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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
jose.angel.jimenez
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    So basically "when do technical needs override my ethics" which leads to a different answer for every person which leads to nothing else but opinions. – PlasmaHH Nov 06 '15 at 21:36
  • When you are talking high-volume consumer electronic products, every sub-cent counts, only if your company is big enough to cut on the margin you will be able to use the more costly solution. – Arsenal Nov 06 '15 at 21:57
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    "I am focusing here on high-volume consumer electronics products, discarding specifically power electronics applications, where other considerations may apply." So you're not interested in power conversion and management applications within consumer products? That's where the choice of capacitor is most critical for many of the reasons you listed. – John D Nov 06 '15 at 22:22
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    My rule is no tantalum. Period. I design battery powered hand-held stuff for the consumer market. If I need more than 22 uF, I use aluminum electrolytic. Most of the time 22 uF is enough. This is not driven by ethics. It is driven by my nightmare memories of the great tantalum shortage during the dotcom boom era. My circuits are not the kind that would have problems with microphonics. But my understanding is that it can be a real problem in some applications. – user57037 Nov 07 '15 at 01:59
  • @mkeith: then you can't work at Apple... – Fizz Nov 07 '15 at 03:30
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    If I go work at Apple, and they want me to design in tantalum, of course I will do it. Apple has the ability to source parts when other companies can't. Suppliers give priority to Apple (even de-allocating supply promised to other companies). And Apple has margins that can absorb high tantalum prices if it should come to that. Although they also have the ability to negotiate good pricing. – user57037 Nov 07 '15 at 03:38
  • @mkeith Thank you! You have basically summarized my rule (MLCC for up to 20-22uF, Alu for anything above that). – jose.angel.jimenez Nov 08 '15 at 20:25
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    @John-d Your are absolutelly right. My statement about "power electronics applications" is not very clear. I intended to say I was not interested in high power applications. But that is not to rule out power conversion circuits, which are virtually needed everywhere. I will update my original question. – jose.angel.jimenez Nov 08 '15 at 20:35
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    Thanks for sharing the information about Coltan mining. Very eye-opening. – jalalipop Aug 10 '18 at 16:54

4 Answers4

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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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jose.angel.jimenez
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user19579
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I might add: Tants do not like applications where high turn-on surge currents are possible…output of a regulator yes (current is limited)…input to a regulator no (current is probably not limited). This can be partly mitigated by derating the voltage by as much as possible, using a 35v tant in a 10 volt application for example.

Robert Endl
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The only place where I've seen them [personally] in a mass-market product this century was in the VCO [for the wireless] of a Uniden cordless phone.

Since you made me curious about this, I've done a bit of googling (for tantalum and VCO) and found MAX2572EVKIT which doesn't terribly ancient (2004), and has some tantalum caps in its BOM. This is a GSM VCO. Also found a teardown of a [rather looking ancient] GSM phone, and they found tantalum caps in it, but the don't say in what subsystem.

Also found some in the datasheet of HMC836LP6CE; this isn't clearly dated, but the revision number looks like 2011 or 2012. This is a 4G PLL/VCO so it can't be incredibly ancient. Another teardown found some on the PCB of the iPhone 6; these ones made by Rohm, their role in the phone not stated there, but claimed to be "the most expensive capacitor in the iPhone 6".

Also note this story for a tantalum cap on an Arduino GSM module catching fire. Of course, parts selection for an Arduino shield is probably done at much lower standards than Apple's...

It's not totally clear to me what you mean by "discarding specifically power electronics applications", but in case others are interested in this, some were also found in a teardown of an iPhone charger.

Fizz
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    Thanks for your useful links and great insight! You are right, my statement about "power electronics applications" is not very clear. I intended to say I was not interested in *high power* applications. But that is not to rule out power conversion circuits, which are virtually needed everywhere. – jose.angel.jimenez Nov 08 '15 at 20:33
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My decision to use ceramic or tantalum capacitors in most cases is based on cost. When i need capacitances bigger than 10uF, ceramic capacitors are expensive and tantalum capacitors are a good option.

Gabriel Rezende Germanovix
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