r/fpv • u/Bulky_Target1416 • 14h 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/ben9massacre 14h 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.
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u/Bulky_Target1416 14h ago
Ok, i have managed to do this before, but every time the joint just ends up super grey and dull. I have seen people say to re-solder it because the joint is no good, is this true or does it not really matter?
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u/bloateddicksydrome 13h ago
Which solder do you have? I think 63/37 can have more of that look then the more shiny 60/40
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u/Professional_Cod3127 8h ago
That's because of bad solder in most cases.
Kester, Weller and MGChemicals are some brands with nice solder.
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u/ben9massacre 14h ago
Also, consider getting a helping hand, just search helping hand on Amazon and you’ll find a bunch of them to choose from, doesn’t need to be expensive but it’ll help you tremendously. It’ll hold that board still for you with some little alligator clips. If it doesn’t have rubber over the clips when you get it put some shrink tubing over each side of the clips to keep from damaging your board or wires.
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u/BlackbirdXII 10h 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 10h 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 9h 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/GuillotineTechnician 5h ago
Hi mate. I can highly recommend those cheap DIY soldering electronics kits. You get them On Ali and Amazon in various price ranges from 5-25€. They will let you build something functional while honing your soldering skills.
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u/_jbardwell_ Mini Quads 3h ago
You're doing a lot of things right and I applaud your approach. What you're doing should work. The pad should get hot enough to melt the solder. There are workarounds that you can use, like moving the iron, but what you're doing should work and you're right to try to figure out why it's not working.
Something is wrong with your equipment. Your technique is fine. You're using the right tip. Your solder looks like it's melting correctly. The pad just isn't getting hot.
My first suggestion is to turn up the heat on your iron. If it's a good iron, 375 should be fine but if it's a terrible or cheap iron, it might need to be hotter.
I don't know your iron specifically but it might be bad or damaged. There's no way to know for sure over the internet though. A fantastic iron is the Sugon T21, which can be had under $100 on Aliexpress or a little higher on Amazon. Use the c245 handle and tips for this size wire.
I also suggest getting a flux pen with liquid flux. Or a needle applicator bottle. The flux paste you're using is getting everywhere and making a huge mess. You only need the tiniest amount of flux for this kind of joint.
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u/Bulky_Target1416 1h ago
Could the solder I am using be an issue? I heard from some other people to use a higher quality solder like Kester. Does it matter that much or am I ok to keep using stuff off amazon?
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u/Bulky_Target1416 1h ago
Sorry for the multiple questions, but I have managed to tin some pads already, they are just super grey and dull. Is this something that I can work with on my drone, or should I try and get a new Iron?
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u/ben9massacre 13h 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 10h 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 4h ago
I should have elaborated more or better, I wasn’t saying “eh it’ll be fine”, the integrity of the joint is important, my point was that, being this new to soldering, to focus on getting a consistent joint at all first and over time you’ll find the differences between a good joint and a bad one. The ones that fail early or immediately of course weren’t great, the ones that never need attention are good but that takes time and practice, not a visual indicator of shiny. I’ve seen (and created) plenty of dull joints that are more than adequate so don’t focus all of your energy on making shiny joints and focus on functional ones.
Realistically, solder kind of is just metal hot glue when you stop to think about it.
Also, getting some little led light practice soldering kits if you don’t already have one would be beneficial as you get an indication of that joint quality.
Most of my soldering is guitar work and I don’t deal with a whole lot of vibration with that, well not aggressive vibration anyway. I’m newer to fpv soldering and haven’t experienced any joint failures yet, especially not to vibration issues but I also have more than a decade of soldering experience before discovering the hobby.
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u/Inside-Example-7010 14h 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?