Hardness Variation of Ball Bond Wire Bonding

Abstract

In semiconductor packaging, conventional test procedures for evaluating mechanical properties of ball bonded gold wire bonding are well established. However these tests do not provide clear understanding related to the strength mechanism leading to improper reliability data. The nanoindentation approach, uses equipment called nanoindenter, gives advances mechanical (sub-micromechanical) characterization, particularly the combination effect of elastic and plastic deformation. Wire bonding process was prepared using thermosonic-wire bonding technology with 25m diameter gold wire and copper as substrate. To obtain mechanical properties, ball-bonded was cross-sectioned diagonally before indented at various locations. Results show that mechanical properties vary according the locations throughout the surface; at the centre, at the edge and at the area near intermetallics layer. This indicates test location plays important role in determining ‘meaningful’ mechanical properties.