A Case Study of Nickel Dendritic Growth on Printed-Circuit Boards

Dendritic growth is a rare short-circuit electrochemical phenomenon that can occur on printed-circuit boards (PCBs) in the presence of ionic contamination, high humidity and voltage bias. The elevated temperatures at which most electronic hardware operate lowers the relative humidity enough to dry the surface contamination that under humid conditions approaching condensation would result in dendritic growth. Silver is most prone to dendritic growth followed by copper and tin. Nickel dendritic growth has rarely been reported. This paper is a case study of nickel dendritic growth under moisture condensation condition on freshly produced circuit boards contaminated with sulfuric acid etchant. The sulfuric acid contamination on the as-manufactured PCBs got trapped in the solder mask crevice and under high humidity condition spread out across the gap between gold-on-nickel edge connector contact pads. The paper describes the electrochemistry of nickel dendritic growth phenomenon in some detail and concludes that nickel dendrites will grow only when the relative humidity of the environment is near or higher than the deliquescent relative humidity of the contamination on the printed circuit board.