Experimental investigations on the effect of addition of Ag into ternary lead free solder alloy Sn-1Cu-1Ni

Lead cannot be used in solder alloys due to its deep-rooted toxicity. In the view of this fact, much legislation came into existence to prohibit the usage of lead in solder joints. Many lead free solder alloys came to replace the conventional Sn-Pb solder alloy. This study investigates the effect of addition of Ag (0.25, 0.5, 0.75, 1 wt.%) on the melting behavior, wetting characteristics, hardness and microstructure properties of ternary lead free solder alloy — Sn-1Cu-1Ni. Melting temperature is found to be decreased slightly from 232.2°C to 228.7°C. The distance between the adjacent atoms and the root mean vibration amplitude determines the melting temperature property. Ag₃Sn formed in the matrix has changed the melting point characteristics which resulted in the slight decrease of the melting temperature. Contact angle get reduced from 36.75° to 22.87°. Hardness value is found to be increased from 16.1 to 19.2. Ag is found to be uniformly distributed in the microstructure analysis. As far as the data available show, the microstructure of this lead free solder alloy consists of coarse β-Sn grains. Ag₃Sn, Cu₆Sn₅ and tin in the alloys are found in the eutectic region. The refinement of β-Sn grains is happened in a good manner due to the addition of particle of Ag. The recommended amount of Ag addition in to the Sn-1Cu-1Ni is 1wt.%. This lead free alloy can be used in electronic packages exposed to relatively high temperatures.