Wick cleaning a through-hole pad without lifting it
Desoldering braid is the fastest way to clean a pad and the fastest way to destroy one. The difference is dwell time: braid that has already absorbed its fill stops conducting heat into the joint and starts conducting it into the adhesive, and the pad comes up with the braid.
Procedure
- 1
Cut a 25 mm length of 2.5 mm braid and lay it flat across the joint so it overhangs the pad on both sides.
- 2
Add one drop of RMA liquid flux to the braid, not to the board.
- 3
Set the 3.2 mm knife tip flat on the braid directly over the pad and hold for one to one and a half seconds.
- 4
Lift the iron and the braid together; do not drag the braid sideways across the pad.
- 5
Repeat with a fresh braid segment if any solder remains, and finish with an alcohol wipe plus a flux residue check.
Workshop notes
Braid width should match the pad, not the joint
Use braid 0.5 to 1 mm wider than the pad so the copper contacts the pad edges and pulls solder sideways. Braid narrower than the pad leaves a solder rim at the pad perimeter; braid much wider wicks solder from the neighbouring joints and creates a second defect. For a 2.0 mm pad the working width is 2.5 mm.
Fluxed braid versus adding your own
Pre-fluxed braid from a sealed reel works, but the flux dries once the reel has been open for a few weeks. Add a drop of RMA liquid flux on top of the braid every time, and the wicking action becomes noticeably faster. Never press down hard: pressure squeezes the molten solder out of the copper strands and back onto the board, which is the opposite of what you want.
Change braid segments instead of holding longer
When a segment has filled, cut it off and start a fresh one. A filled segment is a copper-solder composite with roughly half the thermal conductivity of clean braid, so the joint cools while you keep pressing. One 25 mm segment clears one 2.6 mm through-hole joint; budgeting one segment per joint is cheaper than replacing a board.
Practice drill
Take a scrap board with 30 soldered through-hole joints and clean all of them, then inspect under 10x for pad-edge damage. Then repeat with the iron set 30 degrees hotter and one-second dwells, and compare pad survival.
Failure modes
| Symptom | Cause | Treatment |
|---|---|---|
| Pad lifts off the laminate | Filled braid held in place for three seconds or more, heating the adhesive past its glass transition | Cut a fresh segment every joint, cap the dwell at 1.5 seconds, and let the board cool for ten seconds before revisiting the same footprint |
| Solder rim remains around the pad perimeter | Braid narrower than the pad, so the outer 0.3 mm never saw copper | Go up one braid width and rotate the approach by 90 degrees for the second pass |
| Braid sticks to the joint and tears | No flux added and the copper strands oxidised, so the solder froze into the weave | Add flux, reheat the braid in place for one second before pulling, and lift vertically rather than peeling sideways |
Supplies
- 2.5 mm RMA-fluxed desoldering braid
- RMA liquid flux
- Isopropyl alcohol 99.9%
- Lint-free swabs
Tools
- Station set to 350 degrees C
- 3.2 mm knife tip
- Flush cutters for trimming braid
- 10x loupe
Safety
Braid heats along its whole length, not only at the tip - hold it with tweezers past the point you cut, and never with bare fingers. RMA flux is a rosin sensitiser; ventilate and wash skin contact promptly.
Neighbouring cards
- Drag soldering a 0.1 in header 360 °C / 1.2 s
- Diagnosing and repairing a cold joint 340 °C / 2.5 s
- Through-hole fillet baseline 340 °C / 2.0 s
- Hook splice on stranded wire 330 °C / 2.5 s