Soldering Iron tip - black residue

[MosherIV]

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.

That is correct. The nickle plating is just there to allow other metals to adhere to it, since it is virtualy impossible to get iron to directly adhere/plate to copper.

Yes, I am aware that the tip is iron plated and chrome is used further up the tip to stop it oxidizing.

The point is, as far as I aware, there are NO solid iron soldering tips - they are all copper with iron plating.

I do not have a problem with using damp sponges to clean tips, I actually think they are better at cleaning the flux residue off than the wire wool stuff. I do not think there is a problem with thermal shock with damp sponges, I think this was a marketing ploy to get people to buy the new thing in town at the time - brass wire wool tip cleaners. 

I have been told to NEVER use steel wool, only brass. I am not actually a fan of these types of tip cleaners. I think they are too abrasive.

[KL27x]

Who ever suggested that soldering irons were made of solid iron? Read my post again. I'm differentiating between elementally pure iron and high carbon types of iron. Which are harder than brass and even steel wool.

I like the brass wool. When I finally wear out a tip, I'll reevaluate. I am going on 3+ years with my current favorite hakko tips. The cost per tip so far is $3.00 a year and dropping, so I think it is going to work out.

[MosherIV]

Who ever suggested that soldering irons were made of solid iron? Read my post again

You said

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

Saying the tip is 'cast iron' implies that the whole tip is iron and has been cast.
The clue is in the name - 'cast iron'
Casting iron is a process.

You cannot plate cast iron onto something.
You can plat the same grade of iron as cast iron. This is where we have a dissagrement in the language used.

[KL27x]

Cast iron is a type of iron. It does not mean that the iron was cast in a mold. That's not how I meant it, anyway. Sorry for the confusion.

I suspect the iron which is plated over the copper is a high carbon iron such as cast iron or other perhaps some other form with additional ingredients. Cast iron for instance has high hardness and high wear resistance. Two features which would be desirable in a soldering iron tip. And of course, solder will readily wet to it. It is also much more rust resistant than carbon steel. Perhaps not as good as stainless steel, but stainless steel doesn't wet to solder, and it has poor thermal transfer compares to cast iron.

One of my original points was that the iron plating on the average hakko tip is pretty thick. Mil or more. You can certainly judiciously file or sand it without exposing the copper core. The chrome plating is the part that can be better measured in microns.

You cannot plate cast iron onto something.
You can plat the same grade of iron as cast iron. This is where we have a dissagrement in the language used.

I'm not sure the definition of "plating," but certainly we "plate" iron over cylinder heads. And it's not elementally pure iron. In case of cylinder heads, the iron may contain high amount of carbon, including actual graphite, which is not unlike cast iron. In fact, cast iron is a type of iron which has defined amount of carbon, among other things. It is named so, because it in fact can be cast with relatively little warpage. We also cast steel, but there is no steel known as cast steel. So after we do the act of casting pure iron, or other alloys of iron, I suppose we can call these "cast iron," after the fact, but I think that would be somewhat vague, lol. At some point, all iron and steel is cast into ingots, but we have different names for these different alloys; names which are more useful. If the ingot is over 4% carbon, we call it pig iron. if it's less than 2% we call it steel. if I take a piece of cast iron and mill it into shape, I don't called it milled iron.  So I will agree to disagree.

[Specmaster]

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.

I agree with turning the iron off, I do this, as you say, it is just seconds these days with a decent soldering station to get back to temperature. On the topic of temperature, 400C is most certainly too hot for most PCB work, especially with the really fine solder that you're using and the extra heat will make it too easy to lift pads / traces as it will tend to kill the adhesive that bonds them to the board, And it will certainly cause the tip to oxidise very quickly just like the old fashioned mains directly heated irons with no temperature control used to if you had a break in soldering for a few minutes.

I tend to set my station to around 320 to 330C and that is sufficient for most jobs unless there is a large mass or a ground plane to suck away the heat, especially with a small tip as there is going to be insufficient thermal capacity for large bits of soldering.

[IanB]

Cast iron is a type of iron. It does not mean that the iron was cast in a mold.

 

It actually does mean that. It means exactly that. The molten iron is poured out of a furnace into a mold where it solidifies.

That's not how I meant it, anyway.

[KL27x]

@Ian B. Perhaps you can google the definition of cast iron and tell us what you find?

[IanB]

@Ian B. Perhaps you can google the definition of cast iron and tell us what you find?

I did 

[KL27x]

 

[CJay]

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 

I had to give up taking fun jobs* from one 'repairer' local to me because he was using plumber's flux on boards, including SMD, I realised when a job was returned to me as 'gone again' and the board was covered in green residue from the acid flux.

* the difficult ones that'd been around half a dozen places and failed to be repaired

[BravoV]

From Hakko ..

[KL27x]

http://www.freepatentsonline.com/y2004/0226981.html

I bet this is how (at least some of) these iron tips are made. The iron is powdered and sintered in a die to produce the outer shell. The inner die is withdrawn revealing the hollow. The copper core is pre-swaged into gross shape; the inner iron sleeve is sintered separately, made like a blind rivet, which is slipped over a shouldered pin/mandrel, and this is hydraulically pressed into the copper/outer tip to swage everything together. The whole thing is then heated to melt the powdered silver between the layers to braze everything together. These are machined and polished to final dimensions. Then the chromium layer is plated on.

It's possible that on the longer skinnier tips, the hole for the copper core may have to be drilled out of the sintered tip. Then the copper wire inserted and swaged to fit. Then the outer iron ground down to size. Bent tips... hmm. Perhaps they have a joint that is brazed, at the bend. Or maybe they are just bent, after the fact, using a ductile iron jacket. I doubt electroplating can be done this thick and be as economical (cheap) as these tips are. That would just be a PITA. I.e. expensive. The conditions would have to be surgical, and the tips would still require post plating machining to even out the lumps and bumps. (The first 10 microns is easy; this is how radio shack firestarter tips are made. After that, it is increasingly difficult to make the plating consistently thicker. The shoulder area of the hakko tip has several thousands of microns of iron "plating").  And the space required and upkeep/tweaking of the plating tank and equipment would be considerable.

In any case, the iron is a cast iron alloy the carbon content of the iron is over 2%, otherwise it would be called steel.

[John_ITIC]

Buy this: http://uk.rs-online.com/web/p/soldering-station-accessories/5078698/

[stj]

it would be cheaper to throw the tip in the bin and buy some fresh ones!

[BradC]

it would be cheaper to throw the tip in the bin and buy some fresh ones!

It would, but those tip cleaners will restore a *lot* of tips.

[rolycat]

I find brass wool does an excellent job of cleaning tips, but many of the "brass" tip cleaning aids sold on eBay and similar sources are actually copper plated steel and are both overly abrasive and much less effective. The product pictures may also be doctored to look more like brass.

[stj]

i get my brass cleaners from Rapid to hopefully avoid that problem.

[KL27x]

It would, but those tip cleaners will restore a *lot* of tips.

I tried the little cans of tip cleaner/tinner when I had a Radio Shack iron with the pure copper tips with the micro-thin nickel plating. Wrong thing for that job. Those tips just die, and once the plating is gone, you might as well just file them. If you're counting on some black magic where this stuff restores the actual plating, it does not. It works by removing material, and the "tinning balls" in there might as well be regular solder. Don't get me wrong, it's good in the fact that is gets into nooks and crannies, removing mostly just the oxides and not the good metal. Also there is advantage in solder holding ability if you leave the surface textured/micro-pitted, by using a chemical cleaner. But in average tip, there is plenty of iron there, and the "gentleness" is not needed, if you stay away from the thin chrome plating.

With proper temp controlled station, it is rare to ruin a tip at leaded solder temps. It's not that buying a new tip would be cheaper... just that a stone or sandpaper is a generally useful thing the rest of the time it's not needed for a soldering iron. It just depends on what iron you got and how you use it. I have tried to intentionally oxidize a bevel tip on my old velleman station. Trying to make a CF tip. I sanded the tip, tinned just the face, and left it at 450 for several hours. It still tinned like nothing happened. In hindsight, after reading this thread, I could have coated it with zinc chloride flux to induce surface "rust."

Update on the steel wool. My own firsthand experience now says, yes. It's too aggressive. It is wearing away at the edge of the chrome plating, already. At least on the Chinese T12 tips. (But boy does it clean crusted residue - it gets down to the chrome, removing that last layer of residue that brass wool leaves behind).  I can tell the difference between the real hakkos and the Chinese knockoff. It's the level of machining/polish on the tips before the chrome plating is put on. The Chinese tips have profound grind marks and also voids/defects from the casting/MIM or however the iron part is made. I'm sure the real Hakko chrome plating won't break/flake as easy. It's just a matter of how much time and $$$ spent in the manufacturing process.

As an experiment, I filed away at the working end of the tip deep enough to remove the machine marks. No surprise to me, the copper is not exposed and the tip still works. I'm sure there is a lot more iron there. I have cut apart a few of them. If the iron was chocolate and the copper was caramel, it would look like the cross section of a Rolo. When you consider the prying/twisting forces you can put on these tips, you know there is considerable iron there for structural integrity as well as to protect the copper from dissolving. If it was just a thin electroplating, I would have bent some of my tips into pretzels, by now. Dropping the handpiece on the ground, point down on a CF15 tip, it would be bent at least 45 degrees at the base. Instead, this results in just a tiny curl at the edge of the tip.

The very existence of the deep machine marks in the Chinese tips is indicative of the thickness of the iron. These kinds of marks would not be left on copper. Copper would be cut and swaged, and any grinding/polishing would not likely be so rough. The machining is surely done after the tip is made, just before the final chrome plating. If there's enough iron there for the factory to grind on it with what looks like a 60 grit belt, there's enough for gentle sanding, galore.