I'm an electrical engineer and I just spend the whole day yesterday reworking some factory-made Sn/Cu/Ag boards in the lab. What kind of parts are you soldering

I'm an electrical engineer and I just spend the whole day yesterday reworking some factory-made Sn/Cu/Ag boards in the lab. What kind of parts are you soldering? Thru-hole parts are easy. Surface-mount parts can go quickly from annoying to very hard/nearly impossible to work with Sn/Cu/Ag, depending on their size and thermal sinking ability. Sn/Cu/Ag solder has a narrow window where the solder is melted and wets pads but the FR4 substrate isn't yet degrading. If you have sensitive plastic parts like connectors, etc. the window is even narrower. This is doable in an industrial reflow owen. However when doing hand work or repair, it's impossible to control the temperature this well. For example, after years of experience, I'm still unable to desolder large BGA or PGA parts without visibly degrading the board (i.e. there's usually a brown mark left on it - unfortunately the boards I commonly work with these days use white soldermask, which makes this even more obvious). That's with a temperature controlled pre-heater and a hot-air station. I won't even attempt to solder such parts manually with Sn/Cu/Ag.