Energetic analysis of solder paste deposits as reference for soldering with selective heat

Strictly speaking standard reflow soldering processes are inefficient in terms of energy consumption. A large amount of energy is needed to heat up comparatively small solder joints. As a result the whole electronic assembly is stressed with heat, of which only a fraction is going into soldering. A reduction of process temperatures would improve this disproportion. To compensate for the resulting lack of energy, an exothermic reaction, releasing additional heat inside the solder paste deposits, could be applied. The potential of such a process has already been proven in earlier works [1], [5]. For the adjustment of such a sensitive process a better understanding of the energetic requirements for solder paste deposits in dependence of their size and temperature is required. In this work such results are generated by a practical measuring approach. Here, a chip resistor is used as a model to melt up particular solder joints through joule heating. The thermal energy is calculated by measuring electrical power over time.