Advantages and disadvantages of fiber laser technology for copper welding

Advantages and disadvantages of fiber laser technology for copper welding

The consumer electronics and automotive industries are important drivers of the increasing use of copper in industrial processing and product manufacturing.

As new battery technologies develop and battery capacities become higher, the demand for corresponding connection technologies is also increasing. While soldering remains the dominant technique for low-power applications in consumer electronics, it must be applied in situations where high transmission currents are present, or where joints are subject to high loads and dynamic load stresses.

In the past, laser technology has been limited in welding copper and copper alloys due to the physical properties of the material. Today, the advent of high-power and high-brightness fiber lasers has overcome these limitations, and with new and suitable processing techniques, stable, defect-free joints can be created in an efficient welding process.

The challenges of laser welding copper are related to two main physical properties of the material: low absorptivity to most high-power industrial lasers and high thermal conductivity during the process. We know that the absorption rate of copper increases with decreasing wavelength, which means that lasers in the visible band will yield significant advantages for copper welding.

Infrared lasers create absorption problems when dealing with solid materials. If the material melts or even evaporates by deep penetration welding, its absorption rate increases significantly. The absorption rate of solid copper is less than 4%, while the absorption rate of copper vapor (keyhole penetration welding) is higher than 60%. This absorption problem can be overcome by very high power densities, which greatly speed up the melting and evaporation of copper and thus increase its absorption.

Another problem with the copper soldering process is instability at low speed soldering. Generally, welding speed less than 5m/min will face the problem of welding instability, such as spatter, porosity and irregular weld surface. As the welding speed increases, this instability gradually disappears, and the welding process tends to be stable. In the welding speed range of 5-15m/min, the quality reaches an acceptable level. If the welding speed is higher than 15m/min, the resulting weld is basically free of defects. This means that the optimal welding parameters are within the limits of what conventional motion systems such as robots can achieve. In addition, the weld depth decreases as the welding speed increases, and the weld becomes very narrow.

This must be achieved with higher laser powers, resulting in higher system capital investment. New process studies have shown that this can be completely avoided and that process stability can be achieved not only by increasing the speed of the welding direction, but also by the dynamic position change of the beam-guiding mirrors. This so-called wobble technique makes it possible to form stable welds at relatively low welding speeds and to significantly reduce weld depths.