JPH1075022A - Circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable observation of whether a first circuit board and a second circuit board are surely fastened to each other, even after the first and the second circuit board have been conductively fastened with solder filled in a through-hole. SOLUTION: A circuit board is provided with a first circuit board 11 which has a through-hole that passes through the board and has a through-hole conductor 15, constituted of a conductive film formed in the periphery of the through- hole and a second circuit board 17 which has a land electrode 18, formed in correspondence with the through hole 12. In the first circuit board 11, a through- hole 13 for visual observation is formed continuously with the through-hole 12. A conductive film is not formed on an inner wall of the through hole 13 for visual observation and a conductive binder will not stick to the inner wall of the through hole 13. The first circuit board 11 is mounted on the second circuit board 17 to conductively fasten the through-hole conductive 15 of the first circuit board 11 to the land electrode 18 on the second circuit board 17. Under this condition, the fastened state of the solder 20 can be observed visually via the through-hole 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board in which two circuit boards are conductively fixed with solder or a conductive adhesive. For example, a through-hole conductor of a first circuit board is used as a land electrode of a second circuit board. The present invention relates to a circuit board in which land electrodes formed by soldering or formed on the back surface of a first circuit board are soldered to land electrodes of a second circuit board.

[0002]

2. Description of the Related Art FIGS. 8 and 9 show two circuit boards conductively fixed using through-hole conductors. A through hole 2 is formed in the first circuit board 1, a through hole conductor 5 made of a conductive film is formed on a peripheral wall of the through hole 2, and the through holes 2 on both front and back surfaces of the first circuit board 1 are formed. A land electrode 4 made of a conductive film is formed around the periphery. Further, a circuit pattern 6 for electrically connecting the through-hole conductor 5 to another circuit portion is formed on the land electrode 4. On the other hand, a land electrode 8 is formed at a position corresponding to the through hole 2 on the surface of the second circuit board 7.

[0003] Paste solder is filled in the through holes 2 of the first circuit board 1, and the first circuit board 1 is mounted on the second circuit board 7 in this state. Then, the paste solder is reflowed and re-hardened, so that the through-hole conductor 5 of the first circuit board 1 is soldered to the land electrode 8 of the second circuit board 7 as shown in FIG. Is done. As a result, the circuit pattern formed on the first circuit board 1 and the circuit pattern formed on the second circuit board 7 are connected via the solder 9 in the through hole 2.
Alternatively, a land electrode may be formed on the back surface of the first circuit board, and the land electrode may be soldered to a land electrode formed on the surface of the second circuit board.

[0004]

In the case where the two circuit boards 1 and 7 are connected via the through hole 2 as in the former, the through hole conductor 5 of the first circuit board 1 and the second circuit board are connected. 7 are connected to the land electrodes 8 by solders 9 filled in the through holes 2. However, in this state, as shown in FIG. 2, the solder 9 fills the through holes 2 of the first circuit board 1, so that the solder 9 and the second circuit board 7 The joint with the land electrode 8 is hidden. For this reason, it cannot be visually observed whether the through-hole conductor 5 of the first circuit board 1 and the land electrode 8 of the second circuit board 7 are securely soldered.

Further, even in the latter circuit board, since the land electrodes are soldered between the two circuit boards, the connecting portions of the land electrodes of the two circuit boards are hidden by the circuit boards, and the two It is not possible to visually observe whether the land electrodes of the board are securely soldered. For this reason, it has been difficult to ensure reliability after soldering. The same applies to the case where the through holes and the land electrodes of the two circuit boards are connected with a conductive adhesive. The present invention has been made in view of such a problem in a conventional circuit board, and makes it possible to easily observe whether or not portions of two circuit boards to be conductively fixed are securely fixed even after fixing. The purpose is to:

[0006]

According to the present invention, in order to achieve this object, a through hole 12 in a first circuit board 11 is provided.
Or a through hole 13 for visual observation is provided adjacent to the land electrode 21 on the back surface of the first circuit board 11,
Further, a conductor film was not formed in the through-hole 13 for visual observation so that solder and a conductive adhesive did not adhere. Thus, the state of fixation by solder or the like can be visually observed through the through hole 13.

That is, a circuit board according to the present invention has a first circuit board 11 having a through-hole 12 penetrating the board and having a through-hole conductor 15 made of a conductive film formed on the peripheral surface thereof; A second circuit board 17 having a land electrode 18 formed on the surface corresponding to the first circuit board 12; the first circuit board 11 is mounted on the second circuit board 17; A through-hole conductor 15 is conductively fixed to a land electrode 18 on a second circuit board 17.
2 is characterized in that a through hole 13 for visual observation is formed in tandem with 2. Then, no conductor film is formed on the peripheral wall of the through hole 13 for visual observation, and the peripheral wall is a wall surface on which the conductive fixing material does not adhere.

In such a circuit board, a through-hole 13 for visual observation is provided continuously with the through-hole 12 of the first circuit board 11 which is filled with a fixing member such as solder or conductive adhesive. There is no conductive film there, and no solder or the like adheres. Therefore, even if the through hole 12 is filled with solder or the like, the state of the solder or the like fixed to the through hole conductor 15 of the first circuit board 11 or the land electrode 18 of the second circuit board 17 passes through the through hole 13. It can be visually observed.

Therefore, if a plurality of through holes 13 for visual observation are provided around the through hole 12 having the through hole conductor 15, the above-mentioned state of fixation of the solder or the like can be confirmed from a plurality of directions. Further, if the through hole 13 for visual observation is larger than the through hole 12 having the through hole conductor 15, even if the solder is small, the fixed state thereof can be easily observed visually.

Further, another circuit board according to the present invention includes a first circuit board 11 having a land electrode 21 made of a conductive film on the back surface, and a land electrode 18 on the surface corresponding to the land electrode 21. The first circuit board 11 is mounted on the second circuit board 17, and the land electrodes 21 on the back surface of the first circuit board 11 are connected to the second circuit board 17. 17 is characterized in that the through-hole 13 is formed adjacent to the land electrode 21 of the first circuit board 11.
Also, a conductor film is not formed on the peripheral wall of the through hole 13 for visual observation, and the peripheral wall is a wall surface on which the conductive fixing material does not adhere.

Also in this circuit board, a through hole 13 is provided adjacent to the land electrode 21 on the back surface of the first circuit board 11, and there is no conductor film there, and no solder or the like adheres. Therefore, the fixed state between the land electrode 21 of the first circuit board 11 and the land electrode 18 of the second circuit board 17 can be visually observed through the through hole 13.

[0012]

Embodiments of the present invention will now be described specifically and in detail with reference to the drawings. FIGS. 1, 2 and 3 show examples in which two circuit boards 11 and 17 are conductively fixed using through-hole conductors. The first circuit board 11 has a circuit pattern formed on the surface or inside of an insulating substrate made of alumina, glass epoxy resin, or the like. A through hole 12 is formed in the first circuit board 11, and a land electrode 14 made of a conductive film is formed around the peripheral wall of the through hole 12 and the through holes 12 on both the front and back surfaces of the first circuit board 11. . Further, a circuit pattern 16 for connecting the through-hole conductor 15 to a circuit is formed on the land electrode 14.

Around the through hole 12, three through holes 13 for visual observation are formed at intervals of 120 ° so as to be continuous with the through hole 12. No conductor film is formed on the peripheral wall of the through hole 13 for visual observation, and the surface of the insulating substrate is left as it is, or an insulating coating is applied. On the other hand, a land electrode 18 made of a conductive film is formed at a position corresponding to the through hole 12 on the surface of the second circuit board 17.

A paste solder (not shown) is filled in the through holes 12 of the first circuit board 11 shown in FIG. 1, and the first circuit board 11 is mounted on the second circuit board 17 in this state. You. Then, the paste solder is reflowed and re-hardened, so that the through-hole conductor 5 of the first circuit board 11 is soldered to the land electrode 18 of the second circuit board 17 as shown in FIGS. Solder at 20. As a result, the circuit pattern formed on the first circuit board 11 and the circuit pattern formed on the second circuit board 17 are connected via the solder 20 in the through hole 12.

In this state, as shown in FIG. 3, the through hole 12 of the first circuit board 1 is filled with the solder 20, and the through hole 13 for visual observation is connected to the through hole 12. Provided, and there is no conductor film, and the solder 20 does not adhere thereto. Therefore, whether or not the solder 20 filled in the through hole 12 is fixed to the through hole conductor 15 and the land electrode 18 of the second circuit board 17 can be visually observed through the through hole 13. In particular, in the examples shown in FIGS. 1, 2 and 3, since a plurality of through holes 13 for visual observation are provided at equal angular intervals around the through holes 12, the above-mentioned fixing state of the solder or the like is plural. And visual observation can be performed easily and reliably.

The through holes 12 and the through holes 13 can be formed, for example, by the following method. When the insulating substrate is a glass epoxy resin substrate, a through hole 12 for forming the through hole conductor 15 is formed in the substrate by a drill or a punch. Next, this through hole 1
A conductive film of Cu or the like is formed on the surface of the circuit board including the peripheral surface of No. 2, and this conductive film is patterned by means such as photoetching. Thereafter, a through hole 13 for visual observation is formed in the substrate by a drill or the like. When the insulating substrate is an alumina substrate, a through hole 12 forming the through-hole conductor 15 is formed in the substrate by a drill or a punch. Next, a conductive paste is screen-printed on the surface of the circuit board including the peripheral surface of the through hole 12 in a predetermined pattern. Thereafter, a through hole 13 for visual observation is drilled in the substrate with a drill or the like, and the conductive paste is baked.

Next, an example shown in FIGS. 4 and 5 will be described. In this example, a visual observation of a rectangle having a width larger than the diameter of the through-hole 12 is provided in connection with the through-hole 12 provided with the through-hole conductor 15. Through hole 13 is provided. Through hole 13 not having this conductive film
As a result, the through hole 12 is cut substantially in the radial direction, so that the through hole 12 has a semicircular shape. In this example, since the through-hole 13 for visual observation is large, even if the solder 20 in the through-hole 12 is small, it is easy to visually observe the fixed state of the solder 20.

FIG. 6 shows another example of the shape of the through hole 12 provided with the through hole conductor 15 and the through hole 12 for visual observation. In the example shown in FIG. 6A, a circular through-hole 13 for visual observation having a diameter larger than the diameter of the through-hole 12 is provided following the through-hole 12 in which the through-hole conductor 15 is provided. Further, in the example shown in FIG. 6B, two circular through holes 13 for visual observation having a diameter larger than the diameter of the through hole 12 are connected to the through hole 12 provided with the through hole conductor 15. It is provided. Also in these examples, since the through hole 13 for visual observation is large, the through hole 1
Even if the solder 20 in 2 is small, it is easy to visually observe the fixed state.

Further, in the example shown in FIG. 7, a land electrode 21 provided on the back surface of the first circuit board 11 and a land electrode 18 provided on the front surface of the second circuit board 17 are not formed by through-hole conductors. This is an example of soldering with solder 20. A through hole 13 for visual observation is provided adjacent to the land electrode 21 of the first circuit board 11. In such a circuit board, the solder connection portions of the land electrodes 18 and 21 are located between the two circuit boards 17 and 18. However, the through-hole 13 for visual observation allows the solder 21 to fix this portion. It can be easily visually observed. In the above example, the connection between the circuits of the two circuit boards 11 and 17 is
Although the example is shown with 0, it is clear that the present invention can be similarly applied to connection using a low melting point metal other than solder or a conductive adhesive.

[0020]

As described above, in the circuit board according to the present invention, the first and second circuit boards 11, 17 are provided by the solder 20 or the like filled in the through holes 12 of the first circuit board 11.
Are connected, the through-hole conductor 15 of the first circuit board 11 and the land electrode 1 of the second circuit board 17 are connected.
The state of fixation of the solder 20 to 8 or the like can be visually observed through the through hole 13. Also, the first circuit board 1
Electrodes 21 formed on the back surface of the second circuit board 1
In a case where the land electrode 18 formed on the surface of the fixing member 7 is fixed by soldering, the fixing state can be visually observed through the through hole 13. In this way, it is possible to reliably observe whether or not the portions of the two circuit boards 11 and 17 to be conductively fixed are securely fixed even after the fixing, so that reliability can be ensured.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a main part of first and second circuit boards showing an example of a circuit board according to the present invention.

FIG. 2 is a plan view showing an example of the circuit board in a soldered state of first and second circuit boards.

FIG. 3 is a sectional view taken along line AA in FIG. 2;

FIG. 4 is an exploded perspective view of a main part of first and second circuit boards showing another example of the circuit board according to the present invention.

FIG. 5 is a vertical sectional side view of a soldered state of first and second circuit boards showing an example of the circuit board.

FIG. 6 is a main part plan view showing an example of a shape of a through hole of a second circuit board.

FIG. 7 is a vertical sectional side view of a soldered state of first and second circuit boards showing another example of the circuit board according to the present invention.

FIG. 8 is a plan view showing a soldering state of first and second circuit boards showing a conventional example of a circuit board.

FIG. 9 is a sectional view taken along line AA in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 1st circuit board 12 Through hole for connection 13 Through hole for visual observation 17 2nd circuit board 18 Land electrode of 2nd circuit board 20 Solder 21 Land electrode on the back of 1st circuit board

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuo Taguchi 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Denki Co., Ltd.

Claims (6)

[Claims] A through hole (12) penetrating a substrate, and a through hole conductor (1) made of a conductive film is formed on a peripheral surface thereof.
5) a first circuit board (11) on which a land electrode (1) is formed on the surface corresponding to the through hole (12);
8) having a second circuit board (17) formed thereon, mounting the first circuit board (11) on the second circuit board (17), and passing through the first circuit board (11). Hall conductor (1
5) the land electrode (18) on the second circuit board (17)
The first circuit board (1)
1) A circuit board characterized in that a through hole (13) for visual observation is formed in connection with the through hole (12). 2. The circuit according to claim 1, wherein a conductor film is not formed on a peripheral wall of the through-hole for visual observation, and the peripheral wall is a wall surface on which a conductive fixing material does not adhere. substrate. 3. A through hole (12) having a through hole conductor (15) for a visual observation through hole (13).
2. A plurality of circumscriptions are provided around the periphery of the sphere.
A circuit board according to claim 1. 4. A through hole (12) having a through hole conductor (15) for a visual observation through hole (13).
The circuit board according to claim 1, wherein the circuit board is larger. 5. A land electrode (2) made of a conductive film on the back surface.
A first circuit board (11) on which 1) is formed, and a land electrode (18) on the surface corresponding to the land electrode (21).
And a second circuit board (17) on which the first circuit board (11) is mounted on the second circuit board (17).
In a circuit board in which the land electrode (21) of the first circuit board (17) is conductively fixed to the land electrode (18) on the second circuit board (17), the land on the back surface of the first circuit board (11) A circuit board having a through hole (13) for visual observation formed adjacent to an electrode (21). 6. The circuit according to claim 5, wherein a conductor film is not formed on a peripheral wall of the through hole for visual observation, and the peripheral wall is a wall surface to which a conductive fixing material does not adhere. substrate.