Buried Capacitance In PWB

Hadco offers a technology of building in a "buried" capacitance layer (& other embedded passives) in organic PWBs (FR4 for example). see http://www.hadco.com/prod03.htm and a design manual is posted here: http://www.hadco.com/pdfs/bcguide.pdf I am coming up to speed with this technology, trying to understand the pros and cons, limitations, costs, assembly concerns, etc. Does anybody have any experiences to share on this technology? I would like to consider using this technology with high speed digital devices packaged in BGAs.

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| Hadco offers a technology of building in a "buried" capacitance layer (& other embedded passives) in organic PWBs (FR4 for example). see http://www.hadco.com/prod03.htm and a design manual is posted here: http://www.hadco.com/pdfs/bcguide.pdf | I am coming up to speed with this technology, trying to understand the pros and cons, limitations, costs, assembly concerns, etc. | Does anybody have any experiences to share on this technology? | I would like to consider using this technology with high speed digital devices packaged in BGAs. | It ain't no big deal. I was introduced to this stuff years ago. Basically, the capacitance planes are patented, if you can believe that, core material. That is, the board shop of choice buys simple, plain old core material, in a specified thickness for specified capacitance requirements and puts it into normal, impedance controlled MLB constructions.

The buried resistor stuff was created by a now defunct material supplier years ago as well. Simply it is a resistive material placed into the MLB construction. The resistors are similar to those used in Hybrid thick film circuitry - right down to the trimming process.

Both materials work in certain applications. For the real scoop, go to the material laminators who make it all. You know, Polyclad, GE, Fortin, Nelco, Isola, etc.

Earl Moon

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