Film and Ceramic Capacitor Leakage Current - Page 1
Forum section: electronics / general

author: chuckb
author_rank: Frequent Contributor
timestamp: June 14, 2020, 04:42:23 am
content: 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?

author: bsw_m
author_rank: Frequent Contributor
timestamp: June 14, 2020, 11:23:51 am
content: Time ago I'm measured leakage of elcap Epcos B41859 100uF 35V. After 1 hour this cap has leakage 180nA at rated voltage and 11nA at 10V.I can add measurement results as they are carried out.To measure I'm using V7-49 electrometer.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 14, 2020, 04:48:26 pm
content: It is really difficult to tell apart true leakage and dielectric absorption. The settling over time is a characteristic of dielectric absorption current. When testing with an applied external voltage source, one also has to care about drift of the voltage source - this would look like additional current.A way to separate leakage from DA would look like first recording the apparent leakage with voltage applied to the capacitor, keep the capacitor charged for a longer time (e.g. 10 x the initial test, e.g. over night) and than discharge the capacitor and measure the apparent current from charge recovery after the same time. The 2 nd current would be a approximately (lower limit) to the DA contribution in the first test.I have tested few small (2.2 nF) C0G and PP , PS caps and found about comparable DA. The TDK brand C0G was considerable (e.g. 5-10x) lower DA. Over the time scale tested (100 µs to 40 ms) the DA is dominating over leakage.Polyester film is way higher DA than PP or C0G. So it can take considerably long time (e.g. more like days) to really see leakage.

author: bsw_m
author_rank: Frequent Contributor
timestamp: June 14, 2020, 05:35:45 pm
content: Murata RPER71H104K2S1A03A after 5 hours settling time: 29pA at rated voltage. But this cap have big DA.

author: bsdphk
author_rank: Regular Contributor
timestamp: June 14, 2020, 05:55:03 pm
content: When I did something similar, I found that a lot of the actual leakage was crepage across the exterior plastic surface of the capacitors.Wash the capacitors in isopropanol and distilled water and measure again, without touching them with your fingers.The lowest leakage I found were high voltage (>=500V) wide lead-spacing (37.5mm) film capacitors.Art of Electronics has useful wisdom on this topic.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 15, 2020, 01:42:35 am
content: A few other data from John Larkin:https://www.dropbox.com/sh/m0m2zjljysms4yc/AACA2-BIGYDgHNRQN0PuaQOAa?dl=0Tim

author: chuckb
author_rank: Frequent Contributor
timestamp: July 03, 2020, 10:58:10 pm
content: Here are the results from 6 more capacitors I tested.I checked a TDK X7R, lots of leakage and DA.The leakage current for the KEMET X8L capacitor did not change much with temperature. It was high all the time. The leakage current for other caps typically changed 5-10x when the temperature changed from 31C to 61C. The X8L leakage current only changed 3x. The current seemed to settle quickly like it did not have much DA but it may have just been the high leakage hiding the DA.The WIMA Polypropylene cap (MKP4) had much better leakage (100x less) than the WIMA PE (MKS2) units.The leakage of the 1.8u Panasonic PE caps compared to the 10u version was reduced by a factor of 5 as you would expect.I checked a new Nichicon 63V100u1000uLow Leakage Electrolytic cap,UKL1J102KHD. After 1 day at 7.15V it had an steady state leakage of 10na. Then I did a day at 63V to form the dielectric. After I discharged and reapplied voltage the 7.15V leakage was 1.4na.

author: chuckb
author_rank: Frequent Contributor
timestamp: August 16, 2020, 04:08:35 am
content: One addition this time. It is a Wurth 0.033u, 50V, 1812 package. With it's low capacitance it achieved a very low leakage current.I corrected the capacitance of the Nichicon low leakage cap in the last post.

author: TiN
author_rank: Super Contributor
timestamp: August 16, 2020, 06:29:55 pm
content: I can also share my old results withwet slug tantalum XTVcaps. It's the same cap that Jim Williams used in AN124 preamp.Cap #1, XTV138T030P4L = 1.2 nA, 10V bias, measured by Agilent 41420A SMUCap #2, XTV138T030P4L = >50 nA, 10V bias, measured by Agilent 41420A SMUCap #3, XTV138T030R4L = 2.8 nA, 10V bias, measured by Agilent 41420A SMUCap #4, XTV138T030R4L = 3.5 nA, 10V bias, measured by Agilent 41420A SMU

author: dietert1
author_rank: Super Contributor
timestamp: August 16, 2020, 06:42:59 pm
content: Connected a Wima MKS2 6u8 50 V, fresh from the bag. Exponential decay stopped at about 1,8 nA. After about 3 hours it sits at 480 pA, which is a confirmation of the original post. Ambient is 25 °C and i used a 1 MOhm resistor to measure the current with a FLUKE 8600 in its 200 mV range (resolution is 10 pA).Regards, Dieter

author: bsw_m
author_rank: Frequent Contributor
timestamp: November 30, 2021, 06:40:47 pm
content: Some new measurement for Wima MKP4 capacitors and Epcos B41858C5477M000 100uf electrolytic capacitor.All info in attached graphs.Also if You need more data, I'm attached raw data (first column is time in unixtime format, second column - current).All measurement done by my V7-49 electrometer.

author: mzzj
author_rank: Super Contributor
timestamp: November 30, 2021, 07:23:43 pm
content: Tested at 10 volts:22nF OLD stock Suflex polystyrene: 0.3 pA and the measurement is starting to get quite sketchy. (would need some shielding or I have to sit quietly without moving)1.5uF 400v Wima MKC 4: 2pA after couple of minutesAnother 1.5uF 400v Wima MKC 4: 3pA (lazy to wait)Philips MKP 1.8uF 250V <4pAEvox MMK 4.7uF 100V 40pAMMK(polyester) is behaving just like expected with 10x leakage current(or DA, didn't wait for ages)

author: bsw_m
author_rank: Frequent Contributor
timestamp: November 30, 2021, 10:29:25 pm
content: Wima MKP4 4.7uF test at 50V

author: David Hess
author_rank: Super Contributor
timestamp: November 30, 2021, 11:37:46 pm
content: I have tested low voltage polypropylene capacitors for leakage at high temperatures and found considerable variation between manufacturers. For a 0.47 microfarad capacitor, I needed less than 10 picoamps of leakage at 150F or so. If you are looking for characteristics which are not guaranteed in the specifications, then this is just what you have to do.

author: bsw_m
author_rank: Frequent Contributor
timestamp: December 01, 2021, 12:23:25 am
content: David HessThanks for Your reply.I am not looking for any special capacitor at the moment.I make these measurements out of curiosity (and perhaps, as a reserve for the future, if I need a component with any characteristics that are not indicated in the datasheets, I will know which components should be paid more attention to). And also in order to share with the public. For the same reason, I provide not only the leakage current data at the end of the component measurement, but also the complete measurement graph. Perhaps this information will be useful to someone.Unfortunately, I am not able to measure a large number of samples of the same type for two simple reasons - they need to be purchased, it takes a lot of time to measure them.

author: JohnG
author_rank: Frequent Contributor
timestamp: December 01, 2021, 01:43:52 am
content: Quote from: David Hess on November 30, 2021, 11:37:46 pm150F!?! That musta been a hella big polypropylene capOh, wait, I should read more carefully...

author: David Hess
author_rank: Super Contributor
timestamp: December 01, 2021, 12:48:22 pm
content: Quote from: JohnG on December 01, 2021, 01:43:52 am0.47 microfarads was quite big enough in a polypropylene part.

author: bsw_m
author_rank: Frequent Contributor
timestamp: December 17, 2021, 01:37:45 pm
content: Hitano 0805N101J500NT. 100pF 50V NP0 capacitor. (8fA leak at 10V after 3 minutes).In this test, I did not shoot the graph. 3 minutes after applying the test voltage of 10V, the current through the capacitor was 8fA.With a test voltage of 50V, the leakage was 55fA

author: serg-el
author_rank: Regular Contributor
timestamp: December 27, 2021, 02:47:28 pm
content: After molding 12.2 V for 16 hours.Self-discharge.Not ceramic and film. Electrolytic and solid state.For comparison and preliminary assessment.

author: bsdphk
author_rank: Regular Contributor
timestamp: December 27, 2021, 05:07:27 pm
content: Have you measured the leakage of the protoboard you are using ?I would expect that to account for a relevant part of your result.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 27, 2021, 05:13:40 pm
content: The prototype boads are often not that bad with leakage. I have not measured it directly, but the leakage currents can be quite low ( pA range). So with the electrolytic capacitors this is likely still to a large part leakage of the capacitors and maybe the input current to the meter to measure the voltage. For the initial phase (e.g. less than 20% drop) the dielectric absorbtion in the capacitors can also be an important factor.

author: ZhuraYuk
author_rank: Regular Contributor
timestamp: January 25, 2022, 07:18:35 pm
content: Here is the leakage of two 10uF polypropylenes from WIMA and JB capacitors. The WIMA is 4 times more expensive than JB.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 25, 2022, 09:25:26 pm
content: Much of the current seen with the PP caps could still be from dielectric absorbtion. It is at least hard to tell from the curves shown.At least the intial part (e.g. the first 15 minutes) it quites clearly something transient and not really leakage.

author: MiDi
author_rank: Frequent Contributor
timestamp: February 21, 2022, 05:26:05 pm
content: Bit OT:1000µF 50V 85°C Panasonic series M-A @10V is down to 1nA after 3 days.Leakage current can be approximated by a * t-bafter ~2s (and to at least 3 days), which corresponds to a straight line in a loglog plot.

author: chuckb
author_rank: Frequent Contributor
timestamp: December 07, 2022, 01:24:14 am
content: Continuing this thread. Attached is some more testing I did while locked in for COVID.The leakage of film caps (maybe all caps) is nonlinear with voltage.For example my favorite Panasonic ECQ series 10uF, 100V Polyester cap.Changing the bias voltage from 10v to 50V results in 5-6 times more leakage.Changing the bias from 50V to 100V causes 8 times the leakage.Some spark gaps were tested with fa leakage.

author: Echo88
author_rank: Frequent Contributor
timestamp: December 07, 2022, 09:37:40 am
content: Very nice, thanksI set up my K617-testbox last week again also to measure some more FETs, caps and SSRs.Is it possible to get your list as an excel-file/similar, to which i could add my measurements? Just if thats okay for you.

author: 3roomlab
author_rank: Frequent Contributor
timestamp: December 07, 2022, 10:06:50 am
content: I entered some of the data from various threads here and there (mF=1000uF)I included some supercaps (datasheet values)And there is the uA/Farad leak column value for rough comparisonThe UKL 2.2mF is really something*the ECQ-E1106 in the list is 100v (2uA/F), the 250v E1106KF would have 0.8uA/F

author: chuckb
author_rank: Frequent Contributor
timestamp: December 09, 2022, 08:23:25 pm
content: Quote from: Echo88 on December 07, 2022, 09:37:40 amHere is the Editable file.AddChange the date at the end of the file name so we can keep track of versions.Add you name on the left column if you add an entry.I use a Keithley 617, if you use something else make a note in the comment column.An organized person would probably have a seperate TAB for each dielectric.Thank you for contributing.Chuck

author: chuckb
author_rank: Frequent Contributor
timestamp: December 09, 2022, 09:38:54 pm
content: Here's the file.

author: chuckb
author_rank: Frequent Contributor
timestamp: December 10, 2022, 05:00:15 pm
content: When you "form" the dielectric of an Electrolytic capacitor does it stay formed? Can you form a batch of capacitors then put it on the shelf till you need it?I attempted to answer that question with a Nichicon low leakage 2200ufd 16V cap. This cap took about a month at 16v for the leakage to reduce from the 1 day value of 200na to less than 20na. This was at 32 deg C. Higher voltage rated Nichicons (63v and 100v) seem to form within a week.For this cap I applied rated voltage for 20 days, applied 0v while traveling for 2 weeks, then reapplied rated voltage for 10 more days. Within a day of reapplying voltage the current was the same as before I shut it down for travel. So the Dielectric Forming was not lost.Then I tested leakage at 10V. The leakage dropped from 17na to 4na as the voltage changed from 16V to 10V, and a few more days passed.I will check this same capacitor for leakage next year, if I remember.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 10, 2022, 08:08:59 pm
content: The build-up / degradation of the dielectric layer is expected to be a little asymmetric, especially as the idele state is with zero voltage and not a reversed voltage.AFAIK the formation is from genrating new oxide layer by oxidation. The degradation is more by the formation / groß of holes (e.g. at defects / grain boundereies) in the oxide layer by movement of oxide to a different, slightly more favorable position near by. So the 2 processes are quite different. Normally the formation should last quite long, like a few years, but things can vary with temperature and type.The other superimosed effect is the dielectric absorbtion. This part should be similar for charge / discharge - here the 14 days off can reverse most of the effect of 20 days under voltage.

author: Echo88
author_rank: Frequent Contributor
timestamp: December 30, 2022, 02:30:51 pm
content: Attached is the reformatted file from chuckb, with added measurements from my side.I hope i didnt delete or change any measurement-infos that belonged together from chuckbs-measurements.The measurements take a lot of time, so i havent added much yet. The list may contain errors.The leakage current/capacitance column was just done by me to have some figure of merit when intercomparing capacitors.Especially measuring film-caps in the µF-range have shown to be really difficult as even a roomtemp-stability of +-1°C is apparently enough to mess with the pA-measurement due to K617-TC and filmcap-TC: the current measurement then reads for example -40pA because the cap has a slightly higher voltage.Usually i use a 33M-resistor in series with the capacitors, as thats necessary to get stable low current noise readings. What resistor and procedure do you use chuckb?Forming some 400V electrolytic caps meanwhile and measuring some supercaps for additional fun.

author: bsw_m
author_rank: Frequent Contributor
timestamp: January 01, 2023, 09:47:09 am
content: Quote from: Echo88 on December 30, 2022, 02:30:51 pmHello! I'm use this setup for these measurements. Best if diode have leakage current as low as possible.The resistor may vary from 10kOhm to 1MOhm.

author: chuckb
author_rank: Frequent Contributor
timestamp: January 27, 2023, 04:32:53 am
content: Quote from: Echo88 on December 30, 2022, 02:30:51 pmMy setup includes a large metal cast box, an RC filter for the Applied Voltage and two Kapton heaters to change temperature.I use a a Hammond 1550H enclosure, it is roughly 100mm tall, 140mm wide and 200mm long. The current output connector is a Triax connector with two small alligator clips on the inside. Smaller caps are suspended in mid air by the connector leads. Larger caps rest on a teflon sheet covering the bottom of the box. The metal cover of the box has to be fastened down or a weight applied to keep it from moving. Any moving metal will add noise to the readings.The Excitation voltage from the K617 passes through a 200k resistor and a 100ufd PE cap for 20 sec of RC filtering. This reduces the apparent current flow caused by voltage noise on one side of the cap. All charging and discharging of the cap under test happens through the 200k resistor.The metal box sits directly above the K617 to keep the leads short. The triax is fixed in place so it does not move around and cause noise.I attached two round 75mm dia. kapton heaters to the outside of the metal box. At 10V they draw 2 amps total. This 20W of heat raises the box temperaure up to 63 deg C. If the box is 63C the capacitor inside will eventually reach 63C. I usually wait an hour for the cap to catch up to box temperature before I start a test. The box is covered with a heavy cloth for insulation. I measure the box temperature with a handheld Fluke Termocouple thermometer. I do not try to measure the capacitor temperature directly as this would upset the current leasurements.With smaller caps the meter input current temperarily changes when the K617 changes ranges. With some caps, if I leave it in Auto Range, the meter can go into RANGE oscillation. For these caps I watch the display and manually change the ranges. The meter could use a little more hysterysis on the Auto Range change.I have a Agilent GPIB to USB adapter and software to collect and store the data from the test.

author: ArgyllGargoyle
author_rank: Contributor
timestamp: February 12, 2023, 06:01:39 pm
content: Have you tested any tantalum capacitors for leakage?I recall having good luck with the orange Vishay Tantamount variety (e.g. 597D family).

author: chuckb
author_rank: Frequent Contributor
timestamp: February 14, 2023, 08:58:12 pm
content: In general, Tantalum caps have a lower leakage current than normal aluminum electrolytics. I have checked several Tantalum caps and I'm finishing up a week of looking at one right now. I will update the list in a few days.I'm testing a 35V 6.8uF, series 150 from Vishay (Sprague). The leakage current is very nonlinear with applied voltage.At 32 deg C,Bias voltage3V 4pa5V 20pa10V 100pa35V 1.5na

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 14, 2023, 10:54:45 pm
content: I once did an accelerated aging process, which seemed to help; I took a few 1-4.7uF 100V metal case (M39003 style) dry tantalums, biased them to near 100V (I forget if it was over or under the rating), and sat them inside a power resistor cooking at, something elevated, 100, 130°C, something like that. Let that sit for a couple days while monitoring leakage. Then cooled back down and tested at lower voltage.I forget what the exact figures were though, or other relevant information (brand, production date, etc.). It was good enough for my application (a little sample and hold circuit), an improvement over polypropylene.Tim

author: TimFox
author_rank: Super Contributor
timestamp: February 14, 2023, 11:01:51 pm
content: Quote from: T3sl4co1l on February 14, 2023, 10:54:45 pmWas that an improvement in leakage current over polypropylene, or just an improvement in size/footprint?According to Vishay, a 5 uF polypropylene capacitor should have a leakage resistance of about 20 G(100,000 M-uF), falling by a factor of 100 from 20oC to 100oC.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 15, 2023, 01:36:55 am
content: Improvement in time constant; the others I had used (including polystyrene) just didn't perform well. I'm not entirely sure where the leakage currents were in there, but it didn't seem to improve with capacitance, across film types. For a while, I had a 10nF PS in there, but almost 1nF (C0G) to 100nF (PE, PP) didn't seem to make much difference, strangely. I also don't have any PP in ~uF handy, that would fit in the space -- so the tant was a reasonable choice.One-off proto thing BTW, not a production item.Tim

author: Kleinstein
author_rank: Super Contributor
timestamp: February 15, 2023, 08:04:36 am
content: For a S&H circuit the other problem is dielectric absorbtion. Already mica and polyester capacitors are thus not a good choice. Electrolytic capacitors usually have very high dielectric absorbtion.The case with a very long hold could be a reason to look for rather large capacitance. Other leakage paths (e.g. FET or OP-amp) could be a reason that a relatively large capacitance is needed and very low leakage of the capacitor not really needed.Build up of the oxide layer at a higher temperaure makes sense, as a thicker and stable oxide can help to keep leakage low, though possibly at the price of a reduced capacity.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 15, 2023, 07:42:22 pm
content: Not actually much of a problem in that one, as updates were small changes. But a big deal for general applications of course!I don't think I had tried an electrolytic, assuming they'll be too leaky (and even with the small changes, the absorption probably sucks anyway). With some of the numbers here, maybe I should've!Tim

author: MiDi
author_rank: Frequent Contributor
timestamp: August 01, 2023, 02:27:43 pm
content: Attached some leakage results for different film caps @100V.

author: MiDi
author_rank: Frequent Contributor
timestamp: August 01, 2023, 03:35:05 pm
content: Attached some DA results for different film caps discharged from 100V to 0V.

author: MiDi
author_rank: Frequent Contributor
timestamp: August 01, 2023, 03:47:30 pm
content: Attached some leakage results for different film caps@10V.

author: MiDi
author_rank: Frequent Contributor
timestamp: August 01, 2023, 03:59:27 pm
content: Attached some DA results for different film caps discharged from 10V to 0V.