Soldering iron tip problematic

[akis]

When I apply solder onto the tip, it seems to defy gravity and concentrates higher up, as shown on the sketch I have made. This makes it hard to solder fine parts as there is no solder right when you need it. The temperature at the point the solder concentrates appears to be higher than at the tip, maybe that's an explanation. Can anyone suggest a solution?

Edit: I have attached the sketch

[Fortran]

Tried a solder tip cleaner?
They're getting hard to find these days but works good.

[FlyingHacker]

Your picture did not come through, but it sounds like oxidation on the tip is preventing solder from bonding to it. The tip should be coated in a thin layer of shiny solder.

Wipe the tip with something... (While hot) I like the brass colored metallic sponges Hakko supplies, but even a cloth is better than nothing.

You could try literally putting the tip directly into some paste flux. I have heard comments about the temperature differential being an issue when doing this, and some people suggest dipping it in flux with the iron cool and then turning it on.

Then keep adding solder to the tip until you get it to bond to the tip. Every time you take a break from soldering a few joints, coat the tip in solder. Always coat the tip in solder before turning the iron off. It should be shiny. Before turning off I add some solder, wipe off in the brass sponge, and then add some more solder before shutting down.

[akis]

The tip is clean and I clean it when it gets dirty. It is not dirt that causes the solder to flow upwards! I think it is temperature differential, the tip not being as hot as the middle/upper section.

To clean the tip when it is very bad and normal wiping does not do it, I heat it up to the max (450C or more?) and then I apply lots of solder, wipe it, apply more solder that it barely stays on, then I bring it doen to normal temperature (280C) and then I shake off the excess solder.

It then becomes shiny and clean, but the solder still flows upwards and away from whetever it is I am trying to solder.

[Ian.M]

See http://www.newark.com/pdfs/techarticles/oki-metcal/extendingTipLife.pdf
It sounds like you have an oxide layer built up on the tip + the plated sides of the bit away from the tip have been mistakenly tinned so the solder flows away from the working face.

The tip is probably FUBARed,  but it would be worth trying commercial tip tinner/cleaner and as an absolute last resort, a fibreglass pencil to abrade the oxide layer.  Order a spare tip, you are likely to need one sooner rather than later, and in future remember to tin the bit and switch off if you wont be using the iron in the next five minutes.

[IanB]

Some ways a tip can be damaged like this are using it on plastic or aluminium. Once a tip gets into this state it is very hard to repair it. The easiest option may be to replace it with a new one and then look after the new one carefully.

[xygor]

Is it a long, thin tip?  Did it work correctly when it was new?
Long, thin tips do that for the reason you stated: the tip temperature is lower at the tip.

[akis]

I do not think it ever worked. I need to buy thicker tips then.

Here is a photo - it is not clean now, but it makes no difference even if cleaned and examined under a lens !

[Ian.M]

Tip tinner cleaner is still readily available.  e.g. Maplin stock it in-store as JG06G.   However I'd bet you can get it cheaper from your preferred distributer with your next order.

Overheating a bit causes this sort of problem so your tinning procedure is at fault.  With the bit hot enough to melt solder, wipe off as much as possible of te excess solder with a dry paper towel folded into a thick wad, then tin only the face and just round the edges for chisel and screwdriver tips or just the last 5mm for conical tips using a cake of tip tinner cleaner and a light scrubbing motion.  Do NOT dig it into the cake..  If you cant get it to take solder without balling up, then the oxide layer will need to be removed with mild abrasive (I prefer a fibreglass pencil, used with the tip hot) but the iron plating is very thin, and if the abrasive breaks through exposing the copper core, the tip will rot away due to the solder dissolving the core within a couple of days use, hence my recommendation to order a spare tip.  For through hole work, chisel tips are preferable to conical ones as you get a larger working face with better heat conduction to it. 

[FlyingHacker]

Before throwing it out I would try dipping it in paste flux while hot.  I have recovered a couple oxidized tips like this.

[DimitriP]

There is the "polite way" 

and the not so polite way:

[Ian.M]

Dremel Madness!  If he'd used a brass wire brush in the Dremel, it might have been forgiveable.

I must confess to using 400 grit wet & dry paper on really gnarly bits, and once its obvious the plating has gone, treating them as a bare copper bits one can dress with a file, but that's only to squeeze a couple of days out of it while waiting for the replacement.

[DimitriP]

I don't really mind if the tip is plated or filed down to bare copper, as long as it works !