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
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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
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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
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______________________________ 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]
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