The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Solder flux conductivity problem

What is the conductivity of solder flux, before or after soldering? I want to know if a short could form due to excess flux between two hand-soldered connections. Is there a quick and easy measurement technique? A cleaning technique?

Thanks!

Kevin Gaw
Forensic engineering - Mlt, Washington, USA
2004

It varies with the flux and the environment. Many (most?) fluxes are hygroscopic and will become slightly conductive within hours after soldering. I don't know the numbers offhand, but in one case of replacing a part on a computer motherboard, a new coin-cell Lithium battery (CR2032?) lasted about 3 weeks instead of the usual several years. After cleaning the flux residue, a new battery lasted at least a few years. Another thing that occasionally happens is that a few tiny whiskers of solder get trapped in the flux. With any mechanical stressing they can short-out closely spaced conductors. The above conditions can only conduct a rather low current however, so they may or may not apply to your situation.

Tom Gallant
- Long Beach, California, USA
2004

---

Yes, flux can be conductive and affect your fine pitched component performance.

Most PCB manufacturers use water soluble flux and rinse with warm DI water for cleaning. There are also many flux removers available online made for different flux types. Try searching around places that sell electronic equipment/supplies.

Hung Nguyen
- Latham, New York
2004