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Materials Engineering

Research / Solder Research

Welcome to the solder research webpages

Research into the mechanical behaviour of electronic solder alloys forms a key part of the Materials Engineering group's focus on structural applications of high-temperature engineering materials. The continuing miniaturisation of electronic components has placed ever-increasing demands upon soldered joints to provide structural relaibility. Failure in service commonly occurs due to thermo-mechanical fatigue: temperature variations, due to power-switching or the external environment, cause fluctuating strains because of widely differing thermal expansion coefficients in the various joint materials. A further complication has been the recent and ongoing introduction of new Pb-free solder alloys.

Our research, for which we have developed a worldwide reputation, focusses on quantifying and understanding the mechanical behaviour of Pb-free solder alloys, and of the joints containing them, under the complex conditions likely to be encountered in service. Such an approach is important in supporting reliable design and life-prediction methods.

Our facilities include a fully-equipped creep laboratory, servo-hydraulic test machines for fixed rate and cyclic fatigue-testing, programmable thermal-cycling chambers (-50 º C to 180 º C) and facilities for optical and electron microscopy (SEM and TEM).

Recent key areas of research include:

Creation of a database of mechanical properties for candidate replacement solder alloys as compared with the performance of conventional lead-tin solder. Our main focus has been on three lead-free alloys, namely Sn-3.5Ag, Sn-0.5Cu and Sn-3.8Ag-0.7Cu, although others have also been investigated.

Investigation of tin pest , the allotropic phase transformation that occurs in tin at 13 º C and that can lead to degradation of high tin-content alloys.

Use of an internal stress approach to model the creep behaviour of dispersion-strengthened lead-free solder alloys.

Students interested in working in this area should contact Dr Martin Rist



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