Good morning fellow designers!

HELP!!!!  As I've stated before I'm still new at alying out boards
and need to ask basic questions.  Today's question is: How do I
determine web thickness, etc for thermal reliefs?

I have three pads tied to ground with a small copper area covering
that corner.  The ground plane is on the component side as well as
the solder side.  (Don't ask me why, it's what our EMC guy wants.)
The pads are .060" dia with a .032 hole.  We have a ±.003" tolerance
on finished hole size and ±.001" minimum annular ring.  I'm trying to
use the formula in IPC-D-275, para 5.3.2.3 but I'm confused.  I only
want one web or do I need two?  Could someone out there in the real
world plug my numbers in and walk me through the steps?

The other designers have used reliefs but there is no established
method to the madness.  I refuse to use numbers pulled out of the
"Millenia Year Application Software System".  For those of you
unfamiliar with this, it was a joke - check the acronym for it.
Excuse the language, but y'all know what I mean.  I want to back up
my designs with some reasoning - silly me!

All answers are greatly appreciated. Thank you once again!!


JoAnn L. Amerson
Design Librarian
Red Lion Controls, Inc.
E-mail: [log in to unmask]
Voice: (717) 767-6961 ext 6308

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