
An alternative to solid tantalum capacitors - rbanffy
http://www.electronicsweekly.com/news/now-alternative-solid-tantalum-capacitors-2017-03/
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chiph
Dad used to be head of QC at Kemet (he retired from there in the early 90s).
They were known for high-reliability Tantalums (used in various ICBMs,
undersea cable repeaters, and the System 360). These days they make many
different styles of capacitors and other components.

They did 100% inspection - _twice_ , to ensure they shipped a good product.
Like many electronics production lines, the yield of working product was
important to track. And they didn't have the ability to ship a capacitor with
part of it disabled, like Intel used to do with the 80486DX and 80486SX (the
SX was a DX with a non-functioning floating-point math processor).

Story time: They received Tantalum via truck delivery. And one day the truck
driver failed to clear a rail crossing in time and was hit by a train. He was
fine, but the expensive metal was scattered along the rail bed. Obviously they
couldn't use it after the accident, as it was contaminated. So they paid
employees to go out there and pick up the pieces so they could be returned to
the smelter and get credit for it.

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swamp40
Tantalum died years ago. It was a suicide.

Multiple scarcity events, skyrocketing prices, and then in 2014 you couldn't
buy them even if you wanted to.

Purchasing agents were seen chasing design engineers with pitchforks by
torchlight.

Ceramic MLCC's have filled their spot. Better, much easier to use and safer.

And the modern poly hybrid electrolytics are amazing, as well.

Tantalum poly caps are probably great, but the fear is still there and too
recent - so I doubt they will get very popular except in small specific
instances where they are absolutely better than anything else.

~~~
Ductapemaster
Ceramic MLCC's aren't without their problems, especially in the smaller
packages. Just take a look at a voltage vs. capacitance curve in an 0402
package ceramic cap. When used at the rated voltage, they don't have anywhere
near the capacitance they state. Also the temperature vs. capacitance curves
are less than appealing.

That said, I think a lot of engineers out there have been burned (sometimes
literally) by using tantalum caps in the past and are likely not to design
them in in the first place these days. I know we moved away from them
completely in my last job because enough exploded to scare people off.

EDIT: See dragontamer's comment below for more. Explained better than I did.

~~~
julian_1
Do you have any suggestions for what to use for a regulator eg. lm2940 - that
needs something like 22uF, low ESR on the output pin for stability? MLCCs are
expensive and not very available in this capacitance range.

~~~
Ductapemaster
Sorry, I can't really recommend anything without more information. There's
just too many variables.

I briefly looked at the datasheet for the regulator and it has some
constraints for the output cap that should help guide your choices. For
example, you need to look at what temperature range you expect the
regulator/cap combo to be working at, as certain dielectrics are sensitive to
temperature changes [1]. If you need stability over a wide range, you might go
with an X7R or better, otherwise X5R might do. You will also have to look at
derating the capacitance for the operating temperature - you might find that
in a hot environment you actually need a 47uF cap or greater to meet the
minimum 22uF output capacitance requirement of the regulator.

The other main thing to consider is operating voltage. The regulator you list
is adjustable, so you will need to pick an output cap that has an appropriate
capacitance at the voltage you plan to run the regulator at. The curves drop
pretty steeply, so it's really important to analyze this.

For ESR you should look at manufacturer websites. They often have a "picker"
tool that shows graphs of that (it's dependent on frequency!). You probably
won't have trouble finding caps with a low enough ESR value for this
application as long as you stay away from electrolytics.

Also, you can consider paralleling some lower value capacitors to achieve the
capacitance you need, and reduce the ESR a little. I wouldn't use it as an ESR
lowering strategy however [2]

[1]: [https://www.maximintegrated.com/en/app-
notes/index.mvp/id/55...](https://www.maximintegrated.com/en/app-
notes/index.mvp/id/5527)

[2]: [http://electronics.stackexchange.com/questions/152549/esr-
an...](http://electronics.stackexchange.com/questions/152549/esr-and-parallel-
capacitors)

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2bluesc
For those wanting to learn facts (as opposed to lore) the video at Hackaday
gave me more insight on capacitors then any other single resource I've come
across.

[http://hackaday.com/2016/07/09/capacitors-are-simple-
right/](http://hackaday.com/2016/07/09/capacitors-are-simple-right/)

[https://youtu.be/ZAbOHFYRFGg](https://youtu.be/ZAbOHFYRFGg)

~~~
elmar
How ultracapacitors work (and why they fall short)

[https://gigaom.com/2011/07/12/how-ultracapacitors-work-
and-w...](https://gigaom.com/2011/07/12/how-ultracapacitors-work-and-why-they-
fall-short/)

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niftich
The article focuses heavily on the angle of tantalum ore supply -- but it's
worth noting that Niobium capacitors [1][2] have been gaining prominence since
the 2002 for the same reason. Niobium-based capacitors have some desirable
properties [2] but are roughly comparable to tantalum-based ones; and Niobium
ore is much more abundant.

[1]
[http://www.avx.com/products/niobium/](http://www.avx.com/products/niobium/)
[2]
[http://www.imaps.org/adv_micro/2004may_jun/pages/article_nio...](http://www.imaps.org/adv_micro/2004may_jun/pages/article_niobiumoxide.pdf)

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fredley
Tantalising news. The alternative is still tantalum-based if I understood
correctly, but uses less tantalum. The article doesn't mention how much less.

~~~
unwind
Well, "solid" doesn't have to mean "not a liquid/gas/plasma", it can also mean
"all the way through". For instance a table made of "solid oak" is not trying
to say it's not a liquid, it's trying to say it's not veneered particle board.

That's how I interpreted the use of "solid" here, but I'm no electronics
engineer of course.

~~~
gens
"Solid" in electronics means the former (state), not the latter.

~~~
mbell
It means solid as in the phase of matter in this case. The electrolyte in a
tantalum capacitor can either be a solid or liquid.

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

~~~
2bluesc
Probably because when designed right (they are far more finicky then ceramic)
they typically offer higher energy density.

~~~
jacquesm
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
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.

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ChuckMcM
Interesting article, it reads like they are trying to rehabilitate the
tantalum capacitor market.

Back when NetApp was got a deal to provide filers for IBM to re-label the word
came from IBM that all Tantalum capacitors had to be designed out of the
system. There was an interesting project in engineering to purge the designs
of all tantalum capacitors. IBM's reasoning was that they had been the source
of fires as I recall.

As a result I find myself always hesitating to use one (even in silly one-
offs) and other engineers I've met have similar habits.

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b1gtuna
Great article. Was not aware there is this much stigma around tantalum caps.
There are times when I am forced to avoid ceramic caps for better high
frequency handling. It looks like polymer is the way to go - better longevity
and no ethical issues.

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woliveirajr
Funny that the alternative also uses tantalum and in its solid state... I
know, I know, "solid tantalum" refers to a technology and the alternative is a
new technology, or at least an improvement over the older one.

