Material characterisation of innovative low melting temperature solder alloys

There is increasing interest in solder alloys with melting points about 50 °C lower than the standard SnAgCu alloys used for component assembly on printed circuit boards. The key advantages of these low-melting alloys include reduced soldering temperatures, which are less harmful to components and minimize warpage, thereby preventing defects such as hot tearing or head-in-pillow failures.

Among these alloys, SnBi-based compositions are the most widely adopted. Although concerns about their long-term reliability exist, initial in-house tests show highly promising results, supported by findings in the literature. However, fundamental material properties - such as elastic modulus, yield stress, creep behavior, and fatigue durability - are still insufficiently characterized.

This Master’s thesis aims to address this gap by performing mechanical characterization of bare solder alloy samples to determine key properties, complemented by microstructural analysis of soldered joints to visualize grain structure and intermetallic formation at both component and PCB pad interfaces. The study will focus on a representative SnBi-based alloy commonly available on the market.

The expected outcome is the development of material models suitable for thermo-mechanical simulation tools (e.g., Ansys) to predict the lifetime of solder assemblies.
 

Master's degree: Master of Engineering Science

Required educational background: Electromechanical engineering, Materials Engineering, Mechanical Engineering, Physics, Electrotechnics/Electrical Engineering

Duration: 12 months

University promotor: Michael Daenen (UHasselt)

For more information or application, please contact the supervising scientist Bart Vandevelde (bart.vandevelde@imec.be).