Effects of thermal cycling on the mechanical properties of gold wire bonding

The mechanical properties of gold wire bonding are subjected to thermal cycling (TC) test has been investigated. Gold wire bonding was experienced to temperature cycle of (-65) °C to 150 °C for 10, 100, and 1000 cycles. In order to determine the mechanical properties of gold wire, nanoindentation test was performed. A constant load nanoindentation test was carried out at the center of the gold wire to investigate hardness and reduced modulus. The load-depth curve for the thermal cycled gold wire bond displayed apparent discontinuities during loading as compared to the as-received gold wire bond. The hardness value has increased after the gold wire bond subjected to thermal cycle whilst, the hardness value has decreased with the increment of the TC cycle number. For reduced modulus, the values increased with increase of the TC cycle number. The decrease in the hardness value is in line with theoretical grain size coarsening following thermal treatment. These nanoindentation results are important in assessing the strength of gold wire bond after exposure to the thermal cycles.