JPH035077B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electrically connecting conductive patterns formed on both the front and back surfaces of a printed wiring board.

Conventionally, conductive ink 4 is poured into the through holes 3 of the wiring board 1 to electrically connect the front and back conductive patterns 2, 2 using the method shown in FIGS. 8 and 10.

In the method shown in Fig. 8, a pin 5 with conductive ink 4 attached to the tip is vibrated just above the hole 3 of the substrate 1, and the conductive ink 4 is dripped onto the substrate, and the ink travels along the hole wall due to its own weight. The ink drips down and reaches the back side of the substrate, and the ink adheres to the inner surface and the edge of the hole as shown in FIG. 9 (Japanese Patent Laid-Open No. 139962/1982).

In the method shown in FIG. 10, a pin 5 with conductive ink 4 attached to the tip is passed through a hole 3 of a substrate 1, and in this state, the substrate 1 is vibrated in a plane perpendicular to the pin 5, and the inner surface of the hole 3 and the hole 3 are vibrated. After applying ink to the edge, the pin 5 is removed (Japanese Patent Application Laid-open No. 70696/1983).

However, in the case of the method shown in FIG. 8, it takes time for the conductive ink with high viscosity and poor fluidity to drip down under its own weight and wrap around the lower edge of the hole, resulting in poor efficiency.

Further, in the method shown in FIG. 8, the conductive ink is allowed to adhere to the inner surface of the hole by its natural flow, and when the conductive ink has a high viscosity, it takes time for the conductive ink to flow down, reducing processing efficiency.

In order to lower the viscosity of conductive ink, if the amount of solvent added to the ink is increased, the amount of gas generated increases when the conductive ink hardens, creating voids or cracks in the ink-filled area, and reducing the conductivity. There is a problem in which the reliability of sex decreases.

In addition, in the case of the method shown in FIG. 10, the gap between the pin 5 passing through the hole 3 of the substrate 1 and the hole wall is narrow, and the conductive ink 4 concentrates on the upper and lower edges of the hole 3, and the conductive ink 4 concentrates on the upper and lower edges of the hole 3. 5
The amount of ink remaining in hole 3 is small after removing the
Electrical continuity was unreliable. Furthermore, in the method shown in FIG. 10, the pin must be removed from the hole in the board into which it has been inserted, and at this time air is likely to be drawn into the conductive ink coating layer, resulting in voids.

Furthermore, by repeatedly applying conductive ink to the pin, the effective diameter of the pin becomes larger, and because the conductive ink is applied to the substrate by squeezing the conductive ink at the edge of the hole, it is necessary to adjust the amount of ink applied to the inner surface of the hole. is difficult.

In view of the above-mentioned circumstances, the present invention has been developed with conductive ink 4 at the tip.
The purpose is to provide a highly efficient and reliable method of connecting conductive patterns by reciprocating up and down the pin 5 to which it is attached, approaching and separating it from the edge of the hole on the upper surface of the substrate 1 multiple times. do.

The present invention will be specifically described below based on embodiments shown in the drawings.

FIG. 7 is a sectional view of a main part of a printed wiring board 1 in which both the front and back conductive patterns 2 are formed by the method of the present invention.

The printed wiring board 1 has conductive patterns 2, 2 on both the front and back sides, and a hole 3 is formed through the board 1 at a position opposite to both the patterns 2, 2, and the hole 3 is filled with conductive ink 4 and solidified. I'm letting you do it.

FIG. 1 shows a filling device 50 that fills the substrate 1 with conductive ink 4. The filling device 50 has pins 5 with a diameter slightly smaller than the diameter of the through holes 3 of the substrate 1 corresponding to the arrangement of the holes 3. The planted lifting plate 51 is linked to the first vertical movement device 52 and the second vertical movement device 53,
A tank 41 containing conductive ink 4 below the lifting plate 51
is being deployed.

The conductive ink 4 is a silver paste with a viscosity of 25 to 50 Ps.

Next, the ink filling method will be explained.

By the first vertical movement device 52 of the filling device 50,
The lifting plate 51 is moved up and down once, and the tip of each pin 5 is immersed in the conductive ink tank 41 and pulled up.
Conductive ink 4 is applied to the tip of the (third
figure).

Next, the wiring board 1 is placed opposite to the lower part of the lifting plate 51, and the through holes 3 of the board 1 are aligned with the centers of the pins 5.

While in the above state, the second vertical movement device 52 is operated to lower the elevating plate 51 to a position where the tip of the pin 5 is close to the upper edge of the hole 3, and the conductive ink 4 on the pin 5 is transferred to the hole edge of the substrate 1. (Figure 4).

In the embodiment, the stalk of the second vertical movement device 53 is 10
mm, and the distance between the pin 5 at the top dead center position and the board 1 is also 10 mm.

Therefore, when pin 5 descends, the pin tip and substrate 1
Although the top surface heights are the same, the height is not limited to this. If the conductive ink 4 on the pin can be transferred to the substrate 1, the bottom dead center of the pin 5 may be slightly above the top surface of the substrate or slightly below the hole 3. You can sneak in.

Immediately after the conductive ink 4 adheres to the edge of the hole, the pin 5 is raised.

The ink 4 on the substrate 1 is attached to the pin 5 due to surface tension.
Fill in the hole left and form a circle just above hole 3 (Figure 5).

Next, the pin 5 is reciprocated twice per second for about 6 seconds by the second vertical movement device 53.

As the pin 5 descends to a position close to the upper edge of the hole 3 as described above, the conductive ink 4 adhering across the edge of the hole is pushed into the hole by the pin 5.

When the pin 5 rises, the conductive ink 4 remaining on the edge of the hole on the upper surface of the substrate is drawn into the axial center of the hole 3 by surface tension and becomes rounded.

The pin 5 descends again to force the conductive ink 4 into the hole.

By repeating the above operation, the conductive ink 4
reaches the bottom edge of the hole and the hole 3 is filled with conductive ink 4 (FIG. 6).

When the substrate 1 with the conductive ink 4 filled in the holes 3 is dried, the solvent in the conductive ink 4 evaporates and the ink shrinks, and as shown in FIG. The ink solidifies with a slight depression.

As described above, the present invention forcibly pushes the conductive ink 4 transferred to the hole edge of the substrate 1 into the hole with the reciprocating pin 5, so that the conductive ink travels along the hole wall and is absorbed by its own weight, unlike in the conventional case. Compared to waiting for it to drip,
It takes less time to cover the hole walls with ink,
Work efficiency increases. In addition, since it is possible to use conductive ink with higher viscosity than conventional conductive ink, that is, conductive ink with a small amount of added solvent, less gas is generated when the ink dries and hardens, and there is no void or void in the area filled with conductive ink. It is possible to suppress the occurrence of cracks.

Further, since the pin 5 is lowered only to a position close to the upper edge of the hole and does not penetrate through the hole 3, the hole 3 is almost filled with the conductive ink 4, and the reliability of electrical continuity is high.

It goes without saying that the present invention is not limited to the above configuration, and that various modifications can be made within the technical scope of the claims.

[Brief explanation of the drawing]

Fig. 1 is a front view of the coating device, Fig. 2 is a front view of the coating device with the coating plate raised, Figs. 3 to 7 are process illustrations, and Fig. 8 is an illustration of the conventional example. FIG. 9 is a sectional view of the conventional example, and FIG. 10 is an explanatory diagram of the conventional example. 1... Wiring board, 3... Through hole, 4... Conductive ink.

Claims (1)

[Claims] 1 In a method of electrically connecting conductive patterns 2, 2 formed on both sides of a wiring board by attaching conductive ink to the inner surfaces of through holes 3, 3 made in a wiring board 1, conductive ink is applied to the tips of the wiring board 1. The conductive ink 4 on the pin is moved to the upper edge of the hole 3 by lowering the pin 5 to which the conductive ink 4 is attached until the tip of the pin approaches the upper edge of the hole 3 of the wiring board 1. is raised to separate the pin from the ink on the substrate, and the pin is lowered again close to the upper edge of the hole, and by repeating this back and forth movement of the pin, the conductive ink 4 is gradually drawn into the hole 3.
A method for connecting conductive patterns on both the front and back sides of a wiring board, characterized in that conductive ink is deposited in the hole so as to extend over the upper and lower edges of the hole 3 by pushing the conductive ink into the hole.