DESIGNERCOUNCIL Archives

March 2006

DesignerCouncil@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"Jack C. Olson" <[log in to unmask]>
Reply To:
(Designers Council Forum)
Date:
Wed, 15 Mar 2006 21:45:24 -0600
Content-Type:
text/plain
Parts/Attachments:
text/plain (61 lines)
I have never thought about this until now,
but I'm confused about something...

Many times I have been asked to put a slot
in planes to isolate different areas of a PCB
from each other, almost as part of the floor-
planning. So in other words a power supply
area might be isolated from a digital processor
area by putting an air gap between them, or
maybe between primary and secondary of a
transfomer, or maybe the 3mm clearance
you put under an opto-isolator, right?

on the other hand...

Recently I have been asked to start building
"via fences" between areas, like stitching
ground planes together, and even been asked
to start putting a line of vias all around the
perimeter of the board, too. And flooding ALL
layers with copper and adding MORE vias to
stitch THEM together. In the past I have
used via stitching a lot, but it was for things
like guard traces along RF lines (1.67GHz
cellular signals) and occasionally along the
edges of shields. but not like this.

so...

Today a discussion came up whether to use
air gaps or via stitching, and I had a total brain
freeze. In my mind they both had the same
reason for existence, keeping things from
interfering with each other. But of course in
reality they are the exact opposite of each
other; one method adds conductors and the
other removes them.

Now I can't seem to grasp what I am missing
about this.

There's noise in my head.

So can someone please help me understand
when to choose one over the other, if at all?

(and hopefully the answer will be shorter than
the question?)

Jack


---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
---------------------------------------------------------------------------------

ATOM RSS1 RSS2