JPS6358395B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a flexible printed wiring board used for internal wiring of electronic equipment such as television receivers, tape recorders with radio cassettes, electronic organs, and communication equipment. The aim is to improve the connection reliability of internal wiring,
The purpose is to prevent incorrect wiring, increase wiring density, and reduce wiring man-hours.

The conventional manufacturing method for flexible printed wiring boards involves etching a copper-clad polyimide film to which electrolytic copper foil with a thickness of 0.035 mm is adhered, forming the required copper conductor circuit, and then etching it with polyimide or polyester film. Generally, a method is used in which a solder-resistant coating called a coverlay is crimped onto the copper conductor, but in this case, the maximum copper foil thickness is 70μ and a large current, for example, 20 amperes, is passed through the copper conductor. The copper conductor width needs to be about 10mm. To solve this problem, a copper plate with a thickness of, for example, 0.2 mm is thermocompressed onto a plastic film and etched using a known method to form the required copper conductor circuit. It is also possible to pressure-bond the film onto the copper conductor, but etching from only one side tends to cause so-called undercuts, and the component insertion hole is formed by, for example, press punching the polyimide film sheet after etching and adhering the coverlay. Further, since the film sheet is thermocompression bonded to a copper plate without holes, air bubbles are likely to form.

For the above reasons, in the conventional manufacturing method of flexible printed wiring boards, there are constraints on the hole diameter accuracy and positional accuracy of component insertion hole machining, constraints on the matching accuracy of the metal component insertion holes of the wiring circuit and the component insertion holes of the coverlay,
The restrictions on soldering heat resistance due to air bubbles in the coverlay limited its applications and were a major concern for circuit designers.

The present invention solves the above-mentioned conventional drawbacks, and aims to provide a flexible printed wiring board that is highly mass-producible and inexpensive.

Hereinafter, the present invention will be explained with reference to drawings of embodiments, FIGS. 1 to 9.

A rolled copper plate 1 with a thickness of 0.25 mm shown in FIG. 1 is used as a conductor material. In addition, as an electrically insulating plastic film, the thickness is 0.025 mm as shown in Figure 2.
A polyimide film sheet 2 with a thickness of 0.025 mm coated with a thermosetting adhesive is used. First, as shown in FIG. 3, a circuit is printed on one side of the rolled copper plate 1 by screen printing or photography, and an etching resist is printed on the entire surface of the other side, and then etched with a ferric chloride solution. Then, the desired conductor circuit 3 is formed halfway. Next, as shown in FIG. 4, required through holes 4 corresponding to conductive circuits are provided on the polyimide film 2. Next, a polyimide film 2 is thermocompression bonded to the etched surface of the rolled copper plate 1 to obtain a polyimide clad copper plate shown in FIG. Next, as shown in FIG. 6, an etching resist is printed on the other side of the rolled copper plate 1 in a circuit shape corresponding to the conductor circuit 3 and etched with ferric chloride to form a conductor with desired component insertion holes 5. A circuit 3' is formed.
Next, as shown in FIG. 7, an adhesive-backed plastic film 2' having a thickness of 0.025 mm and having through holes 6 corresponding to the lands of the conductive circuit 3' is bonded by thermocompression onto the conductive circuit 3'. The oxide film on the exposed parts of the copper surface such as the soldered parts called land 7 was removed, and a rosin-based or imidazole-based preflux was applied as an anti-corrosion treatment and the external shape was processed. A flexible printed wiring board as shown is obtained.

Note that during the second etching, a polyimide film that has already been bonded by thermocompression is used as an etching resist to reduce costs.

As described above, the flexible printed wiring board manufactured by the flexible printed wiring board manufacturing method of the present invention has improved precision of component insertion holes by etching from both sides compared to flexible printed wiring boards manufactured by the conventional manufacturing method. , it has the effect of improving solder heat resistance, etc., is also excellent in mass production, and can reduce costs, so it has great industrial value.

[Brief explanation of the drawing]

Figures 1 to 8 are perspective views showing each manufacturing process showing one embodiment of the method for manufacturing a flexible printed wiring board of the present invention, and Figure 9 is a diagram showing a finished product of the flexible printed wiring board manufactured according to the present invention. It is a sectional view showing a part. 1...Rolled copper plate, 2, 2'...Polyimide film with adhesive, 3...Conductor circuit, 3'...Conductor circuit, 4...Through hole, 5...Component insertion hole, 6...Through hole, 7...Rand.

Claims (1)

[Claims] 1. Form an etching resist in the shape of a wiring circuit on one side of a metal plate with a thickness of 0.07 to 0.5 mm, and etch the desired wiring circuit halfway through this metal plate using an etching solution to form the wiring circuit on the metal plate. bonding an adhesive-coated plastic film with a through hole corresponding to the component insertion portion by thermocompression, and forming an etching resist corresponding to the wiring circuit on the non-adhesive side of the plastic film of the etched metal plate; Etch the metal plate with an etching solution to form a component insertion hole in the desired wiring circuit and the land of the wiring circuit, and place a component insertion hole on the non-adhesive side of the plastic film of the etched metal plate at a position corresponding to the land of the wiring circuit. A method for producing a flexible printed wiring board, which comprises thermocompression bonding an adhesive-backed plastic film with through holes.