Faculty Publications
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Item Wettability and bond shear strength of Sn-9Zn lead-free solder alloy reflowed on copper substrate(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Tikale, S.; Sona, M.; Prabhu, K.Lead-free solders are environment friendly and are in great demand for microelectronic applications. In the present study, Sn-9Zn lead free solder alloy was solidified on Cu substrate for different reflow times varying from 10 to 1000s. The influence of reflow time on wetting, bond shear strength and formation of intermetallic compounds (IMCs) was studied using dynamic contact angle analyzer, bond tester and scanning electron microscopy (SEM), respectively. The results indicate that, the wettability of the solder alloy increased with increase in reflow time. Microstructure study revealed the presence of Cu5Zn8 and CuZn5 IMCs at the interface. The thickness of an IMC increased with increase in the reflow time. A mean thickness of Cu5Zn8 IMC layer of about 11μm was obtained for a reflow time of 1000s. The thickness of CuZn5 layer increased up to a reflow time of 100s and decreased thereafter. The bond shear strength increased up to 100s and decreased with increase in reflow time. The decrease in shear strength at higher reflow time is mainly due to the formation of thick Cu5Zn8 IMC layer and diffusion of Sn from bulk solder towards the substrate. The thick IMC layer exhibited micro-cracks leading to the brittle failure of bond under the influence of shear stress. © (2015) Trans Tech Publications, Switzerland.Item Characterisation of Sn–3.5Ag solder/Cu joint under various reflow conditions(Taylor and Francis Ltd., 2022) Georgy, K.; Tikale, S.; Prabhu, K.N.The effect of reflow time and reflow temperatures on wettability and bond shear strength of Sn–3.5Ag solder alloy on a Cu substrate is assessed for reflow times of 10 s, 100 s, 300 s, 500 s and reflow temperatures of 250 °C, 270 °C, 290 °C, 320 °C. The wetting regime was found to have capillary, gravity, and viscous regimes. A microstructural study using a scanning electron microscope (SEM) with energydispersive spectroscopy revealed the presence of intermetallic compounds at the interface between the substrate and solder droplet. The bond strength of the solder joint is maximum at a reflow temperature of 250 °C and a reflow time of 10 s. Bond shear strength decreased with an increase in reflow time from 10 s to 500 s. The effect of different cooling conditions on the solder–substrate joint is also investigated. © 2022 Institute of Materials, Minerals and Mining.