JPH0794838A - Large current circuit board - Google Patents

Abstract

PURPOSE:To improve the junction strength between a heavy-gage circuit and a copper foil circuit pattern and a long-term reliability by increasing the width of the copper coil circuit pattern as compared with the width of a heavy-gage circuit conductor and then forming a solder fillet between the side surface of the heavy-<gage circuit conductor and the upper surface of the copper foil circuit pattern. CONSTITUTION:In a large-current circuit board, a copper foil circuit pattern 2a for large current is formed on the surface of an insulation substrate 1. In this case, the width of the pattern 2a is formed wider than the width of a heavy- gage circuit conductor 3 and the heavy-gage circuit conductor 3 is soldered onto the copper foil circuit pattern 2a via a solder layer 4 so that a solder fillet 4b is formed between the side surface of the heavy-gage circuit conductor 3 and the upper surface of the copper foil circuit pattern 2, thus increasing the soldering area and at the same time making the soldering surface to be solid. Therefore, the joint strength between the heavy-gage circuit conductor 3 and the copper foil circuit pattern 2 is increased, vibration resistance and heat shock resistance are improved, and hence a long-term reliability is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large current circuit board in which a thick circuit conductor for large current is provided on an insulating board.

[0002]

2. Description of the Related Art An example of a conventional large current circuit board is shown in FIG. In this large current circuit board, a copper foil circuit pattern 2a for large current and a copper foil circuit pattern 2b for minute current are formed on the surface of an insulating substrate 1 such as a glass epoxy substrate by pattern etching of a copper foil. A thick circuit conductor 3 for large current, which is formed by punching a copper plate, is soldered with a solder layer 4 on a copper foil circuit pattern 2a for large current. In the conventional large current circuit board, the width of the copper foil circuit pattern 2a for large current is formed to be the same as the width of the thick circuit conductor 3.

[0003]

A heavy-weight circuit conductor of a large-current circuit board is mounted with a heavy weight power component, and the thick-walled circuit conductor itself has a large weight. If it is installed or installed with the surface of the thick circuit conductor facing down, a large load is applied to the soldered portion between the thick circuit conductor and the copper foil circuit pattern. Therefore, when vibration or heat shock is applied, the thick-walled circuit conductor may peel off from the copper foil circuit pattern, which is problematic in terms of long-term reliability.

In view of the above problems, it is an object of the present invention to provide a long-term reliable high-current circuit board having improved bonding strength between a thick circuit conductor and a copper foil circuit pattern. .

[0005]

In order to achieve this object, the present invention forms a large current copper foil circuit pattern on the surface of an insulating substrate, and a large copper foil circuit pattern is formed on the copper foil circuit pattern via a solder layer. In a large current circuit board obtained by soldering a thick circuit conductor for current, the width of the copper foil circuit pattern is made wider than that of the thick circuit conductor, and the side surface of the thick circuit conductor and the upper surface of the copper foil circuit pattern. And a solder fillet is formed between and.

[0006]

According to the above construction, the thick circuit conductor has its lower surface soldered to the copper foil circuit pattern by the solder layer and its side surface soldered to the copper foil circuit pattern by the solder fillet. Therefore, the soldering area becomes larger than the conventional one, the soldering surface becomes three-dimensional, and the bonding strength between the thick circuit conductor and the copper foil circuit pattern increases.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an embodiment of the present invention. In this large current circuit board, when the large current copper foil circuit pattern 2a is formed on the surface of the insulating substrate 1, its width is made wider than that of the large current thick circuit conductor 3, and the copper When the thick circuit conductor 3 is soldered onto the foil circuit pattern 2a via the solder layer 4a, a solder fillet 4b is formed between the side surface of the thick circuit conductor 3 and the upper surface of the copper foil circuit pattern 2. It is soldered to.

Although FIG. 1 shows a copper foil circuit pattern 2b for minute current, this is shown as an example, and the large current circuit board does not have the copper foil circuit pattern 2b for minute current. There are also things.

[0009]

As described above, in the high current circuit board according to the present invention, the lower surface of the thick circuit conductor is soldered to the copper foil circuit pattern by the solder layer, and the side surface of the thick circuit conductor is soldered by the fillet. Since it is soldered to the copper foil circuit pattern, the soldering area becomes large and the soldering surface becomes three-dimensional. Therefore, the bonding strength between the thick-walled circuit conductor and the copper foil circuit pattern is increased, vibration resistance and heat shock resistance are improved, and long-term reliability is improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a large current circuit board according to the present invention.

FIG. 2 is a sectional view showing a conventional large current circuit board.

[Explanation of symbols]

 1: Insulating substrate 2a: Copper foil circuit pattern for large current 2b: Copper foil circuit pattern for minute current 3: Thick circuit conductor for large current 4a: Solder layer 4b: Solder fillet

Claims (1)

[Claims] 1. A large-sized copper foil circuit pattern for large current is formed on the surface of an insulating substrate, and a thick circuit conductor for large current is soldered on the copper foil circuit pattern via a solder layer. In the current circuit board, the width of the copper foil circuit pattern is made wider than the width of the thick circuit conductor, and a solder fillet is formed between a side surface of the thick circuit conductor and an upper surface of the copper foil circuit pattern. High current circuit board.