A soldering iron can reach temperatures of up to 450C. A soldering station will give you the function of being able to set the temperature of the tip. This is usually between about 150C to 450C.
This is a question that comes up a lot from beginners. Most seasoned users of solder stations or soldering irons that can alter their temperature don’t really worry too much about the setting but it does seem a puzzle for those starting out. This is probably due to the reason that the answer they seek is never really black and white and it does vary due to a few considerations. Mainly it will come down to experience with the type of soldering you do and the soldering station or iron that you are using.
The main piece of advice I would give is that just by turning the heat down on a soldering iron doesn’t mean that you have less chance of damaging components. That advice may seem contradictory.
It depends on what type of solder. See What is the best solder for electronics. Of the solder types that are intended for electronics use 60/40 starts to melt at 183C. When it gets to 190C it becomes a liquid. As it cools it becomes semi liquid until it cools to below 183C when it will set.
The 63/37 will melt at 183C and become liquid almost immediately and harden up as soon as its temperature drops below 183C.
Lead free solders melt at hotter temperatures. Depending on exactly what type you use it could melt at 188C or as hot as 203C.
Therefore it’s possible to have the temperature too low to be able to melt the solder properly no matter you hold the irons tip on the joint but there is still enough heat to damage components.
As you can see from the above it’s possible to set your soldering station temperature too low. Not surprisingly it’s also possible to set it too high. It’s not just a case of setting it to the temperature that solder melts. Your soldering iron isn’t going to be able to perfectly conduct the heat it produces. Heat will be conducted away once you touch it on the joint you are making. A small pad and a leg on an IC won’t lose as much heat as a large PCB power rail and a huge capacitor.
I set my soldering stations temperature to 350C and that’s what I consider to be the best soldering iron temperature for circuit boards and small soldering. Anything bigger such as thick wires or screens on metal jack plugs and I put in a bigger tip and turn the temperature up to 370C. For tiny SMD soldering I put in a small tip and drop the temperature to 330C.
Try not to get into the habit of having the temperature higher than you need. One of the first symptoms to turn the heat down that I became aware of was melting the insulation on thin wires. Also the hotter your tip the faster it will oxidise.
Once you start to use your soldering station you will become accustomed to how hot you need the temperature to be. There’s nothing like experience and you will know better than anyone what you need with your particular soldering station, tips, solder and the soldering you do.