Plan Overview:

In recent years, with the increasingly fierce competition in the consumer electronics market, the electronic manufacturing industry has put forward higher requirements for products. Traditional processing methods can easily lead to unstable product quality, melting of parts, difficulty in forming normal melt nuclei, and low yield of finished products. The emergence of laser processing technology can quickly solve these problems for electronic product manufacturers. Laser processing plays an important role in optimizing the volume and improving the quality of high-end electronic products, making them lighter, thinner, and more stable. It is reported that about 70% of electronic product processing and manufacturing processes are applied to laser technology (more than 20 different processes) and related manufacturing equipment.

At present, laser precision spot welding is mainly used in electronic products such as casings, shields, USB connectors, conductive patches, etc. It has the advantages of small thermal deformation, precise and controllable action area and position, high welding quality, the ability to weld dissimilar materials, and easy automation. However, different welding methods are required when welding different materials.

Based on multiple experimental results, Chu Yu Optoelectronics' laser welding engineer has summarized what kind of laser precision spot welding should be used for different materials, such as high reflective materials, sheet metal, and dissimilar materials, in order to achieve the best welding effect.

Laser precision spot welding of highly reflective materials:

When welding high reactive materials such as aluminum and copper, different welding waveforms have a significant impact on the welding quality. A laser waveform with a front peak can break through the high reflectivity barrier, and the instantaneous peak power can quickly change the state of the metal surface, causing its temperature to rise to the melting point, thereby reducing the reflectivity of the metal surface and improving energy utilization. In addition, due to the fast thermal conductivity of materials such as copper and aluminum, slow waveform can be used to optimize the appearance of solder joints.

On the other hand, the absorption rate of laser by materials such as gold, silver, copper, and steel decreases with increasing wavelength. For copper, when the laser wavelength is 532nm, the absorption rate of copper is close to 40%. Comparing the characteristics of infrared laser and green laser, it can be seen that infrared laser has a larger spot size, shorter depth of focus, and lower copper absorption rate. The green laser spot size is small, the focal depth is long, and the copper absorption rate is high. Using infrared laser and green laser respectively for pulse spot welding of copper, it can be found that the size of the weld after infrared laser welding is different, while after green laser welding, the size of the weld is more uniform, the depth is consistent, and the surface is smooth. The green laser welding effect is more stable, and the required peak power will be more than half lower than that of infrared laser.

Laser precision spot welding of metal sheets:

When traditional millisecond laser welding metal sheets, the material is prone to breakage and the weld points are large. However, due to the instability and low absorption rate of solid-state lasers, welding of high reflective materials often results in phenomena such as explosion points and virtual welding. In order to solve the welding problem of thin plates and high resistance metal alloys, the QCW/QCW modes of fiber lasers are modulated with analog and digital signals, respectively. One trigger can output N pulses, and low-power single point multi pulse welding is achieved.

Laser precision spot welding of dissimilar materials:

When laser welding dissimilar materials of thin plates, problems such as virtual welding, cracks, and low connection strength are prone to occur. This is due to the significant difference in physical properties between the two materials, low mutual solubility, and easy formation of brittle compounds, greatly reducing the mechanical properties of the welded joint. By utilizing high-quality nanosecond lasers to precisely control heat input, suppress the formation of intermetallic compounds, achieve the overlap of dissimilar metal sheets, and improve weld formation and mechanical properties.

Quasi continuous fiber lasers and MOPA pulse fiber lasers with adjustable pulse width have become ideal light sources for laser spot welding due to their high beam quality, peak power, adjustability, and controllability.