Low leakage capacitors

[Paul]

Hi,

I'm trying to find the lowest leakage capacitor, somewhere in the
range of 0.01uF to 1uF, *might* be able to live with 0.001uF, for DC
use. I'm not sure if PTFE (teflon) is the best choice, but here's one
-->

http://www.cde.com/catalogs/MCM-MIN.pdf

It says, "Insulation Resistance: 1000 M¥Ø*¥ìF Need not exceed 100,000 M¥Ø
at 25 ¨¬C" What exactly do they mean by "Need not exceed 100,000 M¥Ø" ?

Also I heard polystyrene is good.

I've performed various RC time constant tests on caps by placing a
voltage source on the cap for a period of time, removing the voltage
source and time it, then measure the DC voltage after a certain time
period, and calculate the parallel resistance. It appears that the
longer the voltage source is held on the cap results in more parallel
resistance-- possibly dielectric absorption.

So this makes it more difficult to find the best type of caps for this
use. IOW, perhaps one cap might have less leakage after 1 minute, but
after 10 hours perhaps another type of cap might have less leakage.

I'm looking for a cap that would contain as much charge as possible
for about one day. The voltage levels are around 1 volt.

Any help is greatly appreciated!
Paul

 

[Baron]

Hi,

I'm trying to find the lowest leakage capacitor, somewhere in the
range of 0.01uF to 1uF, *might* be able to live with 0.001uF, for DC
use. I'm not sure if PTFE (teflon) is the best choice, but here's one
-->

http://www.cde.com/catalogs/MCM-MIN.pdf

It says, "Insulation Resistance: 1000 MΩ*μF Need not exceed 100,000 MΩ
at 25 ºC" What exactly do they mean by "Need not exceed 100,000 MΩ" ?

Also I heard polystyrene is good.

I've performed various RC time constant tests on caps by placing a
voltage source on the cap for a period of time, removing the voltage
source and time it, then measure the DC voltage after a certain time
period, and calculate the parallel resistance. It appears that the
longer the voltage source is held on the cap results in more parallel
resistance-- possibly dielectric absorption.

So this makes it more difficult to find the best type of caps for this
use. IOW, perhaps one cap might have less leakage after 1 minute, but
after 10 hours perhaps another type of cap might have less leakage.

I'm looking for a cap that would contain as much charge as possible
for about one day. The voltage levels are around 1 volt.

Any help is greatly appreciated!
Paul

Have you considered glass !

 

[Baron]

I know I hadn't, but it's a cool idea:
http://www.avx.com/docs/techinfo/perform_gl.pdf

Post back and lets know how it goes.

 

[[email protected]]

re : lowest leakage caps :
a high voltage film like teflon or polysulfone would be ok if space is
not a problem.
Otherwise ELNA makes low leakage caps the size of regular RB and RT
electros,
specifically designed for timing circuits.

jcdrisc