Solid–state diffusion–controlled growth of the intermediate phases from room temperature to an elevated temperature in the Cu–Sn and the Ni–Sn systems

Abstract

The solid–state growth of intermediate phases in the Cu–Sn and Ni–Sn systems is investigated in the temperature range of room temperature to an elevated temperature. In the Cu/Sn diffusion couples, Cu6Sn5 and Cu3Sn grow at temperatures 100 °C and only the Cu6Sn5 phase is found at lower temperatures. The integrated interdiffusion coefficients are estimated in the temperature range of 125–215 °C because of the observation of parabolic growth. The activation energies are estimated to be 64 4 and 75 6 kJ/mol for Cu3Sn and Cu6Sn5, respectively. In the Ni/Sn diffusion couples, only Ni3Sn4 grows at higher temperatures. At 50–100 °C, metastable NiSn4 phase is found along with an equilibrium Ni3Sn4 phase. At room temperature, only the metastable NiSn4 phase is found. The activation energy for the integrated interdiffusion coefficient of Ni3Sn4 is estimated as 71.6 5.3 kJ/mol, which is similar to the values estimated in the Cu–Sn system. The growth rate of the product phases, for electroplated couples, is found to be a little higher in the Ni–Sn system as compared to the Cu–Sn system. During storage at room temperature and service at elevated temperatures, the phases in the Ni–Sn system have comparable growth rate when compared to the same in Cu–Sn system.