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Chapter 10 · Building

Soldering is half the hobby

Building and repairing your drone means soldering. With the right tools and a bit of practice, it’s easier than it looks.

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Essential tools

Soldering iron

60 W or more, with adjustable temperature and fast heat-up. A chunky tip for the big pads and a fine one for the small ones.

Solder and flux

63/37 flux-core solder, which melts at a lower temperature and sets instantly, plus a pot of extra flux.

Multimeter

To find short circuits and check voltages before you plug anything in.

Smoke stopper

Limits the current the first time you plug in a battery. If there’s a short, the bulb lights up instead of your electronics burning.

Mechanical

1.5, 2 and 2.5 mm Allen keys, an 8 mm socket for the prop nuts, pliers, wire cutters and wire strippers.

Consumables

Cable ties, heat-shrink tubing, heat-resistant tape, threadlocker, double-sided tape and isopropyl alcohol to clean off flux.

How to make a good solder joint

  1. Clean, tinned tip

    Clean it with brass wool and put a little solder on it: it transfers heat much better.

  2. Temperature

    About 350–380 °C for signal wires and 400–420 °C for the battery pads and thick wires.

  3. Tin them separately

    Put flux and a layer of solder on the pad, and another on the end of the stripped wire.

  4. Join

    Bring the wire to the pad, touch both with the iron and wait for the solder to melt and flow. Remove the iron and don’t move the wire until it cools.

  5. Inspect

    A good joint is shiny and volcano-shaped. If it’s grey, grainy or balled up, it’s cold: reheat it with flux.

  6. Clean

    Remove the flux residue with isopropyl alcohol and a brush.

Don’t leave the iron on a pad for long: it can lift off the board. If it’s struggling, what’s missing is heat (a thicker tip or a higher temperature), not time.

Three wire-to-pad solder joints seen from the side: a good one, shiny and volcano-shaped; a cold one, grey and balled up; and one with too little solder, where the strands are visible Goodshiny, volcano shape✓Coldgrey, balled up✗Too littlestrands visible✗pad
If the joint is cold or skimpy, add flux and reheat it until the solder flows.

The multimeter, your lifesaver

  • Continuity: before plugging in any battery, check there’s no contact between the positive and negative of the XT60. If it beeps, there’s a short.
  • Voltage: check that the flight controller’s regulators give what they should (5 V, 9 V) before connecting the camera or the VTX.
  • Battery: measure the actual voltage and compare it with what Betaflight shows, to calibrate it.

Workshop safety

  • Ventilate: flux fumes aren’t healthy.
  • Safety glasses when cutting wires or soldering close to your face.
  • Keep the iron in its stand; switch it off when you’re done.
  • Wash your hands after handling solder.