JPS6143879B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides a through-hole printed wiring having both a through-hole having a conductive layer on the hole wall (hereinafter referred to as a "through-hole") and a through-hole having no conductive layer (hereinafter referred to as a "non-through-hole"). This invention relates to a method for manufacturing a board.

Conventionally, the method for forming both through-holes in a printed wiring board that has both through-holes and non-through-holes is to first drill holes for through-holes at desired positions in an insulating base material, then sequentially plate the panel and form the circuit pattern. After resist printing, forming a circuit pattern by etching, and removing the resist, the etched pattern is subjected to visual positioning or automatic positioning using numerical control, etc., and holes are drilled to eliminate non-through holes. A known method of forming holes was used.

However, these conventional methods suffer from errors in dimensional accuracy due to resetting the base material on the table during drilling work using an automatic drilling machine using a numerical control device or a copying manual drilling machine using a template method. A relative positional shift occurs between the through hole and the non-through hole, which may lead to a shift of the non-through hole with respect to the land after etching formation, and a defect such as land loss due to this shift. In addition, when drilling holes in etched lands, the land portions have a small contact area with the surface of the insulating base material, so the land portions may be damaged by the mechanical rotational cutting force of the drill during drilling. There was a drawback that a peeling phenomenon occurred in which the material peeled off from the insulating base material.

An object of the present invention is to provide a manufacturing method that solves the above-mentioned problems of through-hole printed wiring boards.

According to the present invention, a first through hole having a hole wall of a conductive layer and a second through hole having no conductive layer on the hole wall are formed at the land position of the printed wiring board, thereby forming a through hole printed wiring board. In the manufacturing method, the step of forming the second through hole before forming the conductive layer on the hole wall of the first through hole, and forming the conductive layer on the hole wall of the first through hole. Sometimes, a step of forming the conductive layer also on the hole wall of the second through hole, and a step of etching away the conductive layer on the hole wall of the second through hole when forming the land and the conductive circuit by etching. There is obtained a method for manufacturing a through-hole printed wiring board characterized by having the following steps.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

1 to 6 are cross-sectional views showing a method of manufacturing a through-hole printed wiring board by a conventional method, that is, a method of forming through-holes and non-through-holes, and FIGS. FIG. 3 is a cross-sectional view showing step by step a method for forming through holes and non-through holes according to the embodiment. Regarding the method of forming one through hole, the conventional method (first
Figures 7 to 6) and the method of the present invention (Figures 7 to 11)
As shown in the figure, there is no difference in the process, but in the conventional method of forming the hole on the non-through hole 2 side, the etching resist 6 is removed and then the hole is formed. (See FIGS. 5 and 6) On the other hand, in this embodiment of the present invention, holes for through hole 1 and non-through hole 2 are simultaneously drilled as shown in FIG. A feature of the present invention is that the walls of the through-holes are simultaneously plated with copper by electrolytic copper plating and electrolytic copper plating. Next, as shown in FIG. 9, when printing the conductive circuit that will become the etching resist 6, a photoresist is applied in conjunction with the so-called tenting method to cover the entire entrance of the non-through hole 2 in a film form on the electrolytic copper plating layer 5 on one surface of the board. etc. are applied. At this time, a cavity 7 smaller in diameter than the non-through hole 2 is provided in the center of the land on the side of the non-through hole 2, and an etching resist 6 is printed to expose the etching solution for removing the electrolytic copper plating layer 5 on the hole wall. Since it flows through the back surface, the circulation of the etching liquid is promoted and etching becomes easier. However, if the design of the printed wiring board allows electrolytic copper to remain on the hole wall of the non-through hole 2, it is of course unnecessary to provide the hollow portion 7. Next, when an etching process is performed as shown in FIG. 10, the electrolytic copper plating layer 5 on the hole wall is removed by the etching solution flowing into the hole, leaving only the copper foil layer 4 and the electrolytic copper plating layer 5 below the etching resist 6. A land is formed on the surface. The so-called cracked area caused by the etching solution on the land around the non-through hole 2 is at most
It is less than 0.1 mm, and there is no difference from the conventional method in terms of solderability between the lead wire and land of the mounted component, which does not affect reliability. Next, as shown in FIG. 11, by removing the etching resist 6, a non-through hole 2 similar to that shown in FIG. 6 is formed.

The method of the present invention allows drilling for through-hole 1 and non-through-hole 2 at the same time, so when using an automatic drilling machine using a numerical control device, the same reference drilling origin can be used in common. There are advantages. Therefore, through hole 1 is smaller than the conventional method.
The method of the present invention is superior in terms of the relative position accuracy of the non-through hole 2 and the non-through hole 2.

Furthermore, as is clear from a comparison between the conventional method shown in FIGS. 1 to 6 and the method of the present invention shown in FIGS. 7 to 11, the method of the present invention requires one less step than the conventional method. There is also the advantage of reducing the total number of man-hours for drilling through-holes 1 and non-through-holes 2 by reducing drilling preparation work and the like.

[Brief explanation of the drawing]

1 to 6 are enlarged sectional views of the main steps of the conventional method, and FIGS. 7 to 11 are through-holes in the main steps of a through-hole printed wiring board for explaining an embodiment of the method of the present invention. FIG. 3 is an enlarged cross-sectional view of a non-through hole. 1...Through hole, 2...Non-through hole,
3... Insulating base material, 4... Copper foil layer, 5... Electrolytic copper plating layer, 6... Etching resist, 7... Cavity portion.

Claims (1)

[Claims] 1. A method for manufacturing a through-hole printed wiring board in which a first through hole having a hole wall of a conductive layer is formed at the land position of the printed wiring board, and a second through hole having no conductive layer on the hole wall. forming the second through hole before forming the conductive layer on the wall of the first through hole, and forming the second through hole when forming the conductive layer on the wall of the first through hole; a step of forming the conductive layer also on the hole wall of the second through hole; and a step of etching away the conductive layer on the hole wall of the second through hole when etching the land and the conductive circuit. A method for manufacturing a through-hole printed wiring board, characterized by: