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Novel testing instrument for lead-free solder characterisation.

Di Maio, D; Thomas, O; Dusek, M; Hunt, C P (2011) Novel testing instrument for lead-free solder characterisation. IEEE Trans. Instrum. Meas., 60 (10). pp. 3444-3450.

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The European Restriction of Hazardous Substances Directive (RoHS) of 2006 has revolution-ised the use of materials for electronic packaging: tin-lead solder has had to be replaced with lead-free solder. Whilst years of experience and data acquired in the field is available for tin-lead solder, the same cannot be said for lead-free solders. The lack of data on these new alloys hinders the use of modelling for predicting the reliability of lead-free solders. This paper describes a new testing machine that can assess the properties of solder joints in a cop-per/solder/copper structure. FEA models using the newly acquired data will improve lifetime predictions. During a typical test, a model solder joint is expanded and contracted in shear. This actuation is achieved from the thermal expansion of a steel tube, which provides a smooth movement at a rate equivalent to that encountered on printed circuit boards (PCBs) when thermally stressed. The applied force is measured using a load cell; the sample displacement is determined from laser displacement sensors. Hysteresis load-displacement loops are obtained and can be used for evaluating the material plastic response and loading history. A camera/microscope system captures time-lapse photography images, which digital image correlation (DIC) software can analyse to obtain strain profiles and study crack propagation. The instrument is capable of investigating creep, stress relaxation, isothermal and thermal-mechanical fatigue behaviour of solder interconnects. Results from this new instrument are presented here for isothermal and thermal cycling fatigue tests.

Item Type: Article
Keywords: lead-free, materials characterisation, RoSH, low-cycle fatigue, thermal-mechanical fatigue
Subjects: Advanced Materials
Advanced Materials > Electronics Interconnection
Identification number/DOI: 10.1109/TIM.2011.2134670
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/5272

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