Soldering is an essential skill in building and repairing a quadcopter, RC plane and mini quad (commonly known as racing drones). Soldering is basically joining multiple conductive metal parts together by melting and flowing solder between the joints.
Soldering takes practice and could be hard at first, but it’s going to be one of the most useful skills you’ll learn in this hobby. It enables you to do other electronics projects and even fix simple electrical devices in the house :)
Tools for Good Soldering
Getting good soldering equipment is just as important as having good soldering skills. The tools that you would normally need for basic soldering jobs are:
- Soldering iron / Soldering station
- Solder Paste / Flux
- Solder Helping Hand (third hand)
- De-solder wick / solder sucker
Visit our list of quadcopter building tools for more ideas.
A good soldering iron makes soldering much easier. The wattage of a soldering iron usually indicates how much heat it can put out and the max temperature it can reach. Adjustable temperature control and accurate temperature output is highly desirable for different situations.
|Wattage||Temperature Range||Changeable tip||Temperature Display||Price|
|Weller WESD51||50W||175°C – 450°C||Yes||Yes||$136|
|TS-100||17W-65W||100°C – 400°C||Yes||Yes||$51|
Soldering iron might come with tips of different shapes and sizes. Pointy tips generally are better for precise soldering while larger, wider tips are better at dealing with bigger components as heat is transferred more efficiently. If you do get a choice of different tips, a pointy tip would be enough for building a quad or RC plane.
There are many types of solder which are formed of different alloys and elements for different results. In our hobby, we highly recommend rosin core 60/40 (60% tin and 40% lead). Thinner diameter solder wire is preferable which allows for more accurate control of solder flow. I personally prefer 0.032″ (0.81mm).
It’s important to get the solder from brand names manufacturers. Try to avoid buying cheap and low quality solder from eBay or Banggood. Brands I personally have had good experience with are Kester and MG Chemical. Many from Asia also suggest Asahi.
Here are the links to these products on Amazon:
Quality solder might seem to be costly, but a roll of these would literally last years.
Here is a discussion of how the quality of solder impacts quadcopter building.
Solder Paste / Flux
When metal are heated up, oxidization takes place on the surface of the metal and it will make solder harder to stick. Applying solder paste or solder flux on the metal before soldering could help prevent this during soldering and make joining easier. I found this especially useful when pre-tinning wires. For example: http://amzn.to/2sttBJj
Soldering Third Hand
When soldering, your one hand is holding the soldering iron while your the other hand is holding one component, you might need a third hand to hold the other component. A “Soldering Helping Hand / Third Hand” will come in handy in this situation.
Soldering Third Hand normally features multiple small alligator clips, and often a magnifying glass as well. These clips can hold components and wires together to free up your hands for other tasks.
- Here is a review of the RealACC soldering helping hand (6 arms)
- There are cheaper ones such as this:
De-solder Wick / Solder Sucker
These tools are used to remove solder off a PCB or wires. You might not need to use this as often as other tools mentioned so far, but it’s handy to have them around.
The De-solder Wick acts like a sponge that sucks up melted solder, while the Solder Sucker uses a small air vacuum to quickly suck solder out of a heated joint.
For example: http://amzn.to/2sta6QV
When your iron tip starts looking dull, and gathering black stuff, you know you need a tip cleaning. Cleaning your soldering iron tip removes impurity and residual and ensures the best possible result. A cleaned iron tip should look shiny.
A cheap and common cleaner is “heat resistant sponge” that is designed for soldering. There is also “brass tip cleaner” which lasts longer than sponge, but for us RC hobbyist this might be an overkill for the little amount of soldering we do.
How to Solder – My Way
Soldering is basically joining 2 pieces of metal with melted solder, it’s not too different from gluing :) The important thing is to have stead hands, get used to the timing of soldering cooling down and solidify, and learn how to not burn yourself :)
Tinning Wires or Pads
Before you begin joining, always tin (aka pre-tin) the wires and components first! (except when you are soldering header pins to through holes)
Tinning is basically covering the wire or solder pads with an appropriate amount of solder, this would make soldering much easier. Apply solder paste first as seen fit.
Soldering a wire to a pad
The most common soldering job is soldering a wire to a pad on a PDB or flight controller.
First of all, tin both the wire and the pad. Heat up the pad and melt the solder on it, and bring the wire to the pad. Once the two joins, gently remove your soldering iron, hold the wire for a few seconds until the solder joint cools down and hardens completely.
The finish joint should look round, shiny and solid.
Pro tip: if you let go of the wire too early before the joint completely hardens, or didn’t use enough solder, you might end up with a cold solder joint or just bad solder joint. A cold solder joint looks bumpy and dull, it makes bad contact between the components and is very unreliable. If this happens, or if you are not sure, simply re-do the soldering until you are happy with how it looks.
Soldering thick wires to PDB
If you are soldering a thick wire (e.g. a XT60 pigtail to the PDB), where you make contact with the wire and the pad at the same time, you can try to heat up the wire first, and let the heat pass down to the pad. It usually takes longer to melt the solder on a PDB because of the larger amount of copper in it, this requires a bit more patience and normally higher temperature on the solder iron. Also try not to press too hard on the wire or the wire strands could flattened.
Soldering header pin to through-hole
When soldering a header pin to a through-hole, you shouldn’t pre-tin the components, otherwise it might prevent the header pin passing through the hole.
- Apply solder flux as you see appropriate
- Insert the header pin through the hole
- Heat up both the header pin and the ring on the through hole for a couple of seconds
- Bring the solder to the joint and it should make a solid, shiny, “volcano” like bond
Here is how you can remove header pins.
Soldering a wire to through-hole
There are 2 ways to approach this, you can either treat the through-hole as a solder pad and solder from the top of the board; Or do it like soldering a header pin to a through-hole. It depends on which side of the board you can access more easily.
Soldering wire directly on top of the through-hole:
Insert wire though the hole, and solder from the bottom:
Soldering a wire to another wire
It’s easier to use a “solder helping hand” for this job.
For small wires and quick jobs, you could simply solder one wire directly next to the other. You could also twist them before soldering to increase mechanical strength.
When joining 2 larger gauge multi-strand wires together, I normally spread the strands first, and push the 2 wires together head to head, then twist them so they don’t come off easily. Now apply some solder flux, and solder them together.
This way maximizes the contact area of the metal and the benefits are the overall smaller and stronger solder joint. Either way works just fine as long as the joint is solid.
Soldering header pin on a pad
You don’t need to tin the header pin nor the solder pad with this job.
- Apply some solder paste on both the pin and pad, and bring the header pin to the pad and hold it there with a Third Hand
- Heat up both the pin and pad for a couple of seconds, and bring solder to the joint
- Remove solder iron and let it cool down
When soldering multiple header pins, I found it gets easier after the first pin, because the whole thing is secured in place firmly by the first pin.
Soldering electrical wires to XT60 connector
- Secure the XT60 connector with a helping hand or bench clamp
- Very slightly tin the inside of the XT60 connector. Do not apply too much solder otherwise you might have difficulty inserting the wire into the holes
- Tin the electrical wire, insert the wire into the hole, and heat up both the wire and the connector
- Bring solder to the joint, until the wire is buried in solder
- Remove solder iron, and allow 10+ seconds for it to cool down
Hotter soldering iron melts solder faster and might seem to be easier to work with. But overheating solder joints on a PCB is generally not a good idea, therefore using appropriate temperature is very important. Overheating could result in 2 issues:
- Heat can build up and damage components on the board
- Copper pads can fall off due to over-heat (possible solution to this)
Here’s a simplified guideline on soldering temperatures I personally follow with good quality 60/40 (Sn/Pd) solder:
- 300 C° (580 °F) – delicate jobs such as joining two small gauge wires together
- 350 C° (660 °F) – signal type of solder joints on a flight controller
- 400 C° (750 °F) – soldering ESC’s power and XT60 pigtail to PDB
I would not go over 400C° just to be safe. If you are having difficulty soldering large connectors or wires, simply use a bigger tip which help transfer heat. And check the quality/type of your solder.
Some Other Resources
- How NOT to solder by IntoFPV – http://intofpv.com/t-how-not-to-solder
- Soldering Guide by RotorRiot – https://www.youtube.com/watch?v=HMSlF1xFozc
- General soldering by Adafuit – https://learn.adafruit.com/adafruit-guide-excellent-soldering