Lead/lead-free solder alloys shear tests correlations with structure at different temperatures

The new RoHS 2 Directive [1] touch up the research work for replacement the lead soldering materials with lead-free types, without compromising functionality and reliability. At least two of the three solder joints functionalities, mechanical and thermal one, are determined by the microstructure morphology and stability. As consequence, any material must accomplish dedicated procedures for qualification to be used for these domains of applications characterized by a large range of working temperatures and high mechanical stress level. According to "Homologous temperature" (T_H) concept, the working temperature for a solder alloy could be expressed as a fraction of its melting temperature measured in Kelvin degrees and must not be over 0.5 value [2]. Shear tests performed at different temperatures are correlated with the microstructure morphology and stability investigates by X-ray Diffraction Analysis.