With all due respect Bruce, I believe you just provided a recipe for
disaster. Ken, if I were you I'd do the math and make sure that the gold
wt% is less than 3 wt%. Furthermore, there are cases where even 3 wt%
causes problems due to segregation of the Au-Sn intermetallic phase at
interfaces due to buoyancy in molten Sn-Pb. I've seen embrittlement
failures on 30 u inch electroplated Au.
Best regards,
Ed Hare
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Misner, Bruce
Sent: Wednesday, October 27, 2004 7:32 AM
To: [log in to unmask]
Subject: Re: [TN] Gold Board
Ken,
If you just do an immersion Au (over Nickel), which by process, will give
you less than 10 u inches Au, embrittlement will not be an issue. If you
need the Au to Au wire bond to, 30 u inches Au will do it with out
embrittlement problems. Over 50 u inches of Au and you should start to be
concerned...will depend on the solder joint sizes. You want to stay under 3%
Au by volume (you can calculate it). As Jiri said, "the more Au the more
embrittlement" and it will manifest itself visually as grainy solder, the
more Au, the grainier.
An alternative could be to do a selective Au plate of the 2 pads...cost
issues.
Regards,
Bruce Misner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bloomquist, Ken
Sent: Wednesday, October 27, 2004 9:53 AM
To: [log in to unmask]
Subject: [TN] Gold Board
Good morning TechNetters (at least here on the left coast),
We have a small assembly that requires a couple of pads to be gold plated.
We would like to gold plate the entire board but we're concerned about gold
embrittlement when we solder the components in. The board is completely
through hole and will be both wave soldered and hand soldered.
Do you think we have any concerns? Oh by the way this is a class 3 assembly.
Thanks,
KennyB
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