JoAnn about the trace widths it is or should I say was true, about price
going up as the trace with and trace  spacing went down.
About 2 year ago, A board shop I used to deal with Would charge more for 8/8
width/space as opposed to 12/12 however if you talk to them and ask them
first, it could be possible that they could do 10/10 with no penalty in
price.
You also have to understand that in large volumes, the board fab house would
scrap a lot more boards at 8/8 than at 12/12.
I have talked to a few board shops and it seems that 10/10 is pretty much
the norm.
Now 8/8 it is still a bit higher in price. You might get lucky and find a
board shop that won't charge a premium for that kind of spacing.

Patrick Jabbaz
Halliburton Energy Services
Circuit Board Designer
(281) 596-6697
[log in to unmask]

-----Original Message-----
From: JoAnn Amerson <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Monday, April 13, 1998 1:31 PM
Subject: [DC] Trace width


Once again I turn to you pleading for help.  The "powers that be" are
requiring us to use a 12 mil wide trace as a minimum unless we
absolutely cannot because of lack of space.  It seems our board
vendors have difficulty meeting a width and trace at 8/8.  My pleas
to look into other vendors fall upon deaf ears.  "They're too
expensive!", they cry.  So we pay the price over-designing our
boards.  Our boards are predominantly low current, low voltage.  8
mil usually is more than enough but......I'm sure you've all run into
this argument at one time or another.

What I'd like to hear from everyone are reasons why we *shouldn't*
use a wider trace than necessary - if there are any.  Other than it
takes longer to route a board with wider traces.  They don't care
about that.  What documentation can I offer to them to make our lives
just a tad bit easier?  Or am I lost in wishful thinking?

And also, today's dumb question:
I know that spacing between traces is governed by voltage and the
width is governed by current load and temperature rise above ambient.
If I use a 12 mil wide trace, can I still maintain an 8 mil wide
space to the next trace?  Assume it meets the spacing for that
voltage.  Or is the spacing always at least track width?

I appreciate any and all responses on these issues.  :-)

Jo

JoAnn L. Amerson
Design Librarian
Red Lion Controls, Inc.
E-mail: [log in to unmask]
Voice: (717) 767-6961 ext 6308

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