Evaluation of DirectFET? Flip Chip Packaging Technology, Lead and Indium Solder Alloys in Extreme Cold Thermal Environments

摘要

DirectFET? packaging technology, developed by International Rectifier Corporation, offers substantial improvements in thermal and power efficiencies for power MOSFETs while also reducing device form factor. The use of these devices in space applications could serve to significantly extend mission life by reducing power consumption onboard satellites, deep space probes and planetary rovers. Further thermal and power efficiencies could also be reaped by mounting the power electronics with a thermal conduction path to the spacecraft body. However, exposure to the extreme temperatures in these environments has deleterious effects on some electronics assembly integrity and reliability and has to date, kept electronic hardware within the thermally regulated interior of the spacecraft. To evaluate the effects of these environments on electrical performance and reliability, several sets of DirectFET?? assemblies were fabricated using a variety of lead and indium solder alloys and subjected to temperature cycling. The testing sought to simulate three extreme thermal environments: the "high reliability" environment (-65℃ to +150℃), the Mars environment (-120℃ to +115℃) and the Deep Space environment (-180℃ to +85℃). Results of electrical testing, cross-sectional analyses, and thermomechanical stress simulations are presented within this article.