I have been using my Keithley 617 Electrometer to measure the leakage current of large Electrolytic capacitors for several years. It has an internal +-102VDC source for biasing the Capacitor Under Test.
I was working on an error budget and I needed to know the actual leakage current of some small filter capacitors. I ran into some surprises with C0G ceramic caps and PE film caps.
The AVX and TDK C0G caps are very low leakage. Other brands of C0G have 20x more leakage and a large Dielectric Absorption. To be fair the leakage of the other caps is within their specifications. However, if you want some very good caps, see the attached pdf.
I do not have the time or budget to test all available brands and configurations. This is just what I have measured.
NOTE: This article is just to caution you to check all your components before you use them in critical applications. I just did a sample from one batch of parts. I may have a bad batch or a great batch of parts.
I looked into some WIMA film capacitors and was surprised at the rated leakage currents. I simply had not researched them before.
The WIMA MKS2 data sheet states >1000 Megohm-uF for the 6.8uF 50V part. I take that to mean over 147 Megohm or less than 68na of leakage at 20 deg C at 10V. Well, that’s a lot more than I assumed.
When I checked the WIMA MKS2B046801M00JS, 50V 6.8ufd small red film (Polyester film, PE) cap they 30 minutes it has 1500pa of leakage with just 10V applied at 27 deg C. After 12 hours the current had settled to 650pa of leakage. With 50V it had 22,000pa after I let it settle for 30 minutes.
I spent the next week checking a wide selection of new small capacitors. Then of course, I had to expand the testing to two temperatures.
When I warmed the MKS2 cap to 60 deg C (the temp in circuit) the leakage was 5.5na at 10V. With 50V it was 259na, wow.
A physically larger Panasonic 100V 10uF ECQ cap (PE) had 50pa a 10V. This settled to 10pa overnight at room temp. At 60 deg C the leakage current was 150pa at 10V.
What are your experiences with small (<100uF) capacitor leakage current?