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December 2003

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Subject:
From:
Edward Szpruch <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 25 Dec 2003 07:35:00 +0200
Content-Type:
text/plain
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text/plain (64 lines)
Hi,
As far as I remember IPC allow 10% variations in copper thickness.Take into
account that 2 oz is unit based on weight while you are describing
thickness.Add to this topography of the foil from lamination side, thickness
reduction as result of different surface preparation processes - it seems
you need X-mass miracle to get to 4% while you are expecting 0.4%.
Good luck and Happy New Year
Edward


> -----Original Message-----
> From: Carl VanWormer [SMTP:[log in to unmask]]
> Sent: ד דצמבר 24 2003 17:16
> To:   [log in to unmask]
> Subject:      [TN] Question on 2-oz Copper uniformity for current sense
> resistor
> 
> I have a project that seems to be a good candidate for a current sense
> resistor made as a part of the PCB.  I am using the free calculator,
> PCBTEMP, from the UltraCAD website (http://www.ultracad.com/calc.htm) for
> geometry calculations. I need to know the expected variability in
> thickness,
> batch to batch, for the copper foil on 2-oz stock.  I can live with the
> 0.4%
> TC of the Cu, but I need to evaluate all the other variables in my error
> budget before I present my proposal.  I would appreciate any success (or
> horror) stories from people who have (not) used the board copper as a
> current sense method.
> 
> Thanks,
> Carl
> 
> 
> 
> Carl Van Wormer
> Cipher Systems
> 1815 NW 169th Place, Suite 5010
> Beaverton, OR  97006
> Phone (503)-617-7447    Fax (503)-617-6550
> 
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