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I have been studying the derating effects of temperature on voltage rating of capacitors (ceramic). Something like the image shown below:

Enter image description here

The image is the derating curve for a tantalum capacitor. This means that the voltage rating of the tantalum capacitor varies w.r.t temperature. But, does this behaviour also happen in ceramic capacitors?

I had a discussion on the same topic (Capacitor derating).

There I was told that such a behaviour does not affect ceramic capacitors as it does tantalum. But, I just saw a European Space Agency (ESA) document stating the derating curve for ceramic capacitors. The document is in the ESA documents database, and the document is ECSS-Q-ST-30-11C-Rev1.

So in this document a similar derating curve (similar to the tantalum) is shown on page 22.

Enter image description here

Now, I have looked at quite a few space-grade ceramic capacitors, but none have such a derating information. So, what is this paramenter that is being shown in the ESA document?

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    \$\begingroup\$ Do all of us a favor, and download and learn to use Greenshot. \$\endgroup\$
    – Matt Young
    Sep 14, 2015 at 17:51
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    \$\begingroup\$ Could also just use windows Snipping Tool. I use that all the time. \$\endgroup\$
    – Funkyguy
    Sep 14, 2015 at 18:01

2 Answers 2

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That document (ECSS‐Q‐ST‐30‐11C Rev 1) only relates to how the space agency de-rate components because they are trying to maintain the highest reliability for space flight. If you read the document you will see that all the capacitors listed have a de-rating curve as well as the static de-rate that applies to low/normal temperatures.

Anyone sending stuff into space (or flight) will take steps to get the highest reliability without compromising flight performance. That is what this document is about. It covers: -

  • Ceramic caps
  • Tantalum
  • Plastic metalized
  • Glass and porcelain
  • Mica
  • Feedthru types
  • Semiconductor caps
  • Variable caps

Then it moves onto connectors and also de-rates those w.r.t. voltage. Then the document covers all sorts of other electrical components and mainly de-rates devices with respect to voltage, power or current. It's in alphabetical order so caps come first.

Again, it does this in order to achieve a higher-than-average reliable design. It should not be read as a statement about any capacitor technology.

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  • \$\begingroup\$ So, what you say is that the derating curve shown in the document is the standard derating curve for relevant components. For eg - the average space grade ceramic capacitor derates ate at a rate shown in the graph I attached in my question (sourced from that document). Right ? Or am I undertanding your point wrong ? If my understanding is wrong, it means that the capacitor OEMs in their datasheet must specify such a derating curve unique to each family of these capacitors, right? Also, is the graph actualluy a derating of the voltage rating ? \$\endgroup\$
    – Board-Man
    Sep 14, 2015 at 9:01
  • \$\begingroup\$ If so then should it not show 100% at least in the room temperature range ? It starts from almost 60%. So , imagine a space grade capacitor, of 100V rating, will or rather can be used only in a 60V system ? \$\endgroup\$
    – Board-Man
    Sep 14, 2015 at 9:10
  • \$\begingroup\$ Its a general de-rating for any components used in aerospace. No, showing 100% for room temperature does not account for other environmental extremes like vibration, shock, radiation, humidity (lack of it) that occur in aerospace vehicles. A better document that numerically documents how the MTBF for electrical components falls with extreme environments is MIL-HDBK-217F (easily found on the web). It's all about getting the longest mean time between fails (MTBF) for components by relaxing their electrical spec. \$\endgroup\$
    – Andy aka
    Sep 14, 2015 at 9:49
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The ECSS documents describe a wide range of requirements that, when followed properly, guarantee a good level of reliability in space. They should be considered a collection of good practices. Sometimes the information in there applies to the technology itself, but most of the time it is made of lessons learnt after decades of space flight and as such only applies to high reliability equipment launched in space.

In a nutshell, the capacitors manufacturers tell you what the capacitors CAN endure before they break down; whereas the ECSS tell you what the capacitors SHOULD endure at most to avoid breaking down: some additional margin is thrown in (as can be seen on your snapshot: 60% load factor at low temperature).

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