Werner, at least we agree, even if you pipped me to the post by a few
minutes! :-)

Brian

Werner Engelmaier wrote:
> Hi Rudy,
> Your explanation sounds good, but is incorrect--it is not the surface
> roughness that is the problem, it is the variability of the ED copper density. The
> specific gravity (density) of ED copper is less than the specific gravity
> (density) of rolled copper because of organic co-deposits and micro-voids. This
> uncertainty in specific gravity (density) prevents a direct conversion of oz./ft2
> to thickness, and that is why ED copper is specified in oz./ft2.
> The reason weight is used in specifying copper foil is because copper is
> bought and sold by weight.
> So, foil vendors sell copper foil by weight; the laminators resell the foil,
> laminated to epoxy, by area. Want to guess how much foil is produced near the
> upper weight tolerance for any given foil weight class?
> None of thus of course excuses the lazy stupidity in this country that has
> killed the use of the metric system time and again.
>
> Regards,
> Werner Engelmaier
> Fornercahairman of IPC Copper Fopil Committee
>
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