Mike,
     
I would estimate that 75%, if not more, of all fabricators in the states have 
the capability to fabricate .005 lines/spaces in a production mode.  The problem
may be with your fabricator.  I'm not aware of of too many PCB shops that can 
not fab .005/.005.  The game changes once you go beyond this point.  I found 
most of my fabrication problems occured at .004/.004 and .003/.003 lines/spaces.
What has successfully worked is .004/.006 lines/spaces, respectively.  The 
spacing is the driving force behind getting good conductor walls and minimizing 
overetching.  The additional spacing allows for the etch chemistries to 
sufficiently etch copper in the tracks (valleys) and be replinished efficiently.
The chemistries used to etch are isotropic, meaning they etch in all directions 
proportionally.  What I observed on .003/.003 and .004/.004 lines/spaces is 
severe undercut, conductor slivers and bridges.

This is not to say .003/.003 and .004/.004 lines/spaces can not be obtained.  
The fabricator must have the necessary equipments, chemistries and process 
controls in place to do so.  I know of several in the inductry that are fab'ing 
.003 and .004 lines and spaces in volume, but at a premium.  If you need 
assistance, I can probably recommend several fab houses in your region for your 
current .005/.005 requirement.  Hope this helps.


John Gulley 
Inet Inc 
1255 W. 15th St 
Plano, TX 75075-7270


______________________________ Reply Separator _________________________________
Subject: Standard PCB/PWB Trace Width's
Author:  "Michael Forrester"<[log in to unmask]> at Internet
Date:    7/18/97 5:38 PM


     
     
     
     
We currently design boards with 8 mil. traces.  We have recently tried to 
go to 6 mil. traces and found that we had reliability problems from batch 
to batch.  What is the smallest trace that is considered reliable by todays 
standards?  Is it just our PCB/PWB manufacturer that may have a problem. 
Typically what we saw was over etching of the traces.  Thank you.
     
Best Regards,
     
Mike Forrester
LeCroy Corp.
[log in to unmask]
     
     
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