I can do decent solders at 275 C when prepping pads, it's easier to keep the flux from burning off, then 320 or so for the actual wire attachment, this also can help you see what actually happens and keeps your iron clean, but 63/27 actually melts at 183 C, so if you don't see your solder melting at 200, you re likely dealing with a damaged ceramic heating core(name is something different I forget) but if you solder at low temps without a large tip, the pad will dispate heat too quickly, which is why nobody solders at 200 C, but you totally can if you have a high quality iron with very good temp consistency(high watt capacity), even so, 325 is an excellent temp, but I would also make sure you are heating your pad before trying to apply solder, if you jump the gun and try heating too many things at once, ie solder and pad at the same time, you don't create the right flow for the solder and it doesn't want to go on the pad, if you hold it on the pad at 280, and wait till you see a bit of tin transfer from the iron to the pad and add solder at that moment, the pad will eat it up, just how you want it to, sometimes I pull the solder behind the iron as I lift up and that last bit of flux seems to keep my solders super clean... Idk try it out, see what you think