Understanding of within Chip variation of optical appearance of Aluminum Pads

An electro assisted advanced adhesion promoter process is used to increase the mechanical and chemical robustness between mold compound and metal areas in the package [1], [2]. As quality monitoring method optical inspection is used. Where, for one product, a significant color difference between bond pads within a chip was observed. Our investigations proved that the color differences after the plating process are mainly due to the electrical characteristic of the specific chip in the specific product leading to electronegative static charge on individual bond pads.