Doug McKean wrote:
>
> Does anyone know if gridding a ground plane
> under a trace of controlled impedance increases
> or decreases by having to actually work with this?
>
> I can guess and theorize all day long...
> My guess is that since there's more distributed
> capacitance with a solid ground plane, that
> increasing the grid pattern of the ground will
> lower the distributed capacitance thus INCREASING
> the controlled impedance.
>
> big snip <
>
> Is this old stuff being hashed out again?

        Well I lack definitive experience but have found that
        you're not alone.

        In the newsgroup sci.electronics.design this very same
        topic is being debated, relative to techniques for in-
        creasing the impedance of a flex circuit.

        The opinions there agree with your expectation of a mesh
        causing an increase in impedance, for the same reasons
        you cite.

        The only caveat to surface thus far is a quote from
        Howard W.Johnson and Martin Graham's "High-speed Digital
        Design" advising against this technique but perhaps from
        the perspective of _large_ grids such as found in two
        layer boards.

        I believe the module community is doing more with this
        type of geometry than the traditional rigid board world,
        perhaps there would be more experience from the substrate
        folks, "somewhere".

        Good luck,
--

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

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################