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Basic question here, but it's driving me insane!

The solder does not seem to stick to the tip of my soldering iron. After the iron heats up, the tip appears black (sometimes on all sides and sometimes on one side), then either it doesn't melt the solder at all, or it I fiddle around with it for a while; it melts the solder, but the solder rolls into itself into a ball and doesn't stick to the tip.

I've seen this many times while soldering before and usually it's solved by cleaning the tip on a soldering sponge or cooling it down and scraping the tip off with a blade, but I have scraped this particular one many times and still it's the same problem: it heats up and gets black, then the solder doesn't stick to it.

It doesn't help that this soldering iron has a very fine tip and I have to use it to solder very tiny chips and wires under a microscope (I'm just starting to learn soldering under microscopes).

Any ideas on what I can do?

PS: Is scraping the tip a bad idea? I have been doing it with my other bigger soldering irons and it seemed to work (at least in most cases) but I am not sure whether it is a good solution or not.

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First question: How long have you had the tip? You could probably easily and cheaply replace it. If the iron doesn't have replaceable tips, get rid of it!

If you've not had the tip long, then a few pointers to keep in mind:

  • When the iron is not being used, keep some solder on the tip. This prevents oxidation and corrosion.
  • When using the iron, keep a little solder on the tip when the iron is in the stand. Wipe clean before using. Avoid excessive wiping on a wet sponge as this can cause temperature fluctuations which expand and contract the metal, and stress the tip. Consider using brass shavings instead of a wet sponge.
  • Never use sandpaper or abrasives to clean the tip. Also avoid dipping it into flux to clean. (Except for re-tinning which should be infrequent.)
  • Use a good quality solder. Old solder can have contaminants which leave behind residue and basically make soldering more difficult. (By "old" I mean solder that's been around collecting dust, not necessarily that it has a short shelf life.)

Finally, if you've got a cheap iron, it may be too hot or cold and not melting solder at the correct temperature. Consider getting a temperature controlled unit. I could recommend a Hakko FX-888D for ~ $100 US, see also this tutorial.

Some additional soldering tip pointers:

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  • \$\begingroup\$ Great answer and advice from JYelton. If/when you buy a new soldering iron, take the tip to a jeweler and have him gold plate it (new only). Some commercial irons come with nickel plated tips, they tin quickly, even after being overheated, and seem to last a long while. \$\endgroup\$ – Optionparty Dec 21 '12 at 14:22
  • \$\begingroup\$ what I would really like to know is, is it possible I have already damaged it beyond repair? Because I have already scrapped it a few times, but not too hard, and using a sharp blade (not sandpaper or steel wire) \$\endgroup\$ – user13267 Dec 21 '12 at 15:30
  • \$\begingroup\$ From what you describe, yes. Hard to tell without seeing/using it myself. \$\endgroup\$ – JYelton Dec 21 '12 at 15:35
  • \$\begingroup\$ I have a Hakko FX-888. It was ~$80 on Amazon. It works very well for me. I guess they are going away in favor of a similar digitally control interface. \$\endgroup\$ – Hair_of_the_Dog Dec 21 '12 at 16:57
  • \$\begingroup\$ @Hair That is correct, a digital version has been announced for January 2013. \$\endgroup\$ – JYelton Dec 21 '12 at 18:07
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My first guess would be that's just a low quality tip and no scrapping would help. There are some tips nowadays that arent properly coated. They're some alloy plated or even might be died with something and they're just for show. But in that cases whole iron is low quality also.

If it's some quality iron and tip (in its own time) and you scrap it too often it might be you overscrap it or it might even oxidation of inner copper alloy to degrade tip so it's for scrap. If it's HQ tip over years of use it should be replaced.

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imho, there is no substitute for using tip tinner. You can find it easily on eBay or Amazon, and probably other places.

enter image description here

Just heat up the iron and push it into the stuff for a second, then wipe it off on a damp sponge.

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This may sound silly, but some solder is designed for higher temperatures. It is possible you are attempting to melt solder that is a higher temperature grade than your iron is capable of melting. ( I had this problem once ) check it out. A typical iron is 50W you may need 150 or higher.

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  • \$\begingroup\$ A 50W iron can be used with HMP solder. It might be difficult to solder a multi-layer board with it, but getting it to adhere to the tip should not be a problem. \$\endgroup\$ – Oleksandr R. Apr 4 '16 at 14:04

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