 What temperatures should you use with your iron? The short answer? For lead-based solder set the iron to about 650 degrees Fahrenheit and for lead-free solder you can go up to 750 degrees Fahrenheit. And the long answer? Well, it depends on a few different variables, namely tip size. A larger iron tip is better at transferring heat, which means you can use lower temperatures and With a smaller tip that transfers less heat a higher temperature will work better. On the other side of the equation is the solder joint. A large solder joint will require more heat, so a higher temperature setting is appropriate and a smaller joint that heats up faster can use lower temp. Keep in mind that higher temperature settings will reduce the life of the tip faster than low settings. So when in doubt start with a lower temp and increase as needed. You