[SI-LIST] PCB materials, solders, and components for VERY HIGH impedance applications

To all,

I'm wondering if anyone has experience with PCB boards for very high
impedance application (i.e > 100 GOhm). I'm learning about Isolation
Resistance on capacitors and realizing that surface mount capacitors
might only offer ~ 1e9 ohms of isolation. I'm now beginning to think
about PCB materials as well. What kinds of leakage is there on FR-4?
Do I need to worry about this as well. I also have been told that the
right solders and fluxes need to be used as well along with good
baking to ensure all trapped moister, which can lower the impedance,
is used as well. Anyone have any experience with these as well and can
recommend the proper types. Any and all help is appreciated.

The application is a sensor that has a very low capacitance for AC
coupling, a very high impedance input is used to ensure a very low
highpass corner.

Thanks in advance for any help

Steve
-- 
Steve Waldstein
E-mail: swldstn@xxxxxxxxx
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