Effect of magnetic flux density on Sn crystallographic orientation in a solder joint system

Abstract

Electromigration (EM) in Sn-based solder joints has recently been recognized as a reliability issue in high performance semiconductor devices for high end computing systems. EM in power modules is also of concern for the next generation hybrid electric vehicles. It is well known that the EM lifetime becomes significantly longer when the c axis of the Sn crystals is normal to the direction of electron flow. However, there has been no effective way to realize this alignment for the electronics industry. In the present study, the effect of external magnetic flux density on Sn crystallographic orientation was investigated at 0.5 and 1.3 T. The external magnetic field was applied to a solder joint at the solid–liquid coexistence period during solidification. The c axis of the Sn grains started to align normal to the external magnetic field direction at 0.5 T, and completed at 1.3 T.