Material characterisation of innovative low melting temperature solder alloys

Low-temperature solder alloys are attracting growing interest as a promising alternative to conventional SnAgCu solders used in Printed Circuit Board assembly. With melting temperatures approximately 50 °C lower, these alloys enable gentler soldering processes that reduce thermal stress on components, minimize PCB warpage, and lower the risk of assembly defects such as hot tearing and head-in-pillow failures.

Among the available low-temperature solutions, SnBi-based alloys have emerged as the leading candidates for industrial adoption. While questions remain regarding their long-term reliability, both published studies and preliminary in-house evaluations indicate strong potential. However, the fundamental material properties governing their mechanical and fatigue behaviour, including elastic modulus, yield strength, creep response, and fatigue resistance, are not yet sufficiently characterized.

This internship aims to fill this knowledge gap through a comprehensive mechanical characterization of a commercially available SnBi-based solder alloy. Experimental testing will be combined with microstructural analyses of soldered joints to investigate grain morphology and intermetallic compound formation at both the component and PCB pad interfaces.

The ultimate goal is to develop accurate constitutive material models that can be implemented in thermo-mechanical simulation tools such as Synopsis.Ansys or Cadence.Marc, enabling more reliable lifetime prediction of solder interconnections in electronic assemblies.