Subject: | |
From: | |
Reply To: | TechNet E-Mail Forum. |
Date: | Fri, 29 May 1998 13:09:07 -0500 |
Content-Type: | text/plain |
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I think the concern is intermetallic compound formation with attendant
brittle failure. You better do some home work. It might be possible to
qualify the joints, but I doubt anyone would want to risk it.
Pat Hogue
Materials and Processes
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From: Kevin Minney[SMTP:[log in to unmask]]
Reply To: TechNet E-Mail Forum.;Kevin Minney
Sent: Friday, May 29, 1998 10:38 AM
To: [log in to unmask]
Subject: [TN] ADVICE ON GOLD/JOINT EMBRITTLEMENT
Dear Sir/Madam,
I wonder if you can help, please forgive me for emailing you directly I
was unsure as to whether
the Technet forum was open to the 'general public' for posting ..
I stumbled across an article that a Mr Bill Fabry had posted to the
Technet forum
regarding gold and embrittlement. I am working on the design of a single
board computer and have designed in a surface mount connector which I am
now told by the manufacturer (Samtec) that they can only supply with a
gold finish. Our main customer for this board is a defense contractor
and our own in-house rules (derived I assume from military standards) is
that all connectors with a gold lead finish must be solder dipped prior
to assembly onto the board. Our board is FR4 with tin/lead finish on the
pads. So far two sub contractors have failed to solder dip these
connectors, and even if they did succeed there would likely be a
co-planarity problem.
here is an extract of Bill's original posting to the Technet Forum ..
>>SNIP
From: "Bill Fabry" <[log in to unmask]>
Subject: Re: Re[2]- Electroless Ni/Im
To: [log in to unmask], "Thad McMillan" <[log in to unmask]>
Reply to: RE>Re[2]: Electroless Ni/Immersion A
Thad:
Based on a reliability report generated by HP: If the gold content is
less
than 2% of the resultant solder joint volume, no appreciable solder
embrittlement will occur. Therefore, the VOLUME of gold on ANY pad must
be
less than 2% of the resultant solder joint VOLUME, or ~1% of the VOLUME
of
solder paste applied to that pad. (e.g. if 0.005" solder paste is
applied, gold
thickness should be < 50 micro-inches.)
>>SNIP
Could you please advise, or refer me to someone who is able to advise on
the following ..
Q/. could I apply your guidelines to my connector or is it specifically
only applicable to a gold finish on the board ?
Q/. Could you give me a contact where I could acquire this HP
reliability report ?
many thanks, in anticipation,
Kevin Minney
----------------------------------------CUSTOMER FIRST, QUALITY ALWAYS
KEVIN MINNEY DY 4 Systems Inc **** ***
senior designer 333 Palladium Dr M/S 317 *** * *** *** ***
Kanata, ON ** ** ** *** *** *
Tel: 613-599-9199 x208 Canada * *** * *** *** **
Fax: 613-599-7777 K2V 1A6 **** *** ***
Email: [log in to unmask] ***
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