boards. However, in order to obtain sufficient adhesion to the inner layer circuit copper foil and eliminate the need for black processing, Preferably, the average epoxy equivalent is 450
A terminal bifunctional linear epoxy resin having a molecular weight of 6000 or less, typically a bifunctional linear epoxy resin obtained by reacting a bifunctional phenol and epihalohydrin,
There are terminally bifunctional linear epoxy resins obtained by alternate copolymerization reaction of a bifunctional epoxy resin and a bifunctional phenol, and 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 polymerization Products, bisphenol A type epoxy resin and tetrabromobisphenol A copolymer, bisphenol F type epoxy resin and tetrabromobisphenol A copolymer, bisphenol S type epoxy resin and tetrabromobisphenol A copolymer, and the like. For flame retardancy, a brominated epoxy resin can be used.

For aromatic polyamines, 4,4'-
Diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, metaphenylenediamine, 4,4'-
Diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 3,3'-dimethoxy-4,4'-diaminodiphenyl, 3,3'-dimethyl-4,4'-diaminodiphenyl, 2,2 '-Dichloro-4,4'-diamino-5,5'-dimethoxydiphenyl, 2,2',
5,5'-tetrachloro-4,4'-diaminodiphenyl, 4,4'-methylene-bis (2-chloroaniline), 2,2 ', 3,3'-tetrachloro-4,4'-
Diaminodiphenylmethane, bis (4-amino-2-chloro-3,5-diethyldiphenyl) methane, 4,4 '
-Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminobenzanilide, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 9,9'-bis (4-aminophenyl) fluorene , 9,10-bis (4-aminophenyl) anthracene and the like.

Although it is disadvantageous in terms of cost, in consideration of adhesion to raw copper not subjected to black treatment, when an aromatic polyamine having a sulfide bond, a sulfone bond or a sulfoxide bond is used as a curing agent. The adhesiveness is improved by about 10 to 20% as compared with the case where it is not. It is considered that this is because any of the bonds does not directly make a chemical bond with the copper element having the oxidation number of 0, but has high chemical affinity. Diaminodiphenyl sulfone, 2,2-bis [4- (4-
Aminophenoxy) phenyl] sulfone, 3,3'-
Dimethyl-4,4'-diaminobiphenyl-6,6'-
Sulfone, 2,2-bis (4-aminophenyl) sulfoxide, 2,2-bis [4- (4-aminophenoxy) phenyl] sulfoxide, 3,3′-dimethyl-
Examples include 4,4′-diaminobiphenyl-6,6′-sulfoxide, diaminodiphenyl sulfide and the like. The amount of the aromatic amine to be blended is 1.5 to 2.5 in terms of an equivalent ratio to the epoxy resin, which is a preferable range for achieving both heat resistance (particularly, solder heat resistance after moisture absorption) and interlayer adhesion. Usually, the equivalent ratio of the aromatic amine to the epoxy resin is about 1, but in the present invention, it is preferable to make the value considerably larger than this. If the equivalent ratio is larger or smaller than the above range, the heat resistance and the adhesiveness tend to decrease.

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 layer peel strength required for practical use of epoxy resin multilayer printed wiring boards (FR-4 grade etc.) is generally 0.5k.
It is said to be N / m, and the peel strength of the inner layer not subjected to black treatment was at a practically minimum level by using an epoxy resin having an average epoxy equivalent of 450. If the average epoxy equivalent exceeds 6000, the peel strength of the inner layer not subjected to the black treatment is 1.1 kN / m, which is a sufficient level, but the necessary moisture absorption heat resistance is not exhibited. This is probably because the epoxy groups, which are cross-linking sites, are too far apart. In the present invention, as the filler, calcium carbonate whose surface is treated with a saturated fatty acid, a coupling agent and the like is blended, so that the epoxy resin having a smaller molecular weight can be used.

The curing accelerator for improving the curability of the undercoat agent is not particularly limited, but an imidazole type curing accelerator and a phosphine type curing accelerator are preferably used. As the imidazole-based curing accelerator,
2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole,
2,4'-diamino-6- [2'-ethyl-4'-methylimidazolyl- (1 ')] ethyl-s-triazine,
2-Methylimidazole / isocyanuric acid adduct, 2-
Methylimidazole / trimellitic acid adduct and the like, and as the phosphine-based curing accelerator, there are triphenylphosphine, triphenylphosphine phenol salt and the like, and more preferably, 2-undecylimidazole,
1-Cyanoethyl-2-undecylimidazole or 2,4-diamino-6- {2′-undecylimidazolyl (1 ′)} ethyl-s-triazine can be used alone or in combination. The amount of the curing accelerator based on 100 parts by weight of the epoxy resin is preferably 0.2 to 0.9 parts by weight. If the addition amount exceeds 0.9 parts by weight, the curing speed is too fast to deteriorate the moldability, and the solder heat resistance and the interlayer adhesion after moisture absorption are not compatible, or both properties are deteriorated. On the other hand, if the addition amount is less than 0.2 parts by weight, the heat resistance becomes insufficient due to insufficient curing, and the adhesiveness also decreases.

The calcium carbonate used in the present invention whose surface is hydrophobically treated with a saturated fatty acid, a coupling agent or the like can improve both solder heat resistance and adhesion. The hydrophobic treatment is necessary so as not to dissolve into acid such as etching and plating performed during the circuit processing process. The compounding amount with respect to 100 parts by weight of the epoxy resin is preferably 30 to 160 parts by weight. If the amount is less than 30 parts by weight, the effect of improving the heat resistance is insufficient. If the amount exceeds 160 parts by weight, the adhesiveness is reduced, and the appearance after moisture absorption treatment is particularly deteriorated, and peeling may occur. In particular, the best characteristics are obtained in the range of 40 to 100 parts by weight. The average particle size is 0.
The range of 7 to 1.8 μm is preferable. If the thickness is less than 0.7 μm, manufacturing costs are high, and the viscosity of the undercoat agent increases, the amount of the solvent increases, and the appearance after application and drying on a circuit-processed substrate tends to deteriorate, because the viscosity of the undercoat agent increases and the amount of the solvent increases. Not usually used because it is. Also, 1.8 μm
If the average particle size exceeds, the effect of improving the solder heat resistance and the adhesiveness becomes small.

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.

Depending on the coating method, in addition to the hydrophobically treated calcium carbonate, an inorganic filler may be added for the purpose of imparting thixotropy and solder heat resistance. For example, aluminum hydroxide, hydrated silica,
Alumina, antimony oxide, barium titanate, colloidal silica, calcium sulfate, mica, silica, silicon carbide, talc, titanium oxide, quartz, zirconium oxide, zirconium silicate, boron nitride, carbon, graphite, etc. What was done is even better.

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, a titanate coupling agent, an aluminum chelate coupling agent and the like can be used. For example, chloropropyltrimethoxysilane, vinyltrichlorosilane, γ-glycidoxypropyltrimethoxy Silane, γ-mercaptopropyltrimethoxysilane, N-β- (aminoethyl)
-Γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, isopropyltriisostearoyl titanate, isopropyltrimethacrylate titanate, isopropyltri (dioctylphyrophosphate) titanate, isopropylisostearoyldi (4-aminobenzoyl) titanate, etc. Is exemplified.

It is also possible to add a silicone type defoaming agent, an acrylic type defoaming agent, a fluorine type surfactant or the like in order to have a defoaming function and a defoaming function. Further, it is generally known that imparting toughness is very effective for improving the peeling strength of the inner layer circuit copper foil. For example, it is possible to add carboxy-terminated butadiene acrylonitrile rubber (CTBN manufactured by Ube Industries, Ltd.), epoxy-modified polybutadiene rubber, etc. However, it should be noted that a large amount of the compound tends to lower the heat resistance. is there.

As a method of 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 undercoat agent of the present invention, it is possible to eliminate the need for the black processing conventionally required for a multilayer printed wiring board. 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 the undercoat layer is formed on the upper surface of the circuit-processed copper-clad laminate, the circuit pattern gap can be filled with resin in advance, so that bubbles remain even when prepregs are stacked and laminated. It can be molded without causing it to form. 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 few types of prepregs.

Further, the time required for filling the etched portion of the inner layer copper foil of the prepreg becomes unnecessary. Conventionally, since it is necessary to secure time for defoaming, the heating rate is 2 to 5 ° C /
However, in the present invention, since the temperature rising rate can be increased to 6 to 15 ° C./minute, the pressing time can be reduced to about 80 minutes or less. It will be possible to shorten the manufacturing cost, the manufacturing cost will be greatly reduced, and the man-hours for quality control and inventory control will be greatly reduced.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments.

Example 1 100 parts by weight of diglycidyl ether bisphenol A (epoxy equivalent: 475) was dissolved in 120 parts by weight of ethyl carbitol. There 4,
When 11.7 parts by weight of 4'-diaminodiphenyl sulfide (2 times equivalent to the epoxy resin) was added and stirred, it was easily dissolved. Further, 0.5 parts by weight of 2-undecylimidazole and calcium carbonate hydrophobically treated with a saturated fatty acid having an average particle size of 1.2 μm (Nitto Koka Kogyo Co., Ltd.)
NCC-1010) 80 parts by weight, hydrophobic ultrafine particle silica R-972 (manufactured by Nippon Aerosil Co., Ltd.) 20 parts by weight,
After adding 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 0.1 mm, copper foil thickness 3
A 5 μm glass-epoxy double-sided copper clad laminate was surface-polished, soft-etched to remove the rust-preventive treatment, and then etched to form a circuit. Normally, black processing is performed after circuit processing,
Without this black treatment, the undercoat agent was screen-printed on one surface of the inner layer circuit board, then heated in a dryer at 120 ° C. for 5 minutes to be tack-free, and then the same on the other surface. An undercoat agent was applied and dried.

Further, FR-4 prepreg 100 μm thick (EI-6765 manufactured by Sumitomo Bakelite Co., Ltd.), which was obtained by impregnating a base material with an epoxy resin and drying it, was laminated on each side of the above dried undercoat agent one by one. Then, a copper foil having a thickness of 18 μm was superposed one by one on the upper surface, and the material was heated and hardened in a vacuum pressure press at 80 ° C. for 80 minutes including the maximum temperature reached and 170 ° C. to obtain a multilayer printed wiring board. . The characteristics 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 prepared in the same manner as in Example 1 except that the composition of the undercoating agent was changed as shown in Table 1, and the characteristics were evaluated. Table 1 shows the compositions and evaluation results.
As in the first embodiment, no halo phenomenon occurs.

[0025]

[Table 1]

DDDM: 4,4'-diamino-3,3'-
Diethyl-5,5'-dimethyldiphenylmethane-C11Z: 2-undecylimidazole-Filler A: aluminum hydroxide, filler B: barium sulfate, filler C: calcium carbonate, filler W: wollastonite (both (No hydrophobic treatment)

Comparative Examples 1 to 8 Laminates were prepared and evaluated in the same manner as in the above Examples except that the composition of the undercoat agent was changed as shown in Table 2. Table 2 shows the compositions and evaluation results.

(Comparative Example 9) An inner layer circuit board was prepared in the same manner as in the Examples and Comparative Examples except that no undercoat agent was applied and oxidation treatment was performed, thereby preparing 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 manufactured in the same manner as in Comparative Example 3 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.

[0030]

[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. Outline punching property: A portion 30 to 40 mm from the outer periphery of the multilayer printed wiring board was punched out in a straight line, and the peeling of the undercoat layer was measured. 3. Adhesion: A multilayer printed wiring board is manufactured by the method described in the Examples or Comparative Examples except that an inner layer circuit board having a circuit only on one side is used, and the inner layer circuit board and the prepreg are peeled off. The strength was determined, and the adhesion was determined. 4. Moisture absorption solder heat resistance: PCT treatment of multilayer printed wiring board (125 ° C, 0.5 hours) and soldering at 260 ° C for 20 hours
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]

[0033]

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.

Claims (5)

[Claims] 1. A method for producing a multilayer printed wiring board, comprising laminating and pressing a circuit-processed single-sided or double-sided copper-clad laminate with a base material impregnated with a thermosetting resin and drying the prepreg. On the circuit surface of the processed copper clad laminate, (1) epoxy resin, (2) aromatic polyamine,
And (3) the surface of the inorganic filler is saturated fatty acid,
A multilayer characterized in that after coating and drying an undercoating agent containing calcium carbonate as an essential component that has been hydrophobically treated with a coupling agent, etc., the substrate is impregnated with epoxy resin and the dried prepregs are stacked and laminated. Manufacturing method of printed wiring board. 2. An epoxy resin having an average epoxy equivalent of 45
2. The method for producing a multilayer printed wiring board according to claim 1, wherein the epoxy resin is a bifunctional linear epoxy resin having a terminal number of 0 or more and 6000 or less. 3. The method for producing a multilayer printed wiring board according to claim 1, wherein the curing agent in the undercoat agent is an aromatic polyamine having a sulfide bond, a sulfone bond, or a sulfoxide bond. 4. The calcium carbonate has an average particle size of 0.
7 to 2.5 μm, and the compounding amount of the epoxy resin 10
30 to 160 parts by weight with respect to 0 parts by weight.
2. The method for manufacturing a multilayer printed wiring board according to 2 or 3. 5. The circuit-processed double-sided copper-clad laminate is not subjected to oxidation treatment.
A method for producing the multilayer printed wiring board according to the above.