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May 2000

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Fri, 5 May 2000 06:08:19 -0400
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you may want to check IEEE Transactions on Components and Packaging
Technology Vol 22, pp.139-140: J.E. Morris "Forward, Electrically conductive
adhesives and underfills (special section intro)".  You get Morris' address
as well as latest infor on conductive adhesives..;-)
                                  jk
At 12:57 PM 5/4/00 +0200, you wrote:
>I have fired this very challenging and hard-to-get-answer question before,
but as I'm not much wiser I do it again. If anyone has the e-mail adress to
James E. Morris at Binghamton, I would be glad to have it, lost it a year ago.
>
>Now, as all know the conductivity of e.g. silverepoxy changes little around
certain fill factor, let's say 70%, but below that, a dramatic change will
occur, exp change and finally abrubtion in the electrical joint. At
microwave freq the skin dept in silverepox and in a homogenous conductor are
dissimilar, therefore, a good thumb rule is to make the silverepoxy
conductor sq root of 10 thicker than the metal dito. The cause is the ratio
of Ag-metal/Ag-organic, being approx. 10. A TechNet guy named Richard
somwhere in the US used to apply similar  'home made'  formulas, but I have
lost his identity, maybe he will see this mail and respond once more.
>
>In RF circuits, good ground (current return) is vital for many applications
where RF chips are used up to 70 GHz. If you solder the chips, there use to
be no trouble, but epoxying, that's something else. Mike Joyce, Carey and
many fellows know a lot of the conducting mechanisms in such matrixes, maybe
I can get some pearls from them also. This was the background to my question
that follows:
>
>Anyone with praxis from silverepoxying large chip mounting and multiGHz
applications? Do you have appointments on the  AC conductivity vs, inherent
curing, fill factor, geometry and suppliers in the game? What are your
requirements on voids and wetting percentage, meniscus and other possible
factors that have paramount impact on said RF parameter (current return).
Father Gilleo couldn't give very good answers, so I see one is in the
few-mans-land.
>
>If you think this topic is too far from PWB and like TechNet things, maybe
I can get a knock on the door offline?
>
>Said
>
>Ingemar Hernefjord
>Ericsson Microwave Systems
>
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