It can be hard to explain in words how a good solder joint should look, but getting your soldering technique right and using the right equipment can often mean the difference between a reliable build and something that will fall out of the sky at any moment.

I've started collecting examples of "how not to do it", and here's my first one:



This is a great example of using an iron that was too cold, or possibly from using solder that does not have a core of flux, which is essential to helping the solder to flow. Where the signal wires are soldered to the flight controller, the connections are just big blobs of solder. The solder should melt completely so that it flows into the holes and leaves a joint where the solder is smooth and shiny.

The second wire from the left on the rear row doesn't look as if the solder has even started to flow and is probably only making a connection by virtue of the blob of solder at the top of the wire stopping it from falling out.

The connections to the PDB at the bottom of the picture show similar problems. Lots of solder, but none of it has flowed into a nice smooth and shiny joint. For power wires especially, this can lead to connections that have high resistance which can cause overheating or even burning and will give problems with the ESCs not getting enough power when they ask for it.

More to come!

Great timing since I am working on soldering right now! It's one thing to read instructions and tips but seeing this with your explanations help even more. Thanks Unseen!

Here's another really illustrative photo:



This soldering job, while nice and shiny, is a disaster just waiting to happen. The uninsulated length of wire that is coming out from the various pads is inviting a short circuit to happen. If the pad is just 1mm wide, then there shouldn't be any more uninsulated wire than is needed to make the connection to the pad.

With the nasty PVC insulation on most ESC signal wires, the insulation tends to shrink back if you apply heat to the wire for more than a fraction of a second or if your iron is too hot. So, strip the wire, tin it and then cut it back so that there's absolutely no more exposed wire than is needed. Solder the wire swiftly to the pad and don't use any more time and heat than is absolutely necessary.

This example shows clearly what happens when your soldering iron does not have enough power to solder PDB connections that suck away the heat faster than the iron can produce it:



The power leads are just tacked onto the original solder that was applied during tinning without melting and reflowing all the solder on the pad. The idea is that you solder the wire to the pad, not that you solder some solder to more solder!

If you can't get all of the solder to melt within a couple of seconds at most, then either the temperature is too low, you are using too small a tip on your iron for the job, or most likely, you need a more powerful iron (at least 60W) so that the iron does not cool down while you try to heat the pad and wire up.

Nice idea - it's an art soldering small components and makes a change to see pictures of how it shouldn't be done!

And one more...

This shows what happens when your soldering iron is way too cold. Instead of a nice smooth and shiny joint, the solder looks more like rough concrete. This just won't give a good connection, either physically or electrically.

Great great great thread Unseen! (Where was this when I was learning ) just like any learning curve, we all start at the same place. This is an excellent way to illustrate bad joints that not only offers the solutions but teaches why the problem occured in the first place

"Give a man a fish and you feed him for a day. Teach a man to fish, and you feed him for a lifetime."

I'm glad people are finding this useful!

I have a kind of macabre fascination with poor soldering, so as I find more good examples, I'll add them to the thread. I have a strong suspicion that many people who have problems with their first build are falling victim to some of these common mistakes so anything I can do to save you from them helps.

(18-Apr-2017, 04:13 PM)unseen Wrote: I'm glad people are finding this useful!

I have a kind of macabre fascination with poor soldering, so as I find more good examples, I'll add them to the thread. I have a strong suspicion that many people who have problems with their first build are falling victim to some of these common mistakes so anything I can do to save you from them helps.

Well... in that case as a future first builder (I give it about a month) I thank you in advance.

This is great stuff, and if someone was like me and likes to pile on extra knowledge there is plenty here to spark some obsessive google searches for even more detail.

Here are also a few examples how not to solder, and how to solve it.



This is maybe interesting to read:
http://store.curiousinventor.com/guides/How_to_Solder

Maybe I can blow my own horn a little...

When tinning the pads on a PDB, there is no reason to completely flood the pads with solder as many people do, it's just adding extra weight! The wires should be in contact with the pads, not floating inside a huge blob of solder.



Note how the insulation on the wires goes all the way onto the pad.

Here's the flight controller on my Armattan Hexacopter. With six motors and only 12mm for the flight controller and PDB, I had to replace the signal wires from the ESCs with new wires made from much thinner 30AWG wire. All the wiring here (apart from the wires to the current sensor) is done with 30AWG silicone insulated wire. Without it, I wouldn't have been able to get the top plate on!



The huge advantage with silicone insulated wire is that the insulation won't shrink back or burn when you solder the wires. Plus, it's way more flexible and much easier to work with than PVC insulated wire. I have various sizes of silicone insulated wire and use it for pretty much everything now.

Great Video Ikkuh!

I hope there are some lurkers out there getting as good of an education out there as I am right now

When I said there wasn't much room for the flight controller, I wasn't joking!

(18-Apr-2017, 09:37 PM)Carl.Vegas Wrote: Great Video Ikkuh!

I hope there are some lurkers out there getting as good of an education out there as I am right now

The video on the site that Ikkuh linked to really is excellent, so I'll link directly to it on Youtube. It shows really nicely how the solder should flow when you do it properly.

I'm glad I could help and I hope your soldering will be better and less drones falling out the sky because of a bad solder joint. Thanks Unseen for the direct link that's easier.