Soldering Irons are needed to construct, Capitols, Pressurized Roads, Solar Power Plants, Casinos, Airport Terminals, Airport Repair Shops, and Design Studios. Soldering Irons can be manufactured at a Machine Shop or an Electronics Factory.
At a Machine Shop, 10 units of Metal and 10 units of Natural Gas are needed to make 20 Soldering Irons. Electricity and a Fitting Wrench are not required but will decrease production time. A Computer would increase production output.
At an Electronics Factory, soldering irons are instead constructed using Metal and Plastic