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Date: | Fri, 24 Apr 1998 08:22:07 +0000 |
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> From: [log in to unmask]
>
> Example: Assume finished plated through hole size of 0.034+/-0.003";
> minimum annular ring requirement of 0.002"; and, FA = 0.014"
>
> Therefore: P = (0.034 + 0.005) + 0.014 + 2(0.002) = 0.057"
>
>
> Using the information from the above example, I would answer your
> questions as follows:
>
> #1 Maximum finished hole size = 0.034 + 0.003 = 0.037
>
> #2 Value to add to nominal hole size = 0.005 + 0.014 + 0.004 = 0.023
This thread is of interest to me. We don't use a standard formula
here but I would like to try to have one. One of my
responsibilities is to develop a "guideline" (the word "standard"
isn't allowed) on creating component footprints. Right now I can't
justify the pad sizes we are using. If I had a formula I could start
using that and feel beter about the numbers I come up with.
I was doing fine with Mr. Wolf's explanation until he popped in real
numbers. He started with .034±.003". Then he states P = (0.034 +
0.005) Where did that .005 come from? Or was that a typo?
Anyone care to help me? I know it's early, and it's Friday, but
surely someone has a few brains cells they can show off this morning.
TIA,
Jo
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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