LASER CUTTING OF CERAMICS USED IN ACTIVE METAL BRAZED SUBSTRATES FOR EV POWER ELECTRONICS.
The MTC successfully demonstrated the laser cutting of ultra-thin ceramic tiles, creating high quality cuts that are free from micro cracks, and can be utilised to manufacture active metal braze (AMB) ceramic substrates, ideal for high voltage and current circuit boards, commonly used in power electronics assemblies.
THE CHALLENGE
- With the drive for electrification in the automotive sector, power electronic substrates are vital structures for placing semiconductors and interconnects on, to create electronic circuits with long term performance through mechanical robustness and effective thermal shock resilience.
- These substrates are made with an active metal braze (AMB) process whereby 2 layers of copper foil are bonded to either side of a ceramic sheet. The ceramic, typically either Aluminium (AlN) or Silicon Nitride (Si3N4), provides excellent thermal conductivity, resistant to high mechanical stress and suitability in a wide range of operating temperatures. Despite this, they are challenging to machine due to these properties as well as being incredibly brittle.
MTC'S SOLUTION
- Lasers offer a viable solution to cutting these hard to machine materials. Due to ceramics being prone to thermally induced cracking, a laser process that minimises the heat input into the material is required. Two laser processes were developed for cutting these high-performance ceramic substrates.
- Water Jet Guided Laser cutting (WJGL) - the laser beam is guided to the workpiece using a high-pressured waterjet, this provides high accuracy machining capability and minimum thermal effects.
- Ultra Short Pulsed laser cutting (USP) – using a laser with a picosecond pulse duration significantly reduces thermal input into the substrate, minimising thermal damage compared to conventional laser cutting.