--- In
Homebrew_PCBs@yahoogroups.com, "lcdpublishing"
<lcdpublishing@...> wrote:
>
> Hi Guys,
>
> I buy all my PCBs from "Surplus" dealers. Now that I have a bit of
> collection going AND that some of my designs are getting a bit
> more "powerful", the weight of copper is getting important. Does
> someone know what the thickness of copper is for the different weights?
>
> Example 1 oz. copper is .001" thick or something similar
>
> Thanks
>
> Chris
>
I saw the following on a web site and wanted to follow thru on the
math, so here it is:
Density of copper is 8.94 grams / cc. (cc = cm * cm * cm)
Recall that there are 454 grams per pound (3 places, rounded)
Thickness in um =
0.5 * 10000 454
---------------------- * ---- = 17 um
2.54 * 2.54 * 16 * 144 8.94
Some of the numbers used (for reference):
0.5 = ounces/sq-foot (amount of copper)
10000 = um/cm (microns per cm)
2.54 = cm/inch
16 = ounces/pound
144 = square inches/square foot
It boils down to:
oz/sq-ft * 34.16 = micron thickness
(applying a 25.4 um/mil conversion)
oz/sq-ft * 1.34 = mills thickness (thousandth of inch)
A calculator program comes in handy to figure this out, along with
some unit analysis to make sure it all fits.
I saw other references, but this "formula" seems to have some basis on
it. If some of the constants are wrong, feel free to correct them.
One reference indicates a density of 8.92 grams / cc for copper.
As a side note, sometimes I hear on _This Old House_ (the PBS TV show)
the rain gutter workers refering to 20 oz copper stock. Turns out
that those guys measure it the same way, so it is probably a copper
industry standard. I suspect that 1 oz copper wouldn't work in that
application.
Hopefully this will help someone.