Thermal Fatigue Reliability Evaluation for Micro-Sintered Compact Joints Made from Sub-Micron Gold Powder

Mechanical properties of sintered gold compacts with sub-micron gold powders have been evaluated, and mechanical shear fatigue tests for flip-chip specimens with sintered gold bumps were carried out as a new inner bump material. From tensile-relaxation tests, material properties of gold sintered compacts depend on the sintering temperature (S.T). SEM observations reveal that the microstructures of sintered gold compacts could be classified into clusters and void-filled structures. Sintered compacts with clusters showed creep properties equivalent to those of lead-free solder alloys at 150degC. Low-cycle fatigue strength of the compacts was as high as tin-based solder alloys on the basis of Manson-Coffin´s law when the sintering temperature was 230degC. Inelastic strain range generated in the compacts is smaller than in tin-based solder materials because the Young´s Modulus of the compacts is smaller than that of tin-based solder materials. Observations of fracture surfaces suggest that cracks initiate in the sintered compacts when the sintering temperature is 230degC. Moreover, the microstructure near the interface between the bump and pad is similar with a void-filled structure that has superior tensile strength. Therefore, the gold compacts have sufficient fatigue strength as a new inner bump material