The root causes of the “Black pad” phenomenon and avoidance tactics

Abstract

The “black pad” phenomenon of Ni-P electroless plating has been one of the serious electronics failures in the market although this plating is known to be a useful barrier coating against oxidation. To understand the mechanism of this phenomenon, the weak interfaces of Ni-P plating soldered with leaded and lead-free solders have been analyzed with the aid of transmission-electron microscopy. Two causes of degradation are described in this paper. One is the initial degraded Ni-P plating covered with gold thin plating. In this case, the surface of the Ni-P plating was locally corroded to form a sparse amorphous oxide structure beneath the gold plating. The other is the extreme interface reaction between the Ni-P plating and solders. Based on the findings, it was concluded that the quality of the Au/Ni-P plating and the process conditions of soldering are to be carefully controlled.