Lead/Lead Free solder joints comparative shear tests function of working temperature and soldering thermal profile

The domains exempted by the RoHS EU Directive, as aerospace, where Sn₆₃Pb₃₇ eutectic solder alloy with low silver content addition are used, are characterized by a large range of working temperatures and high mechanical stress level. In the paper, the mechanical strength of solder joints produced using Lead and Lead-Free solder pastes into Vapor Phase Soldering processes characterized by different cooling rates, were benchmarked by temperature in respect to the concept of "Homologous temperature". The experiments were done by measuring the solder joints shear forces and keeping the surface of test boards at temperatures up to 398.15 K (125°C). The experiments results consist in qualitative/quantitative light microscopy analyses and values of solder joints shear forces. The results offer the possibility to create a data base useful to define a methodology for future qualification of lead-free solder alloys according to the RoHS EU Directive.