Comparative shear tests of two low melting point solder pastes relating to their thermal diffusivity

摘要

In a vehicle, for electronic components, the working temperature may vary between the limits 358K and 478K. The manufacturing costs reduction necessity combined with the RoHS2 EU Directive consequence lead to create new Low Melting Point Lead-Free (LMPLF) solder pastes family. In the paper, are presented the shear tests of the solder joints (SJ) and thermal diffusivity (ThD) measurements made on samples cast from LMPLF solder pastes (ALPHACVP-520, and ALPHAWS-852) into Vapour Phase Soldering Process (VPSP) characterized by different cooling rates (0.5K/s and 4.0K/s). The paper deals with the continuation of studies on the influence of thermal transfer (mainly thermal diffusivity) in the VPS process on the mechanical properties (shear tests) of the solder joint, for the new LMPLF alloys recently implemented in the automotive industry [1]. In this regard, it is emphasized the influence of solder joint shear force (SF) properties, depending on their ThD as function of solder alloy, which “set” the rate of heat transfer (convective versus conductive) to the substrate (PCB).