Werner,
Is the same true for smaller components?
We are using mostly 0402 components. We have experienced, in the LF
soldering experiments, lack of self alignment of the components. That is
- if the component is located off-position, it will stay right were it
was placed, hence being held only by portion of the area. Further -
misalignment of the printing, if to the other opposite of the placement
error, will reduce the holding area further. My experience is that
designing a land bigger than the leg compensate ay least partially for
the process inaccuracies.
Regards
Ofer Cohen
Manager
Quality Assurance, Reliability and Production Technologies
Seabridge Ltd. - A Siemens Company
Siemens COM FN A SB
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Monday, June 13, 2005 11:42 PM
To: [log in to unmask]
Subject: Re: [TN] Ceramic MLCs and Leadfree, John Maxwell case?
Hi Ioan,
Well actually, the landpattern would be the size of each of the
metallization
projections; about 60 mils wide and 20 mils long times two, of course.
You would inspect those solder joints the same way you inspect the
solder
joints of BGAs--you do not. I always found it curious that people want
to design
things so they can be better inspected, not that they function bettter.
Remember, the J-lead/gullwing arguments?
First, the CCs would swim up--the solder has nowhere to go. Second, many
of
these chips are glued anyway. Third a soldermask dam underneath the CC
serves
well.
Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
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