Influence of copper wire material to corrosion resistant packages and systems for high temperature applications

Abstract

We present studies for a newly developed gold-palladium coated copper wire with focus to the automotive industry. This wire material was designed to prevent halide induced interface corrosion and also sulphur induced pitting corrosion. The base material was alloyed with special element to systematically adjust the intermetallics formed at the interface to the pad metallization and to define the microstructure of copper base material to prevent sulphur enhanced corrosion. For reliability testing the wire was bonded to a silicon die with aluminum metallization and a nickel-palladium-gold plated lead frame. The mold compound contains sulfur as well as low amount of chlorine (<; 10 wt ppm). The package was tested by high temperature storage at T=175 °C for 2,000 hours in comparison to a standard gold-palladium coated wire and a bare copper wire. We show results of high resolution analyses (Scanning Electron Microscopy, Transmission Electron Microscopy, nanospot-EDS-mapping) for the characterization of the intermetallic compounds formed between bond wire and die metallization and also for the stitch bond contact itself. The running corrosion mechanism will be investigated in detail. The results show that the newly developed gold-palladium coated copper wire shows a much higher reliability compared to the standard wire materials.