Black wire corrosion of electrical conductors 2

[smaher]

I have seen a problem with copper wires turning black after a system level cyclic damp/heat test.
The wires are inserted into a plastic (PBT?) header and soldered into a PCB using a no-clean flux and PbSn solder.
The possible potential on the wires is 5 volts.
I have managed to find reference to this form of corrosion on radio control aircraft sites but have not managed to find any reference to the mechanism.
Any pointers to possible sources of information would be greatly appreciated.

 

[TVP]

ASM HANDBOOK Volume 13 Corrosion would be one place to look. You can order it from ASM International (

http://www.asminternational.org)

or try to find a reference copy at a good university library.

 

[bilge]

This type of corrosion happens commonly on the positie post of automotive batteries. Its known as the "black post problem."

I've been able to alleviate the problem by painting the post with asodium-silicate solution, what old farm kids will remember as "egg saver."