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February 2007

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From:
Seth Goodman <[log in to unmask]>
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Date:
Thu, 15 Feb 2007 12:03:10 -0600
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Steve Gregory wrote on Monday, February 12, 2007 11:11 AM -0600:

> Mornin' All!
>
> What kind of resolution should a LPI be able to give you?
> Specifically, LPI's should be able to give you a solder mask dam
> between 20-mil pitch leads if you have 8-mils of space between
> the pads shouldn't it?

I agree with Michael that most shops I deal with here in the States can
now reliably produce LPI mask dams that are 4.0 mils wide without a cost
adder.  However, most of them also require 2.5 mils clearance to pads
for their standard processes.  This means 9.0 mils between copper pads,
so at 0.5mm lead pitch you end up with 10.7 mil wide pads.  This
normally works out, though you sometimes wind up with no side fillet at
the tolerance limit.

--
Seth Goodman

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