JPH09148740A - Method for manufacturing multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve adhesiveness between undercoating material and copper foil and to ensure sufficient properties of laminate without black treatment of circuits on internal layer. SOLUTION: By this method of manufacturing a multilayer printed wiring board, a pre-preg consisting of a substrate impregnated with a thermosetting resin and dried is overlaid on the circuit surface of the copper-clad laminate with circuit patterns and pressed for lamination. On the circuit surface of the copper-clad laminate prepared by the above method, (1) a terminal bifunctional group straight-chain polymer epoxy resin whose average epoxy equivalent is 450 or more and 6000 or less, (2) a novolak and (3) an undercoating material whose essential component is a curing accelerator are applied and dried. Then a pre-preg consisting of a substrate impregnated with an epoxy resin and dried is overlaid and pressed for lamination.

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]

According to the present invention, a base material is impregnated with a thermosetting resin on the circuit surface of a circuit-processed copper-clad laminate.
In the method for producing a multilayer printed wiring board in which dried prepregs are laminated and pressed, in the circuit surface of the circuit-processed copper-clad laminate, (1) a terminal bifunctional having an average epoxy equivalent of 450 or more and 6000 or less. A linear polymer epoxy resin, (2) a novolac type phenolic resin, and (3) an undercoating agent containing a curing accelerator as an essential component is applied and dried, and then an epoxy resin is impregnated into a base material and a dried prepreg is overlaid. The present invention also relates to a method for manufacturing a multilayer printed wiring board, which is characterized by stacking and pressing together.

Hereinafter, the present invention will be described in detail. An object of the present invention is to provide a method for manufacturing a multilayer printed wiring board, which can eliminate the need for black treatment of the inner copper foil surface, as described in the section of the problem to be solved by the invention. The present inventor has conducted diligent studies on the composition of the undercoat agent, and as a result, not only when black treatment is performed but also when no black treatment is performed, a terminal bifunctional linear polymer epoxy resin having a constant molecular weight, It was found that by combining the novolac phenol resin and the curing accelerator, sufficient adhesion and heat resistance to the inner layer circuit copper foil can be secured.

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.

The molecular weight of the epoxy resin will be mentioned.
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, the surface thereof is blended with saturated fatty acid, calcium carbonate hydrophobically treated with a coupling agent and the like, and ultrafine particle silica hydrophobically treated, so that the epoxy resin has a smaller molecular weight. Even things can be used.

The novolak type phenolic resin which is a curing agent will be described. Phenolic compounds include bifunctional phenol compounds such as orthocresol, paracresol, paraethylphenol, parapropylphenol,
Paratertiary butylphenol, paraoctylphenol, paranonylphenol, etc., and in the case of trifunctional or higher functional phenol compounds, phenol, metacresol, 3,5-xylenol, resorcinol, catechol, bisphenol A, bisphenol F, etc. A novolac type phenol resin can be obtained by reacting one or more selected from the above with aldehydes such as formaldehyde. Among them, para-cresol is used as a phenol compound in 50
A novolac type phenolic resin containing at least wt% is preferable in terms of adhesion to the inner layer circuit. Further, a novolac type phenol resin containing 50% by weight or more of the para-cresol type novolac resin is also preferable.

The novolac type phenol resin preferably has a melting temperature of 80 to 135 ° C. If the temperature is lower than 80 ° C, many of them have a low molecular weight and the heat resistance improving effect may be small, and if the temperature is higher than 135 ° C, the properties are good, but the production is difficult. Further, the amount of free phenol is preferably 1% by weight or less for heat resistance and adhesion. The compounding amount of the novolac type phenolic resin is 0.7 to 1.4 in terms of heat resistance (especially,
This is a preferable range in order to achieve both solder heat resistance after moisture absorption) and interlayer adhesion. If the equivalent ratio is larger or smaller than the above range, the heat resistance and the adhesiveness tend to decrease.

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 is preferably 0.2 to 0.9 parts by weight with respect to 100 parts by weight of the epoxy resin. 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.

Further, if necessary, thixotropy,
It is also possible to mix an inorganic filler for the purpose of imparting solder heat resistance and adhesiveness. For example, aluminum hydroxide,
Hydrated silica, alumina, antimony oxide, barium titanate, colloidal silica, calcium carbonate, calcium sulfate, mica, silica, silicon carbide, talc,
Titanium oxide, zirconium oxide, zirconium silicate, boron nitride, carbon, graphite and the like are exemplified, but those subjected to hydrophobic treatment are preferable.

Among these, hydrophobically treated calcium carbonate can achieve 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 it is less than 30 parts by weight, the effect of improving heat resistance is insufficient,
If it exceeds 160 parts by weight, the adhesiveness will decrease,
In particular, the appearance after moisture absorption may be deteriorated and peeling may occur. In particular, the best characteristics are obtained in the range of 40 to 100 parts by weight. About the average particle diameter, 0.7 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. Further, when the average particle size exceeds 1.8 μm, the effect of improving solder heat resistance and adhesiveness becomes small.

Furthermore, if necessary, ultrafine silica particles may be added to improve heat resistance and adhesion.
As the ultrafine particle silica, one that has been subjected to a hydrophobic treatment is preferable because the dispersibility is improved. This is because SiOH that is usually present on the surface of particles is hydrophobized by further covering it with a hydrophobic group such as a methyl group or an ethyl group, and secondary disaggregation is small, dispersibility is good, and heat resistance is improved due to poor dispersion. There is little concern that the effect will decrease. It is particularly preferable for improving the moisture absorption heat resistance. The amount of the ultrafine silica is preferably 5 to 30 parts by weight based on 100 parts by weight of the epoxy resin. If the amount is less than 5 parts by weight, the effect of the compounding is small, and if the amount is more than 30 parts by weight, the viscosity of the undercoat agent is increased, so that the amount of the solvent needs to be increased and the heat resistance also decreases. Average particle size is 10-19nm
Is preferable, and more preferably 12 to 16 nm. In this range, a sufficient heat resistance improving effect is exhibited.

When the above-mentioned 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.

A coupling agent may 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.

Further, in order to have a defoaming function and a defoaming function, it is possible to add a silicone defoaming agent, an acrylic defoaming agent, a fluorinated surfactant or the like. 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.

The undercoat agent can be applied by 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 mentioned. 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, it is possible to eliminate the black treatment 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.

Furthermore, the time required to fill the inner layer copper foil etched portion of the prepreg is no longer necessary. 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.

[0023]

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

Example 1 100 parts by weight of a bisphenol A type epoxy resin (epoxy equivalent: 475) was dissolved in 120 parts by weight of ethylcarbitol. Novolak type phenol resin using para-cresol as a phenol compound there (PR-53447 manufactured by Sumitomo Dures Co., Ltd.)
Was added and dissolved in an amount such that the equivalent ratio to the epoxy group of the epoxy resin was 1. Furthermore, 0.8 parts by weight of 2,4-diamino-6 {2′-undecylimidazole (1 ′)} ethyl-s-triazine and hydrophobically treated calcium carbonate having an average particle size of 1.2 μm (Nitto Koka Kogyo Co., Ltd. ) NCC-101
0) 80 parts by weight, 20 parts by weight of colloidal silica (R-972 manufactured by Nippon Aerosil Co., Ltd.), and 1 part by weight of γ-glycidoxypropyltrimethoxysilane were added and then 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, the substrate thickness is 0.1 mm and the copper foil thickness is 35 μm.
The surface of the glass-epoxy double-sided copper-clad laminate was polished and soft-etched to remove the rust-preventive treatment, and then processed by etching. Normally, black processing is performed after circuit processing, but without performing this black processing, the above undercoat agent is screen-printed on one surface of the inner layer circuit board, and then in a dryer.
After heating at 0 ° C. for 5 minutes to make it tack-free, an undercoat agent was similarly applied to the opposite surface and dried.

Further, a 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 superposed on each of the above dried undercoat agents one by one. , 18 μm thick copper foil was laid on top of each one, and the maximum temperature reached by the vacuum press was 170 ° C.
It was cured by heating in 0 minutes 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 6) 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.

[0028]

[Table 1]

(Comparative Examples 1 to 3) Laminates were prepared and evaluated in the same manner as in Example 1 except that the composition of the undercoating agent was changed as shown in Table 2. Table 2 shows the compositions and evaluation results.

(Comparative Example 4) An inner layer circuit board was prepared in the same manner as in the Examples and Comparative Examples except that the undercoating agent was not applied and oxidation treatment was carried out, and a multilayer printed wiring board was prepared. . Table 2 shows the evaluation results of the characteristics. The halo phenomenon occurs due to the oxidation treatment.

(Comparative Example 5) A multilayer printed wiring board was produced in the same manner as in Comparative Example 2 except that the circuit surface of the inner layer circuit board was oxidized (blackened). Table 2 shows the evaluation results of the characteristics. The halo phenomenon occurs due to the oxidation treatment.

[0032]

[Table 2]

(Measurement method) 1. 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]

[0035]

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 for the inner layer circuit board, which is essential in the conventional method, can be eliminated. Therefore, since the halo phenomenon does not occur, high-density wiring can be easily achieved, and further, the man-hours spent for quality control in the black processing step can be reduced,
It is expected that production costs will be reduced.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication // B29L 31:34

Claims (4)

[Claims] 1. A circuit surface of a circuit-processed copper-clad laminate,
In a method for producing a multilayer printed wiring board, in which a base material is impregnated with a thermosetting resin and dried, and prepregs are laminated and pressed, in a circuit surface of the circuit-processed copper-clad laminate, (1) average epoxy equivalent End functional bifunctional linear polymer epoxy resin having a value of 450 or more and 6000 or less, (2) a novolac type phenolic resin, and (3) an undercoating agent containing a curing accelerator as an essential component, dried, and then an epoxy resin A method for manufacturing a multilayer printed wiring board, comprising: prepregs obtained by impregnating a base material with a substrate and drying the layers, and laminating and pressing the prepregs. 2. The method for producing a multilayer printed wiring board according to claim 1, wherein the novolac-type phenol resin is a novolac-type phenol resin containing 50% by weight or more of para-cresol in a phenol compound. 3. The method for producing a multilayer printed wiring board according to claim 1, wherein the compounding amount of the novolac type phenol resin is 0.7 to 1.4 in the ratio of the hydroxyl group to the epoxy group of the epoxy resin. 4. The method for manufacturing a multilayer printed wiring board according to claim 1, 2 or 3, wherein the circuit-processed copper-clad laminate is not subjected to an oxidation treatment.