Welding aluminum pressure-tight in series with a laser

Challenges

The heart of electric vehicles is the battery and the battery management controller (BMC). It monitors, controls and optimizes the power, safety and service life of the battery, by regulating parameters such as charging status, temperature and cell voltage. The performance electronics installed convert the direct current from the battery into the alternating current required for the drive. This generates heat that can impair the electronics. Modern cooling devices provide a remedy. They can be integrated as a medium-thickness "cover" in the BMC housing and connected to the vehicle cooling circuit. The cooling unit must be in direct contact with the performance electronics to ensure effective cooling. For this it is necessary that the cooling unit is completely flat. It should also be light so as not to unnecessarily increase the weight and should meet the pressure test requirements of the vehicle manufacturer. 

"Our customer has requested a cooling plate made from drawn aluminum, measuring 900 x 200 millimeters - a real challenge, even for our most experienced specialists", explains Joseph Gampp, Head of Department for Product Management at Feinwerktechnik hago. But challenging tasks motivate the team. "After extensive trials and tests with TRUMPF we have found a process-reliable solution and can now produce the cooling device in series", Gampp proudly reports. 

Solutions

With BrightLine Weld, TRUMPF has been offering a tried and tested laser welding process for years, which allows for fast, non-porous and gas-tight welding of stainless steel. The Multifocus optics developed in 2021 further increased application possibilities: In combination with BrightLine Weld it even allows for the pressure-tight welding of aluminum. To do so, the optics split the laser beam of a TruDisk laser into a ring and core beam, which are then split into four spots and positioned in such a way that a common weld pool is created. The resulting continuously open keyhole prevents the keyhole from collapsing, which enables a pore-free weld seam to be created without gas inclusions, even during the quick welding process. 

Implementation

Initially, the team under Joseph Gampp tried to weld the aluminum cooling device using available machines. The sticking point: The first tight weld seams did not withstand the required application pressures and broke apart. "That was a crucial criterion for our customer, as the vehicle manufacturer insists on so-called pressure pulsation tests before approval", says Gampp and added: "The entire assembly must withstand a certain pressure at least 100,000 times. As soon as we tried it out with our test parts, our weld seams folded."  

The hago specialists therefore worked meticulously with TRUMPF to create a stable process suitable for series production. In the TRUMPF laser application centre it quickly became apparent that all challenges could be mastered with the BrightLine Weld and Multifocus optics. The weld seam is so stable that it can even withstand high pressures.  This allows the parameters to be set flexibly so that the laser also welds long seams in a manner that is quick, process-reliable and distortion-free. This is important because the cooling device must be completely flat so that it is in direct contact with the performance electronics in the BMC and can be cooled effectively. "We now manufacture the component with a reproducible flatness of under a millimeter", says Gampp.  

By investing in a TruLaser Cell 7040 laser welding system with BrightLine Weld and welding optics with Multifocus technology, hago has met the requirement for the series production of the cooling plate. The pre-series with around 3,000 components has been completed. Within the next six years, over 610,000 cooling devices should be produced by hago. "We have managed what many deemed impossible", says Gampp proudly adds. "That's what makes us special." 

Forecast

The concept of integrated cooling in battery management controllers is relatively new, but has great potential. Joseph Gampp therefore hopes that knowledge acquired from working together with TRUMPF can also be used in further projects. "The technology fits perfectly into our strategic alignment", he says, and is confident that the time-consuming development project will be worth it. 

Updated: 2025-05-14