If you want a conductive aluminum coating take a look at alodine.
http://en.wikipedia.org/wiki/Chromate_conversion_coating  But I'm confused.
 You said chromate coatings were non-conductive... I thought they were?

Gary

On Fri, Feb 10, 2012 at 12:51 PM, Blair Hogg <[log in to unmask]> wrote:

> I've got a slightly off-topic question for Technetters, but I know there
> is probably a few here that would have a good answer.
>
> We are looking at creating shorting plates for use in a self check
> application for our in-circuit test machines. The idea is that we would
> test resistivity of the test probes through a shorting plate on a periodic
> basis to determine when we needed to replace the probes in our fixtures.
>
> I was thinking aluminum, and I don't believe that the small layer of oxide
> that forms would add significant resistance. The oxide may cause some
> problems and the plates may need to be specified to have a cleaning process
> prior to use.  Chromate coatings are non-conductive, and the probe pressure
> probably won't penetrate the coating in a reliable manner if any at all. A
> copper clad board with ENIG plating or Au electroplating would probably be
> better, but cost may be a factor. And since I would need one for every
> fixture I have to match the physical characteristics of the board I need to
> be cost conscious while ensuring adequate performance.
>
> So the question is, would the Al oxides adversely affect performance?
> Would Cu clad FR4 with ENIG plating last long enough as the ENIG is rather
> thin? Any other ideas?
>
> Thanks,
>
> Blair
>



-- 
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