At 03:11 PM 2/4/99 -0700, Theodore M. Nathan wrote:
>Hi All,
> I need your in-the-trenches opinions on panalization dwgs. An engineer at
another plant of ours, wants us to include a panalization dwg with our pcb
fab dwg to "reduce cost and provide complete design integrity against a
vendor incorrectly scoring or putting perforating tabs in the wrong place".
I think of this as methodising a process that I don't have to, but I may be
wrong.

I would agree with Mr. Nathan. In general, specifications should control
results, not process; while there can be exceptions if a process can
produce hidden damage, this would be more appropriately controlled by
*limiting* process, not by specifying it.

Specifying the panel size and methods, rather than the desired results,
will frequently result in increased cost because the vendor is not free to
match the process to the vendor's efficiencies. Further, a good process, in
theory, will not necessarily produce better results than a less desireable
process if the vendor is more familiar with the latter, and more able to
control it.

If one is concerned about the vendor "incorrectly scoring," then specify
the board finish and qualities. If the board meets these, why would one
care if the vendor made errors along the way?

There are always exceptions to any rule, including this one. (Don't think
too hard about this. :-)

If one is paying the vendor cost plus, which is pretty unusual now, I would
think, one might want to specify process; even then the process should be
negotiated with the vendor and not simply imposed.

Overspecification is why the proverbial Air Force hammer cost the
proverbial fortune.

[log in to unmask]
Abdulrahman Lomax
P.O. Box 690
El Verano, CA 95433

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