I am currently plating aluminium pads on semiconductors with electroless Nickel. The pretreatment is a double dip zincate technique. The pads are about 100 µm in diameter and have a thickness of 0.8 µm AlCu0.5%. I am wandering that this pretreatment leads sometimes to a completely dissolved aluminium pad on the semiconductor. The reaction of electroless nickel cannot appear at these positions. Neighbouring pads seems to be okay.
Can this be a problem of the semiconductor or local potential differences ? Has anyone observed similar behaviour and what can I do to avoid this problem ?
