Here are the details for the OU
Lead-Free Project Introduction
The Open University Solder Research Group aims to facilitate the implementation of lead-free solders by evaluating their mechanical properties, especially those which are influential to their service performance.
Examination of the corresponding behaviour of model solder joints and comparision with the performance of entire boards provides the underpinning correlation for life prediction and design, and ensures that selection of specific lead -free alloys is soundly based.
Current Position/Results
An extensive assessment of the tensile, creep, fatigue and fatigue-creep behaviour of bulk specimens of Sn-37Pb, Sn-3.5 Ag, Sn-0.5 Cu and Sn-3.5Ag- 0.5Cu has been carried out over a range of temperatures. (down to -40 C in some cases). The effects of temperature and strain rate on monotonic strength are substantial, and may alter the ranking of the alloys.
Fatigue performance may be severely impaired by the presence of a dwell period in the strain cycle although there appears to be a saturation of this effect, in terms of dwell duration. The silver- containing alloy has substantially the best creep resistance.
Tests on simple 'pin-in-ring' joints are beginning and a programme of thermal cycling of complete boards is planned.
Contact Professor W J Plumbridge Materials Engineering Department The Open University Walton Hall Milton Keynes MK7 6AA UK
Tel: 01908 652630 Fax: 01908 653858 Email: W.Plumbridge@open.ac.uk
Full details are available on: http://www-tec.open.ac.uk/materials/srg/srg-hp.html
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