Soldering iron tip oxidization confusion - Page 1
Forum section: electronics / beginners

author: nickajeglin
author_rank: Newbie
timestamp: March 23, 2019, 02:18:14 am
content: Hello everyone. I'm having a problem where my soldering iron tip will be perfectly fine for weeks, then suddenly and for no apparent reason, it will grow thick black oxidization. This usually happens after 3-4 minutes of it sitting without soldering, but that's standard procedure for me. I often let it sit hot for several minutes while placing components without an issue. I have read all the recommendations to prevent oxide, and tried many things, but it still seems to happen quite randomly. Eventually (several hours of soldering), if I elevate the temperature enough, the oxide will flake off in large chunks, and I'm back to normal operation. I have been doing a ton of smd soldering over the past couple of months, and it's driving me crazy that everything will be fine for weeks on end, and then suddenly I can't solder a THT resistor.Here's some relevant information:solder station: circuit specialists station-60 (temp controlled)normal temp: 350-425c depending on if smd or tht stufftip: hakko chisel tipflux: kester 186 flux pen (rosin type, no clean, and I smear it all over everything all the time)cleaning/storage method: I clean on damp (not wet) cellulose sponge after every joint, and always store the iron with solder coating the tip.I really have 2 questions:1: Why does this happen? In particular, why does it only happen intermittently, even with all the precautions I'm taking?2: Once the tip is badly oxidized, how do I clean it as quickly as possible?Things I've tried to get the oxide off once it's started:1: elevating the temperature2: reducing the temperature3: smearing rosin flux all over the tip4: smearing aggressive plumbers acid flux all over the tip (this one actually makes it worse)5: thermal cycling the tip as quickly as possible (eg. dunking it in water while hot)6: banging it against the side of the iron rest (this only helps once it starts flaking off)I just bought one of those brass brillo pad cleaners off amazon, along with a tin of "tip tinner". I'm hoping that I can use the brillo pad deal to scrub off the oxide more quickly since it seems to flake off on it's own eventually.Please help, this is driving me insane.

author: nickajeglin
author_rank: Newbie
timestamp: March 23, 2019, 02:25:34 am
content: I forgot to mention that I'm using lead free solder. 99.3/0.7 and 30/70 (Sn/Cu). The problem seems to be more associated with the high tin solder.

author: KL27x
author_rank: Super Contributor
timestamp: March 23, 2019, 04:49:10 am
content: This doesn't sound like oxidized iron tip. If the tip oxidizes, it is part of the tip. It doesn't fall or flake off.Thick black layer that can flake off sounds like burnt rosin flux residue. It happens when you get flux on the tip. So if you are using a lot of flux, it will build up rapidly. If you are feeding solderwire only onto your joints, it will occur more slowly. There's a solder layer, still, underneath the burnt flux. So over the iron part of the tip, this burnt flux can flake off fairly easily. When it gets up over the chrome, it is more stubborn, since there's no solder layer. It gets caked on there, good.If the sponge doesn't work, I would suggest you clean it mechanically with brass wool.

author: jwm_
author_rank: Frequent Contributor
timestamp: March 23, 2019, 04:54:48 am
content: Are you using rosin meant for leaded solder temperatures with lead free temperatures? Could of just be charging on the tip. Perhaps your irons temperature is off. Also, what is in the core of the solder you use?

author: TheNewLab
author_rank: Frequent Contributor
timestamp: March 23, 2019, 10:45:14 am
content: Quote from: KL27x on March 23, 2019, 04:49:10 amMy method is to have both a sponge and brass wool. When I put it away, a slder the tip and then poke it into the brass wool. I have had happen what you describe and it comes off once I stick the tip into the brass wool

author: David Hess
author_rank: Super Contributor
timestamp: March 23, 2019, 03:41:45 pm
content: Quote from: nickajeglin on March 23, 2019, 02:18:14 amWhile soldering, clean the tip with the sponge *before* making a joint and place the iron into the stand without cleaning. I had the same problem you described sometimes before I stopped wiping the tip off before holstering but never since.QuoteI have a sal ammoniac (ammonium chloride) block intended for cleaning and restoring soldering iron tips. Honestly it is difficult for me to say that it works but it is better than filing the tip.https://www.evilmadscientist.com/2014/tinning/

author: nickajeglin
author_rank: Newbie
timestamp: March 23, 2019, 07:17:05 pm
content: Thanks for the thoughts everyone.I never suspected flux buildup. There's definitely something in the core of the higher tin solder I'm using. It's not labeled well, but smells very much like rosin. The 30/70 stuff is labeled 2% flux, and also smells like rosin.Quote from: jwm_ on March 23, 2019, 04:54:48 amCan you elaborate on leaded vs. lead free temperatures? I assume that leaded is lower than lead free, but how does this affect the flux? Here's the datasheet for the flux:https://www.kester.com/DesktopModules/Bring2mind/DMX/Download.aspx?Command=Core_Download&EntryId=3764&language=en-US&PortalId=0&TabId=96They claim "High" thermal stability, and elsewhere on the website state that it is compatible with both leaded and lead free solder.

author: KL27x
author_rank: Super Contributor
timestamp: March 23, 2019, 07:45:28 pm
content: Usually this burnt residue starts higher up on the tip above the part of the tip that is being used. Gravity pulls any solder bead down (and you ought to be in the habit of NOT cleaning/wiping the tip before putting it up, as other posters have mentioned). And the flux tends to wick up the side of the tip above the bead, where it burns.If you see how I solder, it would make you ill. I primarily use a CF tip, which is a bevel that only wets on the cut face. Normal modus operandi for me is to ignore the burnt residue unless it gets so bulky it reduces my view. Because the sides of the tip don't wet, the black residue builds up all the way down the sides. The tinnable face is never affected. As we speak, it has a jet black crust over the chrome and I have used it that way for several big soldering sessions without touching it. If I see bits of this residue break off and fall onto the board, it really only bothers me if it's jammed between pins, and I'll pick it out. If it settles somewhere else in the flux pool, I just assume it will freeze there and be no worries, lol. Or if I clean the board, it will be washed away.The CF tip is unique, though. Because of the shape, the tinnable area always is very well protected, and the crust is very well bonded to the chrome layer. The cut face and the chromed areas are separated by a sharp corner, so the two shall not mix. And the tinnable surface is a flat oval. Any solder bead on the cut face tends to spread in a meniscus that protects the entire tinnable surface. In most use, and more importantly while in the stand, the cut face is held pretty much level/horizontal, so there's no part of the tinnable surface that tends to get dry (and form crust). On most other tip shapes, the crust will form over parts of the tinnable area and slowly creep down and impinge on the working surface and will eventually start flaking off in huge chunks.Whenever I do eventually get around to cleaning it, swiping it on brass wool removes 95% of it. Lightly scraping with the end of a bit of brass tubing will get all of it without damaging the chrome.

author: nickajeglin
author_rank: Newbie
timestamp: March 24, 2019, 07:31:15 pm
content: Thanks for the tips everyone. I'll start wiping the tip before instead of after, and I'll cut back on the flux use a little bit.My "tip tinner" got delivered today. It's like a little compressed tablet of powdered tin solder and ammonia phosphate. It instantly cleaned the black coating and tinned the tip. The tip isn't as good as it was, because it wants to re-oxidize (or get burned flux stuck on it) pretty quickly, but at least I can solder again. Highly recommended. Here's a link to what I ended up with:http://www.thermaltronics.com/downloads/datasheets/TMT-TC-2_Technical_Datasheet.pdf(standard disclaimer blah blah I'm not affiliated with them, it was just the first thing that popped up on amazon)

author: nickajeglin
author_rank: Newbie
timestamp: June 04, 2019, 04:09:27 am
content: Sorry to resurrect this thread, but I just had a breakthrough.My circuit specialists iron died, so I bought a weller WLC100, and associated tips. With these brand new (and higher quality) tips, I noticed that my Mudder brand solder didn't oxidize the tip, but the cheapo radio shack stuff I've had for years (part number 6400217) oxidized it pretty much instantly. I've thrown away the radio shack junk, and for now I'm only using the mudder stuff. It's thin gage, so I'll probably buy some heavy gage kester solder for through hole components in the near future.So for anyone else who is having a similar problem, try switching solder compositions, or throwing away the roll of radio shack that's been in a drawer for 10 years.

author: Shock
author_rank: Super Contributor
timestamp: June 04, 2019, 09:46:37 am
content: Just adding this about cleaning:The IPC training from when lead free solder was introduced says it's preferable to use brass wool (the type made for soldering). It works well on lead free and leaded solder. If you use a sponge, the heavy metals/minerals in tap water makes it unsuitable. It will lead to oxidization/corrosion, so instead use a small amount of distilled or deionized water.To prevent tip oxidization, load the tinned portion of the tip with solder when you return the iron to the stand. It helps if your station supports a low power mode, this prevents the tip from "cooking" while you are not using it, otherwise you can just switch the station off. When you resume soldering and have melt clean that solder off the tip. If it's been maintained well it should have a nice fresh shiny surface over entire tinned area.Don't be afraid at any time to load the tinned part of your tip with solder and then clean it, the flux in the solder will help dislodge oxides and freshen the surface. A clean tip helps with performance, makes soldering easier and prevents the need for more aggressive cleaning later.

author: tooki
author_rank: Super Contributor
timestamp: June 04, 2019, 03:10:46 pm
content: Quote from: nickajeglin on June 04, 2019, 04:09:27 am1. We established it’s burnt flux, not oxidation.2. Radio Shack solder was actually quite good quality, so what you probably saw happening “instantly” is the flux burning on an iron set too hot. Leaded solder melts at a lower temperature and so the flux didn’t need to handle the higher temperatures of lead free, so it will burn if you use it that hot.3. You can just twist together a few strands of thin solder to make a thick one, if you don’t use thick solder that often. I don’t own anything larger than 0.8mm/.032” any more.

author: mikerj
author_rank: Super Contributor
timestamp: June 04, 2019, 04:40:27 pm
content: Quote from: nickajeglin on June 04, 2019, 04:09:27 amNote that unlike your previous iron, the WLC100 is not temperature regulated. If it's left on without being used the tip temperature may get quite high which promotes oxidation.