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April 1999

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Subject:
From:
Hans Rohr <[log in to unmask]>
Reply To:
Date:
Thu, 22 Apr 1999 21:16:41 -0400
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Lee,
The responses you received to your question were very good and the
information at Accusystem's FAQ is correct.  We have used it several
times to settle disputes with our customers.  However, I think we can
get closer to the source of your problem with a bit more information:

1. How are you measuring the board width: edge to edge or edge to some
zero datum point on the board (such as an unplated hole)?

2. Is this a double sided board or a multi-layer board and what is the
nominal board thickness?

3. Is the board scored in one direction only (width) or in two
directions?  You indicated that it was the width that was out of
tolerance.

4.  What is the tolerance now and how far out of 6 sigma is the width
falling.

Our experience as a board fabricator has been that this type of problem
relates more to the dimensional stability of the substrate than the
actual scoring equipment itself.  Most scoring operations are performed
in panel form and the panel is held in the machine at one end on tooling
holes.  If there is a dimensional shift in the panel length and/or width
after hot air leveling (and there is always some) the score line spacing
will be correct but the score line position relative to a datum feature
may be out of tolerence.

Hans Rohr

Lee PengSoon-CPL035 wrote:
>
> Hi all,
> We are have problem on oversize pcb width due to the bad cpk of the v-cut
> location.
> what is the v-cut tolerance should be set so that it is 6 sigma achieveable?
> Any industrial standard??
>
> Regards,
> Lee

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