Wire bond metallurgy for high temperature electronics

Harsh environment electronic packaging is needed to assure the reliability of distributed electronic controls for operation at 200/spl deg/C ambient temperatures. The wire bond interconnects are a critical contributor to overall packaging reliability. The present study will investigate the use of aluminum wires on nickel metallized substrates. This metallurgy maintains the monometallic aluminum couple at the bond wire to die metallization interface while utilizing established nickel substrate metallization technology to provide a stable connection at the substrate. Thermal aging of Al-1%Si wires on nickel metallized substrates was conducted. Both a bulk nickel metallization on alumina and a nickel plate on silver thick film on alumina were evaluated. Intermetallic formation rates will be determined for both the Al/Ni couple and the Al/Ni/Ag thick film couple. In addition, fatigue tests will be conducted on Al-1%Si wires bonded to various substrate metallizations. The effects of intermetallic formation and fatigue on wire bond reliability will also be assessed.