Application of laser precision spot welding in consumer electronics industry

In recent years, with the increasingly fierce competition in the consumer electronics market, the electronic product manufacturing industry has put forward higher requirements for products. The traditional processing method is easy to lead to unstable product quality, parts melting, difficult to form normal nugget, low yield. The emergence of laser processing technology can quickly solve these problems for electronic product manufacturers. In the production process of high-end electronic products, laser processing plays an important role in the volume optimization and quality improvement of products, making products lighter, thinner and more stable. It is reported that about 70% of the electronic products processing and manufacturing links are applied to laser technology (more than 20 different processes) and related manufacturing equipment.

At present, laser precision spot welding is mainly used in the shell, shield, USB connector, conductive patch, etc. of electronic products. It has the advantages of small thermal deformation, precise control of the working area and position, high welding quality, welding of different materials and easy to realize automation. But different welding methods are needed when welding different materials.

According to the results of many experiments, the optical welding engineer summed up in the manufacturing process of consumer electronics, which way should be used for laser precision spot welding of high reflection materials, metal sheet, dissimilar materials and other different materials, in order to get the best welding effect.

1. laser precision spot welding method of high anti material

When welding high anti materials such as aluminum and copper, different welding waveforms have great influence on welding quality. The laser wave with the front peak can break through the high reflectivity barrier. The instantaneous peak power can change the metal surface state quickly, and make the temperature rise to the melting point, thus reducing the reflectivity of the metal surface and improving the energy utilization rate. In addition, due to the high thermal conductivity of copper and aluminum materials, the appearance of solder joints can be optimized by using the slow down wave.
On the other hand, the absorption rate of gold, silver, copper, steel and other materials decreases with the increase of wavelength. For copper, when the laser wavelength is 532nm, the absorption rate of copper is close to 40%. The results show that the infrared laser has large spot size, short focal depth and low absorption of copper; The spot size of green laser is small, the focal depth is long, and the absorption rate of copper is high. The results show that the solder joints of the infrared laser are not the same after welding, while the size of the solder joints of the green laser is more uniform, the depth is consistent and the surface is smooth (Fig. 1-2). The welding effect of green laser is more stable, and the peak power required will be lower than half of that of infrared laser.

2. laser precision spot welding of sheet metal

When the traditional millisecond level laser is used to weld metal sheet, the material is easy to be broken down and the solder joint is large; Because of its instability and low absorptivity of laser in solid state, high reflection materials often have the phenomenon of burst point and false welding. In order to solve the welding difficulties of thin plate and high anti metal, the QCW / CW mode of fiber laser is modulated by analog quantity and digital quantity respectively. N pulses can be output at one trigger, and single point multi pulse welding can be realized with low power.

3. Laser precision spot welding of dissimilar materials

When laser welding dissimilar materials, it is easy to appear the problems of false welding, crack and low connection strength. This is due to the large difference of physical properties between the two, low mutual solubility, and easy to generate brittle compounds, which greatly reduce the mechanical properties of welded joints. Using high beam quality nanosecond laser, through high-speed scanning mode, accurately control the heat input, inhibit the formation of intermetallic compounds, realize the overlapping of dissimilar metal sheets, and improve the weld forming and mechanical properties.

150W / 1500W quasi CW fiber laser
The product has a variety of compatibility and control modes, can switch pulse and continuous mode, and simultaneously handle the processing tasks of the previous two different lasers. The pulse width waveform is flexible and adjustable, the heat dissipation is fast, and the electro-optic conversion rate is more than 30%. It is another choice for long pulse width and high peak power applications.

120W MOPA pulse width tunable fiber laser
The two-stage amplification of pulse width tunable fiber laser is constructed by MOPA, and the pulse width and frequency can be adjusted independently, which makes more laser applications possible. The pulse width is 60 ~ 350ns, the peak power is 10kW, and the repetition rate is 1000khz. Equipped with self-developed online isolator, it is an ideal laser source for laser fine processing.