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May 2000

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Subject:
From:
"Stephen R. Gregory" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 17 May 2000 14:16:06 EDT
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In a message dated 05/17/2000 12:10:55 PM Central Daylight Time,
[log in to unmask] writes:

<< I believe I have searched through all the latest IPC specifications.  I've
 not found any specific criteria that cover the Design and/or Finished board
 requirements related to external annular rings on Blind Vias, let alone the
 requirements when the design is via in pad for a .8mm BGA.  I believe we are
 in new territory.  Any information would be greatly appreciated.

 Dawn Patterson >>

Hi Dawn!

Did you look in the IPC-A-600F? I know this is the Acceptability of Printed
Boards manual, but maybe by looking at what the minimum acceptable is, you
can design your board so that it meets the minimums (and the the fab vendor
is able to do).

On page 54 when it talks about external annular rings for supported holes,
the minimum required is .050mm (.002") for class 3. On page 55 for
unsupported holes the minimum is .15mm (.00591") for class 3. On page 76 when
it talks about internal annular rings the minimum is .025mm (.000984") for
class 3 (of course that can only be measured by cross section.

-Steve Gregory-

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