JPS61140365A - Electric resistance welding method - Google Patents

Abstract

PURPOSE:To form the joint pat having good operability and sufficient joining strength by performing an electric resistance welding with interposing an Ag inserting material between high conductive materials to be welded. CONSTITUTION:A welding current is flowed between electrodes 3, 4 by interposing Ag inserting material 5 between the lead frames 1, 2 consisting of a high conductive material, by pinching from the upper and lower parts by electrodes 3, 4 are with pressing, if necessary. A contact face 10, 10a is therefore formed between said inserting material 5 and lead frames 1, 2 respectively and the contact resistance is increased by the increase in the contact area. Because of there being the oxidized film having big resistance on the surface of the inserting material 5, the Ag inserting material 5 and lead frames 1, 2 are fused without depositing the electrodes 3, 4 and lead frames 1, 2 and the lead frames 1, 2 are strongly joined each other.

Description

[Detailed Description of the Invention] [Industrial Field of Application J] The present invention provides a joint portion that is easy to work with and has sufficient joint strength for electrical resistance welding of highly electrically conductive materials to be welded together. The present invention relates to an electric resistance welding method that allows for.

[Background Art] Semiconductor devices such as ICs have made remarkable progress, and the demand for lead frames that support IC packages has also increased significantly. Important properties required for such lead frames include moldability, adhesion of bonding plating, and thermal properties. That is, as the size of computers progresses, the amount of computer operation required (1$4rl:) also increases.

If the heat storage capacity of each component becomes too large and the temperature of the computer body rises excessively, computer functions may be impaired. Therefore, materials for forming lead frames are desired to have a low calorific value and good heat dissipation, that is, materials with high electrical conductivity and thermal conductivity. They are being replaced by alloys.

By the way, when constructing a computer by combining ICs, etc., lead frames are often joined together, but electric resistance welding is used for this joining, and there is no particular problem when using Fe-Ni alloys. A good joint was obtained. That is, when electrical resistance welding the lead frames together, for example, as shown in Fig. 2, lead frames 1 and 2 are placed one on top of the other, held between '1Ji 3 and 4, and welded between electrodes 3 and 4 while pressing. A current is flowing through the lead frame (Fe-Ni alloy: 3
Since the electrical resistance of %IAC3) is considerably larger than the electrical resistance of the electrode, heat is generated mainly in the lead frame portion and the contact surface 6 of the lead frame 1.2 is fused.

By the way, since current flows through the electrodes, in order to prevent the electrodes from generating heat, they are generally made of a Cu alloy with high electrical conductivity, and the electrodes themselves are also usually water-cooled. However, since temperature rise cannot be completely prevented, high mechanical properties are also required in order to prevent deformation under the temperature rise. However, since electrical conductivity and mechanical properties are contradictory physical properties, it is necessary to sacrifice electrical conductivity to some extent in order to satisfy mechanical properties. -C
The electrical conductivity of the u alloy is approximately 90% lAC3.

However, the lead frame is made of a highly electrically conductive material (approx.
In the case of OO%IAC3), the electrical resistance of the lead frame becomes small, and it is difficult to expect heat to be generated in the facing parts of the lead frames, so it is difficult to weld the lead frames together, and in some cases, it is almost impossible to weld them together. becomes impossible. Therefore, the idea of increasing the above heat generation by increasing the welding current has come up, but since the electrical resistance of the electrode is greater, the heat generation on the electrode side increases more than necessary, causing contact between the electrode and the lead frame. Coupled with heat generation due to surface resistance and pressure applied to the contact surface, the contact surface of the electrode and the lead frame are fused together, resulting in the inconvenience that the lead frames cannot be fused together.

Therefore, we had no choice but to use a Cr-Cu alloy electrode 3.4 with carbon or tungsten 8 coated on the tip of the electrode in order to increase the amount of heat generated, as shown in Figure 3, and a brazing material between the lead frame 1.2. Brazing is performed by intervening. However, in the case of brazing, the brazing material 9 melts due to the heat generated by the electrode tip 8, and the bonding strength is low because the brazing material 9 is only connected to both lead frames 1.2 by wetting.

[Problems to be Solved by the Invention] The present invention has been made by paying attention to these circumstances, and it is possible to weld a highly electrically conductive material without welding an electrode and a highly electrically conductive material (for example, the above-mentioned lead frame). The object of the present invention is to provide an electric resistance welding method that can join materials to be welded together with sufficient strength.

[Means for Solving the Problems 1] The gist of the present invention, which combines the above-mentioned objects, lies in the fact that electrical resistance welding is performed by interposing an Ag-based insert material between highly electrically conductive materials to be welded. .

[Function] FIG. 1 is a schematic diagram for explaining the basic configuration of the method of the present invention. When bonding lead frames made of highly electrically conductive materials, Ag is placed between lead frame 1 and lead frame 2. A system insert material 5 is interposed, and the electrode 3.
In step 4, sandwich this from the top and bottom in the figure and apply pressure as necessary while applying welding current between electrodes 3 and 4. By doing this, the Ag-based insert material and lead frame 1.2 are fused together and the lead frames are made stronger. Join.

In the present invention, electric resistance welding is achieved as described above by interposing the Ag-based insert material between the Ag-based insert material 5 and the lead frame 1.2, respectively, at the contact surfaces 10. This is because 1Oa is formed and the contact resistance increases due to the increase in the contact surface.Furthermore, due to the oxidized S that protects the surface of the Ag-based insert material, the loA contact resistance value is lower than that of the contact surface between lead frames. We believe that this is because it becomes larger than the contact resistance value. That is, as the contact resistance increases, the amount of heat generated between the lead frames increases, and as a result, the Ag-based insert material and the lead frame melt and fuse together.

In addition, the insert material in the present invention must be an Ag-based insert material, that is, the insert material itself is located at the connection part between lead frames made of a highly electrically conductive material, so it must itself be highly electrically conductive. Ag-based insert materials not only have high electrical conductivity but also must provide high bonding strength to the joints between lead frames. As is clear from the phase diagram, Ag and Cu, which are the main components of the insert material, form a solid solution with each other to form a eutectic, and a brittle intermetallic compound is formed between Cu and Ag. There is no fear, therefore high electrical conductivity and excellent bonding strength can be obtained. Such Ag-based insert materials include Ag, Ag alloy, and
Examples include g wax, etc.

[Example 1] The highly electrically conductive materials to be welded shown in Table 1 were arranged as shown in Figure 1, and electrical resistance welding was performed under the conditions shown below and in Table 1. Conductivity was measured.

Welding conditions Electrode: Cr-Cu alloy 8mm diameter Pressure force: 100kg As shown in Table 1, no insert material was used for No. 1, No. 1, and No. 14, so the materials to be welded did not fuse together. In the examples in which tough pitch copper or Fe-P copper alloy was interposed as the insert material for No. 2 and No. 54t, respectively, the type of insert material was inappropriate, so they were not fused.

No. 6 was an example in which a phosphor bronze insert material was used, and not only the electrical conductivity of the joint was poor, but also a sufficient value of joint strength could not be obtained. For these, No. 3 and N
Since Ag was used as the insert material in No. 017, it was possible to obtain a joint that satisfied both the joint strength and electrical conductivity.

Furthermore, there was no welding between the electrode and the material to be welded during joining.

[Effects of the Invention] The present invention is configured as described above, and since electrical resistance welding is performed by inserting an Ag-based insert material between highly electrically conductive materials to be welded, the joint strength and electrical conductivity can be improved. It is possible to obtain a joint that satisfies both aspects.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a welding mode according to the present invention. FIG. 2 is a schematic diagram showing a conventional electric resistance welding mode. FIG. 3 is a schematic diagram showing a conventional wax Mi malfunction.

Claims (1)

[Claims] An electric resistance welding method characterized by interposing an Ag-based insert material between highly electrically conductive materials to be welded.