Publication:
Improvement of Cu-Al bond integrity on low k pad structures

Date
2011
Authors
Kid W.B.
Leng E.P.
Yong C.C.
Yi O.X.
Kar Y.B.
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Research Projects
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Abstract
Gold wires are commonly used for wire-bonding and it fits well the industrial requirements. However, the price of Gold wires increasing significantly, Copper wires is a potential replacement for Gold due to their superior electrical and mechanical properties. In order to incorporate Cu in the wire-bonding process, substantial data regarding aging and intermetallic formation of Cu-Al bonds is required and the results are compared with Au samples. In this study, the bond integrity and thermal aging of Cu-Al and Au-Al wire-bonds were investigated. The Copper and Gold wire-bonds samples were heat-treated at temperature of 225�C for 4.5, 13.5, 26, 52 and 97 hours respectively. The intermetallics of the wire-bonds, and in particular the Al-Cu interface, were studied. Discontinuous and non-uniform of Cu-Al intermetallics regions were found in the thermal aging samples. The thickness of Cu-Al intermetallics is growing linearly with the temperature as the diffusion rate increases in higher temperature. The Cu-Al bond is weak compare to Au-Al in accordance with aging through wire pull test. � 2011 IEEE.
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Keywords
Copper , Electric properties , Gold , Intermetallics , Mechanical properties , Thermal aging , Wire , Bond integrities , Copper wires , Diffusion rate , Electrical and mechanical properties , Gold wire , Higher temperatures , Industrial requirements , Intermetallic formation , Pad structures , Wire bonds , Wirebonding , Aluminum
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