Solder makes a thin filament when lifting the iron

Thread Starter

Andrea Luciano Damico

Joined Jun 4, 2018
2
Hello everyone and congratulations for the awesome website.
I'm very new to electronics and soldering in general and I thought that assembling simple DIY kits would be a great way to getting started. Before I delved into it, I did a bit of research on electronic components and soldering technique, but now that I'm making practice, I'm finding it very difficult to do stuff well.
Many BS things I do I'm aware are my own fault and I know what I'm doing wrong, but there's one thing that I can't really figure out: most of the time, when I lift the iron up after applying solder, the tip (which is a flat one) itself pulls upwards a thin filament of solder that solidifies and gives the impression that the component has "two legs" per pad.
Here's how I solder: first I heat up the pad and leg, then I lean some solder onto the heated pad, lift the solder strand, keep the iron there for a couple seconds, and lift it up. Has anyone any suggestions on how could I do stuff better and/or general tips?
 

dl324

Joined Mar 30, 2015
12,522
Welcome to AAC!

That shouldn't happen. The iron should be hot enough to prevent filaments from forming.

What kind of soldering iron are you using?
 

Tonyr1084

Joined Sep 24, 2015
5,723
Don't run and hide in shame. There's no shame in making mistakes. Everyone here has made them, and still makes them. The fact is that we can learn more from our mistakes than we do when everything runs smoothly. Tinning the iron is basic. And everyone of us has at one time had to learn the basics. When I was seven years old I started playing with my father's Weller soldering gun. I made some horrid looking solder joints, but as a kid, what did I know. Today I'm a rather accomplished solder-er. If there is such a word.

A tinned iron brings heat and thermal transfer. Flux prevents oxidation. Prolonged exposure to the heat of the iron burns off the flux and oxidation begins, and that's where those spiky filaments develop. In fact, I've purposely made solder trees by drying out the flux and pulling it up higher and higher. I was doing deliberately what you were likely doing by accident.

Sufficient heat and the proper solder and flux and soldering should go smoothly. A clean and well maintained tip works wonders. Every now and then it becomes necessary to replace the tip on my irons. Yes, irons (plural). In fact, I have one monster iron for soldering things like ground planes or power planes. They take a lot of heat away from the solder and the iron, so you need greater thermal mass. There's a whole science to it, but most of us never learn the science, we just develop the technique by trial and error. Eventually we discover what works and run with it. You'll develop too. Just don't be afraid to ask dumb questions. Actually, the only "DUMB" thing to do is to NOT ask a question. Even if you think it's dumb, you can still learn stuff from it.

Welcome to AAC.
 

oz93666

Joined Sep 7, 2010
737
While on the subject of soldering ..... Can someone explain why after just a few minutes soldering the tip is covered with what I guess is oxide , not easy to clean off ...

I realise the higher the temperature the quicker this will happen , I'm not running excessively hot.

What the world needs in no corrosive tips ...I've even thought of trying to make some silver tips ... or is the problem from oxidising solder??
 

nsaspook

Joined Aug 27, 2009
8,028
While on the subject of soldering ..... Can someone explain why after just a few minutes soldering the tip is covered with what I guess is oxide , not easy to clean off ...

I realise the higher the temperature the quicker this will happen , I'm not running excessively hot.

What the world needs in no corrosive tips ...I've even thought of trying to make some silver tips ... or is the problem from oxidising solder??
I normally use a

to keep the tip clean.
http://www.hakko.com/english/products/hakko_599b.html
 

oz93666

Joined Sep 7, 2010
737
I clean the oxidation from the tip using solder with a flux core. I keep it clean during use by wiping the tip on a moist sponge before soldering.
Thanks ... I will have to get some sponges ...

Not all lead tin solders are the same ...I always use flux cored 63/37 tin/lead ... it has the lowest melting point which must be the main consideration ... cheaper solder uses slightly less of the expensive tin , 60/40 ...

After a search it seems there maybe more involved ...
"For applications such as wave soldering of electronic assemblies, the requirement for a solder with a relatively low melting point in conjunction with a short freezing range leads to the choice of 63/37 or 60/40 Sn/Pb alloy. Although 63/37 is the eutectic alloy, 60/40 is often used in practice as the slightly higher 5°C freezing range of 60/40 is of no practical significance and 60/40 is a little cheaper than 63/37. Under conditions of slow cooling, 60/40 may give duller joints than 63/37 but this is a purely cosmetic effect. Lowering the tin content increases the pasty range and raises the liquidus temperature whilst of course reducing the cost of the alloy...."

the same document .. http://www.farnell.com/datasheets/315929.pdf ...suggests that cheaper fluxes (in the core of the solder) cause quicker corrosion of the tip .. could this be part of my trouble??
 

SLK001

Joined Nov 29, 2011
1,548
While on the subject of soldering ..... Can someone explain why after just a few minutes soldering the tip is covered with what I guess is oxide , not easy to clean off ...

I realise the higher the temperature the quicker this will happen , I'm not running excessively hot.

What the world needs in no corrosive tips ...I've even thought of trying to make some silver tips ... or is the problem from oxidising solder??
Some tips are easier to clean than others. I use Hakko soldering irons and tips and they are iron plated. They resist the dissolving of the tip by the metal quite well. I also have a Weller soldering iron and its tips dissolve away to stumps way too quickly in my opinion. You also have to properly tin your iron plating to "wet" the heated surface in order to make the oxide removal fairly easy. Tinning must be done at just above the melting temp of the solder for it to properly wet the surface. During use, application of solder is important to keep the tinning in place.

However, even with a properly prepared iron, sometimes the oxides can be stubborn and not easily removed. I keep a brass brush handy to scrub off the oxide when that happens. I use brass because I don't want to compromise the iron plating of the tip - once compromised, the copper in the tip will diffuse into your soldered joints, eventially rendering them useless.

Also, the correct temperature is necessary to keep oxidation to a minimum. I keep my tip around 700F for most purposes. If I have a large ground plane that needs solder, I use a heat gun to raise the ground plane to approx 150F. Now soldering, even on the ground plane, is a breeze.
 

Tonyr1084

Joined Sep 24, 2015
5,723
Something I haven't read here is keeping the iron tinned when idle. If you clean the tip and then set it in the cradle it will oxidize. If you put a coating of solder over the iron the tip will not oxidize. The long heated and dry solder can be removed by a wet sponge just before you solder. Again, just before you solder you want to tin the tip. In part to keep oxidation at bay, but also for the purpose of thermal transfer.

Remember, when two round objects touch each other, they touch in a very tiny spot. Heat transfer through such a tiny spot is very difficult. But if the iron is tinned, when you touch the round iron to the round lead you get a larger area of connection, transferring more heat into the joint to be made.

I've seen people bring a pile of molten solder to a joint that has been fluxed. This often produces a really good looking solder joint, but the problem here is the thermal shock of having such a large amount of heat - I said "Large", not "High" - the problem with bringing that much thermal energy into a solder joint in such a short period of time can lead to micro fractures within the structure of the board itself. Those fractures can hold on to contaminants and can degrade your workpiece over time. Or worse, they can fracture partly or completely through an inner layer connection, rendering the board unusable without stringing wires all over the board just to bypass the fractured joint. The WORST possible case is a fractured joint that makes intermittent contact. Those of us who've tried to troubleshoot an intermittent issue can tell you how exasperating that can be. So bringing a pile of molten solder to the joint is not advised for these above reasons.

Just enough solder on the iron to create a thermal connection between the iron and the joint and the application of more solder will flow easily and make the perfect joint - provided you apply the appropriate amount of solder. Too much is wasteful and too little is unreliable. But there's a large margin between the two. If your solder joint looks like a Hershey's Kiss then you have a perfect joint. However, you don't need that much solder. According to the J standard or the IPC standard you can have a reliable joint with as little as 75% of the joint filled. So the margin for error is pretty big. No need to put a ton of solder on a joint. Just avoid those spiky spires of solder by not dwelling too long on the joint. If you DO get them just add a little flux and reflow the joint. Again, don't dwell on the joint. If you have to dwell then maybe your iron is not hot enough.
 

AlbertHall

Joined Jun 4, 2014
10,921
Can someone explain why after just a few minutes soldering the tip is covered with what I guess is oxide , not easy to clean off ...
Apart from keeping the iron tinned while not using it anothe contribution to this problem is with irons which are not temperature controlled. For these irons the tip will get too hot while it isn't being used. Better, and more expensive, is a temperature controlled iron which has a thermostat to stop the iron getting too hot. They also get up to temperature quicker from a cold start because they can use more power without risk of overheating.
 

Tonyr1084

Joined Sep 24, 2015
5,723
One of the irons I like (and don't have) is one that when the iron is in the cradle it lowers its resting temperature until picked up again. My biggest problem has been turning my iron on and then leaving it on for hours. So I took an old microwave oven control board and rigged it up so that I can run an iron for up to 99 minutes and 99 seconds. (100 minutes 39 seconds) Or less. That way I don't needlessly burn up my iron. Mine is temperature controlled, and I could set one of the presets down around 350˚, but then I'd have to remember to idle my iron; and when I pick it back up I'd have to remember to hit one of the higher presets.
 

SLK001

Joined Nov 29, 2011
1,548
... My biggest problem has been turning my iron on and then leaving it on for hours.
My iron at work would sometimes be left on over the weekend! After I cleaned off the black crust from it, I was surprised to find out that it survived my carelessness with no problem (although I do NOT advocate doing this)!
 

dl324

Joined Mar 30, 2015
12,522
When I was an R&D tech, I left my soldering iron on all day. I'm still using the same soldering iron over 40 years later and I'm using the same tip.

I bought a dozen replacement tips and have heard that the newer ones aren't as durable as the ones from decades ago. Fortunately, several of my spares are from that era.
 
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