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Sep 11, 2019, 10:19 AM
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Soldering thin wires to esc without play

Hi All

I had a mishap the other day with my ESC. I had soldered the motor wires directly onto the ESC. The wires had quite a bit of play on the ESC pads but I had kept it this way and flew with that for several flights.
I put ESC-motor in a new plane and this time I decided to apply a little bit of hot glue over the solder connections on the ESC to reduce the play. Anyways after a full throttle test this is how it ended up (long story short)...

I guess I have a couple of questions now...

My skill level with soldering is this... I can solder wires and I have seen tutorials on YouTube but I am by no means an expert.

How do I correctly go about soldering when the wire sizes are different between the ESC and motor?

In an effort to save weight if I were to wire up anESC to the motor directly how do prevent the play on thin wires connected to ESC pads?


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Last edited by dropout; Sep 11, 2019 at 11:37 AM.
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Sep 11, 2019, 10:20 AM
Registered User
Just copy and paste

Neither link works for me
Sep 11, 2019, 11:38 AM
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Thread OP
Originally Posted by John61CT
Just copy and paste

Neither link works for me

I just copied and pasted now. Please have a look. TIA

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Sep 11, 2019, 12:28 PM
AndyKunz's Avatar
Are you talking about splicing the leads to the motor, or soldering the motor leads directly to the PCB?

To prevent play, you always fixture things. You've seen those multi-alligator clips holders? Get one. It'll pay for itself really quick.

Sep 12, 2019, 10:56 AM
Registered User
Soldering is a skill that can be learned at any age.

The rules are pretty simple:
  • Use a temperature controlled soldering iron with good tips of the right size for the job. And good solder (for a hobbyist, use the ones with lead, lead free solder is harder to use, and for the amount a hobbyist use, lead is not an issue). Without the right soldering iron, tip and solder, everything else is pointless
  • When preparing a wire for soldering, remove the least amount of insulation you can, and pre-tin the copper part. When you pre-tin, the insulation will pull back some more, exposing more wire. If too long (>3mm), trim it
  • Pre tin the pad where you plan to solder, with the least possible amount of solder on it (pre-tin means "wetting" the pad, not depositing a huge blob)
  • Put the wire onto the pad, with a tiny bit of insulation over the pad, too. Touch the pad and wire with the soldering iron tip, wait a second, add a tiny bit of solder, remove the solder, remove the tip once the solder has flown nicely everywhere, and make sure that you do not move the wire until the solder joint is cold enough. Yes, you need 3 hands since that's not possible, either a holder, or learn to pinch wires and solder with only 2 fingers (that part is hard and requires more finger flexibility than most)

Most people strip too much insulation, solder with a lot of exposed copper wire (the insulation should touch the solder joint, if done properly), put too much solder on the pad or, worse of all, load the soldering iron tip with solder, then try to solder (at that point, all the flux is gone). Or use a soldering iron too hot or too cold

If you end up with too much exposed wire and play, remove the wire, clean the pad with fresh solder and and solder wick, trim the exposed wire, and repeat
Sep 12, 2019, 11:16 AM
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GeoffS's Avatar
I've become a huge fan of adding flux in addition to the little bit in the solder itself.

A bit on a bare pad means you can tin it just by putting a bit of solder on the iron and just touching the iron to the pad.
Since there is flux covering the pad to start and molten solder on the iron, the thermal contact with the pad is very good.
The pad heats up quickly and the solder flows onto it as soon as it's at the right temperature leading to less possibility of overheating the pad and tearing it off the PC board (esp. if you repeatedly solder leads to the pads).

Flux is also great when you're joining two already tinned items (ex. wire and pad).
Just hold the two parts together and touch them with the iron (with a bit of solder on the tip) and the solder will re-flow making a nearly perfect joint.

A little 91% isopropyl alcohol and a cotton-swab cleans the excess flux away after the soldering is complete.
Also, I'm a big fan of using silicone insulated wire. It's a lot more flexible than PVC and doesn't melt during soldering.

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