How to make laser welding of different materials more precise and achieve better process effects

In the production process of high-end electronic products, laser processing plays a major role in product volume optimization and quality improvement, making the products lighter, thinner and more stable.

In the production process of high-end electronic products, laser processing plays a major role in product volume optimization and quality improvement, making the products lighter, thinner and more stable.

At present, laser precision welding is mainly used in casings, shields, USB connectors, conductive patches, etc. of electronic products. It has small thermal deformation, precise and controllable area and position of action, high welding quality, can realize welding of dissimilar materials, and is easy to implement. Automation and other advantages. But when welding different materials, different welding methods are required.

Based on the results of many experiments, laser welding engineers have summarized what methods should be used for laser precision spot welding of different materials such as highly reflective materials, metal sheets, and dissimilar materials in the manufacturing process of consumer electronics in order to obtain the best results. Good welding effect.

1. Laser precision spot welding method of highly reflective materials

When welding highly reflective materials such as aluminum and copper, different welding waveforms have a great impact on the welding quality. Using a laser waveform with a leading peak can break through the high reflectivity barrier. The instantaneous high peak power can quickly change the state of the metal surface and raise its temperature to the melting point, thus reducing the reflectivity of the metal surface and improving energy utilization. In addition, since materials such as copper and aluminum conduct heat quickly, the appearance of the solder joint can be optimized by using a slow-down waveform.

On the other hand, the laser absorption rate of gold, silver, copper, steel and other materials decreases as the wavelength increases. For copper, when the laser wavelength is 532nm, the absorption rate 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 sizes of solder joints after infrared laser welding are inconsistent (Figure 1), while the green laser solder joints are more uniform in size, consistent in depth, and have a smooth surface (Figure 1) 2). Therefore, the welding effect of green laser is more stable, and the required peak power will be more than half lower than that of infrared laser.

2. Laser precision spot welding method of metal sheet materials

When traditional pulse lasers weld metal sheet materials, the materials are prone to breakdown and the welding spots are large; while highly reflective materials often have explosive spots and virtual welding due to their own instability and low laser absorption rate in the solid state. Welding and other phenomena. In order to solve the difficulty of welding thin plates and high-reflection metals, the fiber laser QCW/CW mode is subjected to analog and digital modulation respectively. N pulse outputs can be achieved by triggering once, and single-point multi-pulse welding can be achieved with smaller power.

3. Laser precision spot welding method of dissimilar materials

When laser welding thin plates of dissimilar materials, problems such as false welding, cracks, and low connection strength are very likely to occur. This is due to the large difference in physical properties between the two, low mutual solubility, and the easy generation of brittle compounds. These compounds reduce the mechanical properties of the welding joint. Performance is greatly reduced. High-beam-quality nanosecond lasers are used through high-speed scanning to accurately control heat input to suppress the formation of intermetallic compounds, achieve overlapping of dissimilar metal sheets, and improve weld formation and mechanical properties.

Domestic advanced laser's quasi-continuous fiber laser and MOPA pulse width adjustable pulse fiber laser have become the ideal light source for laser precision spot welding due to their advantages such as high beam quality, high peak power, adjustable and controllable.

4. Introduction to the lasers used

A. 150W/1500W quasi-continuous fiber laser

It has various compatibility and control modes, can switch between pulse and continuous modes, and handle the processing tasks of two different lasers at the same time. The pulse width waveform is flexible and adjustable, air-cooled for heat dissipation, the electro-optical conversion rate is more than 30%, and it is a long pulse width. Another choice for high peak power applications.

B. 120W MOPA pulse width adjustable pulse fiber laser

The pulse width adjustable pulse fiber laser uses MOPA to construct two-stage amplification. The pulse width and frequency are independently adjustable, making more laser applications possible. The pulse width is flexibly adjustable from 60 to 350ns, the peak power is up to 10kW, the repetition frequency is up to 1000 kHz, and it is equipped with an online isolator. It is an ideal laser source for fine laser processing.