Abstract
A new process was developed to characterize the mechanical strength of small bonding wires under extreme temperature environment. By the combination of innovative fixture designs and a commercially available mechanical tester, both Beryllium and Calcium doped wires were evaluated for their strengths in the temperature range of −55°C to 250°C. Results indicated that the tensile break strength of Beryllium doped wire decreased with an increase in temperature throughout the temperature range tested whereas for Calcium doped wire it remained generally constant throughout. In addition, percent elongation of Beryllium doped wire significantly increased above 200°C whereas Calcium doped wire exhibited a constant decrease with an increase in temperature. Up to a tensile load of 27.5 grams, both wires were loaded less than their elastic limit under normal operating conditions (−40°C to 150°C). Hence, the cyclic load would not weaken the wire. If that limit is exceeded, Beryllium doped wire would weaken. Calcium doped wire has the advantage of resisting extrusion after the formation of wire bond giving added strength in normal operating conditions.
