Soldering Iron tip - black residue

[pigtwo]

Hello everyone,

I'm soldering a board and I'm running into a problem with my soldering iron.  There is a black film(residue) developing on the tip and solder will not stick to this(see attached picture).  It's making it very hard to solder as I have to scrub it with the brass pad thing about every 30 seconds and it doesn't even remove all of it.  I'm not sure why this is happening as I've used this soldering iron probably about 8 hours before this and I haven't seen this yet. 

I've seen some stuff online saying to wipe it off on a wet sponge but that doesn't work for me.  I have the temp at 400c with 63sn/37pb solder.  The soldering station is a Hakko FX888D-23BY. 

Does anyone know why this is happening and how to clean the tip?

Thank you!

[IanB]

I'm soldering a board and I'm running into a problem with my soldering iron.  There is a black film(residue) developing on the tip and solder will not stick to this(see attached picture).  It's making it very hard to solder as I have to scrub it with the brass pad thing about every 30 seconds and it doesn't even remove all of it.  I'm not sure why this is happening as I've used this soldering iron probably about 8 hours before this and I haven't seen this yet. 

I've seen some stuff online saying to wipe it off on a wet sponge but that doesn't work for me.  I have the temp at 750c with 63sn/37pb solder.  The soldering station is a Hakko FX888D-23BY. 

Does anyone know why this is happening and how to clean the tip?

This has happened to me once when I was experimenting with soldering aluminium. Contamination from what I was soldering ruined the tip in the way you described and made it very difficult to recover. So I wonder what you are soldering? Is it clean and free from contamination, and is it copper, tin or iron?

Also, I hope a temperature of 750°C is a typo! For tin/lead solder I usually find 350°C / 650°F works fine. If you have the iron too hot it will burn the flux which is not good.

Lastly, try not to "scrub" the tip as you can damage the protective plating. Usually a gentle wipe is all that is required, and keep it well covered in solder at all times. You should just be wiping off the oxidized liquid solder, not actually cleaning the tip.

[IanB]

One last thought might be about the quality of the solder and the flux core. Not all solder is equal, and poor solder might lead to poor results.

(And if you really need to clean the tip, get a tin of tip cleaning/tinning compound.)

[pigtwo]

Yeah 750c was wrong.  For some reason I assumed the displayed temp was in C but then I realized that was way to high.  The real temp was 400c.  Maybe I'll bring this down to 350c.

I'm soldering a basic circuit board.  ENIG coated copper I believe.  Your comment about scrubbing the tip too hard may be my issue.  Once I started seeing the problem I started rubbing it really hard trying to scrape it off.  So maybe that was my issue.   

I'm using 0.3mm solder with 1.2% flux.  Is this good enough?  Does anyone have a recommendation for a high quality solder?

Thanks!

[stj]

your burning flux,
350 is good for lead-free,
for eutectic stuff like yours you should really only be using 300 - maybe less.

soldering is a balancing act, you want enough heat to melt the solder, but not so much that the flux burns.


btw, what brand/series solder is it you have?

[pigtwo]

Ok thanks for the advice, I'll turn it down to 300.  I almost turned it up because I couldn't get solder to wick to solder wick but I think it's because the film or whatever was decreasing the thermal conductivity. 

I was using Koocu 0.3mm 63/37.  But I know nothing about solder brands so I have no idea if it's bad or not.  I also have Jinliyang 0.5mm 63/37.  I haven't used this one much because I was soldering 0.5mm pitch QFPs so I wanted slightly smaller. 

[pigtwo]

Also, do you think the tip is salvageable?  I don't really mind buying a new one it just sucks to have to wait for the new one arrive. 

[MosherIV]

Hi

It is natural that some flux will collect on the tip. Just use a damp spong and wipe the tip across the spong every 2/3 joints to clean the flux off.

Is the tio salvagable ?
Just try it, try and tin it.

Get some tip tinner. It is expensive for what it is but it brings a tip back to life.

[forrestc]

Ok thanks for the advice, I'll turn it down to 300.  I almost turned it up because I couldn't get solder to wick to solder wick but I think it's because the film or whatever was decreasing the thermal conductivity. 

Too high of a temperature will definitely cause the symptoms you are seeing, or at least similar symptoms.

[pigtwo]

Well I'm glad I know why.  This actually makes sense because I have a very nice soldering station at work but it's fixed temp and I've never had this problem with it.  I think the tip is done.  I can't tin it except for this one spot that isn't black.  And I can't remove the black stuff at least without using sand paper or something.

Thanks for all the help!

[Ian.M]

The black stuff is probably a combination of carbonised flux residue and black iron oxide from oxidisation of the tip plating.   With the bit cold and removed from the iron, you *may* be able to salvage it with a fiberglass pencil to abrade away the oxide layer, followed by retinning with tip tinner/cleaner but if too much of the plating thicness has oxidised, that will expose bare copper and the bit will then rapidly erode.    To minimise future problems, especially at higher temperatures, make sure the bit is cleaned and re-tinned with ordinary solder, leaving solder on it, if its going to be longer than a minute or two before the next joint, then wipe immediately before use. 

N.B. tip tinner/cleaner is too aggressive for regular tip tinning - don't use it unless you are having difficulty getting ordinary solder to take, and when you use it, wipe off the residue and re-tin with ordinary solder as soon as possible, certainly before touching a PCB with that bit!

[pigtwo]

Ah ok, I don't think I fully understood the purpose of tinning until now.  The basic idea is you don't want the tip to hot and exposed to air for very long. 

I'm probably just going to buy a new tip.  They're luckily not very expensive. 

[IanB]

Ah ok, I don't think I fully understood the purpose of tinning until now.  The basic idea is you don't want the tip to hot and exposed to air for very long.

Yes, and in particular if you keep the tip thoroughly coated with solder all the time then it is the solder that oxidizes rather than the surface of the bit. By doing this you should be able to wipe off the old solder and get a clean, shiny surface each time you need to make a new joint.

FYI, I run my FX888 at 350°C without any trouble. Also I turn off the iron if I have a pause between joints. It only takes 30 seconds to warm up again, so this is no trouble at all and it helps keep the tip clean.

[Brumby]

I run my iron at a maximum of 350ºC.  Generally it's 330ºC or less, but sometimes when I'm on a roll, I might nudge it up to maintain the heat when doing multiple joints in quick succession.

I have also stepped away from using the wet sponge.  I now use a cheap metal scourer (well, half of one) from the local $2 shop which works a treat.  A fresh drop of solder, a couple of jabs and it looks like a new tip every time - cleaning all sides of the tip at the same time.  No more rolling the iron in multiple swipes down a sizzling sponge.

I made this move when the topic of the "wet sponge" highlighted issues of thermal shock to the tip, as well as the loss of heat.  I've never felt happier.

[Ian.M]

The sponge should be damp rather than wet, i.e. wet enough for it not to char, but not so wet it significantly quenches the bit.  Brass turning panscourer or brass wool (*NEVER* stainless panscourer) are supposed to be kinder to the bit but IMHO are less effective at removing the last traces of corrosive residue from more aggressive fluxes (but more effective at removing heavy residue).   If you do choose to use the traditional sponge, it should be an undyed cellulose one, and needs to be washed thoroughly before first use to remove plasticisers then washed regularly to prevent buildup of contaminates.   Squeeze out as much moisture as possible before use, and if its still too wet, repeat on a pad of kitchen paper.

[Tom10000]

if its been burning flux than get really fine sandpaper and sand it a tiny bit down until the it is not that black and go out and buy some tip tinner from your local electronics store use that on it regularly.

[KL27x]

If brass wool, flux, and tinning/solder don't restore the tip, ^+1 you can use sandpaper. Or what I would prefer is a fine stone file.

But you have to be careful. There's a line between the end of the tip which carries tin, and farther up where it won't. The reason it won't hold tin away from the tip is due to a chrome plating. (The chrome plating also protects the untinnable area from oxidizing; to protect the tinned area of the tip, you try to keep it coated with solder as much as possible). This chrome plating is very thin. If you are going to use gentle abrasion or perhaps a stronger acid to remove oxides from the tip, be sure to stay away from the chrome.

Underneath the chrome is a thin layer of nickel to bond the chrome. And under that is a thick layer of cast iron which covers the entire tip. This is what carries the tin and protects the copper core. In hakko tips, this layer is quite thick. There is no reason to chuck your tip without giving it a second chance. There's a decent chance it will work for many more years.

The temp is adjustable so that you can use the lowest temp that works well for a given task. Sometimes you gotta turn it up, and sometimes you can turn it down. I do 95% of my soldering with my 888 between 315 and 335C. But anything up to about 350 is much easier on the tip than 400. Somewhere in that area between 350 and 400 is where tips go to heaven. And lead-free soldering equipment manufacturers rejoice. Below that, you will have to work pretty hard to wear out a hakko tip, although the pointed tips are the ones that wear out the fastest due to having very thin conduit to transfer heat to the tip, so you have to run them hotter, and because the solder tends to pull back and bead away from the very end, making it harder to keep them protected.

[kalel]

Ah ok, I don't think I fully understood the purpose of tinning until now.  The basic idea is you don't want the tip to hot and exposed to air for very long.

Yes, and in particular if you keep the tip thoroughly coated with solder all the time then it is the solder that oxidizes rather than the surface of the bit. By doing this you should be able to wipe off the old solder and get a clean, shiny surface each time you need to make a new joint.

FYI, I run my FX888 at 350°C without any trouble. Also I turn off the iron if I have a pause between joints. It only takes 30 seconds to warm up again, so this is no trouble at all and it helps keep the tip clean.

Yes, this seems to make a lot of difference. Even my cheap $1 or less tips seem to last a lot longer than before, by following this technique. That is, applying some solder on the soldering iron after use (usually just after unplugging). During soldering I frequently use the sponge (a sponge, something wet), as it didn't cause any oxidation or other issues yet. Then again I'm neither good at soldering or use good tools - but this does make a big difference regarding longevity of the tips.

[KL27x]

Also I turn off the iron if I have a pause between joints. It only takes 30 seconds to warm up again, so this is no trouble at all and it helps keep the tip clean.

If tip life is a concern for you, you might want to give C (bevel) or CF (bevel tip, tinned face, only) tips a try. Because the working part of the tip is a disc-shaped surface facing down,  any solder you put on it tend to spread over the entire face and to stay there. As you solder, the bead stays on the face. Whenever you touch the tip to rosin/flux, flux tends to drip to the bottom, where the face and the bead are. When the iron is in the stand, the bead stays on the face. When I'm debugging/troubleshooting, I might leave my iron on for 6 hours straight, making only a few connections in that time. I have zero concern for the tip oxidizing. Even when doing a straight forward build or batch assembly, I often just walk away for a break and come back... whenever. 5 minutes. An hour. It doesn't matter. I have used the same Hakko T18 tips for many years and many, many hours. I have only worn out 1, and it was a fine pointy tip I left at 400C overnight.

[Electro Detective]

FWIW, this is my go to Youtube video to get a crusty overbaked soldering iron to perform better
Hats off to the gent as he explains it in a no brainer fashion 

youtube.com/watch?v=7PWmMxjXwYE

There are other vids worth watching in that URL too on the right side selection menu

Good luck 

[Ian.M]

Hmmm.   I wouldn''t really recommend that video.  A new soldering iron bit should tin easily, AS LONG AS YOU APPLY SOLDER IMMEDIATELY, but you have to rub the end of the solder into the bit surface so the flux cores melt with the solder, and keep the temperature down to just above the solder melting point. so for non-temperature contrplled irons, as soon as the solder starts to take, switch off, and carry on applying solder till it becomes more difficult to melt then switch back on, continuing till all the active tip surface has been tinned.   Wrapping the solder round the bit like that video DOES NOT WORK WELL - there is no flux on the outside of the solder so as it first melts it oxidises and then its no longer being pressed against the bit and most of it just drops off without taking.  If you want to try wrapping the bit in solder, you'd need to add extra flux then wrap it in a little aluminum foil to hold the solder against the bit even after it's melted.

Acid flux is evil stuff - Apart from the toxic fumes, it usually has acid Zinc Chloride as the active ingredient, which (+ added moisture) is corrosive to iron and steel parts of the iron, so if you use it for tip tinning, after tinning,  you should ideally remove the tip and wash it thoroughly in boiling water to remove any residual acid.  Ammonium Chloride flux is a little less evil, but its residue should still be cleaned off properly.

Tip tinner/cleaner - a compressed cake of Ammonium Chloride mixed with finely divided solder particles is much easier to use for tinning.   Simply scrub the ckeaned bit surface across the face of the cake  - don't dig it in as that just breaks up the cake, and causes the solder powder to form big blobs of solder that are less effective. You will probably still need extra solder, but the tip tinner/cleaner does most of the work for you.

Also, if a plated bit is FUBARed, its often salvageable as a plain copper bit by grinding back the plating and reshaping it as needed.  Plain copper bits don't last well, especially at higher temperatures, (as, with every joint, some copper from the tip dissolves in the solder unless it already contains around 2-3% copper) but you should be able to get enough extra life out of it to tide you over while you order and wait for the spare bit you should have had in stock.  Bits are wear items - order a new one as soon as you put your spare into service.

Using sheet abrasives like sandpaper really doesn't work that well - there's a tendency for the edges of the bit to get more abraded, breaking through the iron plating, and ruining the bit. Also they don't stand up to a hot bit so its difficult to spot clean an area that wont tin.   A fine grained oilstone can be used *extremely* gently, but I recommended a fiberglass abrasive brush, because its harder to damage the plating with one.  Steel wool can be used on badly oxidised bits if you have nothing better, but as it may be harder than the iron plating shouldn't be used for regular bit cleaning as you are working. You also shouldn't need it for tinning a new bit - if you do it means you screwed up and let it oxidise before you applied flux and solder.

[macboy]

My two cents:
The Iron is to hot. 300 c is fine for leaded solder.  The black stuff is oxidized solder and or iron from the tip plating. Once this happens I find that the best cure is to use a tin of tip cleaner (mine is Archer brand from radio Shack, ancient but effective). After cleaning in tip cleaner, wipe on a damp (NOT wet) sponge, then thoroughly cover in solder, to the point where it is dripping off the tip. Add more fresh solder every ten seconds for about a minute. Let the tip bake like this for several minutes, adding lots of fresh solder every minute or so. After this baking process, bump the solder blob off of the tip then wipe on the damp sponge. You should be good to go now. If well cared for (no overheating, always tinned when idle), you shouldn't need to repeat this fix.

[KL27x]

Steel wool can be used on badly oxidised bits if you have nothing better, but as it may be harder than the iron plating shouldn't be used for regular bit cleaning as you are working.

I have felt pretty sure that the tip is cast iron or some other form of high carbon iron, all of which are harder than steel wool.

The coarseness of the wool is also a large factor. For removing rust on blued steel, for instance, you can use 0000 steel wool with care, but 00 wool will remove the finish before it removes the rust.

I have put this to the test recently, having added a very coarse stainless steel wool cleaner to a new iron holder I made. So far, so good. The stiffness of the coarse wool gives it a lot of bite. If this is to cause a problem, I should know in a few months. So far, I don't see any problem under the microscope.

Regarding plumber's flux, I think is probably not that bad. At one point, I used it fairly frequently. At that time, I only used the one pointy tip for everything, on my old velleman station. I only wore out one tip (and one handpiece) over probably 4-5 years. The flux induced rust in soldered iron/steel like mad, but perhaps due to the solder that ordinarily coats a tip, or to the specific kind of iron in the tip, the halides did not cause the soldering iron any great problem. Well, on second thought, it might be an addictive thing, where it is strong enough to clean off the oxides it creates, as long as you occasionally use it. But it you stop using it, the iron might stop wetting.

[MosherIV]

I have felt pretty sure that the tip is cast iron or some other form of high carbon iron

No, most soldering iron bits are copper core with nickle and  iron plating :
https://en.wikipedia.org/wiki/Soldering_iron
(see the section on tips)

Regarding plumber's flux, I think is probably not that bad. At one point, I used it fairly frequently.

The flux induced rust in soldered iron/steel like mad

Is that not a clue that plumber's flux is no good for electronics work?!?
Cannot imagine what it is doing to soldered up circuits 

[KL27x]

Is that not a clue that plumber's flux is no good for electronics work?!?
Cannot imagine what it is doing to soldered up circuits 

If you wash off the conductive, hygroscopic, water soluble residue, probably same thing it does to copper water pipes. A good job.

It's the halides that do a number on iron/steel. They imbed in the metal and induce rust. They can't be washed off with water. This does not appear to affect copper, tin, or lead.

copper core with nickle and  iron plating

Iron plating does not necessarily mean pure elemental iron. Pure iron has very little use. The amount we produce and use amounts to squadoosh. Whereas we use a high volume of high carbon irons, such as cast, white, grey, and other types. High carbon iron can be plated hard as woodpecker lips over engine cylinder heads and whatnot. It has high rust resistance at high temp. And solder will wet to it. Elemental iron pretty much sucks in these qualities.  And I don't think Hakko tips are plated in nickel at the working end. The nickel is just to adhere the chrome plating where solder is not supposed to stick. Some irons may use nickel. But I don't suspect it provides much benefit and/or it doesn't last long, else more tips would use it.