After years of development in the lithium battery industry, from the initial AC pulse spot welder to the energy storage spot welder, intermediate frequency spot welder, transistor spot welder, and then to the laser spot welder, spot welding equipment has been continuously upgraded. The quality is also constantly improving.

AC Pulse Spot Welder

The thyristor is controlled by the single-chip microcomputer to intercept the AC pulse voltage to the primary coil of the welding transformer, and the transformer converts the high-voltage pulse into a low-voltage large current and outputs it to the spot welding needle for discharge spot welding.

The advantages of AC pulse spot welding machine are low cost and low failure rate. The disadvantage is that once the thyristor is triggered and turned on, its turn-off must wait until the AC zero-crossing point before it can be turned off, which leads to prolonged welding time. It is not beneficial to the welding effect, it will only increase the temperature of the solder joints, and it is easy to cause the power to be reduced and the virtual welding to be reduced, and the frying welding and tin melting, etc. to be increased. This phenomenon is very common in the spot welding of nickel sheets on the protective plate, because the tin under the pads of the protective plate is very sensitive, which reflects the indisputable fact that the spot welding temperature of AC pulse is high. Therefore, when spot welding the negative electrode of the aluminum shell or the positive electrode of the steel shell, due to the small area of ​​the rivets, it is not easy to dissipate heat, and the sealing ring is often melted. The phenomenon.

Energy storage spot welding machine

The energy storage spot welding machine has concentrated discharge energy, short welding time and relatively low cost, which is very suitable for battery spot welding. However, it has a large welding spark and a high failure rate. The capacity attenuation of the energy storage capacitor will also lead to a decline in welding performance. Especially in recent years, with the rise of welding automation, limited by the charging time of the energy storage capacitor, the welding energy cannot be quickly and stably output. Therefore, It is only suitable for manual spot welding.

Intermediate frequency welding power source

The frequency and control method of the inverter welding machine are important indicators for judging its performance. Generally 1-10KHz inverter frequency is collectively referred to as intermediate frequency, and above 10KHz is referred to as high frequency. In the control mode, the primary side constant current is an ideal control method. The primary side constant current adopts closed-loop control, which can adjust the high-frequency pulse width according to the actual output current. If it is worse, it adopts fixed pulse width modulation, which belongs to open-loop control. During spot welding, the spot welding needle and the weldment itself will have a great influence on the welding, so the stability is relatively poor. The frequency of intermediate frequency welding power supply is generally better at 4-5KHz. On the one hand, a stable welding waveform can be obtained at the output end, and on the other hand, a large discharge current can be fed back and controlled in this frequency band. The transformer needs a certain response time, and the frequency is too high. , the current does not do much.

Transistor welding power source

The most ideal resistance welding power source does not need a welding transformer, the current rises quickly, and the current waveform is directly output at high frequency. You can choose constant current, constant voltage or constant current and constant voltage control mode, but it also has the disadvantage of being expensive.

Laser spot welding machine

It is composed of crystal, xenon lamp, condensing cavity, optical resonant cavity, cooling filter parts and laser power supply. In the battery industry, the welding of steel shells and aluminum shell cover plates has long been widely used. In recent years, spot welding of polymer PACK protective plates has also been used. Compared with resistance welding, laser welding machine has the advantages of not needing to grind the spot welding needle, the welding is firm, the welding spot is uniform, and it is not easy to produce false welding.

From the manufacture of lithium-ion battery cells to battery pack grouping, welding is a very important manufacturing process. The conductivity, strength, air tightness, metal fatigue and corrosion resistance of lithium-ion batteries are typical of the quality of battery welding. evaluation standard. The selection of welding methods and welding processes will directly affect the cost, quality, safety and consistency of lithium-ion batteries.

Among many welding methods, laser welding for lithium-ion battery processing stands out with the following advantages: First, laser welding has high energy density, small welding deformation, and small heat-affected zone, which can effectively improve the accuracy of parts, and the weld seam is smooth without impurities, uniform and dense , No additional grinding work is required; secondly, laser welding can be precisely controlled, the focus spot is small, high-precision positioning, and it is easy to realize automation with the mechanical arm, improve welding efficiency, reduce man-hours, and reduce costs; in addition, laser welding of thin plates or small diameters When wire is used, it is not as susceptible to meltback as arc welding.