For most electronics work with leaded solder, set your iron between 315°C and 370°C (600°F to 700°F). For lead-free solder, you’ll need to go higher, typically 370°C to 400°C (700°F to 750°F). These ranges sit well above the solder’s melting point, giving you enough thermal energy to heat both the pad and the component lead quickly without lingering too long on delicate parts.
Melting Point vs. Working Temperature
The temperature you set on your iron is not the same as the solder’s melting point, and understanding the gap between them matters. Leaded solder (the traditional tin-lead mix) melts at about 183°C (363°F). Lead-free solder, which is now standard in commercial manufacturing, melts closer to 217°C (425°F). You need your iron set significantly above these numbers because the tip loses heat the instant it touches a component or pad. The extra thermal headroom ensures the joint heats up fast enough for the solder to flow properly.
A good starting point for leaded solder is 340°C to 360°C (roughly 650°F to 680°F). For lead-free, bump that up to 370°C to 400°C. An iron set to 650°F or 700°F will still melt lead-free solder comfortably, so if you switch between the two types, somewhere around 370°C works as a reasonable all-purpose setting.
Why Component Size Changes Everything
Small surface-mount components (resistors, capacitors, tiny IC pins) need less heat than large through-hole connectors or ground planes. A chunky ground pad on a multilayer PCB acts like a heat sink, pulling energy away from the tip faster than you can deliver it. If you’re working at 290°C on a large pad, the solder will barely flow and you’ll end up holding the iron in place far too long, which causes more heat damage than a hotter, quicker touch would.
A practical approach is to keep three mental temperature tiers. Around 290°C to 315°C works for fine surface-mount work on small pads. For general through-hole soldering, 340°C to 360°C is the sweet spot. And for desoldering, pad cleanup, or heavy ground connections, 370°C to 400°C gives you the thermal mass you need. Some soldering stations offer preset levels at roughly these tiers for quick switching.
How Your Iron Affects the Real Temperature
The number on your station’s display is the set temperature, not necessarily the temperature at the very tip when it contacts a joint. Depending on the design of your iron, the actual tip temperature can drop significantly the moment you start soldering. Cheaper irons with the heating element positioned far from the tip lose more heat and recover it slowly. This is why budget irons often need to be set higher to achieve acceptable results.
Higher-end stations use what’s called an active tip design, where the heating element and temperature sensor sit as close to the tip as possible. These irons recover heat almost instantly, which means the set temperature stays much closer to the real tip temperature during use. If you’re using an active-tip station, you can often work at lower set temperatures (say, 315°C to 340°C for leaded solder) and still get clean, fast joints. With a basic iron, you might need to crank it to 370°C or higher just to get the same performance.
Signs Your Temperature Is Wrong
Your solder joints will tell you if the temperature is off. Learning to read them saves a lot of frustration.
Too cold: the solder looks rough or pockmarked, as if it froze mid-flow. A cold solder joint appears dull and grainy instead of having the smooth, slightly shiny surface of a good bond. The solder barely adheres to the pad or lead, creating a high-resistance connection that can fail intermittently. If you’re seeing this, either raise the temperature or check that your tip is clean and making full contact with both the pad and the component lead.
Too hot: the flux burns off before the solder has a chance to flow properly, leaving dark, crusty residue around the joint. Pads can lift from the board, and nearby components can be damaged by conducted heat. Overheated joints may look acceptable at first but develop hairline cracks over time, appearing shiny initially before dulling with visible stress lines. These joints tend to fail under vibration or flexing.
A good joint is smooth, concave (slightly volcano-shaped around the pin), and wets evenly onto both the pad and the lead. With leaded solder it looks shiny and mirror-like. Lead-free solder naturally has a slightly more matte finish even when done correctly, so don’t chase a mirror shine with lead-free or you’ll overheat the joint.
Protecting Heat-Sensitive Components
Some components, particularly certain sensors, LEDs, and some ICs, are more vulnerable to heat damage than standard resistors or capacitors. The general rule is to minimize contact time rather than drop the temperature too low. A lower iron temperature forces you to hold the tip on the joint longer, which can actually transfer more total heat into the component than a quick touch at a higher temperature.
If a component’s datasheet flags it as heat-sensitive, use a thermal shunt. This is just a small clip (an alligator clip works fine) attached to the component lead between the solder joint and the body of the part. The clip absorbs excess heat before it reaches the component. For boards with many heat-sensitive parts, preheating the entire board to around 100°C to 150°C with a hot plate or hot air reduces the thermal shock from the iron tip and lets you work faster at each joint.
Practical Starting Settings
- Leaded solder, general use: 340°C to 360°C (650°F to 680°F)
- Lead-free solder, general use: 370°C to 400°C (700°F to 750°F)
- Fine SMD work: 290°C to 330°C, with a small chisel or conical tip
- Large ground pads or desoldering: 380°C to 400°C, with a larger chisel tip for better heat transfer
These are starting points. Adjust based on what your joints look like. If you’re getting dull, grainy results, go up 10°C to 20°C. If flux is charring and pads are lifting, come down. The goal at every joint is the same: get in, flow the solder, and get out in two to three seconds. If you’re holding the iron on a joint for five seconds or more, something in your setup needs to change, whether that’s temperature, tip size, tip cleanliness, or the amount of flux you’re using.