The effect of isothermal aging on the thickness of intermetallic compound layer growth between low melting point solders and Ni-plated Cu substrate

The growth kinetics of the intermetallic compound (IMC) layer formed between two low melting point solders and electrolytic Ni/Cu substrate by solid-state isothermal aging were examined. The solders were 100 In and In-48Sn. A quantitative analysis of the IMC layer thickness as a function of aging time and aging temperature was performed. Experimental results showed that the IMCs, such as In₂₇Ni₁₀ and Ni₃(In, Sn)₄), were observed for different solders. Additionally, the growth rate of these IMCs increased with the aging temperature and time. The layer growth of the IMC in the couples of indium solder alloy/electrolytic Ni system satisfied the parabolic law at a given temperature range. As a whole, because the values of the time exponent (n) are approximately 0.5, the layer growth of the IMC was mainly controlled by the diffusion mechanism over the temperature range studied. The apparent activation energies for IMC growth were 60.03 kJ/mol for In₂₇Ni₁₀ and 72.84 kJ/mol for Ni₃(In, Sn)₄.