JPH06325802A - Connecting method for printed circuit board conductor and metallic part - Google Patents

Abstract

PURPOSE:To weld a metallic part, such as a lead or the like forming an electronic part, to a conductor on a printed circuit board in low proportion defective. CONSTITUTION:At least one of the interconnected faces of a conductor on a printed circuit board and a metallic part is plated with nickel or gold, so that the amount of an oxide film causing incomplete welding formed on the face may be reduced or completely reduced to zero for welding the part to the conductor. This can reduce proportion defective on the welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting conductors on a printed circuit board and metal parts by welding.

[0002]

2. Description of the Related Art Conventionally, when connecting a metal part such as a lead of an electronic part to a conductor on a printed circuit board, a connector is formed at the end of each part or solder is used between both parts. The method of brazing with a brazing material such as the above is often used.

[0003]

Although the connector connection has the advantage of being removable, on the other hand, an increase in the number of parts is unavoidable, and therefore it is expensive if only the conductors need to be directly connected, and the electronic circuit is small. It is not preferable from the viewpoint of conversion, and it is desirable not to use it as much as possible.

Conventionally, soldering has been often used for the portion where the conductors are directly connected to each other, and a connecting method using bumps has been researched and developed. However, this is not preferable in terms of reliability.

Therefore, as a method for avoiding these problems, it has been considered to directly weld the conductor and the metal component on the substrate. For example, the applicant of the present invention also discloses Japanese Patent Application No. 5-8602.
No. 4 proposes an improved method of conventional resistance welding.

However, in resistance welding, if the surface condition of the interconnecting surface is poor, especially when an oxide is present, the heat generation conditions for energization will delicately vary due to changes in electrical resistance, resulting in a very thin object to be connected such as a copper foil conductor. In the case of, the failure rate was often high due to damage such as welding or no joining at all. As a countermeasure, it is possible to remove the oxide film before welding, but this method increases the process cost, and because the interconnecting surface is exposed to high temperature in the atmosphere, especially when electricity is applied, it is likely that oxidation will occur at that time. However, there is a problem that the effect of the pretreatment (removal of the oxide film) is small because the substance is formed.

[0007]

As a means for solving the above problems, the present invention employs a method in which at least one of the interconnection surfaces of a conductor and a metal component is plated with nickel or gold and then welded.

The thickness of the plating layer made of nickel or gold is preferably 0.1 μm or more and 20 μm or less.

[0009]

In the connecting method according to the present invention, the resistance welding machine is used to carry out electrical heating. The electrodes are arranged so as to contact only the metal parts such as lead wires of the electronic parts, and when the electrodes are energized without contacting the conductors of the circuit board, only the metal parts are electrically heated. Then, when the heated metal part is pressure-bonded to the conductor by the pressing means, the both are firmly joined.

At this time, if the conductor of the printed circuit, the metal component, or both are plated with nickel or gold, the defective fraction of welding is reduced. This is because even if the conductor and metal parts are stored for a long time before welding, if the nickel plating is applied, the oxide film remains very thin and does not grow, and even if exposed to high temperature during welding, the oxide film does not grow. Is due to the fact that it remains thin and difficult to grow as it does during storage. In the case of gold plating, the oxide film itself is not formed, so very good bonding can be expected.

The thickness of the plating is from 0.1 μm to
The reason why 20 μm is preferable is as follows. 0.
In the case of plating with a thickness of less than 1 μm, the surface of the conductor or metal component is likely to be exposed due to plating defects such as pinholes, and the surface of the conductor or metal component is oxidized. On the other hand, even if it is thicker than 20 μm, its effect is not improved, but it only causes problems such as an increase in cost and a decrease in flexibility.

[0012]

Example-Experimental Example 1-A circuit of a copper foil conductor having a thickness of 35 µm was formed on a polyimide film, and a lead pin having a thickness of 0.6 mm was joined thereto by resistance welding. The conductors or lead pins were plated as shown in Table 1. The plating thickness is all 2 μm. The bonding failure rate at this time is also shown in Table 1. Here, the defect is judged to be defective when the conductor is pulled from the lead pin in a direction having an angle of 90 ° with respect to the pin and peeling occurs at the bonding interface.

[0013]

[Table 1]

As is clear from Table 1, if the copper foil conductor or the lead pin is plated with nickel or gold, the defective fraction of welding is greatly reduced.

Experimental Example 2 A copper foil conductor circuit having a thickness of 35 μm was formed on a polyimide film, and a lead pin having a thickness of 0.6 mm was joined thereto by resistance welding. Both the conductor and the lead pin were gold-plated with the thickness shown in Table 2. The conductor and the lead pin had the same plating thickness. Table 2 shows the bonding failure rate at this time. The defect determination in this case is performed with the same contents as in Experimental Example 1.

[0016]

[Table 2]

As shown in Table 2, the plating thickness is 0.1 μm.
When it is less than m, the effect is hardly exhibited, and when it is more than 20 μm, the effect is not improved.

[0018]

As described above, according to the connection method of the present invention, the welding defect rate when welding a conductor on a printed circuit board and a metal component can be reduced, which is advantageous in terms of productivity and cost reduction. The effect that it becomes is obtained.

Claims (2)

[Claims] 1. When welding a conductor and a metal component on an insulating substrate, at least one of the interconnection surfaces is plated with nickel or gold, and then welded. How to connect. 2. The plating is 0.1 μm or more and 20 μm
The method for connecting a printed circuit board and a metal component according to claim 1, having the following thickness.