Corrosion resistant wire for small diameter wire bonding applications

Wire bonding is now a major method of interconnection. Over the years, as electronic packages became more technologically advanced, the wire bonders and the wire had to mature at the same rate. Aluminum wire is one of the main components used in wire bonding these electronic devices. In some applications, this aluminum wire must be able to withstand harsh environments, such as salt spray and autoclave, within a temperature range from -40 to +125/spl deg/C. There was now a need for a wire that would be able to withstand this temperature range and withstand the harsh environment. Wire manufacturers responded by developing an anti-corrosion wire that would withstand the autoclave (pressure cooker) conditions. This aluminum based wire has been used in the larger diameter sizes (127 to 508 microns or 5 to 20 mils) for a few years already in mostly automotive applications. Recently many end-users have utilized this corrosion resistant wire in small diameter applications (50.8 and 76.2 microns or 2 and 3 mils). Most of these applications are also automotive related. Corrosion resistant wire is unique in that there are some essential dopants in the wire that prevent the wire from physical damage. This paper will discuss the composition of this type of wire and review findings from the autoclave test done on various wire types.