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Subject:	Re: solder paste with 2% silver
From:	Werner Engelmaier <[log in to unmask]>
Reply To:	TechNet E-Mail Forum.
Date:	Fri, 27 Jul 2001 16:59:09 EDT
Content-Type:	text/plain
Parts/Attachments:	text/plain (37 lines)

Hi All,
First, Motorola did not invent the BGA, only the PBGA in the form ofthe
OMPAC. Bell Labs had ceramic BGAs in the 1982/3 timeframe, but never
commercialised the packages, and IBM certainly had CBGAs prior to Motorola's
OMPAC.
62/36/2 has a somewhat higher strength than 63/37 and 60/40, but properly
wetted SJs of either solder have more than sufficient strength--so this
difference is immaterial in reality.
62/36/2 has a somewhat creep resistance than 63/37 and 60/40, but that is
only of importance if the temperature cycle dwells are short, as in
accelerated testing--most product experience dwells long enough that this
difference is immaterial in reality.
The non-eutectic 62/36/2 has a somewhat Liquidus temperature than eutectic
63/37 and near-eutectic 60/40--in most applications a lower Liquidus is of
advantage. But ternary alloys have eutectic combinations too, not just binary
alloys; and of course, if you want a pasty range all you need to do is go to
Sn/Pb ratio further removed from the eutectic than 60/40.
This is in addition to what Dave Hillman wrote, which is very good input.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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