JPH0246981A - Resistance welding method - Google Patents

Abstract

PURPOSE:To decrease the fluctuation in joining strength even in case of resistance welding of microparts such as electronic parts by executing welding of works dividely in two stages and specifying the respective pressurizing forces and welding currents. CONSTITUTION:The welding of the works 4, 5 is executed by dividing the welding to preliminary joining and normal joining. The pressurizing force at the time of the preliminary joining is set larger than the pressurizing force at the time of the normal welding and the welding current at the time of the preliminary joining is set smaller than the welding current at the time of the normal welding. The joint surfaces of the works 4, 5 are made into the joint surfaces having the stable resistance welding value in this way. Welding of the joint surfaces having the stable contact resistance value by the prescribed welding current is possible at the time of the normal joining. The fluctuation in the joining strength of the microparts such as electronic parts for which high quality is required is, therefore, decreased and the deformation of the joint part is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resistance welding method for micro parts such as electronic parts, and particularly to a resistance welding method that can obtain stable joint strength.

[Conventional technology]

As prior art related to the present invention, Japanese Patent Application Laid-Open No. 61-529
No. 95 is known. The spot welding robot disclosed in this publication is one in which a movable 1i stirrer is moved by the robot, and when the movable electrode is brought into contact with the workpiece, a pressing force of the first set pressure is applied to the movable electrode, and the welding Sometimes, a pressurizing force of a second set pressure higher than the first set pressure is applied to the movable electrode.

By the way, 1. In resistance welding, a current is usually concentrated in a part of the workpiece, and the workpieces are welded using Joule heat generated by the resistance of the workpiece itself. At the initial stage of energization in resistance welding, the heat generating portion and amount of heat change depending on the contact resistance between the workpieces and between the tti and the workpiece, so it is important to stabilize this contact resistance value.

(Problem to be solved by the invention) However, micro parts such as electronic parts (for example,
．． In resistance welding of lead material with a thickness of 1 to 0.3 fl or wire material of 0.1 to 0.81 m, the range of welding conditions (setting range of energizing time, energizing current, pressing force, etc.) is normal for parts. Since the contact resistance of the joint surface at the start of welding is narrow compared to the t
There was a problem in that it was difficult to obtain a 9-point contact point.

The present invention has focused on the above-mentioned problems, and an object of the present invention is to provide a resistance welding method that can obtain stable joint strength with little variation even when resistance welding minute parts such as electronic parts.

[Means to solve the problem]

A resistance welding method according to the present invention that meets this objective is a resistance welding method in which workpieces are welded together by pressurizing stacked workpieces and passing a current through the pressurized portion, the welding of the workpieces is performed by preliminary joining and main joining. The welding process is carried out in two stages, in which the pressurizing force during preliminary welding is made larger than the pressurizing force during main welding, and the welding current during preliminary welding is made smaller than the welding current during main welding.

[Effect]

In such a resistance welding method, since the pressing force is large during the initial preliminary joining, the contact resistance value of the joint surfaces of the workpieces can be maintained at a substantially constant value.

That is, by preliminary bonding, the bonding surface of the workpiece can be made into a bonding surface having a stable contact resistance value. Then, at the time of main joining, the welding current is made larger than the welding current during preliminary joining, and the joining surfaces having a stable contact resistance value are pressurized with a small pressure force, and welding is performed. Therefore, it is possible to reduce the variation in bonding strength compared to the conventional case of one-time welding, and it is also possible to suppress the occurrence of uneven deformation in the bonded portion.

〔Example〕

Preferred embodiments of the resistance welding method according to the present invention will be described below with reference to the drawings.

FIG. 2 shows a resistance welding device for carrying out the present welding method. In the figure, ■ indicates an air cylinder as a pressure cylinder in a resistance welding device, and air cylinder 1
A movable electrode 2 is attached to the tip of the rod 1a. A fixed electrode 3 is arranged at a position facing the movable electrode 2. Between the movable electrode 2 and the fixed electrode 3, a workpiece 4.5 as a minute component is placed in an overlapping state. The workpiece 4 has a thickness of ll, as shown in FIG.
The workpiece 5 is composed of an M4 plate with a diameter of 0.1 μ.
Thickness l! is made of a 0.8-inch brass plate. This work 4.5 is used as an electronic component that requires high quality.

Air is force fed to the air cylinder 1 only when the workpiece 4.5 is pressurized, and when the workpiece 4.5 is not pressurized, the rod 1a is returned by a spring built into the air cylinder 1. An air pipe 6 is connected to the air cylinder 1, and its upstream side is branched into two air pipes 7.8.

One air pipe 7 is connected to an air regulator IO via a solenoid valve 9, and the air regulator IO is connected to an air supply source 11. The air regulator 10 sets the finishing pressure to be fed to the air cylinder 1, and the set pressure is variable depending on the conditions of the workpiece and the like. The other air pipe 8 is connected to a surge tank 13 via an 'iM1 valve 12. The surge tank 13 is an air reservoir having a predetermined volume, and is configured to temporarily store air discharged from the air cylinder 1.

The surge tank 13 is connected via a solenoid valve 15 to an air pipe 14 that communicates with the outside.

Each solenoid valve 9.12.15 is configured to open and close the pipeline by an electric signal, and during preliminary connection, the solenoid valve 9.
15 is opened, and the tvA valve 12 is closed.

At the time of main joining, the solenoid valves 9.15 are controlled to be closed and the solenoid valves 12 are opened.

Next, the resistance welding method of the present invention will be explained.

When welding the workpiece 4.5, the solenoid valve 9 is first opened,
The mouth 7 door 1a of the air cylinder 1 is expanded by the air pumped from the air supply source 11, and the workpiece 4.5 is squeezed between the movable electrode 2 and the fixed electrode 3 and pressurized. As shown in FIG. 1, the pressurizing force P1 during preliminary bonding is larger than the pressurizing force P2 during main bonding, which will be described later.
The force is based on the set pressure. At the same time that the workpiece 4.5 is pressurized with a predetermined force, a voltage is applied between both electrodes, and welding is performed by applying current (welding current 1.5). In the case of this preliminary bonding, since the pressure applied to the workpiece 4.5 is large, the contact resistance value of the joint surface 21 of the workpiece 4.5 can be maintained at an almost constant value, as shown in FIG. . In other words, a bonding surface with a stable contact resistance value can be formed by preliminary bonding.

When the preliminary joining is completed, the solenoid valve 9 and the solenoid valve 15 are closed, and only the solenoid valve 12 is opened. Therefore, some of the air that was being pumped into the air cylinder 1 is transferred to the surge tank 1.
The pressure of the air flowing into the air cylinder 3 and acting on the air cylinder 1 is reduced. Therefore, the pressurizing force P2 during the main bonding is lower than the pressurizing force P during the preliminary bonding, as shown in FIG. Workpiece 4.5 has pressure P! When repressurized with
Voltage is applied again between both electric wires, energizing (welding current rt)
Welding current I when welding is performed by
! is larger than the welding current ■ during preliminary bonding,
In addition, since the welding time T2 is longer than the welding time T1 during preliminary joining, the joint surfaces are sufficiently melted and the joint strength between the workpieces 4 and 5 is maintained at a desired value.

Table 1 shows a comparison of experimental results of welding conditions and joint strength between the present invention and the conventional resistance welding method.

Table 1 As shown in Table 1, the average value of bonding strength . Also,
The amount of unevenness of the joint part of the workpiece 4.5 is also smaller in the present invention than in the conventional method of welding in one step, and the quality of the joint part is improved.

〔Effect of the invention〕

As explained above, when using the resistance welding method according to the present invention, workpieces are welded in two stages: preliminary joining and main joining, and the pressurizing force during preliminary joining is greater than the applying force during main joining. Since the welding current during preliminary joining is made smaller than the welding current during main joining, the joint surface of the workpiece can be made into a joining surface with a stable contact resistance value by preliminary joining, and the welding current during main joining can be made into a joining surface with a stable contact resistance value. Sometimes it becomes possible to weld a joint surface having a stable contact resistance value with a predetermined welding current. Therefore, it is possible to reduce variations in the bonding strength of microcomponents such as electronic components that require high quality, and also to suppress the amount of deformation of the bonded portion.

[Brief explanation of the drawing]

FIG. 1 is a time chart showing the relationship between welding current and pressing force in a resistance welding method according to an embodiment of the present invention, FIG. 2 is a schematic diagram of a resistance welding device to which the present invention is applied, and FIG. 1 is a partially enlarged sectional view of a workpiece to be joined according to the present invention; FIG. l... Air cylinder 4.5... Work 9.12.15... Magnetic valve IO... Air regulator 13... Surge Tank patent applicant Toyota Motor Corporation glf
lf'z Maesui Duse

Claims (1)

[Claims] 1. In a resistance welding method in which workpieces are welded together by pressurizing stacked workpieces and passing a current through the pressurized portion, welding of the workpieces is performed in two stages: preliminary joining and main joining, and during preliminary joining. A resistance welding method characterized in that the pressure is greater than the pressure applied during main welding, and the welding current during preliminary welding is smaller than the welding current during main welding.