Improvement of nickel wire bonding using Al nano coating

In recent years Ni wire bonding has found some interest as a contacting technology for high temperature applications or for power electronic components. In addition to high thermal stability, further advantageous properties of Ni wires are its good electrical conductivity and a high mechanical strength. On the other hand, the relatively high hardness of the wires entails the risk of defect formation, particularly if applied for bonding on semiconductor components. In the presented investigation it was tried to improve the bond process parameters to lower bond forces by sputtering the wire with nm thick aluminum layer which should support the binding mechanisms. The paper presents mechanical characterization of the wire before and after sputtering, morphology and adhesion behavior of Al sputter layer on the wire as well as the contact formation in the wire bond interface after wedge-wedge bonding on different metallization. Mechanical test methods like tensile test and nano-indentation were performed as well as high resolution preparation and analyzes methods like focused ion beam technique (FIB), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).