Microelectronics | Polymer Capacitors Characterization

Synopsis

A few years ago, I started using solid aluminum polymer capacitors for most projects involving power conversion or digital circuits, either new designs or repairs.

Somehow, I never thought about measuring the parameters of this capacitor type. By hazard, one day I measured a 100 uF / 25 V Kemet polymer capacitor, and it gave a reading of exactly 100.1 uF. That made me curious enough to start collecting some data.

Unfortunately, at the moment, I don't have that many polymer capacitors in stock. Normally, I buy capacitors only when I need them. And generally speaking, I am so excited to advance with my projects that I will use them within 24 to 48 hours from their arrival. But I think I have enough to start the database.

I plan to regularly update this article as long as I order new parts. In general, I use OS-CON, Kemet, and Nichicon, in this particular order. Sometimes, I use capacitors from other reputable brands as well.

Disclaimer: As before, I am in no way affiliated with any brands mentioned in this article, nor do I gain anything from them for writing this essay. I just strive to use the best electronic components for my hobby projects. Thus, this kind of research is mandatory.

Essay

Without further talk, let's get straight to the results. Once again, I will use the Hewlett-Packard 4276A LCZ Meter, letting it warm up for half an hour before taking the measurements.

Even though the settings are stored in battery back-up memory, I re-zeroed the unit with both open and shorted test terminals. The DC bias was turned off and the measurements were taken at 120 Hz.

Research

I took the readings during a hot summer evening, using the old way of noting down on paper whatever the instrument displayed. During warm-up, I repeatedly took measurements of the same 150 uF / 400 V standard electrolytic capacitor that consistently reported 130 uF. Normally I use a hand selected 1 uF / 50 V film capacitor that gives a capacitance reading of exactly 1000 nF and an ESR of 0 Ω. But I was lazy enough to go to my parts drawer and just took whatever I had around. As a side note, this capacitor is going to be installed in the IBM eServer xSeries 330 power supply.

Once the capacitance and ESR display readings stopped fluctuating, I started measuring the polymer capacitors. I sorted the collected data by capacitors manufacturer and series so that we can have a better overview.

I will occasionally update this article, as I order new capacitors for my projects.

The Kemet A759 series designates long life capacitors that can withstand 125 °C. I tend to use these mostly in power conversion circuits.

KEMET A759 SERIES CAPACITOR DATA
BrandTypeStyleRatingCapacityESR
KemetPolymerRadial10 uF / 63 V10.85 uF1.52 Ω
KemetPolymerRadial10 uF / 50 V11.33 uF1.51 Ω
KemetPolymerRadial10 uF / 50 V11.35 uF1.57 Ω
KemetPolymerRadial10 uF / 50 V11.45 uF1.52 Ω
KemetPolymerRadial10 uF / 50 V11.51 uF1.61 Ω
KemetPolymerRadial10 uF / 50 V11.52 uF1.57 Ω
KemetPolymerRadial10 uF / 50 V11.76 uF1.51 Ω
KemetPolymerRadial10 uF / 50 V11.96 uF1.52 Ω
KemetPolymerRadial10 uF / 50 V11.75 uF1.51 Ω
KemetPolymerRadial10 uF / 50 V11.45 uF1.52 Ω

The Kemet A758 series offers long life capacitors that can work up to 105 °C. I use these in power conversion circuits and general computer-related hardware. These A758 capacitors are miniature variants of the A755 series.

KEMET A758 SERIES CAPACITOR DATA
BrandTypeStyleRatingCapacityESR
KemetPolymerRadial680 uF / 10 V741 uF0.02 Ω
KemetPolymerRadial680 uF / 10 V742 uF0.02 Ω
KemetPolymerRadial100 uF / 16 V110 uF0.08 Ω
KemetPolymerRadial22 uF / 25 V23.32 uF1.05 Ω
KemetPolymerRadial22 uF / 25 V23.42 uF0.87 Ω
KemetPolymerRadial22 uF / 25 V23.37 uF0.93 Ω
KemetPolymerRadial22 uF / 25 V23.17 uF0.92 Ω
KemetPolymerRadial22 uF / 25 V23.20 uF0.90 Ω
KemetPolymerRadial22 uF / 25 V23.23 uF0.91 Ω
KemetPolymerRadial10 uF / 25 V10.95 uF2.13 Ω

Kemet 755 series capacitors have a long life at up to 105 °C, and are advertised as good for LED driver power supplies, general computer-related power supply designs, and medical equipment. And that's why I use them for; well, except for medical equipment, as I don't have any experience with that.

KEMET A755 SERIES CAPACITOR DATA
BrandTypeStyleRatingCapacityESR
KemetPolymerRadial100 uF / 25 V103 uF0.13 Ω
KemetPolymerRadial100 uF / 25 V103 uF0.13 Ω

The Kemet A750 series designates radial capacitors with an operating temperature up to 105 °C, and are typically used in the computer hardware field, both server and consumer grade.

KEMET A750 SERIES CAPACITOR DATA
BrandTypeStyleRatingCapacityESR
KemetPolymerRadial470 uF / 25 V530 uF0.06 Ω
KemetPolymerRadial47 uF / 25 V50.15 uF0.34 Ω
KemetPolymerRadial47 uF / 25 V50.62 uF0.32 Ω
KemetPolymerRadial47 uF / 25 V51.14 uF0.30 Ω
KemetPolymerRadial47 uF / 25 V51.85 uF0.32 Ω
KemetPolymerRadial47 uF / 25 V51.92 uF0.32 Ω
KemetPolymerRadial47 uF / 25 V52.01 uF0.32 Ω
KemetPolymerRadial47 uF / 25 V52.43 uF0.30 Ω
KemetPolymerRadial47 uF / 25 V51.68 uF0.30 Ω
KemetPolymerRadial47 uF / 25 V51.44 uF0.31 Ω
KemetPolymerRadial47 uF / 25 V51.72 uF0.29 Ω
KemetPolymerRadial47 uF / 25 V51.98 uF0.32 Ω
KemetPolymerRadial47 uF / 25 V51.59 uF0.31 Ω

The FP series from Nichicon stands for functional polymer. The RNL series designates large sized, high capacitance parts with operating temperatures of up to 105 °C. I use these for power supply repairs and computer mainboard restoration.

NICHICON RNL SERIES CAPACITOR DATA
BrandTypeStyleRatingCapacityESR
NichiconPolymerRadial1200 uF / 16 V1156 uF0.03 Ω

OS-CON SEP capacitors are rated for around 3,000 h. at 105 °C. I use these for computer-related hardware repairs, and new designs.

OS-CON SEP SERIES CAPACITOR DATA
BrandTypeStyleRatingCapacityESR
OS-CONPolymerRadial22 uF / 20 V23.50 uF0.45 Ω

OS-CON SEPC capacitors are advertised as super low ESR (5 mΩ max.) and are available up to 2700 uF at 2.5 V. Capacitors of 470 uF and below are available up to 16 V. These are my go-to capacitors for all digital circuits, especially computer-grade hardware.

OS-CON SEPC SERIES CAPACITOR DATA
BrandTypeStyleRatingCapacityESR
OS-CONPolymerRadial1000 uF / 6 V908 uF0.03 Ω
OS-CONPolymerRadial1000 uF / 6 V913 uF0.03 Ω
OS-CONPolymerRadial1000 uF / 6 V901 uF0.03 Ω
OS-CONPolymerRadial1000 uF / 6 V911 uF0.03 Ω
OS-CONPolymerRadial1000 uF / 6 V903 uF0.03 Ω
OS-CONPolymerRadial1000 uF / 6 V910 uF0.03 Ω
OS-CONPolymerRadial1000 uF / 6 V890 uF0.03 Ω
OS-CONPolymerRadial1000 uF / 6 V885 uF0.03 Ω
OS-CONPolymerRadial1000 uF / 6 V890 uF0.03 Ω
OS-CONPolymerRadial1000 uF / 6 V889 uF0.03 Ω
OS-CONPolymerRadial820 uF / 2.5 V797 uF0.39 Ω
OS-CONPolymerRadial820 uF / 2.5 V759 uF0.40 Ω
OS-CONPolymerRadial820 uF / 2.5 V764 uF0.40 Ω
OS-CONPolymerRadial820 uF / 2.5 V720 uF0.37 Ω
OS-CONPolymerRadial820 uF / 2.5 V776 uF0.38 Ω
OS-CONPolymerRadial470 uF / 16 V475 uF0.04 Ω
OS-CONPolymerRadial470 uF / 16 V460 uF0.04 Ω
OS-CONPolymerRadial470 uF / 16 V475 uF0.05 Ω
OS-CONPolymerRadial470 uF / 16 V468 uF0.04 Ω
OS-CONPolymerRadial470 uF / 16 V489 uF0.04 Ω
OS-CONPolymerRadial470 uF / 16 V489 uF0.04 Ω
OS-CONPolymerRadial470 uF / 16 V491 uF0.04 Ω
OS-CONPolymerRadial470 uF / 16 V484 uF0.04 Ω
OS-CONPolymerRadial470 uF / 16 V479 uF0.04 Ω
OS-CONPolymerRadial470 uF / 16 V472 uF0.05 Ω
OS-CONPolymerRadial470 uF / 16 V479 uF0.04 Ω
OS-CONPolymerRadial470 uF / 6 V445 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V465 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V453 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V452 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V466 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V463 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V466 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V468 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V456 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V461 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V456 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V473 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V462 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V468 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V481 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V458 uF0.03 Ω
OS-CONPolymerRadial470 uF / 6 V436 uF0.03 Ω

OS-CON SEPF capacitors come in large capacitance, high voltage flavours. As above, I use these for computer hardware repairs and new designs. ESR is a bit higher than that of SEPC series, but still low enough for switched mode power conversion circuits.

OS-CON SEPF SERIES CAPACITOR DATA
BrandTypeStyleRatingCapacityESR
OS-CONPolymerRadial120 uF / 20 V113 uF0.15 Ω
OS-CONPolymerRadial120 uF / 20 V111 uF0.15 Ω
OS-CONPolymerRadial120 uF / 20 V109 uF0.15 Ω
OS-CONPolymerRadial120 uF / 20 V112 uF0.18 Ω
OS-CONPolymerRadial56 uF / 25 V55.65 uF0.32 Ω
OS-CONPolymerRadial56 uF / 25 V56.91 uF0.32 Ω

Even though I plan to add more data, the overall picture becomes clear. These polymer capacitors are good. I've had some of the smaller capacity Kemet parts since 2019, and they still measure well within their rated specifications.

Conclusions

The process of collecting and sorting all this data was interesting. I was expecting lower capacitance values, as this appears to be common practice for standard electrolytic capacitors, even for those coming from quality brands. But the readings were pretty consistent. At least almost all Kemet and OS-CON capacitors have either spot on, or close to the advertised capacitance.

For some reason, the Nichicon capacitors report a slightly lower capacitance value. Alternately, some Kemet capacitors have a higher capacity than what's printed on the can.

The low ESR is no wonder as it was quite expected. I randomly analyzed the datasheets for some of these capacitors and the ESR values match or are lower than advertised.

I hope you found this research useful.

Your Help Matters

This essay is provided as-is and is not for commercial purposes. It reflects my experiments and research and should be treated as such. I release my work to the public for educational purposes. I did all this at my own expense and in my free time. So if you like my work, or find it useful or inspiring for your projects, please consider making a donation.


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