Temperature effects on liquid-state Sn/Co interfacial reactions

Liquid-state Sn/Co interfacial reactions were studied at various temperatures ranging from 240 °C to 340 °C. Only one uniform CoSn3 layer was found at the interface at temperatures below 327 °C. Experimental measurements of the layer growth revealed that it appeared to be linear with reaction time. This implied that the CoSn3 growth was controlled by the chemical reaction. The reaction kinetics analysis shows that the apparent activation energy for chemical reaction constant was determined to be 121.1 kJ/mol. When the temperature was increased to exceed 327 °C, the reaction product changed into the CoSn2 phase. Different from the CoSn3 fast growth, the CoSn2 layer was very thin and irregular. Two-stage reactions were carried out to investigate the stability of CoSn2 at lower temperatures. The lower temperature would enhance CoSn3 nucleation and thus accelerate the phase transformation of CoSn2 into CoSn3. We proposed the interfacial growth mechanisms that can interpret reasonably the significant difference in the growth rates of CoSn3 and CoSn2. In addition, the peritectic temperature of Liquid + CoSn2 → CoSn3 was also determined to be around 327 °C.