Study on low melting nanocrystalline Sn-0.7Cu solder alloy

Abstract

Research was conducted to build up the minimal cost nano-crystalline Pb open solder alloy by means of superior strength and compact melting temperature. In this research, a minimal cost lead-liberated solder alloy of Sn-0.7Cu was selected. Elevated energy ball milling method was assumed for the manufacture of nano crystalline solder from this alloy. The milling was conducted for 100 hrs. The milled powders were considered for their crystallite size, changes in morphology as well as decline in its melting temperatures. The outcome reveals that for a milling time of 100 hrs the crystallite size was lessened from 131 nm to 36 nm. DSC evaluations reveal a steady transition from pointed exothermic peak in bulk alloy to broad depleted temperature summits at lessened particle sizes. Nano crystalline powder was compacted into billets with a 98% theoretical compaction density. Microwave sintering technology was adopted to sinter these compacted billets. A series of tests like SEM-EDS, XRD, DSC, salt spray fog corrosion studies, density measurements, mechanical properties like hardness, compression, shear and tensile tests were carried out on these solder billets. Results shows that conversion from micro to nano crystalline structure improved mechanical and corrosion resistance was noticed while lowering the melting temperature.

Keywords: Pb free solders, High energy ball milling, Nano crystalline materials, Low melting point