Dependence of electrical and thermal conductivity on temperature in directionally solidified Sn-3.5 wt% Ag eutectic alloy

Abstract

Sn-3.5 wt% Ag alloy was directionally solidified upward with a constant growth rate (V = 16.5 mu m/s) and a temperature gradient (G = 3.3 K/mm) in a Bridgman-type growth apparatus. The variations of electrical resistivity (rho) with temperature in the range of 293-476 K for the directionally solidified Sn-3.5 wt% Ag eutectic alloy was measured. The measurements indicate that the electrical resistivity of the directionally solidified Sn-Ag eutectic solder increases with increasing temperature. The variations of thermal conductivity of solid phases versus temperature for the same alloy was determined from the Wiedemann-Franz and Smith-Palmer equations by using the measured values of electrical conductivity. From the graphs of electrical resistivity and thermal conductivity versus temperature, the temperature coefficient of electrical resistivity (alpha (TCR) ) and the temperature coefficient of thermal conductivity (alpha (TCT) ) for the same alloy were obtained. According to experimental results, the electrical and thermal conductivity of Sn-Ag eutectic solder linearly decrease with increasing the temperature. The enthalpy of fusion (Delta H) and the change of specific heat (Delta C (P) ) during the transformation at the studied alloy were determined from heating curve during the transformation from eutectic solid to eutectic liquid by means of differential scanning calorimeter (DSC).