Electrical Soldering

Get it right the first time and every time. Article and photos by Michael Ramsey. Featured in the Summer 2008issue of Park Pilot.

Soldering electrical connectors onto motor wires, battery wires and speed control wires isn’t hard to do when you know the steps, and the first step is to think clean. Metal, by nature, oxidizes, and the metal wire and connector must be bonded to each other, not to any corrosion that may be on the surface.


Quality connectors are gold plated because gold doesn’t corrode like copper, which turns green; aluminum, which turns white, or steal, which turns brown. Since electrical solder loves to stick to gold, there’s little you need to do to prepare that part of the job. If you have lacquer thinner on hand, just gently wipe the metal ends of the gold plugs to remove any oil or dirt. The tip of the soldering iron should be “tinned.” Do this by touching solder to the hot tip of the iron to coat it with molten solder. If the wire you will solder has silicone or PVC insulation, it has been protected and won’t need any cleaning. The wire should also be tinned. Once the insulation is stripped from the wire, twist the braids to keep the bundle from fraying.

Apply flux to the bare wire, then tin the wire with a coating of solder. Flux is essential because it helps prevent the metal from oxidizing and helps direct the flow of molten solder. Touch the tip of the iron to the flux-coated wire. The point of contact will sizzle and smoke due to the fast transfer of heat, and the copper wire will quickly turn bright silver. The exposed wire should have a healthy coat of solder.

The tinned wire is now ready to be bonded to the connector, so tin the connector in the same manner as the wire. When the wire and connector are both coated with solder, they can be heated and bonded almost instantaneously. With both the connector and wire tinned, slide on any heat shrink tubing now. Bring the two points together; flux is no longer needed. Use an Excel Extra Hands or similar vice-type tool to position the wire and connector so that they touch each other, then simultaneously apply heat from the iron to both parts. Make sure that the tip of the iron, coated with a tiny amount of solder, contacts both the wire and connector so they heat at the same rate. The wire and connector will bond when you see bright silver solder flowing between them. Remember not to leave the heat on too long or it will melt the connector. A little bit of heat, a little bit at a time, ensures a neat and solid connection.
Hot joint

Besides being neat and clean, the joint has to be strong. If the heated solder doesn’t turn bright silver, it will only surface-bond. It can crack and break off easily. Bright silver solder bonds securely. It’s smooth and has no jagged edges. Strong solder joints prevent broken wires from causing shorts and permanent damage.
Check your work

Heat shrink

Always double-check your work before sealing the connections with heat-shrink tubing. First, check for correct polarities, then tug on each connection just firmly enough to ensure its security. Finish your handiwork by applying heat to the heat-shrink tubing.

Recommended Equipment

30-watt soldering iron 25-gauge lead-free electrical solder Electronic soldering flux Excel Hobby Blades Extra Hands with Magnifier Great Planes Wire Cutter/Stripper Emery board or emery cloth Damp sponge or soft damp cloth


1. Clean contact points 2. Apply electronic flux to contact points 3. Tin contact points separately 4. Slip on heat-shrink tubing 5. Join the two tinned contact points with solder 6. Insulate bare connection with heat-shrink tubing
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Stripping and soldering both wires at the same time is an invitation to a disaster. If both sides of a LiPo touch, the battery can explode. Better to do one at a time I.e., strip, solder and heat shrink the positive then do the same for the negative.

Nice article but to be honest, I'm really surprised to see no mention of the importance of caring for your soldering iron, at a minimum, keeping the soldering iron tip clean and tinned!

You should always wipe the tip clean of crud and solder after every use using either a steel wool cleaner (best) or a damp sponge. If you do not regularly clean the iron's tip, it will collect crud and you will deposit this crud to your next soldered connection. This build-up of crud will eventually eat away your soldering iron tip too!

Also, be sure to unplug your iron after each and every use... not only does this save the tip, but it could also save you from a house fire!

Sorry... Just had to point out this blatant omission... :)

sry... one last note, when applying flux, after soldering, you should always clean off excessive flux as it can eventually eat away and deteriorate your connections over time.

I only want to add ,that at your local hardware store they sell liquid electrical tape. It comes in a can with a brush attached to the underside of the cap. It comes in red or black and works well for that space between the plug,and heat swrink tubing. Its also water proof if you need that.

Very informative and helpful.

Great info,Thanks

Great tips

well presented

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