JPS61285794A - Manufacture of printed wiring board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of manufacturing a printed wiring board having through holes.

<Prior art> Fig. 3 shows an outline of an apparatus for printing printed wiring boards with conductive paste, in which 1 is a vacuum suction box, 2 is an exhaust port of a part of the vacuum suction box, and 3 is an exhaust port on the top of the box 1. A base plate 4 is a wiring board placed thereon, and has a large number of through holes 5.

The base plate 3 also has a large number of holes 6, and these holes 6 are provided to coincide with each through-hole hole 5.

7 is a screen pattern placed on the substrate 4 and stretched over the frame 8. Reference numeral 9 denotes a conductive paste, and this paste 9 is applied onto the screen 7 using a squeegee 10 that automatically reciprocates to print a predetermined wiring pattern on the board 4.

During the printing process as described above, the inside of the vacuum suction box 1 is sucked by a vacuum suction device such as a vacuum pump connected to the exhaust port 2 to maintain a constant negative pressure, thereby printing on the surface of the substrate 4. The paste 9 is sucked together with air into the through-hole 5 to form a paste layer on the inner surface of the through-hole 5.

<Problems to be Solved by the Invention> In the conventional method described above, the suction by the vacuum suction device is constant from beginning to end.

Therefore, if the suction is too strong, the paste 9 on the substrate 4 will be drawn into the through hole 5 too much as shown in FIG. It accumulates thickly near the bottom of the hole 5 and becomes easily broken. Particularly in the case of copper paste, there is a problem that under the above conditions, cracking may occur due to burning.

Also, if the suction is too weak, as shown in Figure 5, the paste 9 will not be sufficiently suctioned into the through-hole 5, and will accumulate near the entrance of the hole 5 and become thick, and when it comes into contact with it, it will form a film of paste 9. The through-hole hole 5 is closed. Further, conductive connection between the front and back surfaces will not be established.

Therefore, the amount of vacuum suction must be finely adjusted, which poses a problem in that the work becomes complicated.

The present invention has been made to solve the above-mentioned problems, and provides a method for manufacturing a printed wiring board that can form a metal film of uniform thickness on the inner surface of a through-hole by a simple operation. The purpose is to

<Means for Solving the Problems> In order to achieve the above object, the present invention weakens the vacuum suction during printing to reduce the amount of paste entering the through-hole, and strengthens the suction after printing is completed. The paste near the entrance of the through-hole is sucked to the inner surface of the hole to form a thin, uniform film on the inner surface of the through-hole.

<Example> Fig. 1 shows a device for carrying out the present invention, in which 11 is a vacuum suction device consisting of a vacuum pump, etc., 12.13 is a pipe branched from the device, and a flow rate regulator 14.15 is installed in the middle of the pipe. A flow meter 16.17 and a solenoid valve 18.19 are provided, and both branch pipes 1
2.13 is connected to the tube 20 connected to the suction port 2 of the vacuum suction box 1 shown in FIG.

In the above case, the printing apparatus shown in FIG. 3 is used, the flow rate regulator 14 adjusts the flow rate to a small flow rate, and the flow rate regulator 15 adjusts the flow rate to a large flow rate.

At the start of printing, the electromagnetic valve 18 is opened and the electromagnetic valve 19 is closed to weaken the suction force, and the squeegee 10 is moved in the same manner as in the conventional method to apply the paste 9 and print on the substrate 4.

While the squeegee 10 is moving and printing, only the solenoid valve 18 is kept open as described above, and when printing is finished and the squeegee 10 stops, the solenoid valve 18 is closed and the solenoid valve 1 is closed.
9 is opened, the vacuum suction is strengthened, and the paste 9 accumulated in the through-hole hole 5 is drawn downward at once.

Through the above operations, the obtained substrate 4 has a thin and uniform paste film 21 formed inside the through-holes 5, as shown in FIG. Then, if necessary, the same operation as above is performed on the back side of the substrate 4 to print a predetermined wiring pattern.

It is preferable that the switching of the electromagnetic valves 18 and 19 and their operating time be automatically performed using a signal from the control mechanism of the squeegee 10 or a timer.

<Effects of the Invention> As described above, in this invention, during printing, the vacuum suction is weakened to collect the paste in the upper part of the through-hole hole, and after printing, the vacuum suction is strengthened to draw the paste into the through-hole hole all at once. A thin and uniform conductive film can be formed on the inner surface of a through-hole without any complicated operations.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of an apparatus for carrying out the method of the present invention, FIG. 2 is an enlarged cross-sectional view of a partially cut away part of a substrate manufactured by the method of the present invention, and FIG. 3 is an example of a printing apparatus. 4 and 5 are partially cutaway enlarged longitudinal sectional views showing each side of a through-hole portion according to the conventional method.

Claims (1)

[Claims] A screen pattern is placed on a wiring board having through-holes, and while printing is performed on the board using the paste on the screen pattern, the paste is sucked from the through-holes of the board to form a conductive film on the inner surface of the hole. , a method for manufacturing printed wiring boards, characterized by weakening the suction during printing to reduce the amount of paste that enters the through-holes, and increasing the suction after printing to create a thin, uniform film inside the through-holes. A method for manufacturing a printed wiring board.