  The electroâmechanical connection between under bump metallization (UBM) and
solder in flipâchip bonding is achieved by the formation of brittle
intermetallic compounds (IMCs) during the soldering process. These IMCs
continue to grow in the solidâstate during storage at room temperature and
service at an elevated temperature leading to degradation of the contacts. In
this thesis, the diffusionâcontrolled growth mechanism of the phases and the
formation of the Kirkendall voids at the interface of UBM (Cu, Ni, Au, Pd, Pt)
and Sn (bulk/electroplated) are studied extensively.

Applied Physics