Life Model of the Electrochemical Migration Failure of Printed Circuit Boards Under NaCl Solution

Abstract

With the miniaturization of the electronic devices, the spacing among the circuit traces on printed circuit boards (PCB) keeps reducing, which increases the risk of insulation failure based on electrochemical migration (ECM), especially for immersion silver (ImAg) plated PCB. Meanwhile, due to the severe air pollution in developing countries, airborne dust can deposit on the PCBs in electronic devices. The soluble salts in the dust can decrease critical humidity and increase the ion concentration in the moisture condensed on the PCB surfaces, so that the failure mechanism based on ECM may be changed and the time to failure (TTF) can be shorten. In this paper, the effect of the soluble salt with various concentrations on the ECM failure on PCB was investigated. The life model of ECM was built up based on the electrochemical reactions on electrodes. Then the ECM of PCB under sodium chloride (NaCl) solution with various concentrations was simulated on Y- pattern PCB by water drop (WD) test method. The failure characteristics of ECM during various stages of migration and under various concentrations of salt solution were analyzed by the morphology and element compositions of dendrite products, as well as real time monitoring of surface insulation resistance (SIR). The TTF of ECM was extracted to fit the life model. Finally, the mechanism and performance of ECM of PCB under salt solution was analyzed. And the application of the life model of the ECM failure of PCB contaminated by soluble salts was discussed.