MLCC X5R capacitor degradation - Page 1
Forum section: electronics / projects

author: CosteC
author_rank: Regular Contributor
timestamp: April 26, 2023, 06:46:15 pm
content: I got interesting issue.There is 0805 4.7 uF 25 V X5R capacitor working in half-bridge bootstrap circuit. Capacitor is charged from 12 V, so well below max rating.It looses capacitance slowly with number of operations - operations happen very slowly - one HB swing every couple of seconds.After some time (thousands operations) capacitance drops to 3.5 uF or so.Temperatures are almost room, 25-30'C. No mechanical shocks.Any ideas what is mechanism of degradation and capacitance decrease?

author: helius
author_rank: Super Contributor
timestamp: April 26, 2023, 06:54:22 pm
content: Class II dielectrics like X5R experience capacitance loss with DC bias.You would have better results with a film capacitor or C0G ceramic.I found this description:https://passive-components.eu/high-cv-mlcc-dc-bias-and-ageing-capacitance-loss-explained-2/

author: mzzj
author_rank: Super Contributor
timestamp: April 26, 2023, 06:59:01 pm
content: High K dielectrics drift slowly down in capacitance. Heating up(soldering) temporarily resets the drift so fresly soldered X5R measures higher than 1 month old or 1 year old.My guess would be that if you resolder the bad capacitor it ”works” again.

author: CosteC
author_rank: Regular Contributor
timestamp: April 26, 2023, 07:14:19 pm
content: Quote from: mzzj on April 26, 2023, 06:59:01 pmNot much. Capacitor measured in circuit (tracks cut to avoid thermal stuff) looses capacitance after some thousands of cycles. Does not seem to re-gain it "overnight". Happens in product and happens from "new" capacitors from Farnell (same type, who knows if same batch).BTW you claim X5T slowly looses capacitance? With or without bias voltage? Any paper about it?

author: floobydust
author_rank: Super Contributor
timestamp: April 26, 2023, 07:33:26 pm
content: MLCC degradation is actually quite bad, to the point equipment fails unexpectedly. There is a need for some standards on this, as Continental lobbied several MLCC manufacturers but I don't know where that left off. It also depends on the cap manufacturer and they did not say who the worst offender is.Here is one curve showing it drops within HOURS- which allows you to make fake claims on a datasheet. And is your basic engineering nightmare why the circuit worked and no longer does.

author: CosteC
author_rank: Regular Contributor
timestamp: April 27, 2023, 04:45:48 am
content: Quote from: floobydust on April 26, 2023, 07:33:26 pmDo you have original/full paper? I think DC bias is not my case, but would like to read more about it. Maybe I am wrong.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 27, 2023, 07:48:07 am
content: mzzj's "claim" is like claiming water is wet, it's not like some extraordinary claim requiring proof to be delivered to you. MLCC aging is obvious to nearly everyone here; yes, it can be pretty bad, and some old assumptions like "X7R is not that bad, only Y2V sucks" are not true. Just do your own homework and use Google, you will find as many papers and appnotes as you want.

author: KE5FX
author_rank: Super Contributor
timestamp: April 27, 2023, 08:20:34 am
content: QuoteThere is absolutely nothing "obvious" about capacitance degradation at timescales on the order of hours. What textbook(s) discuss this phenomenon?

author: Siwastaja
author_rank: Super Contributor
timestamp: April 27, 2023, 08:54:59 am
content: Textbooks? You are looking at completely wrong type of source. Textbooks are great for fundamental physics or methodology (e.g. circuit analysis), but for up-to-date practical information about components, you need to read application notes, reports, websites, even discussion forums such as this one.The fact it can happen within hours is not obvious to everyone, but ageing itself, in timescale of months, is extremely well documented. What difference does it make? If it ages faster, it's only better as the problem will be revealed sooner.

author: tooki
author_rank: Super Contributor
timestamp: April 27, 2023, 10:52:34 am
content: Quote from: CosteC on April 26, 2023, 07:14:19 pmCan you share the capacitor manufacturer and part number?

author: Vovk_Z
author_rank: Super Contributor
timestamp: April 27, 2023, 05:35:10 pm
content: Quote from: CosteC on April 26, 2023, 06:46:15 pmI don't have ideas, I just may recommend to use large caps, e.g. 1206 or even 1210. I gues 4u7 1210 don't degrade at all (comperativly).

author: floobydust
author_rank: Super Contributor
timestamp: April 27, 2023, 06:06:31 pm
content: Quote from: CosteC on April 27, 2023, 04:45:48 amI think it was this one:http://electrical-integrity.com/Paper_download_files/DCE11_200_slides.pdf"Five MLCC manufacturers (AVX Corporation, Kemet Electronics, Murata Electronics Europe, Samsung Electro-Mechanic, Wurth Elektronik) and Continental Automotive as the end automotive user representative at the round table open discussion."HIGH CV MLCC DC/AC BIAS AGEING CAPACITANCE LOSS EXPLAINEDSummary of the outcome:"Open letter to AECQ-200 committee about MLCC class II Capacitance DC BIAS issues”Continental is now managing “DC-Bias Aging” and training their engineers on MLCC values. The meeting did not yield any cap manufacturer improved ratings.KemetAVX fellow was same guy Dave interviewed on X film caps failing. In the end, they have to qualify each capacitor: "Capacitance versus DC-Bias Ageing data measured at room temp., for 24h, at three points: 20%, 40% and 60% of rated voltage."Class-II MLCC DC-Bias Aging Issues in Automotive Applicationswas 2021 update ok to read as welledit: had wrong company for Mr. Demcko

author: CosteC
author_rank: Regular Contributor
timestamp: April 27, 2023, 07:02:06 pm
content: Quote from: Vovk_Z on April 27, 2023, 05:35:10 pmI am not so optimistic as I do not understand mechanism... also if I would have space for 1206 I could put tantallum or other there.I suppose I need to make test couple of hypothesis...KEMET... Exact number I need to check tomorrow.

author: bdunham7
author_rank: Super Contributor
timestamp: April 27, 2023, 07:16:08 pm
content: Quote from: CosteC on April 26, 2023, 07:14:19 pmhttps://www.digikey.com/Site/Global/Layouts/DownloadPdf.ashx?pdfUrl=91D84559BB484E21BD284CC0B41A4783

author: Vovk_Z
author_rank: Super Contributor
timestamp: April 30, 2023, 01:10:13 pm
content: Quote from: CosteCIDK mechanism too, but, e.g. if a problem is a current-related (pulsating current) then large size still must help, because of a large surface arrea and a large volume to dissipate a power.

author: helius
author_rank: Super Contributor
timestamp: April 30, 2023, 05:20:12 pm
content: Quote from: floobydust on April 27, 2023, 06:06:31 pmI re-watched that video yesterday, it was rather an engineer at AVX. (The failed capacitor was from neither company, but a Taiwan cheapie branded "Suntan".)

author: helius
author_rank: Super Contributor
timestamp: April 30, 2023, 05:29:40 pm
content: Quote from: Vovk_Z on April 30, 2023, 01:10:13 pmThe mechanism for "aging" is rearrangement of the crystalline structure of the barium titanate. The stable structures are different above and below the Curie point, so the rearrangement follows an exponential decay pattern starting at the last time it was soldered.The mechanism for capacitance loss with DC bias is that some of the barium titanate dipoles become "blocked" or unable to rotate with the AC field. This is proportional to the DC electric field, so it is a worse problem when the capacitor is smaller.These are both elucidated in the link I gave inReply #1.

author: exe
author_rank: Unknown
timestamp: April 30, 2023, 05:37:00 pm
content: Good manufacturers provide either provide curves DC voltage vs capacitance, or simulators, like murata (https://ds.murata.co.jp/simsurfing/mlcc.html?lcid=en-us).Considering it was 0805, going down from 4.7uF to 3.5uF at 12V is not that bad, imo. Could be worse (see screenshot of random 16V cap). Going with physically bigger mlcc helps with DC bias. Note that this degradation is nothing to do with voltage rating. All MLCCs are affected by this, especially the high-capacity ones.As of ageing without DC bias, Idk about that, but won't be surprised if this happens, but slower.

author: DavidAlfa
author_rank: Super Contributor
timestamp: April 30, 2023, 06:29:20 pm
content: This has completely changed my perception of ceramic caps.-80% at 12V bias?? Holy crap!

author: ejeffrey
author_rank: Super Contributor
timestamp: April 30, 2023, 07:08:29 pm
content: Quote from: DavidAlfa on April 30, 2023, 06:29:20 pmYes. And it isn't solved by derating the voltage. A 35 V and 16 V capacitor of the same dielectric and volume will usually have the same effective capacitance at 12V. If a MLCC manufacturer doesn't provide capacitance vs voltage plots you should probably just ignore them.The way to find the right parts is to use parametric sort to filter by thickness. In a given footprint, the only way to get more capacitance at working voltage is to add thickness. This will help you filter out all the capacitors that are not worth looking at.

author: mawyatt
author_rank: Super Contributor
timestamp: April 30, 2023, 11:25:47 pm
content: Folks, please do a little research before placing all ceramic caps in the same category.It's well known that C0G/NP0 ceramic material is highly stable with temperature, voltage and age. In fact this ceramic is so good that it's utilized in the high end high resolution DMMs as the main integrating capacitor in the multi-slope intergrating ADCsHowever, here's an example of the typical cheap ceramic thru-hole disc that's commonly utilized for power supply decoupling. This capacitor is obviously made with a high K dielectric and shows very poor stability with applied DC voltage and temperature.BTW these plots were produced by some new Python routines for use with LCR meters for frequency, voltage and temperature sweeping and plotting, you can find details here:https://www.eevblog.com/forum/testgear/lcr-meter-plot-software/Best,

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 01, 2023, 02:08:29 am
content: Quote from: DavidAlfa on April 30, 2023, 06:29:20 pmI'd have thought you saw this already; you've been around a while!Well, welcome to thedaily 10,000, and, a good reminder that this will always be new to someone, and so always bears repeating (a thread subject that's otherwise been done to death)!Quote from: mawyatt on April 30, 2023, 11:25:47 pmIndeed, type 2 (X7R etc.) are also highly microphonic (piezoelectric), so are contraindicated for sensitive and low frequency (e.g. audio processing) applications, perhaps controls as well (when precision and stable controls are demanded, or when the environment is high vibration).C0G are nearly ideal; they often have Q factors in the thousands, making them excellent for snubber and resonant applications. They have low absorption and leakage too (which exact brands/families do, however, is a carefully guarded secret), although not quite as low absorption as polystyrene or glass did (I think?).The main downside to C0G is cost: values under 1nF are competitive with X7R etc., but above, they diverge quickly*; and values above 100nF are hardly available at all, and quite pricey at that. Selection doesn't improve at low voltage ratings, because the ceramic layers are just too thin -- density isn't good. (The material has a lower K than titanates, but much higher breakdown field strength.) On the other hand, they excel at high voltages: you can hardly find a 100nF X7R that's any good (read: >= -30% of nominal value) at 250VDC, even in 2220 size; but C0G doesn't depend on voltage at all and a, 1210 I think?, will fit such a value and voltage rating. The energy density at higher voltages (200-600V say) in fact is competitive with electrolytics!*If you're *really* sensitive on cost, or doing large quantities (100k+?), probably the divergence falls at an even lower point. In the thousands, for hand-wavy pricing, it's kind of just in the noise below 1nF.Interesting quirk: the Q is so high, and the values small to modest, that it can be kind of awkward to wire C0Gs in parallel arrays. Even the minor stray inductance along a tightly packed array (say 6nH for a half dozen in a row over ground plane) is enough to resonate them, and you get bathtub-sloshing resonant modes, say in the 10s to 100s MHz -- which can therefore be relevant for EMI purposes, say in SMPS.Tim

author: floobydust
author_rank: Super Contributor
timestamp: May 01, 2023, 04:03:24 am
content: It's calling out the crappy MLCC manufacturers - ones having poor voltage coefficient, hiding that data and then the aging of that parameter which the industry is sweeping under the rug. Some manufacturers have better technology.FFS look at the graph, it infant ages in under 3 minutesContinental's interim solution is requiring qualification and validation from manufacturers. And what about us?Quote from: helius on April 30, 2023, 05:20:12 pmThanks, fixed.Open Letter to AEC-Q200 Committee on MLCC DC BIAS Ageing Capacitance Loss Issueshad present MLCC Manufacturers:AVX Corporation: Mr. Ron DemckoKEMET Electronics: Mr. Wilson HayworthMurata Electronics Europe: Mr. Yuki NagoshiSamsung Electro-Mechanics: Mr. Benjamin BlumeWürth Elektronik: Mr. Paul Le NezetThey didn't name the dog.

author: DavidAlfa
author_rank: Super Contributor
timestamp: May 01, 2023, 06:02:19 am
content: Quote from: T3sl4co1l on May 01, 2023, 02:08:29 amI knew capacity rating was reduced by bias, but not that it was so extreme like -80% lol.I'm no engineer neither I work at hw design, so yep there's still a lot to learn!

author: Siwastaja
author_rank: Super Contributor
timestamp: May 01, 2023, 07:21:46 am
content: Quote from: DavidAlfa on May 01, 2023, 06:02:19 amA lot of damage was made a few years ago on blog posts, youtube videos and this very forum by "helpful" people teaching around that the issue is mainly with Y5V capacitors and X7R is fine. Some rules of thumbs pulled out of thin air, such as "Y5V can drop below -80% under full DC bias but X7R only -30%" or "derating voltage helps". These are all totally false.The best rule of thumb, by far, is simply: if the volumetric energy density is too good to be true, then it isn't. As ejeffrey writes above, if footprint size is a fixed parameter for you, then the height is relevant to look at. And you should really look at joules per volume. And calculate the joules at your DC bias voltage; the rating is meaningless. E / V = ½CU^2 / (width * length * thickness).

author: BravoV
author_rank: Super Contributor
timestamp: May 01, 2023, 08:04:20 am
content: If these are related ?Click images to enlarge.From Kemet.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 01, 2023, 08:47:31 am
content: Quote from: BravoV on May 01, 2023, 08:04:20 amThis is familiar. I'm not aware of anything that drops precipitously like the earlier figure, which very much looks made up, but maybe some manufacturers made something that changes phase very slowly but also rather suddenly (days being slow compared to ~instant changes, and different from the log(time) aging of traditional materials).Quote from: Siwastaja on May 01, 2023, 07:21:46 amYeah, while Y5V and Z5U (there's even a Z5V if you want to go looking for true awfulness) may be the worst, there are no exceptions, all type 2's exhibit the characteristic.I occasionally need to use X5R for the greater density; a modest compromise while temp ratings are respected. I haven't had to use anything worse, at least in quantity. I have heard tale of Z5x being used -- responsibly engineered -- in extreme cost reduction applications.The volumetric point extends with respect to voltage. Like the 2220 I mentioned earlier, you can get a solid 10 or 22nF in X7R at 250V, and while you can buy 220nF or even more with such a rating, none of them offer much more capacitanceat voltage. The C(V)/C(0) ratio can get much worse than for low-voltage types, because the insulation quality is better -- that is, thicker layers are more reliable so can be pushed closer to limit. (Hm, I haven't tested this, but I'm betting breakdown is closer to ratings -- whereas a 16V part might fail anywhere from 40 to 150V, I'd bet a 250V part might fail 400-600V?) So, not even being able to get a proper 100nF at 250V+ even in large chips like 2220 is disappointing, but works out when you do the numbers -- they're bigger, sure, but they aren'tmanytimes larger than say a 1210.Y1/Y2 ceramics are also commonly Y5V. IIRC, these tend to drop off by a couple hundred volts, so are functional at mains voltage, but not under surge conditions -- which might well be a feature rather than a bug, the saturation reducing current flow through the capacitor. The temperature characteristics seem the more important property here, something to keep in mind if you're doing EMI filters for wide temperature ranges. (Or conversely, use then if you don't need to pass tests at temp extremes -- shitty, but may happen that that's what a project needs done.)Tim

author: iMo
author_rank: Super Contributor
timestamp: May 01, 2023, 08:59:28 am
content: Hmm, back to the tantalum capacitors then??

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 01, 2023, 09:05:07 am
content: Nah, no need for conflict minerals plus thermite reaction potential when aluminum polymers exist.Tim

author: mawyatt
author_rank: Super Contributor
timestamp: May 01, 2023, 02:46:59 pm
content: As one who's lived thru the development of the modern ceramic and polymer capacitors, it's interesting to see the diversity of such. Long ago the scarcity/political control/cost of tantalum material became the driver for development of higher density ceramic caps to replace tantalum, later the same for the Polymer types which also help replace some electrolytics.AVX, TDK, Kemet and a few others were the usual suppliers of quality ceramic caps, now you have Samsung, Vishay, Wurth, UCC, and a host of others, including many from China, it's difficult to know which supplier and ceramic capacitor type to use for a given application and why we invested in the means to measure the usual Frequency sweeps, but also Voltage sweeps and even some crude Temperature sweeps.If one is designing a high quantity or mission critical product, as mentioned by others its wise to learn about the various nuances of ceramic capacitors!Best,

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: May 01, 2023, 04:33:16 pm
content: Thought this was a pretty good summary:https://blog.samtec.com/wp-content/uploads/2020/07/07_16_2020_geek_speek_MLCC_losses.pdf

author: TimFox
author_rank: Super Contributor
timestamp: May 01, 2023, 04:54:38 pm
content: In my opinion, if the temperature, voltage, and time variation of capacitor parameters is important to your application, you should only buy from manufacturers (e.g., Kemet, AVX, Murata, etc.) that provide actual datasheets that show how these parameters vary with package size and dielectric.MLCC capacitors from quality vendors need not be expensive.

author: floobydust
author_rank: Super Contributor
timestamp: May 01, 2023, 05:01:04 pm
content: Quote from: Conrad Hoffman on May 01, 2023, 04:33:16 pmIt is a very good summary. First part that upsets me:"It was also shown that in addition to an immediate change of capacitance with the applied bias, there is also a longer exponential relaxation, which can change capacitance further by as much as 25% over the course of a few minutes."Second, is that some MLCC cap manufacturers are -25% and others -70% with bias. Like I need to waste more time searching for and looking at curves for each specific cap and comparing, then purchasing wants to make a substitution and I have to repeat the whole ordeal.

author: TimFox
author_rank: Super Contributor
timestamp: May 01, 2023, 05:05:24 pm
content: Quote from: floobydust on May 01, 2023, 05:01:04 pmBefore I retired, some of my engineer co-workers would design in a particular component that had good performance in the circuit (such as a tantalum capacitor with better-than-normal ESR), but forget to put such specifications into the BOM. Naturally, purchasing would order a cheaper part that met the specifications (usually tolerance and voltage rating) listed in the BOM.For MLCC capacitor dielectrics, the physics of the situation depends on the voltage gradient in the dielectric, which naturally varies with construction and layer thickness.

author: AnalogTodd
author_rank: Regular Contributor
timestamp: May 01, 2023, 05:50:52 pm
content: Quote from: Siwastaja on May 01, 2023, 07:21:46 amI know that while working at a major semiconductor manufacturer, we started looking into ceramic capacitors in the mid- to late-1990's. At the time we started doing the due diligence on MLCC's, we found that Y5V and Z5U were horrid for temperature and voltage characteristics, but X5R and X7R actually held up quite well. What came about was in the early 2000's, more and more people were switching to ceramics and there was demand for higher capacitance values in smaller case sizes (after all, look at the push on how much smaller products have gotten). At first, very few people noticed that there was an issue, but we started getting phone calls about circuits not operating right and our investigations came to the conclusions on voltage coefficient fairly quickly. In 1998, we were including verbiage in the applications sections of our data sheets warning about Z5U and Y5V having issues. By 2003 or so, we were also discussing how it could happen with X5R and X7R and that care should be exercised when using same. We would update older data sheets from time to time and while doing so often updated the relevant text. I of course laughed when competitor data sheets came out a year after we included this info and copied our text word for word.The relaxation in capacitance over time is one of the more recent concerns (again, push the laws of physics and they push back). It doesn't surprise me, manufacturers are trying to get more stuff into smaller packages but are now pushing against the limits of physics. It's like one of those stress balloons filled with goo--squeeze it down and one part will smush out from between your fingers in some location, try and tuck that back in and it squeezes out somewhere else.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 01, 2023, 06:20:50 pm
content: Quote from: floobydust on May 01, 2023, 05:01:04 pmIt's not per manufacturer. They are all using the same materials after all. Pretty much all manufacturers make capacitors that lose 50% of capacity at voltage and those that lose 85%. It's all in the device thickness. If you put a minimum thickness on your BOM and can convince your purchasing people to pay attention to it you will filter out 99% of the inappropriate substitutions. You still have to check a given part, but you will drastically cut down on the number you have to reject.The other option is to just use larger footprint in a low profile such that you are OK with a 80% drop. This is the lazy approach but works if you can afford the PCB space.

author: floobydust
author_rank: Super Contributor
timestamp: May 01, 2023, 06:26:47 pm
content: Huge variations between manufacturers, and also within their product lineup as well.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 02, 2023, 04:12:27 am
content: About the only thing you can say, is there's a certain maximum value, in terms of somewhere between C*V and C*V^2, and that's for C under bias, in a given chip size. You're guaranteed not to reach that maximum at, say, 10nF 50V 0805 -- which is still not to say you're guaranteed a flattish C(V) curve, they can always make thingsworse(i.e. use few, very thin layers, and add more as Cnom goes up) -- but it does mean, as you look at the largest values (say 10uF 6.3V 0805), you're more likely to be pushing that limit because there's just not much wiggle room left: they have to use the thinnest layers, as many as possible, to get the total value, and at a very low defect rate too (which puts pressure towards thicker i.e. more reliable layers).And that doesn't mean much in terms of values -- you aren't going to avoid checking C(V) characteristics in any range of values, and indeed it's all the more important to do so when finding maximal values where you have to feel out where their C(V)*V^x (1<x<2?) limit lies.The one upshot: I haven't seen any small-value parts that aren't widely spaced layers, i.e. they're more or less using the full volume of the chip and spacing out layers rather than using few closely-spaced layers. (Which means a 10nF 0805 might as well be 200V or more, regardless of posted rating?) That doesn't mean theycan't, just that, of the ones I've seen characteristics of, they haven't.Tim

author: CosteC
author_rank: Regular Contributor
timestamp: May 18, 2023, 07:25:12 am
content: Thank you all for support.Original capacitor is: KEMET C0805C475M3PACTU, so not bottom of the barrel.Resoldering this capacitor restores vast majority of initial capacitance, all down to measurement accuracy.I think this document is also revealing how againg accelerates.https://www.vishay.com/docs/45263/timedepcapdrix7rmlccexptoconstdcbiasvolt.pdf

author: PCB.Wiz
author_rank: Super Contributor
timestamp: May 18, 2023, 09:41:45 am
content: Quote from: ejeffrey on April 30, 2023, 07:08:29 pmThat's not quite trueThis curve shows you can de-rate by both voltage and package-size to reduce the change at a given voltage, and X7R is better than X5Rhttps://www.eevblog.com/forum/projects/is-ceramic-capacitor-package-relevant/msg4480996/#msg4480996

author: exe
author_rank: Unknown
timestamp: May 18, 2023, 09:52:44 am
content: Quote from: PCB.Wiz on May 18, 2023, 09:41:45 amNot a capacitor expert, but my conclusion is that the distinction between X7R and X5R is somewhat... arbitrary. At the end, it's just a temparture rating, not a performance indicator. So, an X5R from one manufacturer can be better than X7R from another one. I think an MLCC with large capacitance in a small package sucks no matter what class it is.I'd say the only thing that matters is curves from the datasheet. All that X5R/X7R ratings don't really tell the story. I'd also wouldn't trust the plot that you linked. It's only relevant to the parts that were evaluated. Different parts will behave differently, even if it's all X7R 0805 1u caps.

author: tooki
author_rank: Super Contributor
timestamp: May 18, 2023, 10:31:15 am
content: Quote from: exe on May 18, 2023, 09:52:44 amNo, it’s not just a temperature rating. Yes, the 5 or 7 means the temperature range. But the R means ±15%across the full temperature range, so that means that an X5R at 85C (its upper limit) will show a significantly larger tempco effect than the X7R, because 85C is far away from the X7R’s upper limit of 125C.If your product has the caps operating at anything but ambient temperature, then the real world difference is insignificant. But if your device warms up, then for any application where the capacitance value is important, you want a higher maximum temperature, even if you won’t actually go anywhere near that maximum.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 18, 2023, 10:42:52 am
content: Yep. Like I said -- I don't mind using X5R. Just don't use them beyond their ratings, go for X7R or better in that case.The compositions are probably very similar -- you could imagine a continuously variable formula between them (and beyond), where k, breakdown, saturation, and temp range all vary together, more or less in proportion. So you get a less dense but wider range X7R, or vice versa X5R, etc. Those two cases merely happen to be the most popular, so it looks like a discrete (two valued) system, but that's a consequence of defined standards plus commercial preference, not a limitation of materials science.I don't actually have any clue what the chemistry and variation are like; I would just assume they're variable in a more-or-less continuous manner over some range. The characteristics of X5R and X7R are certainly similar enough to suspect as much. And an extra 10% (in terms of absolute temperature: 85 vs. 125°C is about 40 out of 400K) is hardly anything in the grand scheme of things. Really, these are quite precisely formulated!The comparative plot doesn't really mean anything, because you can look at a dozen "10uF 16V X5R 1206" and get a dozen different curves. Only the highest C(V) among them is representative of maximum possible density. All the rest are either... being lazy in some way, or use an older (less precise? or potentially less cheat-ey..?) formulation. And since there's no part numbers on there, the data are basically useless -- consider it reference material, not hard fact.Tim

author: Siwastaja
author_rank: Super Contributor
timestamp: May 18, 2023, 06:42:42 pm
content: Quote from: PCB.Wiz on May 18, 2023, 09:41:45 amDid you look what you replied to and did you look what you posted? The graph demonstrates exactly what ejeffrey said. For example, curves for 0805-X7R-16V and 0805-X7R-10V are completely similar. Same between 0805-X5R-16V and 0805-X5R-10V. Picking a 16V part and derating it to 10V yields exactly the same result as using the 10V part at 10V - probably because they are actually the same part.

author: Kokoriantz
author_rank: Frequent Contributor
timestamp: May 19, 2023, 06:20:07 am
content: I will be using 2//1uf50v 1206 X7R, as decoupling 36v. How I can determine the value decrease in time?Should I replace by though hole polypropylene?

author: CosteC
author_rank: Regular Contributor
timestamp: May 19, 2023, 07:02:02 am
content: Quote from: Kokoriantz on May 19, 2023, 06:20:07 amWithout datasheet it is hard to tell. I would take ageing (3 decades) + DC bias + temperature worst case.

author: Kokoriantz
author_rank: Frequent Contributor
timestamp: May 19, 2023, 07:53:31 am
content: Decades on the table is in hours. For X7R it is 2%/10 hours. My 1uF will be 0.5uF in 250hrs ?

author: exe
author_rank: Unknown
timestamp: May 19, 2023, 01:07:35 pm
content: Quote from: Kokoriantz on May 19, 2023, 07:53:31 amI think decade means it loses 2% first 10 hours, then another 2% in 100 hours, then another 2% in 1000 hours, etc. I'd check in murata's simsurf for similar capacitors to see which curves they have. Or, better, just buy from vendor that provides such simulators

author: TimFox
author_rank: Super Contributor
timestamp: May 19, 2023, 01:44:42 pm
content: Quote from: Kokoriantz on May 19, 2023, 06:20:07 amEven polyester (Mylar) TH caps will have no decrease in time, with roughly the same loss as X7R, in a smaller package than polypropylene.