Hi Rudy,

Thanks for your input. It seems like the only explanation. I remember a
similar problem from the old days with immersion gold on copper. When the pH
dropped too low in the gold solution there were orange stains on the gold
surface we called orange peel effect. Adding a little ammonia to the gold
solution made it disappear.

Best regards
-----Original Message-----
From: [log in to unmask] <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>; [log in to unmask]
<[log in to unmask]>
Date: 05 July 1998 15:23
Subject: Re: [TN] Au/Ni/Cu PROBLEM


>In a message dated 98-07-05 03:46:42 EDT, you write:
>
><<
> I am a PCB fabricator in the UK and when we started using the electroless
> Nickel and Immersion Gold process we noticed a curious phenomenon. If the
> panels are immersed in DI water or mains water after processing, then
> exposed to air for a minute or two before drying, the gold has reddish
brown
> stains in random areas. Although this did not seem to affect solderability
> to any noticeable extent, it was not cosmetically attractive.
>
>I would like to have an explanation for this mechanism. The immersion gold
> is 0.15 microns max (6 millionths of an inch) over 4 microns (0.00016") of
> electroless nickel. As this occurs with DI or mains water, contamination
of
> the water does not seem to be a factor, but simply exposure to air at room
> temperature when the surface is wet. >>
>
>
>Paul:
>
>Given the thiness of the EN (and Au), I would bet the problem is likely one
of
>porosity, and having some exposed Copper here and there.  And porosity
driven
>by our industry's great nemisis, galvanic corrosion, would give you exactly
>what you are seeing.
>
>Further, I would bet that thicker EN ( 2-3X) would stop the problem.
>
>Rudy Sedlak
>RD Chemical Company

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