The Effect of Thermal Ageing on Solder/Substrate Interfacial Microstructures During Reflow of Sn–37Pb and Sn–3Ag–0.5Cu

  • SatyanarayanEmail author
  • M. C. Kumarswamy
  • K. N. Prabhu
Technical Paper


In the current study, the influence of thermal ageing on evolution of microstructures in the interfacial region between solders (Sn–37Pb, Sn–3.5Ag–0.5Cu) and copper substrates was investigated. Pb-containing and Pb-free solders were reflowed on Cu substrates at 230 °C for 15 min and were isothermally aged at 100 °C for 24 h. As-reflowed Sn–Pb solder/Cu substrate interfacial region exhibited continuous and layered type of IMC at the interface, and this IMC morphology changed to scallop type with isothermal ageing. SAC solder/Cu as-reflowed samples showed continuous and needle-shaped Cu6Sn5 and Ag3Sn IMCs at the interface. However, in an isothermally aged condition, plate-shaped Cu6Sn5 and flower-shaped Ag3Sn IMCs were found inside the solder matrix. Scanning electron microscopic (SEM) study showed that the thickness of Cu6Sn5 IMC was higher in reflowed Sn–Pb/Cu region than in SAC/Cu region.


Solder joint Reflow Microstructures IMC layer Isothermal ageing 



Authors thank former students Mr. Ammer Bilal, Mr. Bharath M M, Mr. Syed Dawood and Mr. Mohammed Sohail of AIET for conducting experiments.

Compliance with Ethical Standards

Conflict of interest

The author(s) declare that they have no conflict of interest.


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Copyright information

© The Indian Institute of Metals - IIM 2019

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringAlva’s Institute of Engineering and TechnologyMoodabidriIndia
  2. 2.Department of Metallurgical and Materials EngineeringNational Institute of Technology Karnataka (NITK)MangaloreIndia

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