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March 2003

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Wed, 12 Mar 2003 08:28:13 +0800
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Hi, Andre,

I don't think the aperture lists have any direct bearing on how wide the
traces and spaces turn out to be. I once had some boards where the traces
were much wider, and the traces much narrower, than they shoudl have been,
simply because the fab house over-estimated its etch-back tolerance - i.e.
the final etch took off much less material than the fab house thought it
would.

How do the spacings between traces compare with the sizes intended by the
design? If they're narrow, the above isprobably your answer and not the
aperture list.

Peter



Andre Leclair <[log in to unmask]>    11/03/2003 08:54 PM
Sent by: TechNet <[log in to unmask]>

Please respond to "TechNet E-Mail Forum."; Please respond to Andre Leclair

              To:  [log in to unmask]
              cc:  (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
              Subject: [TN] Aperture Data








Morning all

I have a question regarding Aperture List for Gerber Data.  This is an area
I know little about so bare with me.
We had an incident with a PCB house which resulted in the boards being
manufactured with all traces/pads 0.020" bigger then they were supposed to
be.  The shop said the problem arouse do to the way the aperture list was
set up.
The list has a set of 24 station #s with dimensions (which I understand get
translated to d-codes).  These Station#s are then repeated further down
plus have extra #s to 999.  We noticed that some of the dimensions in the
2nd set of station #s are differant from the 1st set. The 2nd set are the
correct #s.
The shop tells us their software (Infinite Graphics) will import the 1st
set then ignore the 2nd set of repeated #s then will continue to import any
station #s that are differant.
When we look at the Data with GC-Place and look at the used Apertures we
get the correct values.
Could the error be due to a differance in the way the software interprets
the list?..
The customer's data was created using P-Cad at least 10 years ago.  The
format the Lists are in are the same for all the customers product.  A
previous PCB shop had no reported difficulty.

Any ideas would be helpful
Thanks
Andre

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