JPH11245336A - Manufacture of metal foil-clad laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper base material phenol resin metal foil-clad laminate of a low cost having excellent tracking resistance and solder heat resistance. SOLUTION: In the method for manufacturing a metal foil clad laminate comprising the steps of impregnating a paper base material with a phenol resin, drying it to obtain a resin impregnated paper base material, superposing a metal foil on one or both side surfaces of one or more of the resin impregnated paper base materials, and heat pressure molding it; the resin impregnated paper base material used in contact with the foil is coated with an adhesive given by a tracking resistance, the foil covered with no adhesive is used as the foil, and a thickness of coating of the adhesive is a thickness corresponding to one of the resin impregnated paper.

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 metal foil-clad laminate used for electric equipment, electronic equipment, communication equipment and the like.

[0002]

2. Description of the Related Art In recent years, consumer electronic devices have been reduced in size and density, and printed wiring boards used in these devices have tended to be denser and thinner. Along with this, copper-clad laminates used for printed wiring boards require higher levels of solder heat resistance and peeling strength, and higher levels are required for substrates to which high voltages are applied, such as televisions and power supply substrates. Tracking resistance and arc resistance are required. Conventionally, a paper-based phenolic copper-clad laminate is made by impregnating and drying a phenolic resin containing a flame retardant in a paper base such as kraft paper, and then laminating one or more of the resin-impregnated paper bases on one side or both sides. A copper foil coated with an adhesive having excellent tracking resistance was mounted thereon to produce various requirements.

[0003]

However, the tracking-resistant adhesive used for the paper-base copper-clad laminate having excellent tracking resistance is difficult to achieve both tracking resistance and soldering heat resistance. Was in a relationship. In addition, the tracking-resistant copper foil coated with this adhesive has a large shrinkage of the coated resin adhesive, and the copper foil tends to curl toward the adhesive side, and furthermore, during loading after coating and cutting, Poor slippage between the copper foil side and the adhesive surface leads to poor copper foil alignment and frequent occurrence of defects due to wrinkles, which lowers the yield.As a result, the cost of tracking resistant copper foil is lower than that of ordinary copper foil. Was expensive. At the same time as electronic devices are becoming lighter and thinner, the price of electronic devices is also shifting to lower prices. Inexpensive demands on prices are increasing.

Conventionally, in the production of a copper-clad laminate of a paper-based phenolic resin, a step of manufacturing a resin-impregnated base by impregnating a paper base with a phenolic resin and a step of applying an adhesive to a copper foil are conventionally performed separately. The laminated board was manufactured by combining the resin impregnated base material and the copper foil with the adhesive. The present invention uses a polyvinyl acetal resin modified with carboxylic acid or acrylic acid as the tracking-resistant adhesive, eliminating the trade-off between the tracking resistance and the soldering heat of the tracking-resistant adhesive, making it possible to achieve both characteristics. Becomes The reason is that, by introducing a modifier such as carboxylic acid, the crosslink density between the respective resins is increased and the above characteristics are compatible. Also, without coating the copper foil with an adhesive, the paper substrate is impregnated with phenolic resin and dried to produce a resin-impregnated substrate, and then a tracking-resistant adhesive is applied to the resin-impregnated substrate continuously using a comma coater or the like. By working and drying, the problem of curling of the copper foil and the problem of failure during cutting and stacking which the tracking-resistant copper foil has are eliminated, and the step of applying an adhesive to the copper foil becomes unnecessary. In addition, by providing a thicker adhesive resin layer that has superior electrical insulation properties compared to the resin-impregnated base material, the electrical insulation properties on the circuit side are significantly improved, resulting in copper migration between copper circuits or silver through-hole printing. This is to significantly reduce the occurrence of silver migration on the wiring board. Therefore, the present invention can provide a paper-based phenol resin metal foil-clad laminate excellent in tracking resistance and migration property at a lower cost than in the past.

[0005]

According to the present invention, a paper base material is impregnated with a phenolic resin and dried to obtain a resin-impregnated paper base material, and one or more of the resin-impregnated paper base materials are provided on one or both surfaces. In a method of manufacturing a metal foil-clad laminate in which metal foils are laminated and molded by heating and pressing, an adhesive having tracking resistance is applied to a resin-impregnated paper base material used in contact with the metal foil, and the metal foil is formed. Use metal foil that is not coated with adhesive,
And a method for manufacturing a metal foil-clad laminate characterized in that the coating thickness of the adhesive is the thickness of one piece of resin-impregnated paper. Preferably, the bonding with tracking resistance is provided. As the agent, one containing a polyvinyl acetal resin, a melamine resin, an epoxy resin, and a polyisocyanate resin modified with carboxylic acid or acrylic acid as essential components is used.

Hereinafter, the present invention will be described in detail. Preferred examples of the adhesive having excellent tracking resistance used in the present invention will be described. The polyvinyl butyral resin used for the adhesive is not particularly limited in the degree of acetalization and the degree of polymerization, but the degree of acetalization is 60 to 65 mol% and the degree of polymerization is 100.
Those having about 0 to 3000 are preferable. Further, carboxylic acid or acrylic acid is used as a modifier, and the degree of modification is 0.5 to 5 mol%.
The degree is preferred. Examples of the polyvinyl butyral resin include Denka Butyral 6000-EP (manufactured by Denki Kagaku Kogyo) and Eslek KS-5 (manufactured by Sekisui Chemical).

[0007] The epoxy resin is not particularly limited, but a bisphenol type or a novolak type is preferably used. For example, there are bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin and the like.

The melamine resin is not particularly limited. Usually, melamine (M) and formaldehyde (F) are mixed at a molar ratio of F / M = 1.5-4.0 under neutral or weak alkali, and if necessary, methanol or the like. The reaction was carried out by adding a lower alcohol. It is preferable not to use an alkali metal compound for pH adjustment. The solvent may contain water, but is preferably dissolved in an organic solvent such as alcohol and ketone. There is no particular limitation on the polyisocyanate resin, but tolylene diisocyanate (TDI), diphenylmethane isocyanate (MD
I) and the like are preferred.

The mixing ratio of each component used in the adhesive of the present invention is not particularly limited, but is usually 30 to 70% by weight (hereinafter, referred to as%) of the modified polyvinyl butyral resin, preferably 40 to 65%. %, Epoxy resin 5-4
0%, preferably 10-30%, melamine resin 5-40
%, Preferably 10 to 35%, polyisocyanate 0.5 to 10%, preferably 2 to 5%. The modified polyvinyl butyral resin acts to increase the adhesive strength to the metal foil together with the polyisocyanate resin, and the epoxy resin contributes to heat resistance, particularly to hot adhesive strength. The melamine resin imparts tracking resistance and is also effective in improving the adhesive strength when heated. By setting the proportions of these components as described above, it is possible to achieve both tracking resistance and solder heat resistance, and excellent adhesion to a metal foil is achieved.

If the polyvinyl butyral resin is less than 30%, the adhesive strength tends to decrease, and if it exceeds 70%, the solder heat resistance tends to decrease. When the epoxy resin content is less than 5%, the adhesive strength at the time of heating decreases and the electrical performance decreases. When the epoxy resin content exceeds 40%, the adhesive strength tends to decrease. 5% melamine resin
If the amount is less than the above, the adhesive strength at the time of heating decreases and the tracking resistance becomes insufficient. If it exceeds 40%, the adhesive force tends to decrease. If the polyisocyanate resin content is less than 0.5%, the adhesive strength tends to decrease, and if it exceeds 10%, the tracking resistance tends to decrease. The solvent used is not particularly limited as long as it dissolves the above-mentioned components.

[0011] The coating of the adhesive is not performed by coating a copper foil as in the conventional method, but by impregnating and drying a paper base with a phenol resin to obtain a resin-impregnated base, and then continuously impregnating the resin. An adhesive having excellent tracking resistance is applied to one side of the base material with a comma coater or the like, and the applied amount is 550 g to 600 g / m 2 and dried. By thickly applying the adhesive, one resin-impregnated base material can be reduced. The coater for applying the adhesive is not particularly limited, and may be a coater such as a roll coater, a comma coater, or a curtain coater.
Any coating method may be used as long as the adhesive can be uniformly applied to the resin-impregnated substrate. If the coating amount of the adhesive is less than 550 g, the plate thickness tends to be insufficient, and if it exceeds 600 g, the plate thickness tends to be too thick.

By applying the present invention, it is possible to achieve both the problems of the tracking resistant adhesive, that is, the compatibility between tracking resistance and solder heat resistance. In addition, the problem of the copper foil coated with the tracking resistant adhesive, that is, the problem of lowering the yield at the time of cutting and stacking due to the curl of the copper foil or poor slippage between the copper foil and the adhesive is solved. Eliminating the need for an adhesive coating process on copper foil, and reducing the number of resin-impregnated paper sheets by applying a thick coating of adhesive reduces manufacturing costs, and enables phenol resin metal foil with tracking-resistant paper base. The laminate can be provided at a lower cost than before. Further, the electric insulation is greatly improved, and the copper migration property and the silver migration property are hardly generated.

In the present invention, a roughened electrolytic copper foil, a non-roughened electrolytic copper foil, a roughened aluminum foil, or the like is used as a metal foil not coated with an adhesive. can do. In particular, when an electrolytic copper foil that has not been subjected to a roughening treatment is used, one or more conventional phenolic resin-impregnated paper base materials are laminated, and a copper foil coated with an adhesive is placed on the paper base. Although the method did not provide sufficient adhesive strength, the method of the present invention can provide good adhesive strength.

[0014]

The present invention will be described below in detail based on examples and comparative examples.

Production Example of Melamine Resin Melamine (M) and paraformaldehyde (F) are mixed at a molar ratio of F / M = 2.5, the pH is adjusted to 7.5 with ammonia, and 70 ° C. in a methanol solvent. For 2 hours to obtain a melamine resin having a resin content of 50%.

Production Example of Adhesive Polyvinyl acetal resin Denkabutyral 6000-
EP (manufactured by Denki Kagaku) 45 parts by weight (hereinafter referred to as “parts”) 15 parts of epoxy resin epicoat 1001 (manufactured by Shell Chemical)
37 parts of the melamine resin, M as a polyisocyanate
3 parts of DI was added and dissolved in a mixed solvent of equal amounts of methanol and methyl ethyl ketone so that the resin amount was 30% to obtain an adhesive.

(Example) After a paper base material is impregnated with a predetermined amount of a phenol resin containing a flame retardant and dried to obtain a resin-impregnated base material,
The adhesive was continuously applied on one side (upper surface) of the resin-impregnated base material with a comma coater to a coating amount of 550 g / m ² and dried to obtain a resin-impregnated base material with an adhesive.

Next, six phenolic resin-impregnated base materials containing a flame retardant are stacked, and the above resin-impregnated base material with an adhesive is stacked thereon so that the adhesive-coated surface is on the outside. Co., Ltd. was overlaid with a 35 μm copper foil, and heated and pressed by a conventional method to obtain a copper-clad laminate.

Comparative Example 45 parts by weight of polyvinyl butyral resin ESLEK BX-1 (manufactured by Sekisui Chemical), 15 parts of epoxy resin, 37 parts of melamine resin, polyisocyanate M
3 parts of DI was dissolved in a mixed solvent of equal amounts of methanol and methyl ethyl ketone so that the resin amount was 30%, to obtain an adhesive. This adhesive was applied to a 35 μm copper foil manufactured by Nippon Electrolysis Co., Ltd. at a resin amount of 30 g / m ² and dried to obtain a copper foil with an adhesive. Next, a phenol resin impregnated base material containing a flame retardant was
The copper foil with the adhesive was laminated thereon and heated and pressed by a conventional method to obtain a copper-clad laminate. Characteristics such as tracking resistance of the paper-based phenolic resin-clad laminate obtained in Examples and Comparative Examples were measured. The results are shown in the table below.

───────────────────────────── Test Item Example Conventional Example ──────────ト ラ ッ キ ン グ Tracking resistance (600V) 50 drops or more 50 drops or more Peel strength (25 ° C) f / cm 2.1 2.0 Solder heat resistance (260 ° C) 25 seconds or more 20 seconds ─────────────────────────────

The test method of each performance is as follows. 1. 1. Tracking resistance by IEC method 2. Peeling strength According to JIS C6481. Solder heat resistance According to JIS C6481

[0022]

As is clear from the above examples, the metal foil-clad laminate obtained by the method of the present invention has excellent tracking resistance and peeling strength, particularly excellent solder heat resistance. Therefore, according to the present invention, a copper-clad laminate manufactured by changing the adhesive coating from a metal foil to a resin-impregnated base material has performance equal to or higher than that of a copper-clad laminate manufactured by a conventional method,
The manufacturing cost can be reduced by shortening the process of the present invention.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29L 7:00

Claims (3)

[Claims] A paper base material is impregnated with a phenolic resin and dried to obtain a resin-impregnated paper base material. One or more of the resin-impregnated paper base materials are overlaid with a metal foil on one or both sides, and heated and heated. In the method for producing a metal foil-clad laminate to be pressed, an adhesive having tracking resistance is applied to a resin-impregnated paper base used in contact with the metal foil, and the adhesive is not applied as a metal foil. A method for producing a metal-foil-clad laminate, wherein a metal foil is used, and a coating thickness of the adhesive is a thickness of one resin-impregnated paper. 2. An adhesive containing a polyvinyl acetal resin modified with a carboxylic acid or acrylic acid, a melamine resin, an epoxy resin and a polyisocyanate resin as an essential component as the adhesive having tracking resistance. A method for producing a metal foil-clad laminate. 3. A roughened electrolytic copper foil, a non-roughened electrolytic copper foil, or a roughened aluminum foil is used as the metal foil not coated with an adhesive. A method for producing the metal foil-clad laminate according to the above.