This article is about technique on flight controllers, 4-in-1 ESCs, motor wires and XT60 pigtails. It is not a first-power checklist; for that, see the smoke-stopper guide in this repo.
Tools that actually matter
GetFPV's soldering guide puts the iron first: something in the roughly 20-40 W class with adjustable temperature and interchangeable tips. A fixed cheap iron that runs too hot or too cold makes every later tip harder to follow. Pyrodrone's beginner guide leans the same way: portable "two-button" irons with a DC supply work well if the tip stays clean and the temperature is set on purpose.
Solder: leaded, rosin core, about 0.7-0.8 mm. GetFPV recommends 60/40 tin/lead. Pyrodrone prefers 63/37 because it melts and freezes at one temperature, which reduces the window for cold joints. Unmanned Tech's workshop write-up uses 60/40 at 0.8 mm and warns that lead-free melts hotter and cracks more under vibration. Pick one leaded alloy and stick to it. Use ventilation and wash your hands after.
Flux: the core in the wire is enough for many small pads. On battery pads and large ground planes it is not. Unmanned Tech and Pyrodrone both treat extra flux (paste, pen or dish) as normal for power work. Without it, solder sits on oxidised copper like water on a greasy plate.
Also useful: a brass tip cleaner (better than a soggy sponge for long sessions), helping hands or putty, flush cutters, and solder wick or a sucker for rework.
Temperature: hot enough to be quick
Solder melts well below the tip temperature you set. The tip has to heat the copper mass fast so the joint finishes before the rest of the board soaks. GetFPV's rule of thumb:
| Job | Tip temperature |
|---|---|
| Normal FC / ESC signal and motor pads | about 380°C (700°F) |
| Large connectors and high thermal mass | about 415°C (780°F) |
Pyrodrone typically uses about 350°C and raises heat for XT60s. Unmanned Tech runs about 350°C on power pads and about 300°C on fine signal pads in their workshop, and gives a practical test: if solder does not flow within about two seconds, the iron is too cold or the tip is dirty.
Do not leave a tiny UART pad under a 415°C tip for ten seconds. Short contact at the right heat beats a long bake at a "safe" low setting. Clean and re-tin the tip every time you pick the iron up; oxides block heat transfer.
Tin both sides, then join
The reliable sequence from GetFPV and Pyrodrone is the same:
- Strip only as much insulation as the pad needs. Too much bare wire invites shorts and fatigue breaks.
- Flux the wire and the pad when the joint is large or reworked.
- Tin the wire. Put a small blob on the tip, heat the strands, feed solder from the far side until it wicks into the copper. The exposed length should match the pad so nothing overhangs.
- Tin the pad the same way: tip with a bit of solder for contact area, wait until the blob relaxes and flows, then add just enough for a slight convex puddle. A ball of excess solder will splash when the wire goes on.
- Join. Place the tinned wire on the tinned pad, heat until both pools merge into one smooth fillet, remove the iron, and do not move the wire until the joint has solidified.
A good joint is shiny, smooth and concave where it meets the pad. Dull, grainy or ball-shaped means cold. Unmanned Tech's rework recipe: add fresh flux, reheat until the old solder flows, add a touch of new solder, hold still. That is usually safer than stripping everything to bare copper.
Motor wires and strain relief
Motor joints see continuous vibration. Pyrodrone recommends cutting each wire to length against the pad, tinning a short strip, soldering, and adding a zip tie on the arm for strain relief. Some builders route motor wires back toward the stack and solder "backwards" on the ESC pads to reduce pull. Either layout is fine if the wire cannot flex the joint every prop revolution.
GetFPV's tip for through-hole pads: do not fill the hole with solder first. Tin the wire lightly so it still fits, pass it through, and solder from the far side. In a crash the wire is then more likely to break than rip the pad off the board.
XT60 and other melting plastics
Battery leads are the hardest joints on a 5-inch build: thick copper, thick wire, high current. Use a larger tip if you have one, raise temperature into the high band above, and add flux. Slide heat shrink onto the wire before you solder.
GetFPV's XT60 tip is worth doing every time: plug the mating connector into the one you are soldering. Softened plastic then keeps the cups aligned instead of drifting. Tin the cup lightly, tin the wire well, insert, heat the cup and wire together, and fill until the strands are buried with a smooth fillet at the rim. Watch polarity before the joint freezes.
After soldering
Inspect under good light. Look for bridges between neighbouring pads, solder balls hiding under an FC, and any wire that moves when you tug it gently. Unmanned Tech suggests that tug-and-look pass before each flying session on critical power joints. Continuity across the XT60 with the pack disconnected still belongs in the first-power checklist.
Practice boards exist for a reason. Burning pads on a scrap board is cheaper than lifting a ground pad on a new 4-in-1.