Evaluation of new substrate surface finish: Electroless nickel/electroless palladium/immersion gold (ENEPIG)

In this paper, we studied the wire bonding ability and the solder joint reliability for electrolytic Ni/Au and ENEPIG. For studying wire bonding ability, 4N wire with 20 mum in diameter was used. Pull strength of Au wire and failure mode after each pull test were both the criteria of wire bonding. After wire pull test, the pull strength and failure mode of Electrolytic Ni/Au and ENEPIG were similar. Therefore, it could be supposed the wire bonding ability of ENEPIG is similar with electrolytic Ni/Au. For solder joint reliability, different types of solder joint test were conducted- conventional ball shear test, cold-ball pull test. High speed ball shear test was also applied to simulate high strain rate loading, similar as drop test. Failure mode and micro analysis were carried out by the analytical tools, including scanning electron microscope (SEM) and energy dispersive spectrometer (EDX).