Material characterisation of high thermally conductive die attach pastes for high power applications

For most high-power semiconductor device, the predominant heat dissipation path is through the die attach material. Hence, die attach material must possess excellent conductivity, both thermally and also electrically. Metal based solder alloys such as AuSi and AuSn possess these desired properties, but are relatively more expensive as compared to organic-based adhesives filled with conductive metals such as silver or other metal alloy. This paper discusses the various methodologies used during the material selection of high thermally conductive die attach dispense adhesives intended for power applications, focusing on Ag-filled and mixed-metal alloy adhesives. Carsem's own materials lab was utilized to perform thermal analyses, viscosity and electrical testing on different die attach dispense adhesives. After material characterisation, process characterisation was carried out in order to determine their dispensability and manufacturability. Candidate materials which exhibited good electrical and process characteristics were shortlisted for further evaluation in actual assembly. Finally, reliability testing was performed in order to assess the package reliability.