Dynamic characteristics and mechanism of ions migration and dendrites evolution on the printed circuit board surface

Abstract

Electrochemical migration in electronic devices plays a significant role in lifetime and reliability. In this work, dynamic characteristics of ions migration and evolution of dendrites formation and propagation on the printed circuit board surface are studied, and transient current between silver electrodes is measured in situ to determine the mass transfer and short circuit time. The experimental results show that the current response could be divided into three periods: dendrites incubation, formation and propagation. The time of incubation period is in the same order of magnitude as the diffusion time of silver ions between electrodes. A thin layer of precipitates appears earlier at the anode than dendrites at the cathode due to the higher diffusion coefficient of hydroxide ions. Meanwhile, compared to the initial state, the surface height distribution becomes non-uniform and the roughness increases by about nine times, resulting in the high walls near the anode and cathode sides play different roles on ions migration and dendrites propagation. As both the voltage and the space increase, the reduction in electrochemical migration failure time decreases due to the combined effect of a decrease in electric field and the increase in ions migration path. When the water droplet volume increases, the failure time shows a slight increase following a reduction, which could be attributed to the local silver ions concentration and ions migration path. This study would provide valuable insights for improving reliability and environmental suitability of electronic devices in humid environments.