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| Reply To: | TechNet E-Mail Forum. |
| Date: | Wed, 29 Jul 1998 16:09:03 -0700 |
| Content-Type: | text/plain |
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Hello all!
I getting ready to start making SMT footprints, and now I am faced with the
dilemma of picking a fabrication allowance to use in my land pattern calcs.
(Luckily I already know the placement accuracy value to use)
I am in a catch-22 because we don't know which board manufacturer we are
going to go with until we have some proto stuff to show them, but I need to
know which manufacturer we are going to use in order to have their fab
allowance built into my lands.
The IPC-SM-782 throws out a couple numbers to use, such as a .4mm average,
a .2mm average, and in their pattern calculator a .1mm average.
What is your advice on a number to use? Is .1mm realistic, or is that
considered best-case (high $)?
Dazed and confused,
Mike
( ( ( ( ( (~) ) ) ) ) )
Mike Spencer
Integrated Design Group
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