Solder electromigration failure time as a function of the angle between the c-axis of Sn crystals and direction of electron flow

Abstract

Electromigration (EM) in Sn-based solder joints is recognized as a major reliability problem in high performance semiconductor devices in the current microelectronics area and in power modules in the next generation hybrid and electric vehicles. It is known that the EM failure time becomes significantly longer when the c-axis of the Sn crystals is normal to the direction of electron flow. In the present study, the effect of the angle between the c-axis of Sn crystals and the direction of electrons flow on EM failure was investigated at a low current density of 25 A/mm2 and a temperature of 150°C with Cu/ electrolytic Ni/Sn-0.7Cu solder joints. The EM failure is caused by the fast Ni transportation at the c-axis angles up to 57° to the direction of electron flow, and that in the high angles is caused by Sn transportation. The EM failure time can be expressed in a simple equation as a function of the c-axis angle.