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I just bought a new tip (Weller ST7) for my soldering iron. I've tried tinning the tip, but the solder just keeps forming a ball and then falling off onto the workbench. What am I doing wrong? (I never had any trouble with the old tip.)

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    \$\begingroup\$ At what temperature are you using the tip? My personal preference is around 325 degrees Celcius. Clean the tip using one of these: img.photobucket.com/albums/v166/dc65x/Slot%20Blog-1/Toys/… (brass or steel wool). \$\endgroup\$ – Bimpelrekkie Sep 17 '17 at 20:53
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    \$\begingroup\$ Try a tip tinner/cleaner. \$\endgroup\$ – Steve G Sep 17 '17 at 20:56
  • \$\begingroup\$ @Bimpelrekkie I have no idea. My soldering iron has a scale of 1 to 5, and I set it on 3.5 when I solder. That setting always worked fine with the old tip. That's one thing I don't get about "how to solder" tutorials: they always talk about temperature, but only very expensive soldering irons have a temperature readout. With a moderately priced iron, how do I know? (My soldering iron is a Weller WLC-100.) \$\endgroup\$ – user31708 Sep 17 '17 at 21:02
  • \$\begingroup\$ @SteveG Thanks, I will get a tip tinner/cleaner and try it. \$\endgroup\$ – user31708 Sep 17 '17 at 21:06
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    \$\begingroup\$ There are tip temperature testers, those should be used to calibrate the temp readouts of the expensive stations. Also try and add some flux. \$\endgroup\$ – ratchet freak Sep 17 '17 at 21:06
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While having a temperature controlled soldering iron is always better, even a standard station like the Weller WLC-100 is more than adequate to perform soldering. There are some excellent suggestions in the comments but I wold also add that you really should use some additional flux. You can get No-Clean flux for general purpose usage or some RA/RMA flux if you work on corroded/exposed wires (i.e. point to point wires, guitar pickups, old electronics etc.)

Most good quality solder has flux inside it so you should double check your solder reel or the website of the manufacturer. If it doesn't have flux, you should get proper solder from Multicore, AIM, Kester or MG Chemicals. Avoid the cheap imitations available on some websites.

So use a tip cleaner as Steve G suggested, clean the tip regularly with a brass wire cleaner like @Bimpelrekkie suggests. Don't be afraid to add flux and make sure you have good quality solder wire.

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  • \$\begingroup\$ Thanks, I have ordered a tip cleaner as suggested. As for the solder, in this particular case I was using this solder. (I don't the brand they're reselling, but I trust Adafruit to have quality stuff.) For thicker solder, I have some MG Chemicals solder that says "RA Flux" and "2.2% Flux". \$\endgroup\$ – user31708 Sep 18 '17 at 19:58
  • \$\begingroup\$ @user31708 yeah, that solder is fine for hobbyist use. Just apply more flux when you solder and then clean the pcb with IPA or flux remover. \$\endgroup\$ – Minho Sep 18 '17 at 20:06

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