Figure 1. An Al wire that has been mechanically damaged during wirebonding

Figure 1 shows SEM photos of an aluminum (Al) bonding wire that exhibits symptoms of having been abrasively damaged during wirebonding. Mechanical damage such as this can be due to the accumulation of debris in the wire clamp of the bonder.  Note that this type of damage looks similar to corrosion damage, except that it exhibits no corrosion byproducts.

Since this damage is mechanical in nature, chemical analysis techniques such as EDX analysis will not register any foreign elements in the damaged areas of the aluminum wire. For instance, if EDX analysis is done on the sample, only Al and O will most likely show up in the EDX spectrum. The absence of corrosive elements in the EDX spectrum of the wire will then support the hypothesis that the damage is mechanical rather than chemical in nature.