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Date: | Fri, 29 Jun 2012 18:41:06 +0000 |
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For that THICK layer of Au it does. Honestly, I don't remember seeing any component with that thick Au plating.
One should also keep in mind that bulk percentage of Au in a solder joint may be "deceptive". All it takes is to have enough Au in a narrow band to form Au-Sn intermetallics and cause Au embrittlement.
Regards,
Vladimir
SENTEC Testing Laboratory Inc.
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca
-----Original Message-----
From: Steve Gregory <[log in to unmask]>
Sender: TechNet <[log in to unmask]>
Date: Fri, 29 Jun 2012 14:05:33
To: <[log in to unmask]>
Reply-To: TechNet E-Mail Forum <[log in to unmask]>,
Steve Gregory
<[log in to unmask]>
Subject: [TN] Gold Embrittlement Calculator
Hi All,
Gonna' be another hot weekend here in the Northeast! Mid 90's all weekend
long with heat index up around 100.
Anyways, I found this excel spreadsheet calculating percentage of gold in a
solder joint that was created by Melissa Lau of Lockheed Martin. The link to
it is here:
http://circuitsassembly.com/cms/magazine/95/3630_
I'm just wondering if I'm using it right. For instance I'm trying to
determine what the gold percent is for an 0402 resistor pad on a board that
has 19 microns of gold on it and using a 4-mil thick stencil.
I looked at a Vishay data sheet and I get a lead termination of roughly
10-mils long X 20-mils wide X 14-mils high. The next input is for lead
plating, there's already a .5-mil input there so I'm just going to leave it
at that. I can't find what the lead plating thickness should be in the
datasheet.
The opening in the stencil is 23-mils X 25-mils and it's a 4-mil thick
stencil, so I have to change the formula in the cell under the column
"Solder Paste Wt" since it's based on a 6-mil thick deposit. The gold is
19-microns thick, so that converts over to .748-mils.
What I wind-up with is a solder joint with 36.5% wt in gold! Does that sound
right?
Steve
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