Jul 31, 2020
Laser processing has played a significant role in the volume optimization and quality improvement of high-end electronic products, making the products lighter and thinner and more stable.
At present, laser precision welding is mainly used for electronic products like shielding cover, USB connector, conductive patch, etc. It has small thermal deformation, precise and controllable action area and position, high welding quality, can realize welding of dissimilar materials, and is easy to realize automation. But when welding different materials, different welding methods are required.
Based on the results of many experiments, Maxphotonics laser welding engineers summarized the laser precision spot welding method that achieves the best welding results for different materials such as high-reflection materials, metal sheets, and dissimilar materials in the production and manufacturing process of consumer electronic materials.
1. Laser precision spot welding of high reflective materials
When welding high-reflection materials such as aluminum and copper, different welding waveforms have a great influence on the welding quality. The laser waveform with pre-spike can break through the barrier of high reflectivity. The instantaneous high peak power can quickly change the state of the metal surface and raise the temperature to the melting point, thereby reducing the reflectivity of the metal surface and improving the energy utilization rate. In addition, due to the fast heat conduction speed of materials such as copper and aluminum, the appearance of solder joints can be optimized by using the slow-down waveform.
On the other hand, the absorptivity of gold, silver, copper, steel and other materials decreases with increasing wavelength. For copper, when the laser wavelength is 532nm, the absorptivity of copper is close to 40%. In addition, by using infrared lasers and green lasers for pulse spot welding of copper, it can be found that the size of the solder joints after infrared laser welding is inconsistent (Figure 1), while the size of the solder joints of the green laser is more uniform, the depth is consistent, and the surface is smooth (Figure 2). Therefore, the welding effect of green laser is more stable, while the required peak power is only half of infrared laser.
Figure 1. weilding results with infrared laser(1064nm)
Figure 2. weilding results with green laser(532nm)
2. Laser precision spot welding of metal sheet materials
When traditional pulsed lasers are welding thin metal plates, the materials are easily broken down and the solder joints are relatively large. However, due to its own instability and the low absorption rate of the laser in the solid state of high-reflectivity materials, explosion points and virtual defects often appear during welding. Phenomena such as welding. In order to solve the difficulties in welding thin plates and high-reflective metals, the fiber laser QCW/CW mode is respectively modulated by analog and digital, and N pulse output can be realized once triggering, and single-point multi-pulse welding can be realized with smaller power.
Figure 3. weld seam surface; weld cross section
3. Laser precision spot welding of dissimilar materials
When laser welding thin plates of dissimilar materials, problems such as false welding, cracks, and low connection strength are very easy to occur. This is due to the large difference in physical properties between the two, low mutual solubility, and easy generation of brittle compounds. These compounds make the mechanics of the welded joint. Performance is greatly reduced. The high-beam quality nanosecond laser is selected through the high-speed scanning method to precisely control the heat input to inhibit the formation of intermetallic compounds, realize the overlap of dissimilar metal sheets, and improve the weld formation and mechanical properties.
Figure 4. Scanning method; welding surface forming