Be sure to note that the 3-8 microinches that Tracy calls out is much less
than the minimum 50 microinches that IPC-D-275 Table 3-8 calls out.  There
has been a large shift in the use of Gold as a replacement for solder which
has not been reflected in the IPC specs. (OK, OK, The IPC guys will
probably prove me wrong, but I haven't found it in my small cache of
Specs.)

A lot of this shift is due to getting fine pitch pads flat, PWB
solderability  shelf life issues, no clean solder process improvements, and
to a (much) lesser degree the pursuit of an enviromentally-friendly
"unleaded" PWB.

Steve,
When will the snows start in New South Wales?  Have a great winter!  ;-)

  ====================================================================
                           George Franck
  PWB Product Assurance                     Phone (703) 560-5000 x2648
  E-Systems M/S N408                              Fax   (703) 280-4613
  7700 Arlington Blvd                  E-Mail: [log in to unmask]
  Falls Church Va 22046                      E-Mail: [log in to unmask]
  ====================================================================


>You're going to need to spec a nickel underlayer (barrier and soldered to)
>and a max gold thickness to prevent voiding and gold embrittlement of solder
>joints.
>
>We spec that the nickel be an electroless nickel/immersion gold process be
>used and that the nickel thickness is a minimum of 100 microinches followed
>by 3 - 8 microinches of 99.9% gold.  The gold is also soft, <90 Knoop, and
>can be wire bonded to.  This gold finish is a Type III Hardness Grade A
>strike according to MIL-G-45204.
>
>The immersion gold process is electroless but self limiting, nickel is
>displaced and replaced by gold.  As soon as the surface layer of nickel is
>no longer exposed, the plating process comes to a halt.  Depending on who/what
>PCB shop or chemical supplier you talk to, the resultant gold thickness is in
>the 2 - 12 microinch range.
>
>Tracy Tennant
>[log in to unmask]
>
> ---------- Start of forwarded message ----------
>
>                                                              Message#   802373
>                                                        24-APR-1996 06:42:42.00
>From:   [log in to unmask]
>To:     STHUMMEL,TTENNANT,[log in to unmask]
>Subj:   Re: Gold Flash on PWB's
>
>
>Received: from micron.co by BOGEN4 Wed, 24 APR 96 06:42:13 MDT
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>Subject: Re: Gold Flash on PWB's
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>
>     STEPHEN,
>                IPC-D-275 SECT 3.8.4.3 (SOUNDS LIKE A STAR DATE DOESN'T?),
>     CONTAINS INFORMATION ON GOLD PLATING.  ALSO REFERENCE SECTION 3.8.4.4
>     ON NICKEL UNDERPLATING.  TABLES 3-8 AND 3-9 WILL GIVE YOU AN IDEA OF
>     WHAT YOU NEED FOR YOU'RE END PRODUCT.  AS TO WETHER IT'S WORTH IT, YOU
>     MUST CONSIDER YOUR END USAGE AND THEN TALK WITH YOU'RE FAB HOUSE.
>        REGARDS,
>
>     ROB BUTTERWORTH
>     SR PWB DESIGNER
>     ADC VIDEO SYSTEMS
>     999 RESEARCH PARKWAY
>     MERIDEN, CT 06450
>     [log in to unmask]
>
>
>______________________________ Reply Separator
>_________________________________
>Subject: Gold Flash on PWB's
>Author:  [log in to unmask] at internet-mail
>Date:    4/24/96 2:52 AM
>
>
>Can anyone supply a specification to call up when requesting a Gold
>Flash finish on a PWB and is it worth it today, with the advances
>with the HASL finishes.
>
>Regards
>
>Stephen Cooper
>Manufacturing Projects Manager
>SCITEC LIMITED
>Apollo Place
>Lane Cove NSW 2066
>Australia
>PH  : +612 428 9500
>Fax : +612 428 9589
>Email : [log in to unmask]
>
>
>
>
>