Trouble finding 100uF ceramic capacitors, do they exist? - Page 1
Forum section: electronics / beginners

author: newtekuser
author_rank: Frequent Contributor
timestamp: July 19, 2024, 12:42:33 am
content: I purchased four different brands of 100uF ceramic capacitors from Mouser, each reads between 60uF to 70uF capacitance depending on frequency using my DER-DE 5000 LCR meter. I do know all have +/- 20% tolerance but that should put me close to 80uF.My LCR meter works perfectly as it reads 100uF for electrolytic capacitors.Can someone please explain what is going on here?https://www.mouser.com/ProductDetail/581-08056D107MAT2Ahttps://www.mouser.com/ProductDetail/963-MSASJ21GBB5107MThttps://www.mouser.com/ProductDetail/81-GRM21BR60J107ME5Khttps://www.mouser.com/ProductDetail/187-CL21A107MQYNNWE

author: Psi
author_rank: Super Contributor
timestamp: July 19, 2024, 01:16:33 am
content: Check what frequency your LCR is testing at.Try with the lowest frequency.

author: newtekuser
author_rank: Frequent Contributor
timestamp: July 19, 2024, 01:22:42 am
content: Quote from: Psi on July 19, 2024, 01:16:33 amI tried all frequencies and the highest reading I get is 70uF.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 19, 2024, 03:44:56 am
content: Try bringing them up to soldering temperature, and make sure the voltage of measurement is correct. If your meter's manual doesn't say voltage/current of test, try observing it with an oscilloscope. Also take note of DC voltage bias.Ceramics aren't good at bulk capacitance. Either use a cheaper, bulkier type like electrolytic, or design your converters to need less -- use higher Fsw and faster error amp.And you can always stack parts in parallel, but that quickly takes up a lot of space, whereas electrolytics can grow upward.Tim

author: Psi
author_rank: Super Contributor
timestamp: July 19, 2024, 03:49:20 am
content: Quote from: T3sl4co1l on July 19, 2024, 03:44:56 amI had a look already, it says 0.5V RMS in the manual

author: newtekuser
author_rank: Frequent Contributor
timestamp: July 19, 2024, 04:16:53 am
content: Quote from: T3sl4co1l on July 19, 2024, 03:44:56 amI used hot air gun on them for ~20 seconds, now the capacitance is 85uF and 87uF even after they cooled off.

author: ArdWar
author_rank: Frequent Contributor
timestamp: July 19, 2024, 04:43:12 am
content: That looks about right.For now I'd still consider 100uF at 0805 as novelty gimmick part tbf. Pick bigger package if you want more consistent capacitance. Maybe pick better dielectric too.

author: Whales
author_rank: Super Contributor
timestamp: July 19, 2024, 05:11:32 am
content: 100uF in 0805!https://www.murata.com/en-us/products/productdetail?partno=GRM21BR60J107ME15%23DC resistance seems a bit like an electrolytic but at higher freqs is better. I'm surprised that it can handle 7 amps RMS with such a high value in such a tiny package. One of these shorting in-circuit would look amazing.

author: newtekuser
author_rank: Frequent Contributor
timestamp: July 19, 2024, 05:28:15 am
content: I'm not constraint on space so can go higher to an 1206. In fact I think the 0805 footprint will barely accommodate the 1206 so I don't have to redo the PCB.

author: Psi
author_rank: Super Contributor
timestamp: July 19, 2024, 05:36:10 am
content: You can get 220uF 1206 if you are ok with 4VThat will be above 100uF.Assuming all you need is capacity, then cost wise you will always be better to make it out of many 10uF caps.At least at the hobby level. 10uF caps are just so widely mass-produced they are cheap as dirt.So 10 or 20 in parallel is not normally an issue except when you are space limited.10uF 6.3V are like 0.3 cents each (LCSC)verses like 30 cents for 220uF. 100x the cost for only 22x capacity increase.

author: PGPG
author_rank: Frequent Contributor
timestamp: July 19, 2024, 07:55:01 am
content: Quote from: newtekuser on July 19, 2024, 12:42:33 am20% is only initial tolerance.Open datasheet of capacitor I left from your list at page 14 and have in mind that it is only example. For higher capacitance drop in capacitance can be much higher. If you will measure it with 1mV signal with DC=0V you will probably not notice the effect of this chart.

author: tszaboo
author_rank: Super Contributor
timestamp: July 19, 2024, 09:12:12 am
content: You are seeing the effects of DC bias, and tolerance.Never select a large value ceramic capacitor without investigating what it will actually do at your voltage level. There are no "rules of thumb" they all behave differently. You need to look for actual part numbers.

author: watchmaker
author_rank: Unknown
timestamp: July 19, 2024, 12:39:55 pm
content: Dave explains what everyone is talking about:

author: shabaz
author_rank: Frequent Contributor
timestamp: July 19, 2024, 02:15:56 pm
content: Their resonant frequency is pretty low, just a few hundred kHz. I don't think they can be considered very general-purpose components as a result.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 19, 2024, 02:27:22 pm
content: These high capacity ceramics have terrible DC bias characteristics. The plot below, taken from the data sheet, says it all.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 19, 2024, 03:57:13 pm
content: Only 20% of capacitance left at 5V.That is getting lose to where the capacitor has less stored energy at higher voltage. I wonder what that does with other variables such as dielectric absorption.The Murata datasheet has another gotcha:When AC voltage or pulse voltage is applied, the peak-to-peak voltage shall not exceed the rated DC voltage.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 19, 2024, 04:01:27 pm
content: Quote from: shabaz on July 19, 2024, 02:15:56 pmThat doesn't matter. Check the magnitude impedance at the same point. It's going to be a pretty damn good bypass up to say 10MHz. Which is true of any 0805 chip of at least modest value.Tim

author: MathWizard
author_rank: Super Contributor
timestamp: July 20, 2024, 05:04:07 pm
content: I find it strange that my LCR meter doesn't test DC capacitance, but yeah it's only powered from 12V, but that's more than my DMM.Some day I want to make some other test circuits for capacitors, or maybe try and mod them onto my MS-5308 meter. I'm guessing people have hacked them before.Rating and Derating for Low-Voltage Multilayer Ceramic Capacitors (MLCCs)https://nepp.nasa.gov/files/25843/2013-Teverovsky-pres-MLCCsBME-n263.pdf

author: Siwastaja
author_rank: Super Contributor
timestamp: July 24, 2024, 09:02:12 am
content: Quote from: shabaz on July 19, 2024, 02:15:56 pmSRF is the most widely misunderstood parameter. Ignore if you are not 100% sure you understand what it means. Instead, you should be interested about amount of capacitance, ESR, and ESL. For MLCCs, ESL is basically always directly from the package size, so for minimizing it, choosing smallest package is the key.Simplified, SRF is ratio of ESL to capacitance. If you add capacitance, high-frequency performance isn't getting any better, because it's limited by ESL. Increasing C while keeping ESL constant causes SRF to plummet, giving an impression to young players that high-frequency performance is "getting worse", when in fact it's onlynot getting any better, but being the same as with a smaller capacitance part (in same package size so same ESL).For this reason, largest C in smallest package is optimal for bypassing, for both low and high frequencies, and paralleling MLCCs of different capacitances (especially in same package size) is ridiculous.

author: wraper
author_rank: Unknown
timestamp: July 24, 2024, 09:11:57 am
content: ^Yes, I quite often see datasheets or just people recommending placing a few capacitors of different capacitance (about an order of magnitude for each step) connected in parallel for decoupling with no mention they should be of smaller dimensions for smaller capacitance. Sometimes I see capacitors of the same size in mass produced devices. While in fact you should put the smallest one closest to the IC with the lowest inductance path. So 3 capacitors of the same dimensions are not that much better than using just one of the larger capacitance.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 24, 2024, 09:39:32 am
content: Mmm, reciprocal product (w = 1/(sqrt(LC))), not ratio.Tim

author: shabaz
author_rank: Frequent Contributor
timestamp: July 24, 2024, 01:26:16 pm
content: Quote from: Siwastaja on July 24, 2024, 09:02:12 amHi,That's very good. However, on the topic of capacitor size, it's not really the capacitor "size", it's the inductance. And that's being pedantic since of course size will have an impact except in a few and in some contrived circumstances.Similarly, it's not really the SRF, but it is what we can find in datasheets and charts, so there's nothing wrong with using the information we are given, and it's usually a very good illustration to see why you're going to get no improvement at higher frequencies. Since the dimensions/construction is not changed, then you will still be limited by the inductance, and that's easy to see by looking at impedance charts and realizing that the large capacitance value (in the same physical size/construction) won't get you an improvement because once you hit SRF, the impedance rises (and sure, you can still use the capacitor, I don't think anyone said you couldn't). But you could use a lower value capacitance. You could just as easily use a smaller capacitance in a physically larger size, and in parallel with a lower inductance capacitor (let's say 0603 or 0402), and still achieve lower ESR if that was the goal (although you might want to simulate it). That's why I don't think they are very general-purpose. At least, I have dozens of different value and size tantalum capacitors for instance, a few books of them, but far fewer MLCC of such high capacitance (zero in my case). And there could be (are) good reasons to not use those sometimes too. In other words, 'general-purpose' might mean different things to others with different perspectives.

author: mawyatt
author_rank: Super Contributor
timestamp: July 24, 2024, 03:22:07 pm
content: When considering a Capacitor(s) for Decoupling thinking of impedance magnitude (Z) makes sense when considering Capacitance effects, especially true for Decoupling Specific Frequencies or Frequency ranges.Since Inductance follows device length, then shorter (smaller) devices generally have lower Effective Series Inductance or ESL and lower Z at Higher Frequencies. This is shown when investigated SMD Capacitors which are available in the same package size, but two different orientations. When rotated 90 degrees to the general L/W orientation where L>W the effective ESL is lower and thus higher overall SRF.Best,

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 24, 2024, 10:52:34 pm
content: Wide format, and even LGA (checkerboard pinout), are widely used for interposer or back-of-die/co-pack bypassing of modern SoCs, CPUs, etc.Conversely: have seen wide-format chips used all too often with a lazy dogleg and single via to each plane, lol. You aren't gaininganythingif you aren't also using the minimum-inductance connection (e.g. a pair of vias flanking each pad, as close as possible given pad/drill/via-in-pad rules, and tenting if used).To be completely clear, inductance goes as µhl/w, for height above plane h, length l and width w. In PCB, mu will be µ_0. "Goes as", because this is true in the thin/wide-stripline case, where side fringing and end connections can be ignored. Neither of which is really quite true in a capacitor geometry, but the general trend remains.You also tend to see very thin chips in interposers, which are themselves PCBs made with quite thin and fine-pitch geometry, hence can have quite low Zo, low stray L, while fanning out quite dense structures like ICs. Again, low h makes for low L.The PDN (power distribution network) design of a modern BGA/LGA device, spans many tiers. The die itself has to handle harmonics into the 10s of GHz, and this is largely handled by nearby gates themselves -- with careful design, it can be ensured that only a modest fraction of gates in a general region are toggled each cycle, and thus the static ones (that edge) have capacitance that acts as bypass for the neighbors that are switching. Further up the die stackup, alternating metal grids are used to distribute power, contributing much capacitance in the process (I don't know actual figures, but I would guess this can total several µF; they can interleave a lot here!). Going from chip to interposer, power bandwidth is in the 100s of MHz to low GHz, and a fine pitch PCB is required, with low profile, wide-format chip caps. Finally at the board level, lands/bumps can only ensure up to maybe 100MHz or so bandwidth -- there's simply too much length between PCB and package, at the impedances demanded, to have any effect above 100MHz or so, even if the whole package were an alternating checkerboard of balls -- the fine tiers of on-package filtering are mandatory for practical commercial application!On the upside, the on-package filtering relaxes PCB layout, so that VCORE/VIO/etc. and GND can be placed in more orderly fashion (square arrays, rings, rows, etc. of each connection), and fairly large caps placed on the board (say, 10s uF). Still further away, bulk caps can be placed, perhaps 100s uF polymers, and finally down at a power bandwidth of 100s kHz, maybe low MHz, the PoL converter (across however many phases) supplies VCORE from whatever other bulk source is in use (which might in turn be in the 10s kHz bandwidth, and ultimately supplied from, say, a PFC reservoir capacitor finally with bandwidth in the single-Hz range, or a battery in the mHz to µHz range).Tim

author: thm_w
author_rank: Super Contributor
timestamp: July 24, 2024, 11:19:24 pm
content: Quote from: schmitt trigger on July 19, 2024, 02:27:22 pmSure but that has no relevant effect when OP was testing at 0.5V AC.

author: gamalot
author_rank: Super Contributor
timestamp: July 24, 2024, 11:21:21 pm
content: Try heating them with a soldering iron then waiting for them to cool down and measuring again.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 25, 2024, 01:22:28 am
content: Quote from: thm_w on July 24, 2024, 11:19:24 pmYou are absolutely correct.However, it is still remains useful information.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 25, 2024, 06:59:40 pm
content: Quote from: thm_w on July 24, 2024, 11:19:24 pm"DC bias" is a misleading name - C(V) characteristics is a better name. A capacitor does not understand "DC" or "AC", it just sees a voltage, and the effective capacitance drops. This is evident if you use an oscilloscope to plot the voltage of an AC current source into the capacitor: voltage rise rate is not a constant, but accelerates when the voltage increases. And this is how component testers operate.The point is, if the part is already rated to lose 80% of its capacitance at 5V (note: I'm saying just "5V", not "5V DC bias", which is a confusing way to say it), then surely it loses some capacitance already at 0.5V. How much, look at the manufacturer graphs (if available) very carefully, but it could be something very real and measurable, like 5-10%.So OP would see combination of at least three factors:Lack of high-temperature curing (soldering)"DC bias" effect, even at 0.5V "AC"ToleranceRemember that tolerance also allows manufacturer (who has better quality control than tolerance demands) to manufacture systematically under the nominal spec parts. For example, if component tolerance is given as +/- 20% and manufacturer is sure their process is accurate to +/-10%, they can manufacture parts which fall between -20% and 0% and save some costs while delivering a product that's completely in-spec.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 25, 2024, 07:16:42 pm
content: I also agree with you, capacitance change as a function of the peak applied voltage would be better description.The reason I mentioned DC Bias is because these capacitor’s most common “gotcha” is as a filter on a SMPS output.Common rookie mistake, design a required capacitance value, then failing to take into account the precipitous drop in the value under actual operating conditions.

author: TimFox
author_rank: Super Contributor
timestamp: July 25, 2024, 07:46:05 pm
content: "DC bias" effect is a reasonable term for a capacitor (such as a rectifier filter capacitor) where the DC value of the voltage across it is high, but the circuit requires a value of capacitance (or capacitive reactance) for small (ripple) voltage about that DC value (small AC component of voltage compared with the DC value).A good RLC meter with a DC bias capability measures that effect at a specified DC voltage.

author: thm_w
author_rank: Super Contributor
timestamp: July 25, 2024, 10:28:55 pm
content: Quote from: gamalot on July 24, 2024, 11:21:21 pmThen tell that to your customer in 12 months when the product failsQuote from: Siwastaja on July 25, 2024, 06:59:40 pmLook a little closer at the graph that schmitt posted, and see what AC voltage was used.

author: mtwieg
author_rank: Frequent Contributor
timestamp: July 26, 2024, 12:20:04 pm
content: Quote from: Siwastaja on July 25, 2024, 06:59:40 pmI'm afraid the reality of MLCCs is a lot more complicated than just DC bias effects, and the DC bias curve is likely a red herring in this case. For high density MLCCs with class 2 dielectrics, measured capacitance will depend on applied AC voltage, but in theoppositemanner implied by the DC bias curve. That is, measured capacitance willincreasewith increasing AC test voltage. I've seen examples where this effect can change measurements by up to 50%. Some sources suggest that this is due to hysteresis effects in very thin dielectric layers.Here's a couple links from manufacturers mentioning this effect. Good manufacturers will always mention the AC voltage they use for testing MLCCs (often 0.5V), and this is why:https://product.tdk.com/en/contact/faq/capacitors-0007.htmlhttps://www.murata.com/en-us/products/capacitor/ceramiccapacitor/library/solution/insufficient#Hik03As these links point out, the actual applied AC voltage might be much lower than what your meter displays, especially when the capacitance is very large. If the meter doesn't have some sort of auto level correction, it's worthwhile to verify the actual applied voltage with a DMM/scope.Obviously if one were to continue to increase applied AC voltage the measured capacitance would start decreasing as the DC bias effect takes over. It's unclear how the AC and DC effects interact though. I suspect that applying a DC voltage will reduce the AC "hysteresis" behavior, but have never really investigated this.

author: TimFox
author_rank: Super Contributor
timestamp: July 26, 2024, 04:05:47 pm
content: The implication of all of these valid comments about voltage dependence:Do not use Class II capacitors where you need a linear capacitor that obeysQ=CV: e.g., audio signals, timing circuits, analog filters, L-C resonant circuits.They still are useful for storing charge, so long as you use their actual non-linear characteristics when designing: e.g., DC filter capacitors.Historically, ceramic capacitors were disrespected in audio due to the non-linear Class II dielectrics used in disc ceramic capacitors to obtain useful capacitance values.With modern MLCC construction, C0G Class I capacitors are available up to 100 nF for signal-critical applications.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 27, 2024, 12:08:56 am
content: Heh, they're much too lossy for most LC circuits anyway, but you can get some very strange (if not very useful; but not to say useless, applications might exist) behavior, like a Bode plot that has hysteresis! Or using the C(V) curve as a variable filter (if a crude one, given the losses, poor tolerance, and temperature sensitivity), or the nonlinearity for harmonic generation or other esoterica (parametric amplifier).Tim

author: mawyatt
author_rank: Super Contributor
timestamp: July 27, 2024, 12:38:08 am
content: Quote from: T3sl4co1l on July 27, 2024, 12:08:56 amSorta discussed here about Ceramic Capacitor Behavior.https://www.eevblog.com/forum/projects/ceramic-capacitor-behavior/Best,