Scott,
This is another "Technology specific" value.
The registration tolerance doesn't effect your
"feature to feature" value since it is on the
same side.

However...the values that do effect it are,
etch tolerance, film scaling, material scaling.

Etch tolerance won't effect feature center to
center, but rather the edge to edge. This value
is dependant upon copper thickness. 1oz external
(really 1.5oz) is about +/-.001, 2oz is about .0015-.0020
etc.

Film scaling runs about +/-.001 per inch.

Material scaling is about +/-.0005 per inch.

All this depends on environment and the manufacturer.
Using a mfg that uses the direct imaging may reduce
the tolerance.

Both the film and material scaling are usually measured
at the finished product in terms of tolerance.

That brings up something else. SM pitch is usually noted
for testing. For untested boards pitch isn't critical but
pad width and spacing is. (equiv. of trace and space)

HTH.

Chris Robertson
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> I am looking for the standard industry locational tolerance of copper
> feature to copper feature on a single sided PCB. Since PCB
> fabrication is a
> photographic process, I am assuming it is a function of
> gerber plotter and
> artwork imaging.
> TIA,
>
> Scott Buscomb
>
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