Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Tantalum vs Ceramic Capacitors

  1. Jul 2, 2012 #1
    Hi Guys,

    I'm doing a research on capacitors and wondering if someone would be so kind to give me some help.

    I understand that both tantalum and ceramic capacitors can be used in smartphone/tablets.

    I'm wondering:

    1) What's the advantage of one versus the other?
    2) What is the market trend today? (tantalum caps replacing ceramic caps in cellphones? or the other way around?)

    Thanks in advance for help!!!
     
  2. jcsd
  3. Jul 2, 2012 #2

    davenn

    User Avatar
    Science Advisor
    Gold Member


    they have very different uses, for a start tantalum ones are polarised like the aluminium can type that we have already discussed in your other thread
    ceramic capacitors are not polarised.
    therefore they are not interchangeable in a circuit, so your comment about tant's replacing ceramics is incorrect.
    Tantalum caps as had been also discussed in your other thread are more commonly replacing aluminium can caps because in general they are available in much smaller SMD sizes to suit miniature electronics as found in cellphones etc

    Dave
     
  4. Jul 2, 2012 #3
    Try Wikipedia for descriptions of each.
     
  5. Jul 2, 2012 #4
    Ceramics have lower ESR and higher ripple current, and so are good for bypass caps. Ceramics are known to produce voltage spikes at transients that are near their rated voltage and need to be derated. They also change capacitance when AC voltage is high enough.

    Tantalums generally have lower operating voltage compared to ceramics, and so they have less energy storage ability as a technology. They also are polarized and have higher leakage. Tantalums are good when you need to introduce some ESR such as in LDO designs that the data sheet requires you to use a tantalum output capacitor for regulation stability.
     
    Last edited: Jul 2, 2012
  6. Jul 2, 2012 #5
    This is true, but a ceramic can work if a low valued series resistor is added. A ceramic in series with a 0.22 ohm resistor or so, is more predictable than relying on the tantalum inherent esr. The cap vendor only specifies a maximum esr. The actual value is not very consistent or predictable.

    I agree that the inherent esr in a tantalum can be an advantage. A ceramic has such a low esr, that when it is combined with an inductor in an L-C filter, the Q can be very high. Such high Q values can result in under-damped transient response, i.e. "ringing". An R-C damper can be added to lower the Q, or a series resistor can be added to the inductor.

    Claude
     
  7. Jul 3, 2012 #6
    In my experience this has been an evolving story.
    About 15 years ago we began a transition from aluminium electrolytics to tantalums because of their smaller size per uf. Lately we have shifted from tantalums to ceramics for several reasons:
    1 - tantalum prices rose significantly and lead times became quite long.
    2 - MLCC ceramic capacitor technology advanced to the point where large "bulk" capacitor values became available at low cost.
    3 - we had several instances of high failure rate of tantalums due to surge current. Tantalums are prone to this failure, ceramics are not.

    The increase in price and lead time of tantalums was due to several factors including competition with high value ceramics which had become available, and tantalum being listed as a "conflict mineral".

    This does not mean that ceramics are a panacea. We have had issues with microfracturing of large ceramic capacitors. We recently substituted a tantalum in place of a ceramic to mitigate a microphonics issue caused by the piezoelectric behavior of the large ceramic part. We are also noticing that the capacitance value of large ceramic capacitors is strongly dependent on the DC voltage applied, so we have to consider derating more carefully.
     
    Last edited: Jul 3, 2012
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Tantalum vs Ceramic Capacitors
Loading...