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December 1998

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Subject:
From:
Jeff Seeger <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 7 Dec 1998 15:26:04 -0500
Content-Type:
text/plain
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> On Mon, 7 Dec 1998, CONKNET wrote:
>
> > Successful test of .030 micro-bga's on traditional (bed of nails / grid)
> > equipment is reliable and not too difficult to achieve. It does not require
> > "double density" grids. It does require good fixture design. Test of 30 mil
> > BGA's typically requires 3.75 inch multi-plate fixtures with 12 or 16 mil
> > piano wire pins.  Some care needs to be given to the Z axis load created by
> > the test pins on thin boards. Although Pin Tilt can approach or exceed 1
> > inch, the pad size on BGA's make a big target relative to 15 mil QFP device,
> > so targeting is not normally an issue.
> >

        This technique has already saved the industry, or at
        least bought "this much" time.

        Probable knee breaker is the proximity to the next like
        device, cascading across a 12" board.  Pray for peripheral
        arrays and adequate device-to-device pitch? ("But the parts
        fit!")  Is there a guideline pins-per-square-inch-per-side-
        times-board-area where this technique saturates?

        When and where is the parasitics-based testing technology
        going to come rescue this situation?  Haven't heard a peep
        on this for maybe a year, but I'll confess I haven't been
        looking.  Promised to work on a probe-once-per-net basis
        rather than all endpoints.  Or how about the "touchless"
        radiation/excitation?

        Regards to all,
--

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

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