Soldering
Dialling in your iron's temperature
The temperature of your soldering iron greatly affects your ability to form good joints.
Which temperature should you solder at? It depends:
- For leaded solder, start with a temperature of 290ºC (±555°F).
- For unleaded solder, start with a temperature of 330ºC (±625ºF).
Don't worry about the exact temperature you set it to. It doesn't come very precise: you'll tweak the temperature as you go.
Where does the 330ºC come from? Generally, you want the temperature to be 100ºC above your solder's melting point, plus a little extra to allow for tolerances of your soldering iron. The melting point of lead-free solder is approximately 217ºC, so adding a bit extra to that gives a nice safe point of 330ºC, which is 626ºF.
Usually, you won't need a much higher temperature. As an absolute maximum, we do not recommend soldering at a temperature higher than 380ºC, as there's a large chance of burning either your PCB or the components you're soldering above that temperature.
After setting the temperature, you'll want to dial it in to match your iron. Here are some tips:
- There is no need to solder at the absolute lowest temperature you can get away with. Higher temperatures can make it easier to solder.
- For sensitive components, it's usually not the temperature of the soldering iron that forms a risk, but rather a combination of the temperature and the time at which you heat the component. If you can solder reliably at a high temperature, that's better than having to heat up a joint for a long time before it forms properly.
- Increase the temperature if you're having trouble forming a good joint within a few seconds. Usually, you'll want to be able to form a good joint within about three to five seconds.
- Larger pads may require higher temperatures. A large pad requires more heat to be transferred, which your soldering iron needs to supply. As a result, large pads can cause your iron to cool off more than it has capacity to heat up in a short time. To combat that, you can set your iron to a higher temperature, so it can transfer heat quickly enough to form a joint without damaging the PCB or its components.
- Play with the temperature dial. If you've found a temperature to work for you for a certain size of pad or component, feel free to adjust the temperature between joints: lower for small pads, higher for larger pads. There's no right or wrong here: work at a temperature that's comfortable for you.
Do not apply excess force when soldering. There is never a need to apply much force with your soldering iron: just poking at it to touch both surfaces you want to join is enough. Especially when working at a high temperature, the risk of damaging a pad becomes larger if you do apply excess force.
Solder not melting? Try this first. Especially when you're feeling rushed, it can be tempting to try and press harder when solder is not melting. However, it's not the force that's a problem: the problem is either the temperature or oxidation. You can combat the temperature problem by simply increasing your iron's temperature. Oxidation can be fixed by applying flux to the joint. In a pinch, your solder will contain flux as well, so applying just a little extra solder to the joint will often loosen it right up.
Choosing solder
Solder wire is one of the key parts to soldering.
Soldering healthy joints
Being able to form quality joints make for a long-lasting, reliable project.
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