JPS60239092A - Method of forming conductor in through hole - 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] The present invention relates to a method for forming a conductor in a hole.

Configuration of conventional example and its problems 2 ・＼ 7・ FIG. 1 shows an example of a thick film circuit. The thick film paste printed on the alumina substrate 1 is dried and fired to form a thick film conductor layer 2. A thick film resistor 3 is formed. Thick film paste for conductors is generally composed of silver-palladium alloy powder, glass frit, resin binder, organic solvent, etc. Furthermore, the thick film paste for resistors uses ruthenium oxide instead of silver-palladium, and is made of substantially the same material as the paste for conductors in other respects. A chip capacitor 4 is connected to the thick film conductor layer 2 by solder 6 on the alumina substrate 1 . With the recent demand for smaller electronic devices,
There is an increasing need for the circuit boards used there to be smaller and more highly integrated. Therefore, from the conventional general substrate using only one side as shown in FIG. 1 to the thick film conductor layer 2 formed in the through hole 6 in the alumina substrate 1 as shown in FIG.
Double-sided thick film circuits, which effectively utilize both sides of the substrate, have come into use.

The conventional manufacturing process for double-sided thick film circuits consists of an alumina substrate 1 with a thickness of 0.61111 to 0.6111M, as shown in
After returning the ink, spread the conductive paste 2 containing silver-palladium metal powder on the screen 8 in advance and apply it with a squeegee 9.
Then, while drawing a vacuum from the suction port 11, remove the circuit part 1 on the board.
A method of applying conductive paste 2 into the through holes 3 and 6 is generally practiced.

However, in this method, the base spreads over the entire surface of the screen, and when the squeegee starts suction while descending, the entire surface of the screen is attracted to the substrate, and the paste is sucked from the pattern area of the screen, and the paste adheres to the emulsion 12, causing bleeding. There are cases where In particular, since the suction time for the pattern portion on the end-of-printing side of the squeegee is longer than the position at the beginning of printing, a large amount of paste smudges out, causing smearing. Furthermore, if the suction force is reduced in order to reduce the amount of paste smearing out, the smearing in the pattern area tends to decrease, but there is a problem in that the paste is not sufficiently applied within the through-holes. As shown in FIG. 4, in conventional screen printing, the suction force is maximum at the beginning and end of printing, and decreases as it approaches the latter. The above-mentioned problems occur because the twisting and suction forces are not constant during printing.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks and to print a conductor pattern on a substrate and apply a conductor inside the through-hole at the same time, so that the conductor pattern does not bleed and improves the reliability of the through-hole.

Structure of the Invention The method for forming conductors in through-holes of the present invention includes, during outward printing, a step of arranging a substrate having through-holes, a step of applying a conductive paste onto the substrate with one side of a squeegee capable of printing on both sides, and a step of applying a conductive paste onto the substrate with a squeegee capable of printing on both sides. a step of applying conductive paste to the inside of the through-hole by vacuum suction from the opposite side of the substrate; a step of raising the squeegee and moving the other side of the squeegee to a printable position; and a step of ejecting the substrate. This method of forming conductors in through-holes is characterized in that during return printing, screen printing is performed on the substrate in the step of placing a new board and on the other side of the squeegee, similar to the outward printing.

DESCRIPTION OF EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. Board size: 100mm x 90ff, shoulder xo, st, diameter: 0.6φ
A suction jig 1 sucks an alumina substrate 1 having M through-holes 6.
o, and while suctioning with a vacuum level of 3 cmHg or more with a vacuum pump from the suction port 11, apply silver-palladium paste 2 whose viscosity was adjusted to 200 Pas / 25°C with one side 9a of the squeegee 9 to a stainless steel plate of 260 to 350 mS. Conductor width 0.2111M or more using screen 8 made of
Screen printing is performed on the conductor circuit portion 13 on the board with a conductor spacing of 0.2 mm or more and the inside of the through hole 6, and the squeegee 9 is raised and moved over the paste 2 to a position where it can be printed with the other surface 9b of the squeegee. As shown in FIG. Screen printing is performed on the other side 9b in the same manner as the outward printing, and after completing the outward printing, the squeegee 9 is raised and moved to a position where it is possible to print on the paste 2 with the surface of the squeegee 9a. The discharge was carried out. As a result, the fourth
As shown in the figure, in screen printing according to the present invention, since the paste is not spread on the screen in advance, the suction pressure is constant, so the printing condition is exactly the same on the outward and return passes, and there is no bleeding and the through-hole yield is 100%. was gotten.

Next, a second embodiment of the present invention will be explained with reference to FIG. An alumina substrate 1 having the same substrate size as the first embodiment and a through hole 6 with a diameter of 0.6φ #I shoulder is set in a suction jig 10, and a stainless steel screen 8 with a vacuum pump of 250 to 350 mesh is connected through the suction port 11. conductor width 0.2M
Screen printing is performed on the on-board conductor circuit section 13 and through-hole interior 6 with a conductor spacing of 0.2 mW or more, and the flat squeegee 9 is raised to a position where the paste 2 can be printed with the other surface 9b of the flat squeegee 9. Move to the flat squeegee 9
Change the angle so that the surface b is 70 degrees from the substrate, eject the printed substrate, and insert a new alumina substrate 1' into the suction jig 10 as shown in Fig. 8 in the same way as in the forward printing. As a result of screen printing the silver-palladium paste 2 used in the forward printing on the 9b surface of the squeegee 9 in the same manner as in the forward printing, the same printing results as in the first example were obtained.

Note that the squeegee angle is not limited to a range of 30 degrees to 90 degrees with respect to the substrate and <70 degrees. Further, the timing for ejecting the substrate is not a key point of the present invention, and may be any time after the squeegee is raised.

Effects of the Invention As described above, according to the present invention, unlike conventional screen printing, the base V is not spread on the screen in advance by returning ink, so the suction pressure remains constant from the start of printing to the end of printing, which makes printing extremely easy. A highly accurate substrate can be obtained. Furthermore, whereas in the past, printing was performed once in one reciprocation of the squeegee, in the present invention, printing can be performed twice in the forward and backward passes, thereby improving productivity.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of a thick film circuit, Fig. 2 is a sectional view showing a thick film circuit using both sides of a substrate, Fig. 3 is a sectional view of conventional screen printing, and Fig. 4 is a sectional view of a conventional screen printing method. A diagram showing the relationship between squeegee position and vacuum suction force in screen printing and the screen printing of the present invention, FIG. 5 is a sectional view of the apparatus implementing the first embodiment of the present invention during forward printing, and FIG. 6 is the same. FIG. 7 is a cross-sectional view of an apparatus embodying the second embodiment of the present invention during forward printing, and FIG. 8 is a cross-sectional view of the same during backward printing. 1...Alumina substrate, 2...Silver-palladium paste, 1'...New alumina substrate,
6... Mark/Through hole, 7... Ink return, 8
...Screen, 9...Squeegee, 9
a...One printable surface, 9b...The other printable surface, 10...Suction jig, 12.
... Emulsion, 13 ... Conductor circuit section. Name of agent Toshio Nakao and 1 other person
Figure 4 Figure 3 Figure 4 Jib device - Figure 5 9 Figure 7 Figure 8

Claims (1)

[Claims] During outward printing, there is a step of arranging a substrate with through holes, and applying a conductive paste onto the substrate with one side of a squeegee capable of printing on both sides, and applying vacuum suction from the opposite side of the substrate to clean the inside of the through holes. The process consists of applying conductive paste to the substrate, moving the squeegee to a position where the other side of the squeegee can be printed, and ejecting the substrate. When printing on the return trip, a new substrate is inserted. A method for forming conductors in through-holes, comprising a step of arranging the conductors, and a step of screen printing on the substrate on the other side of the squeegee in the same manner as the outward printing.