Bonding wire characterization using automatic deformability measurement

A promising way to control underpad chip damage in IC packaging caused by wire bonding forces would be to use new wire chemistries that produce softer free-air balls (FABs). The number of new wire types that can be tested is limited by the available resources. The conventional FAB hardness characterization method is the microindentation test, a labour intensive and off-line task requiring cross-sectioning of a large number of samples. To accelerate FAB hardness characterization, an innovative on-line method is studied and presented here, enabling the fast comparison of different wire types. Collection of data from an instrumented wire bonder allows comparison of the deformability, i.e. the average amount of FAB deformation under a defined load. Increased deformability implies a softer FAB. The influences have been studied of changes in capillary, bonding substrate metallization and substrate temperature on the results obtained. It is found that these influences need to be held constant during a comparison study.