Challenges in solder on leadframe packages

Abstract

Power device application is one of the highest growth sectors in today's semiconductor technology. The main applications for power devices are switches or rectifiers used in servers, desktops, notebook, cell phone etc. From a packaging perspective, power devices are characterised by its ability and efficiency in conducting high current. To conduct high current, a power package must have low electrical resistance and good thermal dissipation system. As such, applying solder as interconnect between the die and the leadframe or cu clips to mosfets is by far the best solution for thermal dissipation and electrical conductivity. This is because solder poses superior thermal conductivity performance (approximate 3 times better than high thermal conductive epoxy & approximate 10 times lower in terms of volume resistivity). In the industry today, typical power package that applies conductive epoxy handles about 2~16A current while package applies solder capable to handles 25~60A current. As such, solder will continue to be the preferred material over epoxy for power packages that requires high current. This paper will discuss on the challenges faced when using solder as the die attach material on leadframe based packages.