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 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu