Case Study:

Analysis of Bond Pad Areas on Devices

Device samples, demounted from their packaging, were submitted for analysis following moisture induced stress testing. Failed devices showed areas of contamination or corrosion on and adjacent to bond pad areas, around the perimeter of the device, which were characterized by SIMS imaging.

Equivalent areas of control devices were also analyzed for comparison purposes.

Mass spectral analysis and SIMS imaging (see selected images below) showed, for the failed device, the presence of aluminium and silicon oxides on and around the bond pad regions.

With evidence from the chemical images (in particular Al) which matched the optically observed dentritic structures around the bond pads, these species were strongly suspected to correspond to corrosion products.

In addition, antimony, sodium, potassium, chromium and iron residues were also found to be associated with the oxide-rich areas and were believed to have participated in the corrosion process.

For the control device, analyses also revealed evidence for the early stages of corrosion in bond pad areas.

The corrosion mechanism was interpreted as the result of the presence of two dissimilar metals (e.g. Al, Sb, Cr or Fe), electrolytes (Na, K, Ca and probably Cl) and moisture.

The occurrence and concentration of the corrosion product around the perimeter of the device suggested that moisture ingress had occurred through the packaging.