Case study for high volume lead-free wave soldering process with environmental benefits

This paper discusses case study of Sn/Ag/Cu lead free wave soldering process for high volume production with benefits of environment. Key variables in a lead-free solder wave soldering process are alloy cost, solder pot temperature, dross forming characteristics of the alloy, nitrogen use or air atmosphere, flux selection and activator, flux application system and volume, alloy contaminant effects, alloy elemental concentration control, recycling of spent solder, board/lead finishes, process control changes. In this study, commercially available 99.999% purity nitrogen use in wave soldering was examined and the significance of it in dross rate reduction, product quality and process success was discussed. Dross formation of Sn/Ag/Cu with nitrogen environment was compared with eutectic Sn/Pb bath with air atmosphere and solder bath dross maintenance depending on lot size was evaluated. The effect of no clean VOC free flux on the board quality was also evaluated, recommendations are presented for the improvement of lead free application soldering performance (bridging, wetting and hole filling). For successful process steps in lead-free wave soldering implementation was described. The cost and environmental benefits of nitrogen usage was also presented for high volume single sided lead free assembly.