At 11:37 AM 9/14/99 -0700, Jim Dobbins wrote:
>We have inherited an smd parts library where the pad shapes
>are all rectangles. Our past practice has been to use pads
>with rounded corners. The sm782 land pattern calculator at
>http://search.ipc.org/SM782/default.asp
>has notations that state 'full radius preferred' for smd
>part pads.
>
>Is there is significant difference/risk in choosing rectangular
>pads over those with rounded corners?

My old version of SM782 has nothing but rectangular pads; they seem to be
far more common than rounded corner pads, so they can't be *too* bad.
Theoretically, a square pad might have a greater tendency to peel off of
the board, but that is probably not significant, and there might be effects
at high voltages or frequencies, also not usually much of an issue. There
are two other differences that I can think of:

Rounded corners can give some extra routing space.
Rounded corner pads are not a standard Gerber flash shape, so they can lead
to some confusion in plotting. The corner radius should be specified if
rounded corner pads are to be used.

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Abdulrahman Lomax
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