Partlist Wednesday: Tantalum capacitors

in partlist by Ian | 11 comments

Every Wednesday we highlight a component from the updated Dangerous Prototypes partlist. This week: tantalum capacitors.

We use tantalum capacitors sparingly, usually only when a datasheet specifies. The element tantalum is a conflict mineral, and it’s expensive. For example the PICs on the Logic Sniffer and Bus Pirate have an internal voltage regulator that specifically calls for a tantalum capacitor. 99% of the time you can substitute a electrolytic in a prototype without problems.

Tantalum caps are polarized. There is a +/- side.  + is usually marked by a line etched or printed on the package.

Watch out, these are commonly rated for only 6-16volts. We stock a no-name 10uF/10volt 1206-sized (A case/Kemet A) tantalum and use it in every prototype – even if it calls for a drastically different value.

Tantalum caps are smaller than equivalent surface mount electrolytic caps, but they’re generally more expensive. In a previous partlist post commenters linked to 10uF ceramic caps the same size as tantalum caps, but cheaper. We’re switched to those in new designs.

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Comments

  1. Brian says:

    A small public service comment:

    There is conflict free Tantalum, however please be aware that it can be material that has social implications:

    http://en.wikipedia.org/wiki/Conflict_minerals

    If possible check that the part is sourcing conflict free Tantalum.

    For instance Kemet (the company Ian has selected above) has a policy:
    http://www.kemet.com/kemet/web/homepage/kechome.nsf/weben/KEMET%20Policy%20on%20Conflict%20Minerals

    Always ask the source of such parts from any partners.

  2. bearmos says:

    Here’s a good app-note style document outing the similarities and differences between tantalum and ceramic caps:
    http://www.kemet.com/kemet/web/homepage/kfbk3.nsf/vaFeedbackFAQ/0F05C4C1F74A2D2485256F170052CD15/$file/2008-11%20Update%20-%20Ceramic%20versus%20Tantalum.pdf

    Ironically enough, it’s also from Kemet.

  3. Brian says:

    As a design practice, I tend to design out tantalum caps for two reasons. Their prices have been higher than other types and they are only getting more expensive. The other reason is that when they are used improperly, fail, or the usual act of god happens, they fail miserably. I mean they can catch fire.

    So, to avoid fire, protect against revers polarity, and ensure the max voltage rating is much higher than the expected worse case, including short transients (transient energy adds up).

    my $0.02.

  4. arhi says:

    a link to the 10uF ceramic ? I could not find it :(

  5. arhi says:

    http://uk.farnell.com/multicomp/mcca000542/mlcc-08055v-10v-10uf/dp/1759421RL
    http://uk.farnell.com/multicomp/mcca000564/mlcc-12065v-16v-10uf/dp/1759445RL

    damn how I didn’t know about these el-cheapo ones … looks like only 10uF are cheap, if you go up the price start to go uncontrollably up :( I’m ordering few hundred of 10v and 16v ones .. these can be a big savers, they have better esr then tantalums and are cheaper :) … you could even solder this one instead of decoupling cap for mcu and it will work like crazy :D :D :D

  6. arhi says:

    Wow, I found samsung 10uF 10V 0805 locally for 3.3eur 100pcs + vat … ordered 300 pcs already (checking 16V ones now, I think they are 1206)

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