Role of alternating current shape on microstructure and damage evolution of solder joints

Abstract

Motivated by recent works indicating the role of AC current on the reliability of electronic systems, the microstructural characterization and mechanical properties of solder joints, as vulnerable parts of electronic packages, under different alternating current shapes were investigated. The sine-, square- and triangle-waveform currents were considered for the experiments. The simulation results showed that the triangle shape current creates the highest thermal fluctuations and stress variations in the solder joints. This event was due to the lack of any relaxation time at the critical states, induced by triangle shape current, which leads to the intensification of stress in the solder material. On the other side, the sine- and square- currents have time to relax stresses at their peak temperatures. Moreover, it was found that the stress intensification in the solder exposed to the triangle-shape current leads to the increase of brittle intermetallic compounds and the degradation of mechanical properties. Moreover, thermal resistivity of solder joints was considered as failure indicator and found that the triangle AC current had the significant effect on the increase of thermal resistivity in the solder joint in a certain time compared with other AC current shapes.