That's Different! He's absolutely correct! The gold plating in THAT area
would be desirable, this is no different than a card edge connector. If the
pad on the board is to act as a connector and they will NOT be soldering to
it, I would highly recommend a gold over Ni surface. To rework, can you
strip the solder from the pads and selective NI/gold plate there... and
still protect the circuitry and components from contact with the chemicals?
One alternative might be silver plating.... silver oxide is still very
conductive... but I don't know if it's an option for the company you are
dealing with...

The risk of corrosion degrading the battery performance has to do with the
contact of the battery to the pad on the board. Humidity in the air can
condense between the nickel plating on the outside of the battery and the
Tin/lead solder on the surface creating an electrolyte between dissimilar
metals.... thus oxidation and corrosion will seep into the contact area over
time, reducing the conductivity between the battery and the board.


Bill Brooks
Senior PCB Designer - [log in to unmask] <mailto:[log in to unmask]>

Zoneworx, Inc.
40925 County Center Drive, STE 200
Temecula, CA 92591
http://www.zoneworx.com    <http://www.zoneworx.com>
Tel: (909) 296-1226 x 1037
Co-Director / Education Officer / Webmaster
for the San Diego Chapter of the IPC Designers Council
http://www.ipc.org/SanDiego/index.html
<http://www.ipc.org/SanDiego/index.html>






-----Original Message-----
From: Ralph Richart [mailto:[log in to unmask]]
Sent: Thursday, June 08, 2000 2:33 PM
To: [log in to unmask]
Subject: Re: [TN] still confused


So here's the deal:

They have two large circular pads (like about .750") that they use as
battery
contacts.  He says that this is the place that he has corrosion risk.  I
can't tell if
the corrosion risk is from battery leakage or environmental effects.
Anyway, he says
that corrosion significantly impacts the battery life.

ralph

David Hillman wrote:

> Hi Ralph! Can you provide more information on what the customer
> considers/experienced "corrosion" and what type of use environment he/she
> was talking about?
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> Ralph Richart <[log in to unmask]>@IPC.ORG> on 06/08/2000 11:55:26 AM
>
> Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please
respond
>       to Ralph Richart <[log in to unmask]>
>
> Sent by:  TechNet <[log in to unmask]>
>
> To:   [log in to unmask]
> cc:
>
> Subject:  [TN] still confused
>
> We have answers....
>
> So I had a long talk with my customer this morning to provide input
> based on the invaluable advice from you all.
>
> I said - "is there a specific reason for choosing 3-8u" of immersion
> gold over tin/lead solder?"
> He said - "absolutely, the gold provides corrosion resistance, the gold
> does not"
> I said - "even such a thin amount - only 3-8u"?"
> He said - "definitely, all we need is the coverage, the thickness is
> irrelevant"
>
> Is this true?
>
> Needless to say, we are rebuilding the parts as we speak.  Rework sounds
> difficult to say the least, although I may try to come up with some
> scheme for fun as they have a bunch of boards that are no good right
> now.
>
> thanks for all the help.....
>
> ralph
>
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