19
\$\begingroup\$

What are the advantages of using electrolytic capacitors?

I know in the past electrolytic capacitors would have more capacitance, but with Multi-layer ceramic capacitors (MLCC) they seem completely obsolete. The MLCCs also can have high capacitances, but they have lower equivalent series resistance (ESR), lower Equivalent series Inductance (ESL), and are much smaller physically. I'm just very curious as to why lower-value electrolytics are in production.

Could someone explain why someone would use a high-value electrolytic over a high-value ceramic capacitor?

\$\endgroup\$
15
  • 9
    \$\begingroup\$ Your high value MLCC is a miniscule electrolytic. A 10V, 47uF is tiny for an electrolytic and yet you can't get them as an MLCC. \$\endgroup\$
    – DKNguyen
    Oct 5, 2022 at 14:26
  • 13
    \$\begingroup\$ And what voltage are they? How much do they cost? What is their capacitance under DC bias? \$\endgroup\$
    – DKNguyen
    Oct 5, 2022 at 14:29
  • 15
    \$\begingroup\$ Okay so what about 25V? My point is you're not looking at the entire span of where caps are used. For 1/10th the price I can get an equivalent electrolytic. For the same price I can get much higher voltage, capacitance, or both. \$\endgroup\$
    – DKNguyen
    Oct 5, 2022 at 14:34
  • 9
    \$\begingroup\$ I have four 100,000 uF 200 volt electrolytic capacitors I just could not live without. \$\endgroup\$
    – Andy aka
    Oct 5, 2022 at 14:36
  • 12
    \$\begingroup\$ The highest value MLCC I found on Mouser is 470uF. For a 25V one it's over $35 US. They have 470uF/25V electrolytics for under a dollar for quantity of 1, even less in bulk. That's a big difference when you need one, let alone tens of thousands. \$\endgroup\$
    – GodJihyo
    Oct 5, 2022 at 14:57

7 Answers 7

27
\$\begingroup\$

Voltage rating would be the biggest difference as electrolytics are much cheaper if you need a higher voltage rating in the same value. But there are many different factors to compare and there are really no hard and fast rules.

For example, if you need a 10 μF cap with a 63 V voltage rating a ceramic capacitor can be several times more in cost.

Ceramic caps have better ratings because the leads are smaller, leads and metal have inductance which leads to a lower ESL spec. So electrolytics will have a higher ESL rating usually.

enter image description here Source: https://www.johansondielectrics.com/basics-of-ceramic-chip-capacitors

enter image description here Source: http://en.wikipedia.org

\$\endgroup\$
6
  • 4
    \$\begingroup\$ They also have lower ESR, because the electrolyte isn't very conductive compared to the metal plates in MLCCs. Even (aluminum|tantalum) polymer caps can't compete in terms of ESR with ceramic. \$\endgroup\$
    – Hearth
    Oct 5, 2022 at 14:40
  • \$\begingroup\$ Yeah I need to update this with the ESR also but I'm on my phone I need to look at the dielectric versus ceramic. Also I believe you can get a much closer spacing on a mlcc then you can on electrolytic and that enables you to have much more area in a small space \$\endgroup\$
    – Voltage Spike
    Oct 5, 2022 at 14:42
  • 4
    \$\begingroup\$ Electrolytics are typically larger than ceramics, but they're generally smaller per (capacitance)*(voltage rating), at least other than really small capacitances that you wouldn't normally use electrolytics for anyway. \$\endgroup\$
    – Hearth
    Oct 5, 2022 at 14:44
  • 6
    \$\begingroup\$ Electrolytic capacitors are also more stable with respect to voltage than high-κ (type II) ceramic capacitors. A 10 μF 6.3 V electrolytic will be pretty close to 10 μF even at 6.2 V, but a 10 μF 6.3 V Y5V ceramic will probably measure less than 3 μF at 6.2 V. And 10 μF is just straight up not available in type-I ceramics (like C0G or U2J) that don't show this effect. \$\endgroup\$
    – Hearth
    Oct 5, 2022 at 14:47
  • 5
    \$\begingroup\$ Yep, more linear, if you will. \$\endgroup\$ Oct 5, 2022 at 16:53
31
\$\begingroup\$

What are the advantages of using electrolytics?

  • Available with about 3 orders of magnitude higher capacitance at the same voltage rating
  • Capacitance is stable under DC bias, whereas most (Class 2) MLCCs are not

Essentially they give a lot more capacitance and that capacitance is much more stable, especially above a few volts DC.

I'm just very curious as to why lower value electrolytics are in production.

Skimming Digi-Key, not very many lower value electrolytics appear to be in production. Most are higher value/voltage parts you couldn't get in MLCC. Lower values are still useful though, especially for things like audio amplifiers, where you very often don't want the capacitor value to change with voltage.

\$\endgroup\$
26
\$\begingroup\$

Your average Al electrolytic has a wonderful ESR-capacitance product in order to double as a snubber against nasty ringing at the MHz ballpark. This is cool because such ringing can easily appear due to usual voltage regulator bandwidths and MLCC loads. This can be simulated below by either disconnecting Cel (regulator oscillates), setting it as a MLCC (10 mΩ ESR, oscillates) or having it there as an electrolytic (stable).

schematic

simulate this circuit – Schematic created using CircuitLab

Of course one could emulate this behavior with an MLCC and series resistance, but one would need unusual resistor values on stock such as 33 mΩ or 330 mΩ and one would need a different resistor for different capacitance.

Another disadvantage of larger ceramics is that they are said to be prone to cracking in packages larger than ~1210. So you need loads of small caps to achieve something like 100 μF at 12 V, which is trivial with a single Al electrolytic and saving costs.

\$\endgroup\$
2
  • 2
    \$\begingroup\$ The cracking problem is more to do with package and less materials. If you use a through-hole MLCC, cracking is basically a nonissue. If you were to have an electrolytic capacitor in the same package, mechanical damage would also be a concern. But the closest surface-mount electrolytics (which would be tantalum capacitors) seem to always use a J-lead construction, which allows for more flexion without damage. \$\endgroup\$
    – Hearth
    Oct 6, 2022 at 5:21
  • 1
    \$\begingroup\$ @Hearth I would say it is both. For instance, inductors often have no J leads and packages much larger than 1210. But it seems their material composition allows more ductility than for the average MLCC. Also if you slightly squash an Al electrolytic can with pliers, they probably work on, because everything in them is soft/ductile. Try this with an MLCC 😁 \$\endgroup\$
    – tobalt
    Oct 6, 2022 at 5:28
3
\$\begingroup\$

The MLCC caps can be microphonic which may not be acceptable .If the value is high then a metal film could be too big and /or too expensive. Also MLCC caps have supply problems so some designers place an electro in paralell with several MLCC caps .

\$\endgroup\$
2
\$\begingroup\$

Tangential economics - electrolytic capacitors are still made because they can be made cheap.

The physical equipment/plant still exists and has long-since paid for itself. The incremental cost to continue operating the line is low, so as long as the part can be sold for a profit, the production line can continue to run until catastrophic failure, or wear produces non-functional parts.

We see this with all manner of items - a bicycle freewheel costs $10 whereas the arguably-simpler cassette costs more. Same goes for plastic injection moulds and parts.

Are these components the best? No, but if the final assembly has a lower BOM with the same overall functionality, then the accountants are happier.

\$\endgroup\$
1
  • 3
    \$\begingroup\$ I'd consider this more correct if it weren't for the fact that electrolytic caps are by no means obsolete. Yes, they can be made cheaply, but there is no replacement in the higher capacitance ranges, so it's not like they can be made cheaper than something else. That said, it is still correct. This is probably the only reason 10 nF electrolytics are still made, for instance. \$\endgroup\$
    – Hearth
    Oct 7, 2022 at 22:56
2
\$\begingroup\$

What are the advantages of using electrolytic capacitors?

That they exist, whereas equivalent MLCCs are figments of imagination.

with Multi-layer ceramic capacitors (MLCC) they seem completely obsolete

This does not represent reality at all.

Find us a 650uF 400VDC MLCC capacitor. Plenty of applications exist for such capacitors. Your PC's power supply likely got a few of them.

Try and come up with a MLCC equivalent and tell us how much it will cost, how reliable will it be, etc.

Yeah, it's pure fantasy that MLCCs make electrolytics obsolete. It's not even close!

\$\endgroup\$
-1
\$\begingroup\$

Let's not forget the Inductance of all the foil wrapped into the final shape. I have seen circuits damaged by substituting 'modern' capacitors, only to have a transformer winding fail. That inductance is current limiting, and a replacement transformer for a 1963 'scope is no longer available. When you work on old equipment you need old-style parts.

\$\endgroup\$
1
  • 1
    \$\begingroup\$ the curling foil presents no inductance, because the counter electrode curls in the same way, but current flows oppositely. It is loops that make inductance, and electrolytic caps don't have that to the huge extent that you suggest. the inductance mainly appears due to the height of the part. \$\endgroup\$
    – tobalt
    Oct 11, 2022 at 3:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.