Correlation between the thermophysical properties, geometry and microstructure of the SAC305 and SAC-X typical solder joints

The quality and reliability of microelectronics components and assemblies can be considered as expression of solder joints functionality. The functionality of the lead free-solder joints is in strong connection with the microstructure, which is the result of the temperature gradient action over the trinomial solder alloy/paste, electronic components terminals and PCBs pads finishes, the gradient being determined by the specific thermal profile of the soldering process. These properties are in close connection with the microstructure of the solder joints, which are the result of the ¿4-P Soldering Model¿ (Paste-Pad-Pin-Process), with a special focus on lead-free solder alloys, and by different thermal profiles of the used soldering processes. The experiments presented in the paper describe measurements of the termophysical properties, the macro and micro-structural analysis on surface, in volume and at the interface of solder joints with the metallic substrate effectuated in order to identify the typical solder joints microstructures, over solder joints functionality.