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May 1997

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Subject:
From:
Paul Gould <[log in to unmask]>
Date:
Fri, 9 May 1997 20:49:22 +0100
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 [log in to unmask] writes
>   I am interested in PWB fabrication panel sizes for utilization
>calculating.
>I would like to know what is the standard, favorite, best suited,
>or practical for calculating fabrication utilization.
>But as some of you know with the range of PWB sizes, not everything
>fits a 18 X 24.
>   What are some of the various used in the industry with success
>for through put. 14 X 24??
>
>rich

Hi Rich,

If you are standardising your production panel sizes, it is important to
ensure they cut out of a standard sheet size with no waste. The supplier
will charge for any waste by inflating the panel price so you may as
well take the material.

Find out what sheet sizes are available from your laminate supplier and
then you can work out which panel sizes can be cut from them. There are
many permutations.

For multi-layer panels, there are considerably more types of material
thicknesses and cladding so you do have to limit the number of standard
panels. Also, tooling is expensive so you don't want to have too many
options.

Calculate the optimum production panel size for a given job, this must
include the separation between circuits, and the borders for plating and
tooling. Then check what standard panels are available to suit.

If you select the best standard panel for a given job, but find that
there is a significant amount of waste material, you are better off
removing that waste before production otherwise you are adding material
value to scrap. I estimated as a rule of thumb that it was worth
removing the waste material if it was more than 2" on length or 1.5" on
width. ie the cost of cutting the panels was offset by the saving in
material cost eg dry film, solder mask ink, plating or etching chemicals
etc,.

The main point is that the optimum panel size should be selected for
efficient production, with any significant waste removed at the outset.
There is no need to be tied solely to the standard panel sizes for
production.

Best Regards
-- 
Paul Gould
[log in to unmask]
Isle of Wight,UK

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