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by ipc.org (Smail3.1.28.1 #2)
id m0t8vxm-0000HaC; Fri, 27 Oct 95 16:05 CDT |
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Fri, 27 Oct 1995 15:17:54 -0400 |
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| From [log in to unmask] Sat Apr 27 15: |
15:02 1996 |
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Kevin,
The particular devices that you question are rather large. A full width land
provided too much solder, which tends to place large forces on the component,
resulting in failures of the component.
The Melf patterns contain a slot which tends to hold the melf's location
during the soldering process. The slot, and the solder fillet requirement,
result in a larger land pattern.
The IPC-SM-782 is currently going through a revision. We are attempting to
fine-tune the calculations to reflect the smallest possible foot-print. The
limiting factors are the release EIS and EIAJ specifications for the
component and it's respective tolerances.
You may also adjust the size of the finished land pattern by chosing not to
apply tolerances to the pick and place, fabrication and component numbers,
appearing under the square root sign, in the formulas.
Regards,
Gary Ferrari
Tech Circuits
(203)269-3311
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