Electronics > Beginners
Soldering iron tip oxidization confusion
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nickajeglin:
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 stuff
tip: hakko chisel tip
flux: 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 temperature
2: reducing the temperature
3: smearing rosin flux all over the tip
4: 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.
nickajeglin:
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.
KL27x:
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.

 
jwm_:
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?
TheNewLab:

--- Quote from: KL27x on March 23, 2019, 04:49:10 am ---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.

--- End quote ---

My 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
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