| Copper-based interconnect is an emerging trend in microelectronics packaging. Some studies have shown that copper wires may serve as a viable, cost-effective alternative to gold in some high-end, ball and wedge bonding applications. This study is intended to evaluate the bondability and reliability of single crystal copper wire bonding. Mechanical properties such as break load and elongation of single crystal copper wires are characterized. After annealing, the copper wires are bonded on gold (12 micron thick) and aluminum (2 micron) surfaces without gas protection. Both ball bonding and wedge bonding are performed. Wire pull and ball shear strength are measured. Failure modes of the failed samples are discussed. The intermetallic compounds (IMCs) between copper and gold and between copper and aluminum are identified on the fractured surfaces by EDAX. Optical and SEM microscopy on cross-sections are conducted to inspect the morphology of IMCs. In addition, some specimens are annealed at a high temperature for 500 hrs in order to investigate the effect of thermal aging on wire bond reliability. After thermal aging, wire pull and ball shear tests are performed and the test results are compared with those without thermal aging. Optical and SEM microscopy on cross-sections are also conducted to inspect the changes of IMCs due to thermal aging.From the present study, it is found that single crystal copper wires can be bonded on the gold pad and the aluminum pad by thermosonic ball bonding and wedge bonding without gas protection. Gu3 AU and AuCu IMCs are found at the copper/gold interface while CuAl2 isfound at the copper/aluminum interface. The wire pull strength and ball shear strength appear to be normal. After thermal aging, some effects on wire bond reliability are observed. Furthermore, Kirkendall voids are discovered at the Cu/Au interface after thermal aging. The experimental procedure, test results and comparisons will be reported in details in this thesis.
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