Black Pad Metallography in Electronics

In the last three years solderability defect called Black Pad has gained enclosing attention. "Black Pad" forms during electroless Ni / immersion Au (ENIG) plating on printed circuit wiring board (PWB) copper interconnects, but manifests itself at the board assembly stage as a premature, brittle, interfacial solder joint failure. Black Pad cannot be detected by visual inspection before assembly, and it causes catastrophic failures in assembled electronic devices The purpose of the study was to employ metallography to reveal the Black Pad defect on bare boards, examine the intermetallic structure formation during soldering on defective pads, and determine the failure mechanism.