Investigation of Post-Etch Copper Residue on Direct Bonded Copper (DBC) Substrates

For many years, direct bonded copper (DBC) substrates have proved to be an excellent solution for electrical isolation and thermal management of high-power semiconductor modules. However, in this study we detected a copper residue on the surface of DBC alumina, presumably a result of pattern etching even in industry. As is known, growth of metal dendrites could be observed with the assistance of electric field, temperature, and humidity. Metal dendrites normally grow from the cathode to anode. Silver and copper are two kinds of metals susceptible to migration. In this work, copper dendrites could be formed at 400°C and 50 V/mm between conductors. These dendrites may impact the reliability of DBC in power electronic applications. Therefore, the formation of copper residue is an interesting phenomenon for etched DBC and warrants further attention in the future.