E-cars: Manufacturing is more sustainable with green laser

When welding high-quality electronics, many raw materials can be saved by using a green laser. This is the result of a study at the German electron synchrotron Desy of the Helmholtz Association in Hamburg. High-performance electronics are in every e-car and, as key technology, ensure the best performance of the battery and motor. The Hamburg researchers, together with the high-tech company Trumpf and the Fraunhofer Institute for Laser Technology ILT , have now investigated the laser welding processes used in the production of e-cars.

Trumpf, Fraunhofer ILT, DESY and the Helmholtz Centre Hereon have each contributed their highly specialised expertise in X-rays, laser sources and laser processes. As a result, insights have now been gained for the first time that remain invisible to the naked eye and even to microscopes. The result: using a green-wavelength laser results in far fewer rejects than other laser welding processes. Car manufacturers save on raw materials and thus contribute to more sustainable production.

For their research, the project partners used X-rays from the particle accelerator in Hereon's experimental setup to create high-speed images at several thousand to ten thousand frames per second. "We wanted to use the studies at the particle accelerator to find out what exactly makes the difference when welding copper. A stable welding process is important because electric vehicle manufacturers need to weld several billion joints of the highest quality," said Marc Hummel, scientist at Fraunhofer ILT. Trumpf and the Fraunhofer ILT want to extend the research to other areas in the future. These include 3D printing, laser cutting and laser drilling with ultra-short pulse lasers. In addition, they want to bring other industrial partners on board.

Electromobility poses major challenges for laser technology. Copper is the main material for manufacturing the core components of e-mobility. This non-ferrous metal absorbs only about 5 per cent of laser radiation in the near-infrared (NIR) region. It conducts heat very well. Both properties lead to significant problems in welding. The processes are therefore scrutinised.

Besides NIR lasers, Trumpf also has lasers with a green wavelength in its product range. "Green wavelength lasers are the solution to this problem. In fact, copper can be welded better with these lasers," says Mauritz Möller, Automotive Industry Manager at Trumpf. Copper absorbs the green wavelength much better than infrared. As the material therefore reaches its melting temperature faster, the welding process also starts faster and requires less laser power. "More stable processes in welding mean less rejection and thus more durability. This is an important point in e-mobility," Mauritz Möller says.

To study welding processes in detail, experts from the Fraunhofer ILT, in collaboration with the Laser Technology LLT chair at RWTH Aachen University, are using Desy's Petra III X-ray light source on the experimental setup at the Helmholtz Center Hereon. "Conventional methods actually only see the electromagnetic emissions of the plasma. With Desy's radiation, we can not only see into the melting process, but even visualise the melting dynamics," Marc Hummel explains.

To this end, a team from Fraunhofer ILT and Trumpf studied laser welding processes at Desy using two different laser systems: an NIR laser and a green wavelength laser. "For us, this is a great opportunity to study welding processes on industrial parts. For example, how do spatters and pores form and how does the heat of the welding process affect sensitive components such as electronic parts," said Mauritz Möller.

Source: Fraunhofer
Opening photo: Laser beam welding of metal-ceramic substrates with "green" laser radiation (Photo: Fraunhofer ILT, Aachen, Germany)

See also: Laser technology for energy-efficient battery cell production