JPH03799B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a printed wiring board for forming an electric circuit on an insulating substrate.

Conventional methods for obtaining printed wiring boards include the subtract method, in which circuits are formed by etching from a copper-clad laminate, and the additive method, in which only the required circuit portions are formed by plating on a catalyst-containing insulating substrate. However, in the former subtract method, the amount of copper that is dissolved and removed by etching is much larger than the amount of copper that remains as a circuit forming part, which not only wastes a lot of resources, but also reduces the formation of etching resist.
This method involves complicated steps such as etching, and has many difficulties in terms of uniformity of circuit pattern accuracy, thinning of lines, etc. In the latter additive method, a circuit pattern is formed by plating only the required circuit parts, and although it is an excellent method from the point of view of effective use of resources, it requires a special substrate containing a catalyst as an insulating substrate. Because plating (usually electroless plating) takes a long time, a special resist with excellent durability against plating solutions is required; It is necessary to form layers according to the wiring pattern, and screen printing methods are used, but depending on the printing conditions, defects such as bridging and openings in the printed pattern may occur, so the pattern must be made thinner. There were some difficulties, such as difficulty in Another method has been proposed in which a mold is used to form a recess on an insulating substrate and a conductive paste is filled in the recess to form a circuit. Although this is an excellent method for mass-producing power distribution boards, it is not preferable when producing a wide variety of printed wiring boards because it requires molds that match the wiring patterns. Furthermore, when a conductive paste is embedded, voids, circuit bridging, etc. occur, and deterioration of electrical characteristics cannot be avoided.

This invention was made in order to eliminate the drawbacks of the above-mentioned conventional ones. After forming grooves and through holes in the wiring part on an insulating substrate, the inner walls of the grooves and through holes are selectively metallized at the same time, and a conductive layer is formed. The purpose of the present invention is to provide a method for manufacturing a printed wiring board that is inexpensive, can be highly densified, and has excellent reliability.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. In the figure, 1 is an insulating substrate, 2 and 3 are grooves and through holes in wiring portions, 4 is an activation layer, 5 is a conductive layer, and 6 is a smooth surface of the insulating substrate 1.

First, a laser beam is irradiated onto both surfaces of the insulating substrate 1 according to a predetermined wiring pattern to form grooves 2 and through holes 3 corresponding to the wiring pattern (see FIG. 2). Then groove 2,
The insulating substrate 1 in which the through holes 3 are formed is subjected to an activation treatment for electroless plating (see Fig. 3),
a groove 2 formed on the insulating substrate 1 by cleaning;
After forming the activation layer 4 only on the wall surface of the through hole 3 (see FIG. 4), electroless plating is performed to form the groove 2 on the insulating substrate 1 and the through hole 3.
A printed wiring board 7 is obtained by selectively forming a conductive layer 5 only in portions (see FIG. 5). In this way, the present invention uses a laser beam to form grooves and through-holes corresponding to the wiring pattern on the insulating substrate, making the surface of the insulating substrate rougher than the surface other than the circuit, so there is no need to form a pattern such as a resist. This makes it possible to selectively form a conductive layer. Further, by irradiating with a laser beam, it is possible to form grooves and through holes simultaneously, or by reducing the beam diameter, it is also possible to form fine patterns.

Although a laser beam was used in the above embodiment to form grooves and through holes corresponding to the wiring pattern on the insulating substrate, mechanical cutting with a cutter or the like is also effective. The wall surfaces of the grooves and through-holes in the wiring portion may be roughened compared to the smooth surface.

As a method for forming an activation layer only on the walls of grooves and through holes on an insulating substrate by cleaning after activation treatment, washing with water is sufficient, but it is more preferable to use an activation layer dissolving solution such as an acidic aqueous solution.
This is because the grooves and through holes have rough surfaces compared to the smooth surfaces on the insulating substrate, and a large amount of catalyst is adsorbed during the activation process, making it difficult to clean. Further, the same effect as in the above embodiment can be obtained by mechanical means such as brushing using the unevenness of the surface of the insulating substrate. By selectively forming activation on the inner walls of the grooves and through-holes in this way, a conductive layer can be selectively formed only on the inner walls of the grooves and through-holes without forming metsukirsist in a pattern as in the conventional example. It is something.

The material of the insulating substrate in the present invention is not particularly limited, but when using a composite material made of glass fiber and resin, etc., after forming grooves and through holes, hydrofluoric acid etc. are used to form the grooves and through holes. By selectively etching the glass fibers exposed on the inner wall, the adhesion between the conductive layer and the walls of the grooves and through-holes is improved, making it possible to obtain a more reliable printed wiring board.

As described above, according to the present invention, the wall surfaces of the grooves and through holes are roughened by drawing and forming grooves, through holes, etc. corresponding to the wiring pattern on the insulating substrate. It is now possible to form an activation layer only on the walls of the grooves and through-holes, which makes it possible to selectively form a conductive layer without patterning the plating resist, making it possible to achieve high density at low cost. , a highly reliable printed wiring board can be obtained.

[Brief explanation of the drawing]

1 to 5 are cross-sectional views showing a method of manufacturing a printed wiring board according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Groove, 3... Through hole, 4... Activation layer, 5... Conductive layer, 7... Printed wiring board. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A first step of drawing and forming grooves and through-holes according to the wiring pattern on the insulating substrate individually or simultaneously by machining or laser beam irradiation, and forming an activation layer on the entire surface of the insulating substrate and mechanically or a second step of selectively removing the activation layer other than the inner wall surfaces of the grooves and through holes by washing with water or an activation layer solution; and plating the insulating substrate after the second step. and a third step of selectively forming a conductive layer only on the inner wall surfaces of the activated grooves and through-holes.