((nodding my head))) And try buying 1/4 ounce foil... As I stated earlier,
if I order Class I or II 1/4ounce, I could recieve anywhere from .6 to .8,
but most often, bless those suppliers hearts...it would be .6 (or 14% less
than nominal).

While yes the most common nominal dimension would be .7.....tolerance must
be taken into consideration...especially during design and writing
specifications/requirements...

Franklin

----- Original Message -----
From: <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, October 17, 2002 11:22 AM
Subject: Re: [TN] how thick is ½ ounce copper


> There is no "simple" answer... not if I can help it.
>
> The thickness of Metal Foil -Copper- depends on tolerance type: 10% for
deposited and 5% for wrought.  The nominal thickness listed in IPC-MF-150 is
.68 mils.  My opinion follows:
> If I were producing copper foil daily, by the linear mile, it would be to
my economic advantage to produce to the low side.  Hence the propensity is
for the copper to come in the low side of tolerance.  After lamination (at
laminate supplier and or PWB/PCB fabricator) the copper tendency is to
reduce in thickness due to cleaning [cleaning aka etch, or if it is more
palatable "micro etch"], it definitely doesn't get thicker.
>
> It took me a while to adjust downward from .0007 to .0006 but I did, I
feel it represents worse case.  Different treatments and tooth of copper
also factors, but my simple answer is
> half ounce tends to be .0006 inch thick in the deliverable PCB. Exact
measuring will probably be .00061723.
>
> Brad
>
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