Lead-free soldering-toxicity, energy and resource consumption

Toxicity, energy consumption and economical effects of applying SnPb₃₇ solder and PCB finish, SnAg_3.0Cu_0.5 solder, SnCu_0.75 solder, SnZn₉ solder and Sn as well as Ni/Au PCB finishes were compared to the respective tin-lead soldering materials. All assessed lead-free materials, besides the Ni/Au PCB finish, considerably reduce the toxic releases from PCBs into the environment. Lead-free soldering with SnAgCu and SnCu solders and current equipment increases the energy consumption in reflow soldering. To a minor degree it also enhances the energy demand for metal production. The energy consumption of the reflow oven is an environmental hot spot in the life cycle. The situation will improve with already available new oven technology. Evaluation with the Eco Indicator 95 and the Eco Point method show, that lead-free soldering with current soldering equipment and with the assessed lead-free solders and the tin PCB finish considerably reduces the overall burden to the environment. Surplus energy cost and, especially in case of SnAgCu solder, increased solder cost will hardly affect the total cost of a PCB, as solder and energy cost are only a minor part of the total PCB cost. Due to the silver content, the SnAgCu solder decreases the recycling cost