MECHANICAL PROPERTIES OF LEAD FREE SOLDER ALLOY FOR GREEN ELECTRONICS UNDER HIGH STRAIN RATE AND THERMAL AGING
Muhammad Aamir1*, Riaz Muhammad1, Naseer Ahmed1, Muhammad Sadiq2, Muhammad Waqas3, Izhar1
ABSTRACT
Lead free solder (LFS) alloys have been widely acknowledged due to its good mechanical properties and no
harmful effect on environment. The current work is focused on the examination of thermal aging and strain rates
on mechanical properties of Sn96.5-Ag3.0-Cu0.5 (SAC305) LFS alloy. The selected thermal aging temperatures are 60
°C, 100 °C and 140 °C. Strain rates are measured at 10/s, 20/s, 30/s and 40/s. The microstructure examination
before and after thermal aging is carried out using scanning electron microscopy (SEM) followed by confirmation
of chemical composition with energy dispersive X-ray (EDX). The microstructure is further analyzed using ImageJ
to investigate the Intermetallic compounds (IMCs) particle average size at different aging temperature. Mechanical
properties including Yield strength (YS) and Ultimate tensile strength (UTS) are examined before and after thermal
aging and at different high strain rates from stress-strain curves using universal testing machine (UTM). Results show
that LFS alloys are extremely sensitive to changes in both temperature and strain rate. The microstructure becomes
coarsen after thermal aging due to growth of average IMCs particle size which significantly results in reduction in
YS and UTS. Furthermore, increasing strain rates results in increasing YS and UTS due to less creep deformation.
Mathematical relations are also developed to predict these properties at various levels of aging temperature and strain
rate. A power law relationship exists between strain rate and mechanical properties while a reciprocal relationship
is obtained between aging temperature and mechanical properties.
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