4. Conclusions
Measuring Vickers hardness of copper bonding wire is a challenge due to the physical size of the sample and the
preparation method applied which would lead to variations. Only very low test load of 15 mN or less can be applied to the
20 ìm diameter sample. Even the larger diameter of HAD wire at 80 ìm, the load used should be less than 200 mN,
consider the test criteria and constrains according to standard. It was found that in all tests conducted, the hardness values
decrease with increasing test load. The rate of decrease in hardness will slow down significantly when higher loads are
applied. For the 20 ìm wire, much lower test load of 15 mN or 10 mN must be used to achieve good statistical results. The
hardness of FAB depends on direction of measurement. Hardness at transverse cross-section has hardness value of 8% to
16.6% lower than in longitudinal direction. This is likely due to indentation on large grain than on shallower grain with
adjacent grain’s boundary beneath it. Therefore, for 20 ìm wire, test load still needs to be kept at 15 mN or 10 mN. Since
the hardness of wire and FAB is dependent on test load, the HV value convention of stating test load and dwell time must be
use when quoting hardness value.