Electrochemical Migration of Immersion Silver Plated Printed Circuit Boards Contaminated by Dust Solution

Abstract

Due to the severe air pollution, printed circuit boards (PCB) in electronic products are apt to be covered by airborne dust deposition. The trace amounts of soluble salts in the dust particles increase ion concentration in the moisture condensed on the PCB surface so that the electrode reaction of electrochemical migration (ECM) is aggravated and the time to insulation failure also changes. In this article, based on the ion compositions analysis of soluble salts in natural dust collected indoor in northwest Beijing and eastern Shanghai, China, the effect of the anions in typical soluble salts (NaCl, Na2SO4) in natural dust on insulation failure mechanism and TTF of ECM of PCB is investigated by water drop tests on parallel wires on immersion silver plated PCB. Compared with PCB contaminated by single salt solution with different concentrations, the ECM characteristics of PCB covered by natural dust solution of various mass concentrations are analyzed. A failure physics-based life model of ECM of PCB under contamination of salt solution is fitted by the simulation tests of both the single salt solution and natural dust solution respectively. The mechanism and degree of action of soluble salts in natural dust on the ECM failure on PCB is discussed finally.