Effects of mould on electrochemical migration behaviour of immersion silver finished printed circuit board

The role played by mould in the electrochemical migration (ECM) behaviour of an immersion silver finished printed circuit board (PCB-ImAg) under a direct current (DC) bias was investigated. An interesting phenomenon is found whereby mould, especially Aspergillus niger, can preferentially grow well on PCB-ImAg under electrical bias and then bridge integrated circuits and form a migration path. The cooperation of the mould and DC bias aggravates the ECM process occurring on PCB-ImAg. When the bias voltage is below 15 V, ECM almost does not occur for Ag coating. Mechanisms that explain the ECM processes of PCB-ImAg in the presence of mould and DC bias are proposed.