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The past three companies I've worked for that were doing circuit board design expressly forbid the use of tantalum capacitors because they are surface mounted (

The past three companies I've worked for that were doing circuit board design expressly forbid the use of tantalum capacitors because they are surface mounted (SMT) two-terminal parts that have polarity. In other words, tantalum caps have a + and a - terminal and are damaged when reverse voltage is applied. Blanket ban on tantalum use was to avoid mistakes during PCB assembly in manufacturing where caps are oriented incorrectly. Edit: Maybe I misunderstood the reason for a blanket ban of tantalums. The fact remains, the ban was real. What are some of the places where tantalum capacitors are required and ceramic capacitors just can't get the job done?

Neliquat 10y ago
As a hobbiest, I usually see them in high stability power supplies.
- 2bluesc 10y ago
  Probably because when designed right (they are far more finicky then ceramic) they typically offer higher energy density.
  - jacquesm 10y ago
    Higher capacity you mean (for a given volume), that and also very low leakage current so if you want to make a very efficient device then tantalum might pay off. Another reason is that electrolytic caps are usually wound aluminum sheets which act as a coil. If you don't want any parasitic inductance tantalum is better in that application (better frequency response).
    - LeifCarrotson 10y ago
      Tantalum caps have much worse leakage current than ceramics. The debate for most designs is not tantalum vs. electrolytic, it's electrolytic vs. solid vs. ceramic. And ceramic usually wins.
  - marcosdumay 10y ago
    They have lower internal inductance and resistance than other electrolytics. That is very goo for making the low-pass filters one uses on power supplies.
- arcticbull 10y ago
  They're usually used as bulk capacitance, particularly at the input side of switching regulators. Thing is, their ESR is too high to be used alone so they're usually used in parallel with an MLCC ceramic. I've had success replacing both on the input stage with an aluminum polymer electrolytic (not standard aluminum) due to their low ESR and high capacitance (and better inrush rating). I usually use ceramics on the output. [1] http://www.ti.com/lit/an/slta055/slta055.pdf http://www.ti.com/lit/an/slta055/slta055.pdf This is a great writeup on the various types from Kemet: [2] http://www.kemet.com/Lists/TechnicalArticles/Attachments/5/Avnet2012PowerForum_CapacitorsSelection.pdf http://www.kemet.com/Lists/TechnicalArticles/Attachments/5/A...
2bluesc 10y ago
There are many reasons to not use tantalum caps (inability to handle voltage transients requiring derating being the primary that comes to mind), but I've never heard of a company instituting such a policy because their assembly process was so poor. Did they also blanket ban diodes?
- VLM 10y ago
  Might be a retcon. There are sometimes good reasons not to use tantalum aside from the explosion and fire inevitability. At really high temperatures (engine computers etc) tantalum loses voltage rating down to less than 50% in some cases at the limit whereas ceramics lose capacitance with high temp (weird but true for X7R dielectric). This is a general rule of thumb and I'm sure you can find mfgrs whitepapers explaining how their expensive series is immune to this general class effect. In the bad old days tantalum volume was like 100 times smaller for a given capacitance than a ceramic but its not the bad old days anymore and its like 3:1 ratio for some MLCC and because of voltage derating a tantalum derated to 25V (aka a 50V+ cap) might not be all that much smaller than a 25V rated MLCC. Size of cap is no longer a relevant criteria, but customers are more excited than ever about burning exploding personal electronics, so ... Another fun one is leakage current for tantalum is about three orders of magnitude (whoa!) higher than MLCC. Its possible to build little ultra low power IoT things that sleep most of the time and a tantalum leaks more mAH than the processor but a MLCC would waste less. High frequency response is fun because neither is inherently better but in some applications one or the other is better. Generally the MLCC is going to have a higher Q resonance at a higher frequency. If that freq is irrelevantly high to the app and EMI issues, thats a great cap, whereas maybe for some apps sometimes tantalums could be resonant, admittedly at a lower Q, in the region of freqs important to the app or EMI/EMC issues. Not that ceramics are problem free. Piezoelectric effects are hilarious. Aging after heating drops ceramic capacitance, its possible to solder a SMD cap and watch its value drop a couple percent over the next day or so. As with all effects you can acquire manufacturers whitepapers explaining how their extremely expensive exotic series cap can be soldered in place of another of the same family if there's a design mistake and you need to correct it in production, so sure you can pay a lot of money for tantalums that work at 230C or temperature stable ceramics. Something I don't understand is ceramics being ceramics mean they should be good up to lava like temps and alloys being alloys mean you should be able to find something with a matching coeff of expansion thats good up to liquid metal temps, so why can't you buy ceramic caps rated to orange-hot temps? I haven't looked into it deeply enough to find out. There are practical reasons wet tantalums can't run at cutting torch temperatures but ceramics superficially don't seem to have those limits.
the-dude 10y ago
Low ESR applications.
- dragontamer 10y ago
  Ceramic Caps have extremely low ESR as well however.
  - the-dude 10y ago
    Well, show me a 10uF, 10V below 1 Ohm.
    - dragontamer 10y ago
      Ummm..... http://psearch.en.murata.com/capacitor/product/GRM219R61A106ME47%23.html http://psearch.en.murata.com/capacitor/product/GRM219R61A106... Try below 0.01 Ohms, between the frequencies of 100Hz to 1MHz, in the 0805 form factor. 10uF and 10V as requested. Ceramics are extremely good at low ESR / low ESL / decoupling applications. I mean, so are Tantalum caps, so they're both good for this purpose. If anything, Ceramics might have better ESR.
      - the-dude 10y ago
        He, thank you very much, I will look into this. As a self-taught electronics designer ( https://mecoffee.nl https://mecoffee.nl ) I find the amount of different components ( at Farnell, Mouser et al ) absolutely intimidating. Could you provide some insight into why for tantalums the ESR is specified, while for these ceramics they are not? How should I go about filtering them at Farnell/Mouser ? Thanks again.
        dragontamer 10y ago
        > Could you provide some insight into why for tantalums the ESR is specified, while for these ceramics they are not? Ceramics are highly frequency dependent. Almost every parameter changes with frequency: capacitance, ESR, ESL... you gotta look at charts. For the most part, when picking a Ceramic Cap... you pick a dielectric (NP0 for voltage and temperature stability and accuracy... X5R for "high" values like 10uF). > How should I go about filtering them at Farnell/Mouser The only methodology that seems to work for me is to learn the various types of dielectrics. For the most part, the properties of NP0 ceramic capacitors are the same across all the companies. Class 1 (typically NP0) and Class 2 (typically X7R... but X7S, X5R or whatever is fine) are your main types. Class 1 for temperature and voltage stability and accuracy at the nanoFarad range, Class 2 for "high" values like 10uF.
dragontamer 10y ago
> What are some of the places where tantalum capacitors are required and ceramic capacitors just can't get the job done? Ceramic Capacitors are a class of class of capacitors. We need to break things down further... Your "NP0" ceramics have great overall characteristics, but are very small... 0805 NP0 ceramics top out at 0.01uF (and are quite expensive at such "high" values). To get higher capacitance in a ceramic capacitor, you switch over to lower-quality ceramics, like X5R or X7S. X7S gets to 100uF or higher in the 0805 form factor, but are both temperature dependent and voltage dependent. Yes, Voltage dependent capacitance. http://i.imgur.com/mnqbVJC.png http://i.imgur.com/mnqbVJC.png Here is Murata's "Simsurfing" page, which describes the characteristic on a 100uF 0805 X5R Capacitor. A 100uF X5R ceramic capacitor by only be 15uF by 5V. Its capacitance changes with voltage. Strangely enough, for most purposes (ie: decoupling), that's not an issue. But any precision circuit (ie: OpAmps or timers) will prefer to use a more voltage-stable capacitor. Someone else mentioned power-supplies and energy storage. Yeah, a X5R ceramic capacitor has much less energy storage because it loses capacitance as it stores energy (and "high quality" NP0 ceramics just don't have much capacitance to begin with... so no point using those for energy storage). More issues, see: http://www.kemet.com/Lists/TechnicalArticles/Attachments/93/2008-11%20Update%20-%20Ceramic%20versus%20Tantalum.pdf http://www.kemet.com/Lists/TechnicalArticles/Attachments/93/...
woadwarrior01 10y ago
Don't electrolytic caps have the same issue?
- jacquesm 10y ago
  Almost every part has the same issue except for the most basic, so that's not the reason.
planteen 10y ago
Past 3 companies?!? What? How do you handle diodes, LEDs, batteries, and electrolytic caps? Those are also two terminal devices with polarity. Heck how did you even build cables correctly? I've worked with voltage regulators from Linear that explicitly call out using tantalum caps in the recommended design.
jacquesm 10y ago
A good reason not to use tantalum caps is that 10 years down the line or so they seem to transform into automatic firestarters. But if you aren't able to correctly install parts with any polarity then the only parts that you might be able to use are resistors, coils and capacitors without polarity (which tend to be low capacity), which would make for rather boring designs. Ceramic caps are usually very low capacity, tantalum and electrolytic caps (much) higher.
- Arizhel 10y ago
  >Ceramic caps are usually very low capacity, tantalum and electrolytic caps (much) higher. 30+ years ago, this was true. Not anymore.
  - jacquesm 10y ago
    Show me where to buy a 1000 uF 50V ceramic cap for a reasonable price.
    - Arizhel 10y ago
      That's a stupid demand. You said "very low capacity". You can get MLCC caps in the ones and tens of microfarads easily and cheaply now, which isn't "very low". "Very low" is picofarads. Ceramics advanced from that level ages ago.

Neliquat 10y ago

As a hobbiest, I usually see them in high stability power supplies.

2bluesc 10y ago
Probably because when designed right (they are far more finicky then ceramic) they typically offer higher energy density.
- jacquesm 10y ago
  Higher capacity you mean (for a given volume), that and also very low leakage current so if you want to make a very efficient device then tantalum might pay off. Another reason is that electrolytic caps are usually wound aluminum sheets which act as a coil. If you don't want any parasitic inductance tantalum is better in that application (better frequency response).
  - LeifCarrotson 10y ago
    Tantalum caps have much worse leakage current than ceramics. The debate for most designs is not tantalum vs. electrolytic, it's electrolytic vs. solid vs. ceramic. And ceramic usually wins.
- marcosdumay 10y ago
  They have lower internal inductance and resistance than other electrolytics. That is very goo for making the low-pass filters one uses on power supplies.
arcticbull 10y ago
They're usually used as bulk capacitance, particularly at the input side of switching regulators. Thing is, their ESR is too high to be used alone so they're usually used in parallel with an MLCC ceramic. I've had success replacing both on the input stage with an aluminum polymer electrolytic (not standard aluminum) due to their low ESR and high capacitance (and better inrush rating). I usually use ceramics on the output. [1] http://www.ti.com/lit/an/slta055/slta055.pdf http://www.ti.com/lit/an/slta055/slta055.pdf This is a great writeup on the various types from Kemet: [2] http://www.kemet.com/Lists/TechnicalArticles/Attachments/5/Avnet2012PowerForum_CapacitorsSelection.pdf http://www.kemet.com/Lists/TechnicalArticles/Attachments/5/A...

2bluesc 10y ago

There are many reasons to not use tantalum caps (inability to handle voltage transients requiring derating being the primary that comes to mind), but I've never heard of a company instituting such a policy because their assembly process was so poor. Did they also blanket ban diodes?

VLM 10y ago
Might be a retcon. There are sometimes good reasons not to use tantalum aside from the explosion and fire inevitability. At really high temperatures (engine computers etc) tantalum loses voltage rating down to less than 50% in some cases at the limit whereas ceramics lose capacitance with high temp (weird but true for X7R dielectric). This is a general rule of thumb and I'm sure you can find mfgrs whitepapers explaining how their expensive series is immune to this general class effect. In the bad old days tantalum volume was like 100 times smaller for a given capacitance than a ceramic but its not the bad old days anymore and its like 3:1 ratio for some MLCC and because of voltage derating a tantalum derated to 25V (aka a 50V+ cap) might not be all that much smaller than a 25V rated MLCC. Size of cap is no longer a relevant criteria, but customers are more excited than ever about burning exploding personal electronics, so ... Another fun one is leakage current for tantalum is about three orders of magnitude (whoa!) higher than MLCC. Its possible to build little ultra low power IoT things that sleep most of the time and a tantalum leaks more mAH than the processor but a MLCC would waste less. High frequency response is fun because neither is inherently better but in some applications one or the other is better. Generally the MLCC is going to have a higher Q resonance at a higher frequency. If that freq is irrelevantly high to the app and EMI issues, thats a great cap, whereas maybe for some apps sometimes tantalums could be resonant, admittedly at a lower Q, in the region of freqs important to the app or EMI/EMC issues. Not that ceramics are problem free. Piezoelectric effects are hilarious. Aging after heating drops ceramic capacitance, its possible to solder a SMD cap and watch its value drop a couple percent over the next day or so. As with all effects you can acquire manufacturers whitepapers explaining how their extremely expensive exotic series cap can be soldered in place of another of the same family if there's a design mistake and you need to correct it in production, so sure you can pay a lot of money for tantalums that work at 230C or temperature stable ceramics. Something I don't understand is ceramics being ceramics mean they should be good up to lava like temps and alloys being alloys mean you should be able to find something with a matching coeff of expansion thats good up to liquid metal temps, so why can't you buy ceramic caps rated to orange-hot temps? I haven't looked into it deeply enough to find out. There are practical reasons wet tantalums can't run at cutting torch temperatures but ceramics superficially don't seem to have those limits.

the-dude 10y ago

Low ESR applications.

dragontamer 10y ago
Ceramic Caps have extremely low ESR as well however.
- the-dude 10y ago
  Well, show me a 10uF, 10V below 1 Ohm.
  - dragontamer 10y ago
    Ummm..... http://psearch.en.murata.com/capacitor/product/GRM219R61A106ME47%23.html http://psearch.en.murata.com/capacitor/product/GRM219R61A106... Try below 0.01 Ohms, between the frequencies of 100Hz to 1MHz, in the 0805 form factor. 10uF and 10V as requested. Ceramics are extremely good at low ESR / low ESL / decoupling applications. I mean, so are Tantalum caps, so they're both good for this purpose. If anything, Ceramics might have better ESR.
    - the-dude 10y ago
      He, thank you very much, I will look into this. As a self-taught electronics designer ( https://mecoffee.nl https://mecoffee.nl ) I find the amount of different components ( at Farnell, Mouser et al ) absolutely intimidating. Could you provide some insight into why for tantalums the ESR is specified, while for these ceramics they are not? How should I go about filtering them at Farnell/Mouser ? Thanks again.
      - dragontamer 10y ago
        > Could you provide some insight into why for tantalums the ESR is specified, while for these ceramics they are not? Ceramics are highly frequency dependent. Almost every parameter changes with frequency: capacitance, ESR, ESL... you gotta look at charts. For the most part, when picking a Ceramic Cap... you pick a dielectric (NP0 for voltage and temperature stability and accuracy... X5R for "high" values like 10uF). > How should I go about filtering them at Farnell/Mouser The only methodology that seems to work for me is to learn the various types of dielectrics. For the most part, the properties of NP0 ceramic capacitors are the same across all the companies. Class 1 (typically NP0) and Class 2 (typically X7R... but X7S, X5R or whatever is fine) are your main types. Class 1 for temperature and voltage stability and accuracy at the nanoFarad range, Class 2 for "high" values like 10uF.

dragontamer 10y ago

> What are some of the places where tantalum capacitors are required and ceramic capacitors just can't get the job done? Ceramic Capacitors are a class of class of capacitors. We need to break things down further... Your "NP0" ceramics have great overall characteristics, but are very small... 0805 NP0 ceramics top out at 0.01uF (and are quite expensive at such "high" values). To get higher capacitance in a ceramic capacitor, you switch over to lower-quality ceramics, like X5R or X7S. X7S gets to 100uF or higher in the 0805 form factor, but are both temperature dependent and voltage dependent. Yes, Voltage dependent capacitance. http://i.imgur.com/mnqbVJC.png http://i.imgur.com/mnqbVJC.png Here is Murata's "Simsurfing" page, which describes the characteristic on a 100uF 0805 X5R Capacitor. A 100uF X5R ceramic capacitor by only be 15uF by 5V. Its capacitance changes with voltage. Strangely enough, for most purposes (ie: decoupling), that's not an issue. But any precision circuit (ie: OpAmps or timers) will prefer to use a more voltage-stable capacitor. Someone else mentioned power-supplies and energy storage. Yeah, a X5R ceramic capacitor has much less energy storage because it loses capacitance as it stores energy (and "high quality" NP0 ceramics just don't have much capacitance to begin with... so no point using those for energy storage). More issues, see: http://www.kemet.com/Lists/TechnicalArticles/Attachments/93/2008-11%20Update%20-%20Ceramic%20versus%20Tantalum.pdf http://www.kemet.com/Lists/TechnicalArticles/Attachments/93/...

woadwarrior01 10y ago

Don't electrolytic caps have the same issue?

jacquesm 10y ago
Almost every part has the same issue except for the most basic, so that's not the reason.

planteen 10y ago

Past 3 companies?!? What? How do you handle diodes, LEDs, batteries, and electrolytic caps? Those are also two terminal devices with polarity. Heck how did you even build cables correctly? I've worked with voltage regulators from Linear that explicitly call out using tantalum caps in the recommended design.

jacquesm 10y ago

A good reason not to use tantalum caps is that 10 years down the line or so they seem to transform into automatic firestarters. But if you aren't able to correctly install parts with any polarity then the only parts that you might be able to use are resistors, coils and capacitors without polarity (which tend to be low capacity), which would make for rather boring designs. Ceramic caps are usually very low capacity, tantalum and electrolytic caps (much) higher.

Arizhel 10y ago
>Ceramic caps are usually very low capacity, tantalum and electrolytic caps (much) higher. 30+ years ago, this was true. Not anymore.
- jacquesm 10y ago
  Show me where to buy a 1000 uF 50V ceramic cap for a reasonable price.
  - Arizhel 10y ago
    That's a stupid demand. You said "very low capacity". You can get MLCC caps in the ones and tens of microfarads easily and cheaply now, which isn't "very low". "Very low" is picofarads. Ceramics advanced from that level ages ago.