Laser powder bed fusion of titanium alloyed copper powder for power electronic substrates

Ceramics substrates are key components in high-power electronic modules like inverters for traction or energy applications. Since the state-of-the-art processes active metal brazing and direct copper bonding for the production of structured metallizations on ceramic substrates lack flexibility and require resource-intensive chemical and thermal treatments, an alternative metallization approach based on processing of a copper powder alloy with 2.6 wt.% titanium via laser powder bed fusion is presented in this paper. Within the presented study, the additively metallized ceramic substrates were analyzed via shear testing and cross sections to quantify adhesion and for assessment of the interface with regard to cracking mechanisms and porosity. With the presented powder alloy the formation of a reaction layer at the metal-ceramic-interface after laser fusion was detected via energy dispersive X-ray spectroscopy. In active metal brazing such reaction layers are a prerequisite for wetting of ceramic substrates with an active brazing alloy, which bonds an electrically functional copper layer to the ceramic substrate. Due to the observed formation of conchoidal fractures at the interface and the low electrical conductivity of copper-titanium alloys, an additive multi-material approach with a thin copper-titanium interlayer and an electrically functional copper layer is further presented.