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August 2001

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Subject:
From:
"<Peter George Duncan>" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 22 Aug 2001 11:09:51 +0800
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[This e-mail is confidential and may also be privileged. If you are not the
intended recipient, please delete it and notify us immediately; you should
not copy or use it for any purpose, nor disclose its contents to any other
person. Thank you.]
We used to spec 4.5 microinches gold over 150 microinches Nickel for our
ENIG boards, but after too much late night reading of ENIG Blyton Horror
Stories and some soothing remedies, I have specified 5 micoinches immersion
gold over 235 microinches electroless nickel with a 1 micron min surface
finish for the copper and nickel layers prior to the next metalisation. I
have also tried to ensure that the nickel plating bath phosphor levels
aren't too high by requiring that it be between 6% and 8% at time of
plating.

The gold thickness is a compromise between protection of the nickel plating
underneath and minimising gold embrittlement of solder joints. The
increased nickel thickness is to give a thicker barrier to copper
migration. The surface finish spec is to minimise undesirable metallic
interaction, and the phospohor level requirement is to try and ensure we
don't suffer from the dreaded Black Pad and/or reduced solder joint
strength.

Hope this helps for your data collection

Pete Duncan



                    Rick Thompson
                    <rthompson@VENTURAELECTR        To:     [log in to unmask]
                    ONICS.COM>                      cc:     (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
                    Sent by: TechNet                Subject:     [TN] Solder vs Gold Pads on SMT
                    <[log in to unmask]>


                    08/22/01 01:52 AM
                    Please respond to
                    "TechNet E-Mail Forum."






With all the discussion of ENIG, I was wondering if there are any
'standards' as to the thickness of the immersion gold and nickel?  Anyone
care to share what information you spec to your PCB vendor to ensure you
get
the finish you want?

Thanks in advance,


Rick Thompson
Ventura Electronics Assembly
2655 Park Center Dr.
Simi Valley, CA 93065

+1 (805) 584-9858   x-304  voice
+1 (805) 584-1529 fax
[log in to unmask]

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