Here is guideline I received from the PWB manufacturer:

"The minimums for 4 oz outers:  6 mil space (will finish ~16 mils after
etch) and 18 mil traces (will finish ~8 mils after etch).
The minimums for 3 oz inners:  6 mil space (will finish ~13 mils after
etch) and 15 mil traces (will finish ~ 7 mils after etch).

Please note that these if you design to these values, then we will not
beef up to account for etch factor.  You must take into account a
reduction annular ring also; ~1.3 mils per side per ounce.  So if the
design starts with 15 mils of annular ring on the outer layer, then the
finished annular ring will be ~ 9.8 mils."


Veronika Anderson, C.I.D.
Senior Electrical / Mechanical Designer
 
PerkinElmer Optoelectronics
1330 East Cypress St.,
Covina, CA 91724
Phone: (626) 967-9521 X 236
E-mail: [log in to unmask]
 
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-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Babcock John
Sent: Wednesday, August 16, 2006 9:46 AM
To: [log in to unmask]
Subject: [DC] Etch Factor Design Guidelines

I have a question.  Did you ever develop good guideline numbers for
trace and space when dealing with etch factor?

I've been hearing all kinds of different (minimum) trace/space numbers
lately when dealing with different copper thicknesses.

Cu Thickness    Trace           Space

0.5oz                5          5
1.0oz                8          8
2.0oz                12         12
3.0oz                20         20
4.0oz                25         25

Are these in the ballpark with your guidelines? 


John Babcock, C.I.D.
PCB Designer III
Phone: 509.241.4641
www.spraycool.com

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