Hi JoAnn,

>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.

Take a look at the PCD Magazine May 97. The Designers' Notebook article (by
Mary and Mona) is about holes, and gives the formula. If you can't find the
magazine, let me know and I'll scan the two pages article and send to you.

Regards,

Paulo Egon

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