1991 Volume 9 Issue 4 Pages 587-593
A method of thermal history simulation has been developed to obtain a better understanding of mechanical properties of the grain growth region (heat-affected zone-HAZ) of gold bonding wires.
The simulator is degigned to simulate the HAZ microstructures over a several inches length of the wire, which is necessary for mechanical testing. It has been found that grain size of the coarse grained HAZ cal be satisfactorily reproduced on the simulated thermal history condition. The breaking load obtained in this condition found to exhibit good agreement with the pull load of actual ball bonded wires.
Using the simulator, changes in mechanical properties with varying simulated thermal cycles are briefly studied. With increase of grain size, strength of simulated HAZ decreased. On the other hand, elongation first increased with decreasing the strength but decreased sharply to a very low level. The intensive decrease of the elongation occurs because deformation does not occur uniformely but concentrated on heavily coarsened grains.