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January 2002

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From:
Graham Collins <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 31 Jan 2002 14:10:39 -0500
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Ahne
The last one is a good point!  We do contract manufacturing of military products.  Currently when I need a stencil all I'm sending out is the paste layer gerber file, and the aperture report.  I'd be nervous sending the full design data out, and I'm sure my customer would be unhappy.  Either we would have to get vendors cleared for security purposes, or we would have to manipulate the data here - which I'd rather avoid doing.   Being able to easily send just a layer of the data is very handy.

This is true for many parts of build - getting pwb's made, stencils, wave soldering fixtures, test fixtures...  yikes!



regards

Graham Collins
Process Engineer, 
Northrop Grumman
Atlantic Facility of Litton Systems Canada
(902) 873-2000 ext 6215

>>> Ahne Oosterhof <[log in to unmask]> 01/31/02 12:19PM >>>
Yikes, sorry, wrong button pushed and there went an unfinished
-mail  ------------

Following is a more finished one:

I have been trying to follow the development of new data standards in this
industry. I have listened to the various interested parties make very
interesting claims about the goodness of their products. But at the moment I
hope that the GenCAM type effort is going to win. Even though I have no
reason to wish that Gerber would go away.

The nice things about Gerber are that it is a very simple standard and I can
read and understand the file. Therefore I can check the content of a file
and fix problems with the data. And I have not yet come across images that
cannot be represented by Gerber data.
The unpleasant things that have happened with Gerber is, that there are
always software designers who can and will "improve" things. And now their
"Gerber-like" output cannot be read by input devices that fully comply with
the Gerber Standard.
Then there are software engineers who design input devices and decide that
certain features and rules in the standard are superfluous and exclude those
from their package. The result is of course that their product at times does
not show results that were in the original fully complying data.

With more complex data standards it is hard to believe that these problems
are going away or are going to be easier to deal with. And the reason that I
lean towards GenCAM is that the effort to develop that standard includes
compliance checkers to help users determine that their output or input files
do indeed comply with the standard. The data format is readable so it is
easier to check what is inside the file and there is intent to assure that
all future versions are backwards compatible. So when I store data I don't
have to store interpreters to go with that specific data.

Next question: when is it going to be ready and is it going to be accepted
widely?

And of course a disadvantage of these new all-encompassing data files is
that I only need the layers that have the information needed to make a
stencil and I don't need (and I really don't want) 25Mbyte of data,
including the information on what parts to buy where and how to build and
test the board. We already have received files that include the little note:
Please destroy files after delivery of stencil !!!

Have fun,

Ahne.
A-Laser, Inc.




* I assume you are comfortable with your system outputting gerber, ---

I would also opt for ODB++ as it can carry a lot more than just bare board
information. ---

The problem I have is in archiving any data object in more than one
ormat  ---

how do you insure that both sets of output data are identical in every
way? ---

If the CAD system doesn't produce ODB++ directly, and most don't ----

we use a third party tool (I use CAM350) to translate into ODB++, either
from the native CAD file or from Gerbers. ---

Producing an output file, either Gerber or ODB++, from a native CAD database
is a translation process. ---

I have yet to own a piece of bug-free software. ---

I know from experience that there are flaws in the Gerber data generators in
most CAD programs. ---

Similarly, different Gerber viewers can display the same data file
differently. ---

if an independent industry group produced a validation suite that a program
would have to pass to call itself ODB++ compliant. ---

Gerber, which is truly a rotten old standard. ---

Until ODB++ becomes as universally accepted by fab shops as Gerber ---

Regards,

From Seth Goodman's e-mail.

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