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

From: steve weir <weirsi@xxxxxxxxxx>
To: Steven Waldstein <swldstn@xxxxxxxxx>
Date: Sun, 22 Aug 2010 19:29:19 -0700

Steve, very high impedance circuits (1 TOhm) have typically been built 
on substrates like Teflon with very rigid cleaning requirements.  With 
an adequate cleaning process, and good circuit design:  I highly 
recommend active guard rings, you should be able to deal with 1 GOhm 
without too much trouble.


Steve.
Steven Waldstein wrote:
> 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 Weir
IPBLOX, LLC 
150 N. Center St. #211
Reno, NV  89501 
www.ipblox.com

(775) 299-4236 Business
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References:
- [SI-LIST] PCB materials, solders, and components for VERY HIGH impedance applications
  - From: Steven Waldstein

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

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