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June 2003

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Subject:
From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 2 Jun 2003 07:22:39 EDT
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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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