Rate-dependent indentation hardness of a power-law creep solder alloy

Berkovich depth-sensing indentation tests with different loading rates have been performed on a creep material, Sn-3.5Ag-0.75Cu solder alloy. The resulting indentation load-depth curves are rate dependent and have varying creep penetration depths during the same hold time. Creep indentation hardness H, defined from the concept of "work of indentation," varies with the volume strain occurring during the creep hold time, which is a measure of creep strain rate (epsilon) over dot (cr). Thus, rate sensitivity m of the indented material can be determined from the ln H vs ln (epsilon) over dot (cr) curve. The derived value of m is consistent with the results from conventional uniaxial tensile and compression experiments of bulk solder alloy. (C) 2003 American Institute of Physics.