Insulation Failure Mechanism of Immersion Silver Finished Printed Circuit Board Under NaCl Solution

Abstract

Various kinds of contaminants depositing on printed circuit board (PCB) assembly in electronic products, such as the airborne dust and the process residues, can aggravate the condensation on the PCB surface and increase the ion concentration of the water film on the PCB, which further degrades the insulation of the PCB based on electrochemical migration (ECM). This paper investigates the insulation failure mechanism of immersion silver (ImAg) finished PCB under sodium chloride (NaCl) solution. A Y-pattern PCB was adopted to simulate the ECM failure of the PCB under different concentrations of NaCl solution by water drop tests. Through the on-line monitoring of the surface insulation resistance of PCB, as well as the dendrite morphology and the compositions detection at different reaction stages and different locations between two parallel electrodes, the similarities and differences of the insulation failure characteristics and mechanism of ImAg finished PCB under various concentrations of NaCl solution were analyzed. The effect of chloridion on ECM was discussed by combining the electrochemical theory.