3 to 5 seconds are entirely fine for a solder joint. Given that most components are made for surviving soldering in a hot air oven it became almost impossible to break them by overheating with an iron.
If your solder melts but doesn't flow, it's more likely that your board needs better cleaning. Or you have solder with not sufficient flux inside, there are ones with 1%, 2% and 3% flux embedded. I prefer 3%, but 2% is also usable.
If your solder melts but doesn't flow, it's more likely that your board needs better cleaning. Or you have solder with not sufficient flux inside, there are ones with 1%, 2% and 3% flux embedded. I prefer 3%, but 2% is also usable.
