How To Solder | A Beginner's Guide to FPV Drone Soldering

Soldering is an important skill for FPV, whether you want to build from scratch or repair your prebuilt quads. What many beginners don’t realize is how important the preparation is to how solder joints turn out. Equipment is also key, with poor irons, poor solder, and a lack of flux being some of the most common issues we see.

Equipment and Consumables

Soldering Iron: I’ve found a vast majority of the “two button” type irons work very well. They usually have a small LCD screen, two buttons, lots of programmable features, and a DC input. Because of the DC input, you’ll need a USB PD power brick or another DC power supply to run them. I use the same type of power brick I use for my chargers, and you can also usually use a LiPo battery from a quad.

These irons have a ton of adjustable features, including custom timers and temperatures to control what happens when you set down the iron. My iron will go into a lower temperature state after about 30 seconds of being set down and will turn off completely after a few minutes. This helps prevent the buildup of oxidation on the tip when not in use. I use a Sequre iron similar to this one: https://pyrodrone.com/products/sequre-mini-sq-001-65w-portable-soldering-iron-w-ts-b2-tip-choose-color?variant=31539466076203 

Solder: Lead free solder melts at a higher temperature and is significantly harder to solder with, 63/37 solder melts and solidifies quickly and continuously, and 0.8mm diameter is easy to work with. A good spool of solder can cost more than you would expect, but it will last a long, long time. Something like this is perfect for FPV: https://pyrodrone.com/collections/soldering-gear/products/tbs-solder-spool-100g

Flux: Flux is extremely important, although I’ve found little difference in the performance of different flux types. I use a dish type, although syringe and even pen type dispensers are also common. There are several types available on Pyrodrone: https://pyrodrone.com/pages/search-results-page?q=flux

Tip Cleaner: Brass sponges are best for cleaning the tips of irons. The normal wet sponges that sometimes come with irons will work, but not as well and for not as long.

Practice Board: Practice boards allow you to practice your technique on a board that’s worth less than a set of props instead of a flight controller or esc. While not strictly required, I highly suggest grabbing 2 or 3 of these. https://pyrodrone.com/collections/soldering-gear/products/pyrodrone-soldering-practice-board 

Helping Hands: A set of helping hands can hold wires and boards together while your hands are kept free to control your iron and solder spool. Avoid any types that use crimped-on end clamps, as they come loose easily. Putty is sometimes also used for this. These work well: https://pyrodrone.com/products/helping-hands-for-soldering-and-repairs 

Technique:

Preparation is key to soldering. If every connection has flux, is tinned, and held into place, anyone can make the joint. In addition to this guide, YouTube videos are a great source of information for this.

Step 1: Remove wire insulation and add flux. Before removing insulation, cut wires to length. For motor wires, I hold up each wire to the pad so I know where they should be cut, one at a time. When removing wire insulation, don’t peel back any more than you need to. A common mistake is removing too much insulation and allowing the exposed wire to short on something else or break off from repeated stress. Before you start soldering, remember that if your iron has dark colored build-up on it you should clean it with your sponge. This debris will prevent solder flow and heat transfer. A clean tip should be shiny, this tip needs to be cleaned:

Step 2: Tin all wires and pads. Put a small amount of solder on your iron and apply more while touching the pad or wire. I typically use about 350 degrees C, although larger work may require more heat, such as XT60 connectors. If you are using heat shrink tubing or other wire shields, add them now. I’ll use motor wires on my 4” as an example. I only removed a small amount of insulation before tinning the wire.

Step 3: Using your helping hands, or your own hands, hold your wires/pad together and press your iron into them, melting them together. For motor wires, I often run them into the stack and solder them onto the ESC backwards to reduce stress and keep the build cleaner. I always add a zip tie on each arm as well. On tiny wires, such as camera, VTX, RX, and GPS wires, add slack and solder them flat to the FC to reduce stress. Larger frames make wire management and soldering easier. My 4” quad has folding arms, so I decided to run the motor wires inside the frame on the rear only. 

Happy Flying!

Written by JasonFPV