You probably have a shitty soldering iron which can’t deliver heat consistently. Try grabbing a used Metcal PS900 or MX500 on eBay. I have done zero maintenance

You probably have a shitty soldering iron which can’t deliver heat consistently. Try grabbing a used Metcal PS900 or MX500 on eBay. I have done zero maintenance or tinning on either of mine. They just work. I do SMD and TH stuff and rework no problems at all. Literally everyone who gets one goes “oh so that’s what soldering is supposed to be like” Also might be crap solder. Get some decent Felder or Multicore stuff. Leaded is easier to work with and harmless if you wash your hands and don’t lick your PCBs. Silver bearing leaded from Felder is what I tend to use. But it’s about $70 a roll Edit: I see that you have a Hakko. Buy genuine tips. Or replace it with a different iron. The cheaper Hakkos are terrible.