Vias in DBC substrates for embedded power modules
This paper encompasses an evaluation of five different approaches to produce electrical vias in DBC (Direct Bonded Copper) substrates. The investigated methods of producing vias are based on laser drilling of different via layouts in the DBC substrates. In the next step, a stencil printing, dispensing and mechanical pressing process were tested for filling the via holes. As filling material, copper, silver pastes and copper rivets were used to enable the electrical connection. Before the experiments, electrical simulations have been performed in order to analyse the optimal via layout in the DBC substrates. It could be validated that at high frequency range (1 GHz), the current density distribution improves through the increase of via pitch, via diameter and via numbers. Combined with silver paste as filling material, the electrical characteristics of produced blind-hole vias could be improved compared to the use of copper paste and copper rivets. In conclusion, potential application possibilities for vias in DBC substrate, like three-dimensional power modules, multilayer DBC stacks and chip embedding concepts are discussed.