White residue on PCBs?

[Tom41]

On several devices that I've opened up in the past, I've seen a mysterious white residue on the solder side of the PCB. I saw it a lot when I was opening up old game console cartridges to look at the ROM boards, but I have seen it on other electronic devices as well.

It looks rather like someone has spilled a bit of milk on the PCB, and it's just been left to dry and solidify. The residue easily comes off with a damp cloth, and doesn't seem to affect performance when removed.

Does anyone know what this might be? Solder flux? Something leaking into the device? I'd post a picture, but I haven't seen it on any recent PCBs...

[Maxxarcade]

Re: White residue on PCBs?

I get that residue after using flux remover, it's really annoying when you're trying to get a clean "factory" looking PCB after a recap.

I also have that residue on the power supply board of my old video projector. It almost looks like salt crystals, and it's not dust or corrosion, it's something to do with humidity. Maybe I should scrape some off and send it to a lab

[999999999]

Re: White residue on PCBs?

yes, it's water-soluble flux, and unless you live in an extremely humid environment, it can be left on, in that case removing it would only be a matter of asthetics.