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 >Received: from is04.micron.com by micron.com (SMI-8.6/SMI-SVR4) > id GAA01635; Wed, 24 Apr 1996 06:41:51 -0600 >Received: from simon.ipc.org ([168.113.24.64]) by relay.micron.com with >SMTP id > <185386>; Wed, 24 Apr 1996 06:42:11 -0600 >Received: from ipc.org by simon.ipc.org via SMTP (940816.SGI.8.6.9/940406.SGI) > id HAA28011; Wed, 24 Apr 1996 07:40:35 -0700 >Resent-Date: Wed, 24 Apr 1996 08:40:35 -0600 >Received: by ipc.org (Smail3.1.28.1 #2) > id m0uC3AT-00007KC; Wed, 24 Apr 96 06:55 CDT >Resent-Sender: [log in to unmask] >Old-Return-Path: <[log in to unmask]> >From: [log in to unmask] >Date: Wed, 24 Apr 1996 08:01:25 -0600 >Encoding: 38 Text >Message-Id: <[log in to unmask]> >To: [log in to unmask] >Resent-To: <[log in to unmask]> >Resent-To: <[log in to unmask]> >Resent-To: <[log in to unmask]> >Subject: Re: Gold Flash on PWB's >Resent-Message-ID: <"LqCG41.0.HA9.mQXVn"@ipc> >Resent-From: [log in to unmask] >X-Mailing-List: <[log in to unmask]> archive/latest/3607 >X-Loop: [log in to unmask] >Precedence: list >Resent-Sender: [log in to unmask] > > 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] > > > > >