JPS641955B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for manufacturing a printed wiring board that uses an inexpensive resin material, has strong adhesive strength with metal foil, and has sufficient solder heat resistance.

Conventionally, thermosetting resins such as phenolic resins and epoxy resins have been mainly used as substrates for printed wiring boards, and these resins have been supplied and processed in the form of copper-clad laminates. Thermoplastic resins such as tetrafluoroethylene resin and polyimide resin are supplied as films, but they do not have good adhesion to copper foil, require time-consuming surface treatment, and are more expensive than laminates made of thermosetting resins. It was going around. Polyethylene terephthalate resin is supplied under the name polyester film. Although this material is inexpensive, it cannot be used as a substrate for printed wiring boards because of its lack of solder heat resistance. Polyacetal resins are also unsuitable for use in terms of soldering heat resistance, and polycarbonate resins, polysulfone resins, polyphenylene oxide resins, etc. are unsuitable for use in terms of solvent resistance (for example, the aromatic solvent methyl ethyl ketone). Laminated boards or films coated with copper foil can be used for resist printing,
Since it is made through various steps such as selective etching, resist removal, and hole drilling, the cycle of water absorption and drying is repeated. As a result, there was a problem in that the printed wiring board substrate had uneven characteristics and deteriorated characteristics, and if the production volume was 1,000 square meters per month, it would take more than a week to manufacture.

In the method of the present invention, attention is paid to inexpensive polyethylene terephthalate resin, and a resin whose soldering heat resistance has been improved by changing it to polybutylene terephthalate is used. Flame-retardant molding resin using this type of resin was developed by Celanese Company in 1970.
It was announced in 1971 by GE and Eastman Kodak, respectively. This was made by mixing glass powder or asbestos powder to improve the mechanical strength and temperature characteristics, but it was not developed into a printed wiring circuit board. The reason for this is not clear, but the first reason is probably the fact that it is difficult to adhere to adhesive-coated copper foil (of course it is difficult to adhere to copper foil alone), and the second reason is that the solder heat resistance is not sufficient. It seems to be hot.

The present invention begins by eliminating the first and second causes. First of all, in order to eliminate the first cause, the known copper foil with connecting agent is made of phenolic resin,
It has been found that adhesive properties are poor because butyral resin or synthetic rubber adhesives are used in all or part of the composition. Next, methods of directly adhering rolled or electrodeposited copper foil did not yield very good results. Finally, we discovered that it was possible to bond the molded plate without adhesive by pressing the rough surface of the copper foil, which had been made uneven by liquid honing, onto the molded plate. Although it was possible to bond the entire surface of the copper foil or aluminum foil or the foil in the form of die stamping at the same time during molding, it was also possible to bond the foil to the molding plate after molding. We also discovered that it is possible to reuse resin that has failed in molding or copper foil bonding. This was also an epoch-making fact in that resin moldings that failed to be printed with conductive paint or resistive paint conductors could be recycled and used. In other words, it is possible to recycle defective products in the process and no waste is discharged to the outside. It has also been found that by applying cuprous oxide treatment to the roughened portion on the back side of the copper foil, the roughened surface can withstand long-term storage.

Next, in order to eliminate the second cause, the soldering heat resistance conditions of 260℃ for 10 seconds (dip soldering) and 350℃ for 2 seconds (soldering iron work) are applied to the non-rough side of the copper foil. Considering the fact that the copper foil is exposed to heat, direct heat damage can be alleviated by heat dissipation on the rough surface of the copper foil and the thermal barrier effect of the cuprous oxide layer with a thickness of about 1 μm covering the rough surface. Furthermore, if glass powder, asbestos powder, etc. are mixed into the resin, the heat distortion temperature of the resin itself will apparently increase.If the stress load is ^about 5 kg/cm2, the heat distortion temperature will be 232℃ with 30% glass powder. can get. (Test method is AGTM D648). We also found that under conditions with almost no stress load, it has a non-thermal deformability of 350°C for 3 seconds and 260°C for 20 seconds. It was also possible to make a conductor by adhering copper foil during resin molding and etching it, or to make a flexible wiring board by reducing the amount of glass powder in the resin. Copper foil can be bonded at 200°C after being molded as a single resin plate, and bending can be performed at 80-150°C, and can also be used as a post-forming printed wiring board. It can also be pressed in as a flat conductor when bonding copper foil conductors.

EXAMPLE As shown in FIG. 1, a molding pellet 1 containing 30% glass powder of polybutylene terephthalate resin manufactured by Celanese Co., Ltd. and a mold 2 are prepared and molded using an injection molding machine. At this time, the runner diameter is 3.0mm,
Using a pin gate with a runner length of 60 mm, a gate diameter of 1.0 mm, and a land length of 1.0 mm, a molded plate ⁴ of 10 x 20 cm with a thickness of 1.6 mm was prepared at a temperature of 240°C and an injection pressure of 750 Kg/cm2.
I got it. It was also possible to form a conductor layer 5 in the form of tenting holes formed by pins 3 by arranging the copper foil 5 with its rough surface and cuprous oxide treated surface facing the non-inflow side of the resin.

As described above, according to the method of the present invention, one surface of the metal foil is subjected to surface roughening treatment, and a resin substrate is injection molded to this surface and bonded. and resin can be firmly bonded. Furthermore, by roughening the resin side of the metal foil, when the non-rough side of the metal foil is exposed to heat from a solder bath, heat dissipates from the rough side, improving the heat resistance of the printed wiring board. improves. Therefore, polybutylene terephthalate, which could not be used for printed wiring boards in the past, can be used, and printed wiring boards can be provided at low cost. Furthermore, if the rough side of the metal foil is treated with cuprous oxide, it can be stored for a long time even with the rough surface, and heat resistance from soldering baths etc. is less likely to be conducted to the resin side, further increasing heat resistance. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a printed wiring board manufactured by applying an embodiment of the method of the present invention. 4...Molded plate, 5...Conductor foil.

Claims (1)

[Scope of Claims] 1. One surface of a conductive metal foil is roughened, and a resin base made of a polybutylene terephthalate resin elastomer is injection molded and adhered to this surface to create a flexible material. A method for manufacturing a printed wiring board, the method comprising forming a printed wiring board. 2. The method for manufacturing a printed wiring board according to claim 1, characterized in that one surface of the metal foil is roughened and then subjected to cuprous oxide treatment.