Journal of SMT Article

Effect of Reflow Time on Wetting Behaviour, Interfacial Reaction and Shear Strength of Sn–0.3Ag-0.7Cu Solder/Cu Joint

Authors: Mrunali Sona and K. Narayan Prabhu
Company: National Institute of Technology Karnataka Surathkal
Date Published: 6/1/2015   Volume: 28-2

Abstract: In the present work, the effect of reflow time on wetting behaviour, interfacial reactions and growth of intermetallic compounds (IMCs) were investigated for Sn-0.3Ag-0.7Cu lead free solder alloy on Cu substrate during reflow at 270°C. The reflow time was varied from 10s to 10000s. The contact angle decreased with the increase in reflow time. The thickness of Cu6Sn5 IMC increased with increase in reflow time up to a time of 300s and the thickness decreased for samples reflowed for 500s. The IMC thickness increased with further increase in reflow time. The thickness of the Cu6Sn5 IMC layer formed during a reflow time of 10s was 3.43 µm and its thickness increased to 5.43µm, 8.32µm, 6.30µm, 8.30µm and 9.72µm during 100s, 300s, 500s, 1000s and 10000s reflow time respectively. The bond shear test was performed to assess the integrity of Sn-0.3Ag-0.7Cu solder solidified on copper substrate surfaces. A reflow time of 100 s significantly improved the integrity of Sn-0.3Ag-0.7Cu/Cu joints. The shear strength decreased with further increase in reflow time. In all the samples, the fracture occurred mainly in the bulk solder.

Keywords: 

Intermetallics, lead-free solder, shear strength



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