George, I gotta disagree. If this is the case, why didn't we include a finish like this in our alternative finishes study. And why is it not discussed in the classic texts on soldering and board fabrication. I always assumed that the copper did diffuse through the gold and it did oxidize and quickly became unsolderable . . . If the fluxes are that good at reducing copper oxide, why use a finish at all?

Nickel does not diffuse into the gold. So, it remains protected and solderable, for a while.

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
> Sent: Wednesday, August 14, 2002 10:18 PM
> To: [log in to unmask]
> Subject: Re: [TN] corrosion on gold flashed PCB's
>
>
> Why would you think the copper beneath the 6-8 microinches
> would corrode?  If you're not using a nickel barrier to
> prevent copper diffusion my guess sould be that the copper
> from beneath would diffuse to the surface and oxidize when it
> is exposed to the enviornment.  But then again the fluxes and
> sodler paste being used are usually formuated to reduce
> copper oxide so why worry.
>
> -----Original Message-----
> From: Ray Klein [mailto:[log in to unmask]]
> Sent: Wed 8/14/2002 8:41 PM
> To: [log in to unmask]
> Cc:
> Subject: [TN] corrosion on gold flashed PCB's
>
>
>
> Guys,
>
> We use 6-8 micro inch of gold flash over copper on our
> surface layers.
> Mostly these areas are covered with solder paste and don't
> cause a problem.
> We are considering using large areas of the board as heat
> sinks without
> solder paste and are concerned with corrosion of the copper
> underneath this
> very thin gold layer. Has anyone tested for or had experience
> with this?
>
> Ray Klein
>
> JNI
> 10945 Vista Sorrento Pkwy
> San Diego, CA 92130
>

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------