JPH0445271Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field] The present invention relates to a through-hole printed wiring board.

[Prior Art] As an example of a through-hole printed wiring board in which circuit conductors arranged on the front and back sides of a board are electrically connected to each other through a through hole formed in the board, a structure shown in FIG. 2 has been known. ing.

Figure 2A is a plan view of the through-hole wiring board;
Figure B is a sectional view taken along line A-A in Figure 2A,
As shown in these figures, a through hole 2 is formed in a substrate 1, and on the substrate surface at both the upper and lower ends of this through hole 2,
Upper and lower conductive foil layers 3, 3' made of copper foil and formed in an annular shape are provided.

The through hole 2 is filled with a first conductive paste 4 made of silver paste or the like for conduction between both surfaces of the board, and the first conductive paste 4 is applied to the foil surfaces of the upper and lower conductive foil layers 3 and 3'. It is arranged so that it extends to. On both sides of the substrate, second conductive pastes 5 and 5' made of silver paste for plain wiring are formed so as to be connected to the first conductive paste 4.

In this way, in the above-mentioned through-hole printed wiring board, the second conductive paste 5 for forming a wiring pattern arranged on the front side of the substrate 1 is passed through the first conductive paste 4 in the through-hole 2 portion. It can be electrically connected to the wiring pattern 5' arranged on the back side of the substrate 1.

[Problems to be solved by the invention] As mentioned above, in this type of through-hole printed wiring board, the conductive foil layer 3 is placed on the annular conductive foil layer 3.
The first conductive paste 4 is printed so that its circumference coincides with the outer edge of the conductive foil layer 3, and at the same time it covers the conductive foil layer 3, it enters the through hole 2, and the conductive foil layer is coated in the same manner from the back side of the substrate. By printing the first conductive paste 4' on the through hole 3', the through hole 2 is filled with the conductive paste.

In this case, it is extremely difficult to accurately position the printing mask with respect to the substrate 1, and the first conductive layer is not completely aligned with the outer periphery of the conductive foil layers 3, 3' and the circumference of the conductive paste. Paste 4 is often printed, and when such printing misalignment occurs,
The first conductive paste 4, which tends to bleed onto the substrate 1, protrudes from the conductive foil layers 3, 3', and radial smear of the first conductive paste 4 is formed on the substrate 1. When such a bleed is formed, for example, between four adjacent parts of the first conductive paste (between lands), as shown in FIG.
A short-circuit portion 6 is formed in the wafer, which may cause a serious defect called a short-circuit failure.

Therefore, as shown in FIGS. 4A and 4B, the outer diameter of the first conductive paste 4 is set in advance to be smaller than that of the conductive foil layer 3, and the difference in the outer diameter of the two is utilized to perform the above-mentioned process. It is conceivable to prevent the first conductive paste 4 from protruding from the conductive foil layer 3 even in the case of printing misalignment. However, in this case, the first conductive paste 4 is applied to the surface of the conductive foil layer 3.
Since there is an exposed part that is not covered by the conductive paste, this exposed part is oxidized over time, and in the direct contact area 7 between the second conductive paste 5 and the conductive foil layer 3, the second conductive paste 5 is There is a risk of corrosion due to copper oxide and a disconnection accident.

The present invention was developed in view of the current state of through-hole printed wiring boards as described above, and its purpose is to prevent short circuit accidents due to bleeding of the first conductive paste onto the board, and to
In particular, it is an object of the present invention to provide a through-hole printed wiring broken line in which disconnection of the second conductive paste portion due to corrosion of the conductive foil layer is prevented.

[Means for solving the problem] In order to achieve the above-mentioned object, in the present invention, a through hole is formed in the substrate, and a conductive foil layer made of conductive foil is formed on the periphery of both ends of the through hole. The through hole is filled with a first conductive paste for conduction between the front and back surfaces of the substrate, and a second conductive paste for forming a planar wiring pattern is printed so as to be in contact with the first conductive paste. In the hole printed wiring board, a cutout is formed in a part of the conductive foil layer, and the first and second conductive pastes are connected to each other at the cutout portion.

[Function] In the present invention, the first conductive paste and the second conductive paste for forming a wiring pattern are directly connected to each other in the notch formed in a part of the conductive foil layer. Even if the second conductive paste corrodes over time, the second conductive paste will not be corroded and disconnected. Further, by printing the first conductive paste on the conductive foil layer so that the outer periphery of the first conductive paste is located inside the outer edge of the conductive foil layer, the substrate of the first conductive paste can be printed. It is possible to reliably prevent bleeding from occurring.

[Example] Hereinafter, an example of the present invention will be described in detail using FIGS. 1A and 1B.

Here, FIG. 1A is a plan view showing the configuration of an embodiment of the present invention, and FIG. 1B is a sectional view taken along line C-C of FIG. 1A, which is the same as FIGS. 2 to 4. The same reference numerals are given to the parts.

As shown in FIGS. 1A and 1B, in the embodiment of the present invention, approximately rectangular notches 9 and 9' are formed in a portion of the conductive foil layers 3 and 3' from the outer edge toward the center. There is.

Further, between the upper and lower conductive foil layers 3, 3', a first conductive paste 4 is filled in the through hole 2 by printing, and the conductive foil layers 3, 3' of the first conductive paste 4 are filled with the first conductive paste 4 by printing. The upper outer periphery is located inside the outer edges of the conductive foil layers 3, 3'. That is, the first
The outer diameter of the conductive paste 4 is set smaller than the conductive foil layers 3, 3', and there is an exposed portion not covered by the conductive paste 4 on the outer periphery of the conductive foil layers 3, 3'.

so as to connect with the first conductive paste 4 described above. It extends in a band shape from the center of the first conductive paste 4. A second conductive paste 5, 5' made of silver ink for forming a wiring pattern is printed.
Therefore, the exposed portions of the conductive foil layers 3 and 3' mentioned above are
Both sides of the notches 9, 9' are in contact with the second conductive pastes 5, 5', respectively, and inside the notches 9, 9', the first and second conductive pastes 4 and 5, 5' are in contact with each other. There is.

The configuration of the other parts in the embodiment of the present invention is the same as that of the conventional through-hole printed wiring board already explained using FIGS. 2A and 2B, so a redundant explanation thereof will be omitted.

In the embodiment of the present invention configured as described above, the second conductive paste 5 for forming a wiring pattern disposed on the surface side of the substrate 1 is replaced with the first conductive paste 4 in the through hole 2 portion. Through this, conductive connection can be made to the wiring pattern 5' arranged on the back side of the substrate 1.

Therefore, the wiring patterns arranged on the front and back surfaces of the substrate 1 are reliably connected to each other in a narrow occupied space area by the through-hole printed wiring board shown in the embodiment.

Further, since the outer periphery of the first conductive paste 4 on the conductive foil layer 3 is located inside the outer edge of the conductive foil layer 3, the first conductive paste 4 contacts the substrate 1 only at the notch 9 portion. ing. Since the notch 9 is surrounded by the conductive foil layer 3 and the first and second conductive pastes 4 and 5, the notch 9 is generated by contact between the notch 9 and the first conductive paste 4. No bleed is formed on the outside of the conductive foil layer 3. Therefore, it is possible to completely prevent the formation of a bleed on the substrate 1 of the first conductive paste 4 that could lead to a short circuit accident.

Furthermore, since the first and second conductive pastes 4 and 5 are in direct contact with each other at the notch 9 portion,
Even if a copper oxide film is formed on the exposed outer edge portion of the conductive foil layer 3 due to aging, no cutting accident will occur in the second conductive paste 5 due to this copper oxide film. The above also applies to the back surface of the substrate 1.

In the above embodiment, silver ink was used as the conductive paste, but the present invention is not limited to this embodiment, and the conductive paste may include ink mixed with nickel powder, carbon powder, etc. You can also use

[Effects of the invention] As explained in detail above, according to the invention,
Since the first conductive paste and the second conductive paste are directly connected within the notch formed at the periphery of the conductive foil layer, it is possible to prevent short circuit accidents caused by bleeding of the first conductive paste. Accordingly, it is possible to reliably prevent disconnection of the second conductive paste due to corrosion of the conductive foil layer, and to provide a through-hole printed wiring board with high practical value.

[Brief explanation of the drawing]

FIG. 1A is a plan view of essential parts of a through-hole wiring board according to an embodiment of the present invention, FIG. 1B is a sectional view taken along line C-C of FIG. 1A, and FIG. 2A is a through-hole wiring board. A plan view of the plate, FIG. 2B is a sectional view taken along the line A-A in FIG. 2A, FIG. 3 is an explanatory diagram showing the problems of the conventional example, and FIG. A plan view of the main part of the through-hole wiring board, Fig. 4B is similar to Fig. 4A.
FIG. 2 is a sectional view taken along line BB of FIG. 1... Substrate, 2... Through hole, 3... Conductive foil layer,
4...First conductive paste, 5...Second conductive paste, 9...Notch.

Claims (1)

[Scope of utility model registration request] A through hole is formed in the substrate, and a conductive foil layer made of conductive foil is formed on the periphery of both ends of the through hole,
The through hole is filled with a first conductive paste for conduction between the front and back surfaces of the substrate, and a second conductive paste for forming a planar wiring pattern is printed on the through hole so as to be in contact with the first conductive paste. A through-hole printed wiring board, characterized in that a notch is formed in a part of the conductive foil layer, and the first and second conductive pastes are connected to each other at the notch.