Acceleration of applied voltage on metallic ion migration of wires in NTC thermistor temperature sensors

Abstract

The research on NTC (Negative Temperature Coefficient) thermistors often used in temperature sensors has usually focused on performance, and almost no research have been previously done with the focus on reliability, even though field failures of NTC thermistors caused by ion migration are increasing. Therefore, this paper focuses on ion migration between wires, which has a close relationship with field failures of NTC thermistors by measuring the time when ion migration occurs according to different distances between wires and the applied voltage, and quantitatively analyzing the mechanism of ion migration occurrence, acceleration and correlation with ion migration due to applied voltage. Ion migrations between Cu wires occur because of the absorption and condensation of water. Also, due to the inherently brittle characteristics of the dendrite, repeated separation and coalescence were observed. The results of estimating the time of ion migration according to the applied voltage using both Weibull distribution and the same shape parameter showed a good match with the inverse power model, and an index and a specific parameter expressing the sensitivity of ion migration occurrence could be extracted by analysis.