[log in to unmask] wrote:
>
> Kieth,
>
> I thank you. My concern is what the "average" top 10% board shop can do. I know this is a loaded
> question, but we have serious problems concerning a near 5 mil gap between a trace running parallel
> to a 432 ball perimiter BGA pad pattern with obvious shorting/bridging problems. On about 50% of our
> boards, received from a "top 10" shop, conductor edges are visible causing shorting, without serious
> touchup (with silk screen epoxy hand applied goop) efforts.
>
> I believe what you say. I know in my heart, as I have wittnessed it first hand, what you say can be
> done. You say routinely and I do not question, but how routinely and under what conditions? What
> kind of controls, or process management efforts, must be employed from photoplotting through resist
> stripping?
>
        Hi, Earl -

        Sorry to hear of your plight(s).  I have seen quite a number
        of shops delivering consistently covered traces given a five
        to six mil oversize on the soldermask.  Same roster has no
        trouble keeping mask off of the soldered land at that sizing.

        I wonder how large is the opening you're seeing wrt to the
        land size?  Did the designer specify too large an opening?
        I have also seen CAM groups apply too large an oversize rule,
        and while I've seen CAM systems drc soldermask to minimums I
        don't know if they universally also drc to maximum....

        Best of luck!
--

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

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