Solid-state growth kinetics of Ni₃Sn₄ at the Sn-3.5Ag solderNi interface

Systematic experimental work was carried out to understand the growth kinetics of Ni₃Sn₄ at the Sn-3.5Ag solderNi interface. Sn-3.5%Ag solder was reflowed over Ni metallization at 240 °C for 0.5 min and solid-state aging was carried out at 150-200 °C, for different times ranging from 0 to 400 h. Cross-sectional studies of interfaces have been conducted by scanning electron microscopy and energy dispersive x ray. The growth exponent n for Ni₃Sn₄ was found to be about 0.5, which indicates that it grows by a diffusion-controlled process even at a very high temperature near to the melting point of the SnAg solder. The activation energy for the growth of Ni₃Sn₄ was determined to be 16 kJ/mol.