Electronic – Ceramic (MLCC) versus Tantalum capacitors


From the perspective of an electronics designer, but also taking into account price/cost and social considerations (see Coltan mining and ethics link below), I tend to avoid Tantalum capacitors under many circumstances, while favouring Multi-Layer Ceramic Capacitors (MLCCs).

My question, bluntly stated is: In which specific cases should I be careful and continue using tantalum capacitors? All sorts of answers and technical approaches to this matter will be very useful to me (and surely for other designers).

Some specific aspects to look into:

  • Series equivalent circuit.
  • Microphonics. How bad are MLCC really are in this respect?
  • Capacitance dependence with voltage and temperature.
  • Overvoltage and failure modes.
  • Life expectancy and reliability.

Additional context:

  • I address specifically Surface Mount Technology (SMT), assuming more than 90% of all tantalum electrolytic capacitors are manufactured in SMD style.
  • I am focusing here on high-volume consumer electronics products, discarding specifically high power electronics applications, where other considerations may apply. I am not ruling out power conversion/management circuits, where the above considerations are key for capacitors.
  • You can read more about the Coltan social impact at the Wikipedia: https://en.wikipedia.org/wiki/Coltan_mining_and_ethics

Best Answer

There are lots of application notes on this. Google for "Tantalum vs ceramic capacitors".

Ceramic capacitors are best for its ESR & ESL. So that they can handle huge ripple currents at less temperature rise in power supplies. Same way, they don't disturb signal quality in High-speed systems (AC coupling capacitors). But their DC Bias characteristics are poor. Like a 47uF X5R 6.3V is ~23uF @ 3.3V. This Low ESR & ESL may be bad in some cases. For instance, some Buck converters that require enough ripple at the output to be stable. And lower ESL will react with cable capacitances to give unnecessary oscillations.

Tantalum capacitors are best known for Volumetric efficiency and Cheap cost, but they are prone to failure due to surge currents. There are alternatives like POSCAPs (polymer capacitors).

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