Kemet Capacitors vs. Vishay - Page 1
Forum section: electronics / projects

author: bostonman
author_rank: Super Contributor
timestamp: September 02, 2025, 11:45:49 pm
content: I'm kind of copying an existing design that uses Vishay capacitors. They are VJ1206, X7R, 10%, Ni Barrier (I don't know what that means).Digikey has has these and the price varies from around $0.30 to over $0.50. Since size doesn't matter, I looked for 0805 with all the same specs and Kemet are down around $0.08.Due to not having experience with selecting capacitors in fine detail, I'm wondering if I can get away with 0805 Kemet to save cost since I need many.Also, COT seems better than X7R, but I'm guessing higher cost.Am I overlooking something if I switch from 1210 Vishay to 0805 Kemet and/or switch to COT (assuming this is better and the cost isn't significantly higher).

author: PCB.Wiz
author_rank: Super Contributor
timestamp: September 03, 2025, 12:20:54 am
content: If it is an existing design, a very simple first check would be to swap the most likely same/better candidate and try it in a real system.What values and what currents/voltages ?

author: bostonman
author_rank: Super Contributor
timestamp: September 03, 2025, 02:02:53 am
content: I don't have the system, it's old drawings that I built.

author: tggzzz
author_rank: Super Contributor
timestamp: September 03, 2025, 06:16:21 am
content: Depending on how they are used, it may be important to look at the C-vs-V curve. Cheaper capacitors tend not to specify that.

author: gamalot
author_rank: Super Contributor
timestamp: September 03, 2025, 08:05:36 am
content: Whether MLCCs can replace other types of capacitors depends on the specific application. For instance, using low-ESR MLCCs at the output of certain LDOs may lead to instability.

author: mtwieg
author_rank: Frequent Contributor
timestamp: September 03, 2025, 11:43:12 am
content: Could you provide a specific part number for one of these "VJ" caps? Vishay has many families of MLCCs referred to as "VJ". Some of them them are pretty vanilla, some are highly specialized (for example, they offer some which use noble metal electrodes (NME) so they are non-magnetic). Usually one would not use one of these specialized parts without good reason.

author: PGPG
author_rank: Frequent Contributor
timestamp: September 03, 2025, 12:27:00 pm
content: COTCOG (NP0) capacitors capacitance practically don't depend on temperature and voltage.X7R capacitors capacitance strongly depends on temperature and voltage but they can have much higher capacitance in the same size.X5R are practically like X7R, can have little higher capacitance in the same size, but are specified to work only up to 85°C (X7R up to 125°C).Y5V are much worse than X7R (X5R) but can have even higher capacitance in the same size. I was using them at the beginning of 2000 years when X7R had much smaller capacitance than nowadays. Since about 2010 I am not using Y5V at all.So the simple rules are:- if your circuit depends on capacitor capacitance - use COG (NP0),- if capacitance should be big but exact value not important - use X7R (or X5R if your circuit need not to work in temperature higher than 85°C).

author: wraper
author_rank: Unknown
timestamp: September 03, 2025, 12:36:23 pm
content: It's C0G, not COT. And generally they're not used for decoupling other than for small capacitance in addition to X7R, X5R. They're used where capacitance stability, dissipation factor and microphonic effect do matter.

author: bostonman
author_rank: Super Contributor
timestamp: September 03, 2025, 01:23:17 pm
content: I'm so use to typing COTS (commercial off the shelf) that I accidentally called them COT. Yes, they are COG.After some of the research I did, the conclusion was, as with many other things, it's all about trade offs. Once I saw the price difference between Kemet and Vishay along with 0805's having (what seemed like) the same specs, I didn't know what the advantage was to playing many times more per Vishay cap.One of the part numbers in question is: VJ1206Y104KXAI didn't type a part number before because I didn't want anyone thinking I didn't research it, so that's why I included the specs rather than the part number.Whether the design loses quality as a result of a Kemet cap is a different story, but, going by specs, it seems an $0.08 Kemet cap has the same specs as a Vishay $0.50 cap.

author: mawyatt
author_rank: Super Contributor
timestamp: September 03, 2025, 01:32:29 pm
content: Some component vendors aren't competitive price-wise at low quantities, Vishay generally seems to be in that crowd!WRT the ceramic capacitor dielectric type, the high K dielectrics have a highly dependent capacitance vs voltage characteristic. When using these the average applied voltage across the Cap needs to be well below the Cap voltage rating, otherwise a significant reduction in effective capacitance is expected.Best

author: mtwieg
author_rank: Frequent Contributor
timestamp: September 03, 2025, 02:05:50 pm
content: Quote from: bostonman on September 03, 2025, 01:23:17 pmI don't think this is the complete part number. Searching for it yields no exact matches, digikey turns up four part numbers containing that substring. All are 50V, 0.1uF, X7R, 1206, but belong to three different families.One is a generic part, described as for "basic commodities"Another has noble metal electrodes, and is described as the "commercial series"Another has NME and also "open mode design", described as for flex sensitive applications.The second and third are 2-3x the cost of the first. No idea which one you were actually looking at pricing for.I don't think there's a Vishay vs Kemet issue. Both manufacturers offer specialized product families for special applications, at increased price. This makes an apples-to-apples comparison difficult and complicated.

author: tggzzz
author_rank: Super Contributor
timestamp: September 03, 2025, 02:23:56 pm
content: Quote from: mawyatt on September 03, 2025, 01:32:29 pmAnd if you apply a square wave through a resistor, the waveform can bevisiblynon-exponential!

author: ejeffrey
author_rank: Super Contributor
timestamp: September 03, 2025, 02:34:38 pm
content: Mostly you can replace x7r with x7r as long as you make sure the capacitance at operating voltage is enough. All x7r capacitors will loose capacitance at non-zero voltage, often dropping significantly even above 1 VDC. Reputable manufacturers will give you the derating curve but you often have to dig around on their website.The shortcut for checking voltage derating is to look for the same volume. It's best to confirm by checking the manufacturers data but digikey et al. will let you filter and sort on package thickness which will filter out a bunch of parts that are much thinner than the original and not likely to match its behavior.Other features concern reliability like soft terminations to reduce cracking, or chemical resistance. You need to understand the application and environment to know if you need these.

author: David Hess
author_rank: Super Contributor
timestamp: September 03, 2025, 03:05:26 pm
content: Quote from: bostonman on September 02, 2025, 11:45:49 pmFor dielectrics other than C0G, smaller sizes usually have a worse voltage coefficient of capacitance.QuoteIt should not matter.QuoteC0G capacitors are better, but usually larger and more expensive for larger values.

author: TimFox
author_rank: Super Contributor
timestamp: September 03, 2025, 04:58:08 pm
content: “Ni barrier” is a layer of nickel between the internal metal layers (usually alloys containing silver) and the external solder layer to prevent leaching of the internal metal into the molten solder joint, damaging the component.I believe almost all surface-mount ceramic capacitors use it.

author: hfleming
author_rank: Regular Contributor
timestamp: September 03, 2025, 06:50:25 pm
content: Most caps from these various cap manufacturers are much the same, electrically-wise. However, if you use larger SMD-capacitors, 1812 or so, AND the PCB can flex during vibration/thermal stresses, look at the termination, there it can make a huge difference. Some manufacturers have a more flexible barrier, that do not break so easily under thermal/mechanical/piezo-electric stresses. Back in the early 2000’s there were quite a few technical issues with it. (Just ask me). Lots of manufacturers came up with their own (semi-)flexible terminations with different designations. Just google Flexicap MLCC.

author: PGPG
author_rank: Frequent Contributor
timestamp: September 03, 2025, 07:02:13 pm
content: Quote from: wraper on September 03, 2025, 12:36:23 pmRight, among other it is also my mistake.I will look if I can correct it in the way that previous text will still be seen.

author: bostonman
author_rank: Super Contributor
timestamp: September 03, 2025, 10:04:15 pm
content: QuoteI don't believe anything was incomplete (see datasheet) except marking and packaging (last two digits) which I don't have; and didn't feel it was important.https://www.vishay.com/docs/45199/vjcommercialseries.pdfWell, this has certainly given me more to think about. This isn't under large temp variations (typical room temp variations of maybe 60 to 80 degrees F) or vibrations, just bypassing between 1MHz - 20MHz to the input of op-amps; maybe a smaller frequency range.Just to make sure I understand which specs are the most crucial (some I already know which are the basics): voltage, dialectric, temp range, termination (if we were worried about vibration), and performance over voltage.For a moment let's assume I select all the same specs (X7R, 10%, capacitance value, voltage, and termination), does size matter? It was somewhat answered already, but I'm just clarifying because it seemed size was the only difference in cost (and company).The understanding of capacitors has always eluded me. Since I lack circuit design skills, my experience is whatever is on the PCB I'm repairing/testing is what belongs there. When it comes to actually selecting them, I don't know the understanding on when to use one over another. Prior to starting this thread, I researched X7R, X5R, and COG. Although I'm not currently looking on DigiKey, it seemed I could get an equal (or maybe better) capacitor from Kemet for less maybe because it was smaller (0805).To be clear, I'm not against paying $0.50 per capacitor, but I did a quick cost estimate on my project thinking capacitors (and resistors) would be the cheapest component. Nearly fell off my chair seeing ten capacitors of just one value would be $5; expected to pay $1 at most.QuoteA possibility exists I experienced exactly these issues as I remember seeing an opencapend cap on a SMT 0805 resistor. That was probably my first time seeing an open resistor that wasn't due to being burnt.

author: mtwieg
author_rank: Frequent Contributor
timestamp: September 03, 2025, 11:28:38 pm
content: Quote from: bostonman on September 03, 2025, 10:04:15 pmIn a lot of cases I wouldn't argue, but since you were specifically interested in reducing cost, it seemed worth mentioning that your part number describes a few different parts with very different prices.QuoteFor general bypassing there's usually no reason to consider using a C0G dielectric. The only exception would be due to concerns about piezoelectric effects, but it's very unlikely this would actually be an issue for supply decoupling caps...QuoteAs others mentioned, size will be related to the amount of C-V nonlinearity you can expect. You can definitely find capacitors with those same ratings inpackages as small as 0402. But their effective capacitance is going to be tiny when biased near their rated voltage (that one I linked is 15nF at 50V). As long as you keep that in mind, it's usually fine.

author: bostonman
author_rank: Super Contributor
timestamp: September 04, 2025, 02:40:14 am
content: QuoteI must be missing something because the part number I provided seemed like it eliminated any other capacitors except for one.VJ1206: Case code (VJ1206)Y: dialectric strength (X7R)104: Value (100,000pF or 0.1uF)K: (tolerance) 10%X: termination (Ni barrier)A: voltage (50V)The datasheet states the last two digits are marking and packaging which seem irrelevant to performance.Part of the datasheet I don't understand is the CAP. CODE charts towards the bottom. For mine, it shows a 104 CAP CODE, but I don't see the use for this code.

author: TimFox
author_rank: Super Contributor
timestamp: September 04, 2025, 02:44:58 am
content: Cap code "104" means 10 x 104pF = 100 nF

author: bostonman
author_rank: Super Contributor
timestamp: September 04, 2025, 02:57:06 am
content: hahah oops, that was an easy one that I overlooked; didn't put two and two together. I saw 104 in the part number, but for some reason, not in the chart.Then it's a chart to show the availability of each type based on voltage, case size, etc...

author: mtwieg
author_rank: Frequent Contributor
timestamp: September 04, 2025, 10:47:19 pm
content: Quote from: bostonman on September 04, 2025, 02:40:14 amDon't forget the "process code" field at the end. I belive that's what distinguishes the "commercial" or "commodity" parts from the special ones. Probably does not affect "performance" (i.e. electrical characteristics), but definitely can matter to the price.

author: TimFox
author_rank: Super Contributor
timestamp: September 04, 2025, 11:43:17 pm
content: Quote from: mtwieg on September 03, 2025, 11:28:38 pmYes, size matters. The non-linearity of X7R and other class II materials is an intrinsic property of the material.Therefore, it must depend on the E-field (voltage gradient) inside the material.For a given voltage, that gradient obviously increases as the dimension shrinks.The rated voltage is a smoke value: the manufacturer guarantees the part will not be damaged at that voltage, not necessarily that it has a given performance.

author: bostonman
author_rank: Super Contributor
timestamp: September 05, 2025, 01:30:09 am
content: QuoteThat would make sense. Although price matters, at least it's irrelevant to performance.Ignoring additional PCB space required for larger size capacitors, it seems going bigger will improve the E-field (I was unaware of this term related to capacitors until now) and be the better choice.If I'm understanding, a 0402 capacitor will have a poor performance capacitance curve and a (as an example) 50V will not be as stable at it's working voltage than a 1210?This information has been valuable; I never realized how much can go into a capacitor. Always thought, get the same type (i.e. ceramic), same value, and either the same or higher voltage; and order from a reputable company.Over the years I've searched (and found) various comparison charts for different capacitors, but never really understood mica versus poly, etc...Does a decent chart exist? I know ceramic have polarity whereas tantalum doesn't. Years ago I thought this was the deciding factor on which one to pick, but my later years I've realized it's not.Now that I have more knowledge, having a list of the different types and a comparison of advantages/disadvantages to have on hand may be beneficial.Also, I'm uncertain about MLCC. I've heard and read they are prone to failure. In fact, at my old job they use to place two in series (two 20uF to make 10uF if that was the value needed) so in case one failed shorted, it wouldn't blow the fuse. With learning this about MLCC, I was reluctant to use them, however, it seems they are quite popular.

author: wraper
author_rank: Unknown
timestamp: September 05, 2025, 02:18:52 am
content: Quote from: bostonman on September 05, 2025, 01:30:09 amIt depends. It's about capacitance to size ratio. It will likely be decent enough for 0.1uF but become really crap when going close to max available capacitance for the size. 1210 100uF, and especially 330uF will be total crap too.