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August 2000

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Subject:
From:
Jeff Seeger <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 4 Aug 2000 20:05:59 -0400
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Darrel Therriault wrote:
>
> TechNet Designers,
>
> I was looking in IPC-SM-782 and IPC-D-279 and didn't find anything specific
> on BGA pad guidelines.
> I see in the IPC Technical Info book that there is an amendment 2 that
> addresses BGA pad design.
>
> While I am getting that amendment ordered, is there any standard "rule of
> thumb" for pad size
> relative to ball diameter on 1.27m and 1.0m BGA's that should be followed,
> or that you have found to be
> useful in designing boards with BGA devices?

        I like Motorola's appnote AN1231, which basically espouses
        using the same pad size as the bottom of the substrate.

        Problem is that dimension is not often provided so you
        may have to call you chip vendor's AE to get it, unless
        it's a standard package and you have access to Jedec std 95.

        IPC 782 amendment 2 seems to lean from this dimension to
        20% smaller.

        HTH,
--

      Jeff Seeger                         Applied CAD Knowledge Inc
      Chief Technical Officer                  Tyngsboro, MA  01879
      jseeger "at" appliedcad "dot" com                978 649 9800

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