The influence of porosity and pore shape on the thermal conductivity of silver sintered joint for die attach

Thermal conductivity of a Ag sintered joint was measured using the steady-state comparison method. The results showed that with the increasing sintering temperature, the thermal conductivity increased from 126.3 to 228.5 W/m·K and the corresponding porosity of the Ag sintered joint decreased from 23.4% to 8.4%. However, except for the porosity, there were other factors, such as pore size and pore shape, that affect the thermal conductivity of the Ag sintered joint. Their effects on the thermal conductivity was considered quantitatively by introducing the thermal resistance index of pore (TRIP). The TRIP results showed that the fraction having low TRIP values increased with increasing sintering temperature increased. This indicates that as the sintering temperature increases, the pores of the sintered joint become smaller and develop a more spherical shape, thereby resulting in minimizing a reduction of the thermal conductivity despite no change in the porosity.