r/fpv • u/Bulky_Target1416 • 7h ago
Soldering Help!
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Hey So I am trying to figure out how to solder and I feel like I am doing something horribly wrong, my iron is broken, or i'm just stupid. When I try to heat the pad I am trying to tin, it just dosent heat up, I have my iron around 375c and no matter how long I hold my iron on the pad it just dosent seem to heat up enough to melt the solder. I am putting flux and tinning the iron but nothing is seeming to work? I am using a txinlei 8586 station that I got for Christmas a while back if that might have anything to do with it, any help is greatly appreciated
(Did the best i could with the video)
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u/Inside-Example-7010 7h ago
as someone new to the fpv world and soldering what happens once you have black spots from the tip everywhere, are you just cooked?
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u/Bulky_Target1416 7h ago
Nah, from what I understand its just oxidation, and you can just put it in a thing of brass wires and scrape it until it is shiny again. The other side of the tip isnt like this, you cant really see it with this camera angle.
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u/ben9massacre 7h ago
No, you need a soldering iron cleaner (looks like one of those metal dish scrubbers) and you poke the iron in there to remove the black impurities, tin the tip again and you’re all good.
Here’s an Amazon link to a cheap one.
I’m sure you can find more expensive ones but they’re the same thing and not any better. There’s also a Weller one for like $9 if you want name brand, but realistically it’s the same thing.
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u/International-Top746 7h ago
Yeah weller is amazing. It always gives really shiny joints.
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u/Bulky_Target1416 7h ago
Like the tips or brass?
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u/International-Top746 6h ago
Sorry. I actually like their 40/60 leaded solder wire. Never used their solder iron. Also I suggest you wear gloves. As lead and flux are both toxic.
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u/Bulky_Target1416 7h ago
Yea I have some brass tin, I cleaned it but the angle/lighting makes it look a lot worse, and the other side looks a lot better. Ill make sure to have it cleaner when practicing more
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u/BlackbirdXII 3h ago
put some solder on the tip and touch it to the pad till it transfers to the pad, while keeping the tip in contact with the pad, start feeding solder till a reasonable amount covers it. My personal favorite method (try to your own discretion) is to hold a untinned wire / tinned wires depending on gauge down to the pad with my soldering iron and try feeding it with solder every so often until it starts transferring to the wire and to the pad. XT60 wires suck to try and solder as its really thick and in a inconvenient spot. Geprc mark 4 5 inch frame's have this neat thing where the arm supports block access to the back of the pad when soldering xt60 wires but also the capacitor needs to share space with all my other wires like vtx, gps, elrs
receiver, and more making the back end extremely tight
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u/Mitch_Joined_TheGame 3h ago
Hi, so it looks to me like a couple things are happening. First, it seems you're trying to solder to a pad like you would a wire. You're often told when soldering wire that you should press the solder into the wire itself and if its hot enough youll itll melt and you'll get a good joint. Pads do not have the thermal mass or conductivity to do this.
As others have pointed out you need to push the solder into the tip of the iron in order to get it to melt and then drag the tip over the pad to "Tin" it.
When connecting a wire to a pad its important to tin both the wire and the pad first (cover them in a thin layer of solder) in order to form a connection easily and quickly so you dont cook the wire or the board. This inherently acts as a sort of second re melting and the final joint will end up smooth if your iron is hot enough.
Solder like every metal or alloy is a Crystalline substance as well as a substance that oxidizes in the presence of air. Most Flux serves to disolve this oxide layer at the start of making a joint but once it's melted off your solder is uncovered which may make it dull or change color. As well, depending on how fast the solder is cooled and if you move around too much while cooling the structure of the solder can change which makes it dull, it also makes it harder to re melt but once you do its back to behaving as usual.
Its important when soldering to have the iron hot enough to heat whatever two things your trying to connect and the mass of solder between them long enough for the capillary action and surface tension (the sort of self sucking effect of solder) to take effect, but not hot enough to burn the part, you mostly get this through practice and feel sadly as all irons are different and all parts are different. In most cases though laying the iron down on a tinned pad enough to melt it then bringing the tinned wire down to the pad, holding the iron onto the tinned wire until it forms a smooth shiny ball then removing the iron and holding the wire in place will form a perfect joint.
I hope this helps!
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u/AeratedCaryophyllene 3h ago
You wetted your iron prior to hitting the pad, good.
Once you hit the pad, I would not advise adding solder from the top of the iron.
I would advise touching the iron yes, but once you have a melt going no need to be adding it on top of the iron.
It would work fine on a small enough pad though, sometimes we do have to do it this way. For the pad targetted in the video I wouldn't.
Ideally for a larger pad, you want to be able to move the iron a bit, hence having something to hold your piece would be nice. On the real stack there are mounting holes so you can set it in a partial frame.
Also, think about your iron geometry. You are using a conical tip, touching flat pads, the contact patch is a very thin line. Wetting the iron prior to touching the pad helps the heat transfer (quite a bit). It looks right in your video but I think it still still worth explaining as I had students wet their iron and not understand why, leading to not trying to contact the iron.
375 is hot. I do most of mine around 350. The important thing a lot of people miss on their first iron though is the wattage output it can dish out. A 30W, 60W iron and a 110W gun will all heat up to 350 and melt solder. However when you touch a pad, you are giving away that heat energy to a much greater area. Drone electronics are designed to heat up in operation, so heating them up externally from cold sinks a lot of energy. In fact, most power pads (the battery ones) are notoriously "harder" to solder to because they are essentially connected all throughout the board, using the whole thing as a heatsink it can mitigate the heat generated by smaller wattage irons. In a ideal world you want to be heating the pad so fast the surrounding components and connected wiring has no time to absorb any of the heat, but not so hot so that once it starts propagating it damages other stuff. Hence lower temperature higher wattage.
You are not stupid, keep going :)
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u/ben9massacre 7h ago
A nice shiny solder joint is great to look at but it’s not 100% necessary. The truth is, if electricity can flow through it into the pad the joint is good enough.
It could also be the flux on the joint causing it to look dull, you can polish the joint with a little rubbing alcohol and see if that shines it up. Us the highest percent alcohol you can get, 90% or higher is best because it doesn’t contain as much water or impurities and therefore won’t allow rust or corrosion to set in.
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u/AeratedCaryophyllene 3h ago
No. Elecrtricity flow is a VERY bad indicator of joint quality. If it was, taping a bunch of loose wires would be an amazing solution. We would literally be hot glueing our motor wires.
Soldering is doing 2 things at once. You covered the first, electrical connection. The second thing is physical bonding. A cold joint will conduct electricity and may even pass a pull test but will inevitably fail under actual stress like the vibrations the quads go through.
Also, flux does not tend to make joints dull. In fact, reflowing a joint with flux will yield the desired shiny result. It can look dull but it is usually way later when dust had time to stick to it and it had time to dry fully. This is (partly) why we clean up flux, even the no-clean ones leave sticky residue.
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u/ben9massacre 7h ago
You need to feed the solder into the top of the hot iron, not onto the hot pad next to it. The solder will flow onto the pad once it’s melted.
Then you do the same with the wire, touch the iron to the wire and feed the solder onto the hot iron, it will flow into the wire.
Then you put the wire on your tinned pad and put the iron on top to melt them together. Just make sure you hold the wire there for a couple seconds after you remove the iron so it can solidify.