Here is the thing that would have made your first board much less stressful, had somebody said it at the start:
Almost nothing you do with a soldering iron is permanent.
Wrong component? Comes out. Backwards LED? Comes out. Bridge across four pins? Gone in five seconds with the right bit of braid. Too much solder? Take some away. The main thing standing between you and fixing any of it is not skill, it is knowing that removal is a normal, ordinary operation rather than an emergency.
That knowledge changes how you build. People who cannot undo things solder timidly, hesitate, and make worse joints. People who know they can undo anything solder decisively, which is exactly what produces good joints.
By the end of this lesson you will be able to remove solder from a joint, clear a bridge, take a component off a board without damaging it, and know what to do in the one case that genuinely is difficult.
10.1 The one thing that makes rework possible
The aim of this section is to explain why reheating an old joint behaves so differently from making a new one, because otherwise rework feels inexplicably harder than it should.
You reheat an existing joint. Nothing much happens. The solder softens grudgingly, moves like porridge, refuses to flow. You conclude your iron has lost power.
It has not. The flux is gone.
Section 3.3 explained that flux is a one-shot ingredient, spent by heat. The flux that came in your solder wire did its job the first time that joint was made, and it burned off then. What is left on the board is solder with no cleaning agent in it at all, sitting on metal that has had time to oxidize since.
So the single most useful habit in all of rework is this:
Add fresh solder to an old joint before you try to remove anything.
That sounds backwards. You are trying to take solder away and step one is to add more. But you are not adding solder, you are adding flux, which happens to arrive wrapped in solder. The new flux cleans the joint, the whole thing suddenly flows properly, and now it can be removed.
A flux pen does the same job more directly. Lesson 4. Either way, the joint has to be given its chemistry back before it will cooperate.
Everything in this lesson gets easier once you know that.
10.2 Desoldering braid
The aim of this section is the technique for the tool you will use most, because braid handles the majority of real situations.
What it is: fine copper braid, impregnated with flux, sold on a small reel. Also called solder wick.
How it works: copper braid held against molten solder draws it up by capillary action, exactly the way a paper towel draws up water. The flux in the braid makes the solder willing to wet the copper, and the many fine strands provide a huge surface area for it to climb into.
The technique
- Lay the braid flat on the joint. Not the end poking at it, the flat of the braid lying across it.
- Press the iron down on top of the braid, so the braid is sandwiched between the tip and the joint.
- Wait. Two or three seconds. Heat has to pass through the braid into the solder below before anything happens. This is the step people cut short.
- Watch for the braid to darken and change color as the solder climbs into it. That is the moment it is working.
- Lift the braid and the iron away together, while still hot.
⛔ The critical mistake: letting the braid cool onto the board. If you lift the iron first, the solder in the braid freezes and you have effectively glued a piece of copper braid to your board.
If the braid does freeze on
It will happen at some point. ⛔ Do not pull. Pulling is what takes the pad with it, and a lifted pad is the worst damage in this course. Instead:
- Put a drop of fresh liquid flux on the stuck braid. It wicks under and makes everything flow again as soon as heat arrives.
- Bring a freshly tinned tip down on top of the braid, directly over the stuck section. The film of solder on the tip is what carries the heat in, exactly as in Section 6.2, and a bare tip will struggle here.
- Wait for it to melt, then lift the braid and the iron away together, the same movement you should have made the first time.
- If a long section is stuck, work along it a centimeter at a time rather than trying to free the whole length at once.
Done this way it comes off cleanly and the pad is untouched. It is a two-second recovery, and the only way to turn it into real damage is impatience.
Getting the most out of it
- Cut off the used section. Solder-saturated braid does not absorb any more. A short snip and you are on fresh braid.
- Use the right width. Wide braid on a small joint takes heat away from everything and works poorly. 2 mm is a good general size.
- Add fresh solder first, per Section 10.1. Counter-intuitive, and it works.
- Add a little flux to the braid if it is old. Flux in braid deteriorates over time, and old dry braid is close to useless.
What braid is best at: flat surfaces, bridges, taking excess off a joint, cleaning a pad completely after a component is out.
What it is worse at: getting solder out of the barrel of a plated through hole. For that, a pump.
Figure 10.1: Braid flat on the joint, iron on top of the braid, wait for the color to change, then lift both away together while hot.
10.3 The solder sucker
The aim of this section is the other tool, and the specific knack that makes it work.
What it is: a spring-loaded plunger in a tube with a heat-resistant nozzle. You cock it, hold it against molten solder, press the button, and it snatches the solder up in one violent gulp.
The technique:
- Cock the plunger before you start heating anything. It takes two hands and you will not have two hands in a moment.
- Melt the joint fully with the iron. Genuinely fully. Add fresh solder first, per Section 10.1.
- Bring the nozzle in beside the iron, right against the joint, without moving the iron away.
- Lift the iron and fire the sucker in the same instant. This is the whole knack, and it is a timing thing rather than a strength thing.
What suckers are best at: clearing a plated hole so a component can be pulled through. They shift far more solder than braid, and they reach into the barrel.
Their weaknesses: they are clumsy for fine work, the recoil can knock a board about, and cheap ones seal badly and lose suction. Squeezing the nozzle tip occasionally and keeping the shaft clean helps.
A note on cheap versus not: this is one tool where the very cheap version is genuinely frustrating, in a way that a cheap pair of cutters is not. If you only ever remove the occasional component, braid alone is enough and you can skip the sucker entirely.
10.4 Clearing a solder bridge
The aim of this section is the most common single repair, and the one people arrive at this lesson looking for.
A bridge is solder connecting two pads that should not be connected. Lesson 9. It is a short circuit, and it is the fault most likely to actually damage something on power-up.
Three ways, in the order to try them:
1. Tip between the joints, then up a leg
This is the easiest fix and the one to reach for first. Clean tinned tip, a touch of fresh flux, and then put the tip down in the gap between the two joints rather than on top of the blob. Let the bridge melt, and draw the tip up one of the legs.
The solder follows the leg. That is the whole trick: molten solder would far rather wrap itself around a hot leg than stretch across a gap, so giving it a route up one leg is enough to make the bridge stop existing. You are not scraping solder off, you are offering it somewhere better to be.
Wipe the tip afterwards, since it is now carrying the excess.
2. Braid it
The reliable answer. Braid flat across both pads, iron on top, wait for the color change, lift together. The bridge disappears and both pads are left with a thin correct amount of solder on them.
Often you will then want to add a small amount back, since braid tends to take everything.
3. Add more solder first, then braid
Counter-intuitive again, and it works for the same reason as Section 10.1. A stubborn bridge is usually a dry, fluxless one. Feed a little fresh solder into it, which sounds like the opposite of helpful, then braid the lot away. The fresh flux makes it flow and it comes off easily.
⚠️ Then check. Look along the row at a low angle with a light behind, exactly as Section 9.3 described. And if you have a multimeter, check the two pads are no longer connected, because a bridge you think you cleared is worse than one you know about.
Figure 10.2: Three ways to clear a bridge. Take the tip up a leg, braid it, or feed fresh solder in first and then braid the lot away.
10.5 Removing a component
The aim of this section is the full operation, including the honest difficulty ranking, because a two-legged resistor and a fourteen-pin chip are not the same job.
Two or three legs, and you want to keep the part
This is the easy case: LEDs, resistors, capacitors, transistors.
- Clear the solder from each hole, one at a time, with a sucker or braid. Add fresh solder first.
- Check the leg is free by wiggling the component very gently. If the leg moves in the hole, that hole is clear.
- Once all legs are free, pull the part out from the component side. It should come with almost no force.
⛔ If it does not come freely, do not pull harder. Something is still soldered, and pulling is what lifts pads. Go back and clear the hole again.
Figure 10.3: Clear each hole, check the leg moves freely, then lift the part out with no force at all.
The alternative for two-legged parts: heat one joint, tilt that side of the component out slightly, heat the other, tilt again, and walk it out in two or three passes. Quick, and slightly harder on the pads, so use it when you do not care about the component.
Two or three legs, and you do not care about the part
Cut the legs first. Snip the component body off, then remove each leg individually, which is enormously easier than removing a whole part. Then clear the holes.
This is the right call more often than people think. A resistor costs pennies; a lifted pad costs an afternoon.
Many legs, chips, connectors, headers
This is genuinely harder, and worth saying so. All the legs must be molten at the same time for the part to come out, and a hand iron heats one at a time.
Realistic options:
- Sacrifice the part. For a header, cut the plastic body away and remove each pin individually. For a chip in a socket, just pull the chip and leave the socket. This is what most people should do most of the time.
- Clear every hole thoroughly, then work round the part lifting one side a fraction at a time over several passes. Slow, and it works.
- Hot air, which is the proper tool and is Lesson 12's territory.
⛔ What not to do: heat several joints in rotation while pulling steadily. It feels like it is working, and it is the classic way to lift a row of pads.
10.6 When it does go wrong
The aim of this section is the honest bit: what to do about the damage this lesson's operations can cause.
A lifted pad
The copper pad has detached from the board. Lesson 9 called this the most serious damage in the course, and it is.
It is repairable, but not prettily. The pad is only a connection point; what matters is that the component leg reaches whatever the pad was connected to. So you bypass it: solder a thin insulated wire from the component's leg to the next accessible point on that same track, often the leg of the next component along or a via.
Trace where the track goes first, with a meter or from the board's documentation. Then run a short length of thin insulated wire between those two points and add a dab of glue to stop it flexing. Engineers call this a bodge wire, and it is a normal repair rather than an admission of defeat.
It will look like a repair. It will work indefinitely. Real production boards leave factories with bodge wires on them.
A lifted track
Same principle, worse. Bypass from one solid end to the other.
A hole that will not clear
Sometimes solder simply will not come out of a plated hole. Try: fresh solder in, then the sucker. If it still resists, heat the joint fully and push a stiff wire or a small drill bit through the molten solder from the other side to open the barrel, then clear again.
⛔ Never drill it out cold. You will destroy the plating that connects the two faces of the board.
Knowing when to stop, again
Lesson 9's rule holds here with more force, because rework applies more heat than assembly does. Two attempts, then stop. Let it cool completely. Come back with fresh flux, a bigger tip, or a different approach.
Cold boards forgive. Hot boards do not.
What this sets up
Lesson 11, wires and connectors, has its own removal problems, mostly involving heat shrink that has already been slid into place.
Lesson 12, surface mount, is where hot air stops being optional.
Frequently asked questions
How do you use desoldering braid? Lay it flat on the joint, press the iron on top so the braid is sandwiched between tip and solder, wait two or three seconds for heat to pass through, watch for the braid to darken as the solder climbs in, then lift the braid and iron away together while still hot.
Why won't my old solder joint melt properly? The flux is gone. It was spent when the joint was originally made. Add a little fresh solder, which brings fresh flux with it, or apply flux from a pen. It will then flow normally.
Braid or a solder sucker, which is better? Braid for flat surfaces, bridges and excess. A sucker for clearing solder out of a plated hole so a component can be pulled through. If you only own one, own braid.
How do I remove a component from a circuit board? Clear the solder from each hole, add fresh solder first to bring flux back, check each leg moves freely, then pull the part out with almost no force. If it resists, something is still soldered; clear it again rather than pulling harder.
How do I fix a solder bridge? Put the tip in the gap between the two joints, melt the bridge, and draw the tip up one of the legs so the solder follows it. If that fails, braid it. If it is stubborn, feed a little fresh solder in to restore the flux and then braid the lot away.
Can you fix a lifted pad? Yes, by bypassing it. Run a thin insulated wire from the component leg to the next point on that track and secure it with a dab of glue. It looks like a repair and works indefinitely. Production boards ship with bodge wires.
Why does my desoldering braid stick to the board? You lifted the iron before the braid. The solder froze while the braid was still on the joint. Reheat it and lift both together; do not pull it off cold.
Next
Lesson 11: Beyond the board, wires, heat shrink and connectors. Joining wire to wire is a different job with different rules, and it is where most people's soldering actually gets used.
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