Dear Steve Allen,
[EMAIL PROTECTED] on 2001-05-30 11:49:51 AM
>I'm defining our internal process for designing SMT land patterns. Our
...
>I don't understand
>how to specify the Grid Placement Courtyard (i.e. the silk-screen outline).
...
>Steve Allen
Good question.
There seem to be 2 groups of Protel users:
(a) Make the silkscreen exactly the same size and shape as the actual body of
the component. Use several design rules to give adequate clearance between
components.
(b) Set the only component clearance design rule to give 0 mm spacing between
components. Make the silkscreen so much larger than the actual component that,
when the silkscreen of neighboring components just touches (or overlaps), they
have adequate clearance. (Brian Guralnick was the first person I saw doing
this.)
I was just using the
IPC-SM-782 Land Pattern Calculator
http://search.ipc.org/sm782/
today.
It told me ``PLMT GRID: 4x12'' for the component I looked up, which I think
indicates a silkscreen of 2 mm by 6 mm. But what does this mean ? It's much
bigger than the actual component size, so it's not like (a). But does this mean
I can make a big grid of this component 2 mm center-to-center one way, 6 mm
center-to-center the other way, like (b) ?
--
David Cary
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