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January 2001

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Subject:
two traces between 39 mil spaced via's ???
From:
Stuart Adams <[log in to unmask]>
Reply To:
DesignerCouncil E-Mail Forum.
Date:
Tue, 9 Jan 2001 13:59:44 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (62 lines) 
I have a dense design with many 1mm pitch
BGAs on a small board. The fanouts from
each BGA form a grid of via's spaced 1mm (39.3 mils) apart.

In order to be able to route the board I need to be
able to run two signal traces between the vias.

        39 mils
   <------------>
        |  |
 (VIA)  |  |  (VIA)
        |  |
     (two traces)

Which is the most manufacturable way to do this ???

Option #1
---------
  5 mil traces and spaces
 10 mil drilled via hole in 14 mil pad (6-8 mil finished hole size ?)
  7 mil from drilled hole edge to unrelated copper

Option #2
---------
  4 mil traces and spaces
 11 mil drilled via hole in 19 mil pad (7-9 mil finished hole size ?)
  8 mil from drilled hole edge to unrelated copper

Option #3
---------
  4 mil traces and spaces
 12 mil drilled via hole in 19 mil pad (8-10 mil finished hole size ?)
  7 mil from drilled hole edge to unrelated copper

Is there a better option than one of these ??

(This is a standard .062" 12-14 layer board)

Thanks,
  Stuart

---------------------------------

Stuart Adams
Bright Star Engineering Inc.
19 Enfield Drive
Andover MA 01810 USA
Tel: +1-978-470-8738
Fax: +1-978-470-8878
Email: [log in to unmask]
Web: http://www.brightstareng.com/

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