Beijing Welder Technology Co., Ltd

Abstract: The technical principle, classification, technical characteristics of welding using resistance heat and its application in the field of metal component packaging are briefly introduced.

First, the basic principle of resistance welding technology

Heat is generated when an electric current passes through a conductor, which is resistance heat. According to Joule's law: Q = I2Rt, the heat generated by the current passing through the conductor is proportional to the resistance of the conductor, proportional to the square of the current flowing through the conductor, and proportional to the time of power-up.

Resistance welding is generally a method of applying a certain pressure to the welded workpiece, using the workpiece as a load resistance, supplying power to the workpiece through the upper and lower electrodes, and using the Joule heat generated by the current through the workpiece to melt the contact surface between the two workpieces to achieve two contact surface welding. The welding process is shown in Figure 1, first through the upper and lower electrodes to apply a certain pressure to the workpiece, and then through the upper and lower electrodes to the workpiece to energize a certain time to complete the welding of the workpiece, the right side of the figure is three different workpiece materials corresponding to the temperature curve, from the single workpiece welding temperature curve, in the workpiece contact surface position temperature to reach the highest, in addition to different conductive materials, welding temperature is different.

The general welding process of resistance welding is: pre-pressing, so that the surfaces of the two materials to be welded are in contact; After pressing, the electrode is discharged, and the contact part of the solder material is melted by resistive heat to produce a molten core; Pressing, applying appropriate welding pressure to the solder, so that the molten liquid metal fills the welding surface, and at the same time extrudes excess liquid metal and oxidation inclusions on the end face, so that the clean plastic metal is in close contact, and the solder joint area produces certain plastic deformation to promote the progress of recrystallization, form a common grain, and obtain excellent solder joints.

Figure1Schematic diagram of resistance welding

Second, the characteristics of resistance welding

1. The welding process does not require flux or welding wire, and does not produce waste gas, making it more environmentally friendly compared to traditional welding methods.

2. The welding process does not produce welding slag, and the welding surface is clean and beautiful.

3. The energy is concentrated, the welding time required is short, and the production efficiency is high.

4. The molten core is always surrounded by metal, isolating the air, and the welding quality is high.

5. Resistance welding equipment generally has large power, mechanization and high degree of automation.

Third, the classification of resistance welding technology

Spot welding (Spot Welding): It is a welding method that uses columnar positive and negative electrodes to pre-press, discharge and press the required welding materials, and the stroke is more concentrated. Spot welding is mainly used for thin plate welding.

Seam welding: The process of seam welding is similar to spot welding, which is a welding method that replaces the cylindrical electrode with a rotating disc-shaped roller or ring electrode to discharge and form a continuous weld. It can be divided into roll welding and primary forming welding, which can form a continuous weld. It is mainly used to weld the structure of regular weld and sealing, and the plate thickness is generally below 3mm. In the field of metal component packaging, seam welding is used.

Butt welding (Butt welding): also known as touch welding, is a resistance welding method that welds the weldment along the entire contact surface, and is often used for metal welding of larger contact planes.

Projection welding is a variant of spot welding; There are prefabricated bumps on one workpiece, and when convex welding, one or more molten cores can be formed at the joint at a time.

Fourth, the application of resistance welding technology in the field of metal component packaging

Due to the many advantages of resistance welding methods, resistance welding technology is widely used in metal packaging processes in optical communications, semiconductors, sensors and other industries. For example, resistance welding based on capacitor energy storage can complete one-time welding of TO metal-like packaged components, as shown in Figure 2, and a large current is provided by the upper and lower electrodes to complete a forming seam weld; For SMD (Surface Mounted Devices, surface-mount components), generally use welding power supply to be packaged in parallel seam welding, as shown in Figure 3 for parallel welding equipment working drawing, for some smaller size surface-mount components, in order to prevent the relative displacement of the base and cover plate during the packaging process, it can be packaged by spot welding and then parallel seam welding.

Figure2Upper and lower electrodes of energy storage packaging equipment

Figure3Working drawing of parallel seam welding equipment