ANALYSIS: E-MOBILITY
Laser welding in a vacuum optimises copper welding for e-mobility
Dr Christian Otten, of LaVa-X, demonstrates an alternative to emerging blue and green laser technologies for welding copper in electric vehicle production
The technological development in the automotive industry towards electrification offers many opportunities. But it also comes with some challenges, such as the increasing processing of copper materials. The growing consumption of copper places new demands on the joining process in terms of automation capability, quality of the joint and process speed. Here, laser welding offers enormous potential due to its high precision, high intensities and ease of automation. In particular, laser welding in a vacuum (LaVa welding) delivers
high productivity and high quality using low energy input – even when welding difficult materials such as electrolytic tough pitch (ETP) copper. Due to their properties,
copper materials are now a fundamental component of batteries, electric motors and high-performance electronics in electric cars. ETP copper in particular has established itself as a material in electrical engineering due to its favorable manufacturability, as well as its good conductivity. The problem: these copper materials – such as ETP copper – are only suitable for welding to a very limited extent. Laser welding is particularly problematic for processing.
Challenges in laser beam welding ETP copper Until now, there have been various challenges when welding copper with infrared lasers, for example, with regard to the reproducibility of consistent quality, as well as increased pore and spatter formation. The formation of pores is
a typical defect that occurs more frequently with Cu-ETP materials. Pore formation is also intensified by residues from the insulation layer, which evaporate due to the heat generated by the laser and dissolve in the melt pool. The bigger problem, however, is the strong spattering that occurs due to the low viscosity of the melt. In addition to the loss of mass, adhering spatter can further destroy the insulation layer and cause short circuits. Furthermore, due to its residual oxygen content, ETP copper tends to absorb hydrogen during welding, leading to embrittlement or even cracking. Heat generation due to the
Weld seam top of a bipolar plate made of 1.4301 stainless steel with a wall thickness of 75µm – without post-treatment
20 LASER SYSTEMS EUROPE SUMMER 2022
high reflection properties of copper when processing with infrared wavelengths is also a problem. With classic infrared laser welding, enormous amounts of energy are lost – as well as due to the high thermal conductivity of copper. As a result, many companies have been looking for alternative processes in recent years –
and are focusing on green and blue lasers as the new solution for copper welding. What brings advantages in material processing also means high investment costs for expensive lasers for the companies themselves.
Laser welding in vacuum as an alternative Laser welding in a vacuum, for example, is an alternative that combines high quality with increased productivity – and at significantly lower costs. It uses an infrared laser, but as the name suggests, this process works in a vacuum. Due to the special environmental properties of LaVa welding with infrared laser sources, it is no longer necessary to use lasers with wavelengths from the visible range – blue and green – for copper welding. Ambient pressure and
evaporation temperature are reduced, thus stabilising the welding process and avoiding spatter, cracks and pore formation. While conventional
“It is no longer necessary to use blue and green lasers for copper welding”
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LaVa-X
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