Influence of gold pick up on the hardness of copper free air ball

The effect of substrate material pick up by the Cu wire tail on the hardness of the subsequently formed free air ball (FAB) is investigated with scanning electron microscopy (SEM) and micro-hardness test. The Cu wire bonds are made on Au metallization. Wire residue is not found on the imprint the tail bond leaves on the metallization, but fracture of the substrate metallization is evident. SEM images of the Cu wire tail end clearly show Au …