Nanoindentation of lead-free solders in microelectronic packaging

Lead-free eutectic SnBi and SnAgCu solder alloys were studied by nanoindenter. Eutectic SnPb solder was also examined for comparative purpose. Their mechanical properties including hardness, reduced modulus and creep rate sensitivity coefficient m values were obtained. It was found that eutectic SnAgCu solder is stiffer than both eutectic SnBi solder and SnPb solder, while eutectic SnBi is the hardest among these solder alloys. For eutectic SnAgCu alloy, its m value obtained by nanoindenter was in excellent agreement with that by uniaxial tensile test. Both lead-free solders showed more creep resistance than eutectic SnPb solder. Nanoindenter is a useful way to characterize the small sized materials of electronic components.