I know using flux makes some residue which makes unwanted contacts between components pins. I dont have any washing liquid or spray to remove it so i simply decided to not use them.

But my solder wire has a solid flux layer. while soldering with it, some melted flux splashes around, makes some white smoke too.

After soldering is done, two separated material remains on board

First a glassy solid residue which will break under pressure like sugar!

Second some greasy appearance around soldered areas.

enter image description here

Unlike lotfett soldering grease its residue is not conductive. However i don't know much about it just tested myself.

I need to know about this material. Shall i remove it? Is there any way to remove it from the board?.

I created this question to be some kind of reference for the mentioned product.

  • 1
    \$\begingroup\$ A search for that grease yields: Not suitable for electrical engineering and electronics. (Contains zinc chloride, irritant). Don't ever use it. Wash your board thoroughly with water, alcohol. Then let it dry well before powering. I'd guess that the crystalline residue is safe to leave on the board. \$\endgroup\$
    – glen_geek
    Jan 29, 2019 at 17:26
  • \$\begingroup\$ @glen_geek i did not use any soldering grease any more .just use solder wire with some unknown material. Producers calls it flux. \$\endgroup\$
    – payam_sbr
    Jan 29, 2019 at 17:29
  • 2
    \$\begingroup\$ Flux is a chemical substance that eats away the oxidation layer that metals form when in contact with air. Without it, it'd be much harder to actually solder things together, because that non-metallic oxide would be in the way. \$\endgroup\$
    – Hearth
    Jan 29, 2019 at 17:32

1 Answer 1


There are solders with no-clean flux that you can leave on, but the solder you linked to looks like it has the conventional kind of flux core which should be cleaned off.

You can use a spray can of flux cleaner and a small brush (a toothbrush works great) or you can just use some 90%+ isopropyl alcohol in place of the spray can.

The flux isn't conductive, but can cause long-term problems if left on. The glassy residue is just excess flux, and the "greasy" substance is likely burned flux and condensed water vapor.

  • \$\begingroup\$ Thanks alot. With second option(isopropyl) how many seconds i should left the circuit in alcohol? As you may saw the picture, The circuit is messy (chock-a-block) i can't use brush for unacessable parts \$\endgroup\$
    – payam_sbr
    Jan 29, 2019 at 17:46
  • 1
    \$\begingroup\$ It's hard to give an exact number of seconds. You can try it and inspect for residue after. The spray may be worth getting as it's usually pretty high pressure and can remove flux from areas that are hard to brush. If you have a Fry's Electronics nearby they sell it. \$\endgroup\$
    – John D
    Jan 29, 2019 at 18:40
  • \$\begingroup\$ Sorry for delay, finally i bought a washing liquid plus a general purpose sprayer which makes an acceptable pressure. \$\endgroup\$
    – payam_sbr
    Feb 5, 2019 at 8:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.