Laser Cutting of ceramic materials for ev applications:

Electronics Manufacturing

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.

THE OUTCOME

• The two laser processes were used to successfully cut both AlN and Si3N4 ceramic substrates.  The laser cuts showed no micro-cracking, minimal thermal effects, a low taper and a lower surface roughness than current ceramic substrates on the market, cut with traditional processes.

• Using the WJGL, the ceramics could be cut to size, within +/-0.1mm:

• • 0.6mm thick AlN at a process speed of 0.8mm/s which could be increased to 3.3mm/s through using a partial cut and snap approach.
  • A 0.3mm thick Si3N4 at  a process speed of 3mm/s which could be increased to 10mm/s through using a partial cut and snap approach. 

BENEFITS TO THE CLIENT

• Using the WJGL, a complete through cut process was demonstrated as well as a partial cut and snap process, both yielding high quality although the partial cut and snap process improved processing speed by up to 66%.

• The current standard manufacturing method of mechanical scribing gives an uneven surface profile. Using the laser systems available at the MTC, an improved cutting process was developed which gives a lower surface roughness with no microcracks.

• WJGL has been successfully demonstrated in a prototype manufacturing process of an active AMB substrate, within the IUK project; Ceramic Substrates for EV with enhanced laser features (CervSelf) with SGA Technologies and Custom Interconnect Ltd. 

This project was funded as part of the first round of Advanced Propulsion Centre’s (APC’s) Scale Up Readiness Validation funding from the Automotive Transformation Fund (ATF).