Jon,
there is possibly a misconception here about electrical test,
especially for Proto boards. Did you give them an electrical netlist derived
from your database? If not then this is probably what occurred.
They received your files, used their CAM software to generate a
netlist, however sounds like their CAM software may have misinterpreted some
of the Gerber data for one reason or another. Then they used that generated
netlist complete with the error(s) to test the boards and they all tested
fine. I am sure that you can see what is wrong with this scenario, it relies
on them reading and interpreting your Gerber data correctly. Result, they
may have been tested and they would have tested fine. Sounds like this could
have been the source of your open shorting links as well.
A secondary issue exists for the virtual jumpers, they are opens as
far as your netlist is concerned so if you did send an electrical netlist
the boards should have all failed the test because of the virtual short
where your netlist said there was no connection.
With the shorting links I would not be surprised if those were the
result of some over eager CAM operator who spotted the virtual short,
thought it was an error where the data was off by a factor of about 20 so he
adjusted your virtual shorts to something that would etch out in processing
( I believe you said 4 mils). You must understand that they could possibly
detect the 0.00005" gap with their software and think that they were
supposed to be legitimate opens. I believe that Abd ul-Rahman stated one
time that he sends a readme file to the fabricator which tells the
fabricator that these virtual shorts exist so that they understand what is
going on if they do spot them.
In all fairness to the Fabricator, you should check the Gerbers you
sent him and make sure that the error(s) were not already present in your
Gerber data. If they weren't, then you had a problem with the fabricator and
their interface to your data. I have never met a fabricator yet who didn't
want to get it right the first time.
An old acquaintance, who happens to be Chinese so imagine a strong
stereotypical Chinese accent, used to tell his customers. "Old Chinese
Confucius saying, good no cheap, cheap no good! So you want good or no
good". 8^>
Brad Velander,
Lead PCB Designer,
Norsat International Inc.,
#300 - 4401 Still Creek Dr.,
Burnaby, B.C., V5C 6G9.
Tel. (604) 292-9089 direct
Fax (604) 292-9010
website www.norsat.com
> -----Original Message-----
> From: Jon Elson [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, June 27, 2001 2:47 PM
> To: Protel EDA Forum
> Subject: Re: [PEDA] How do I modify the design rules to allow
> a shorted
> li nk to gnd?
>
>
>
> I used the 'low bidder' to see how they were, and had some problems.
<SNIP>
> But, if the fabricator accepts payment for electrical test
> without doing it,
> who knows WHAT they do in the photoplotting department!
>
> Jon
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