Can Tantalum capacitor explode?

[bobsun]

Hello,

I would like to ask a question on tantalum capacitor.

I have heard that electrolytic capacitors could sometimes break, such as from this Wikipedia paragraph:
Electrolytic capacitor - Wikipedia, the free encyclopedia

Most electrolytic capacitors are polarized and require one of the electrodes to be positive relative to the other; they may catastrophically fail if voltage is reversed. This is because a reverse-bias voltage above 1 to 1.5 V[2][3][4] will destroy the center layer of dielectric material via electrochemical reduction (see redox reactions). Following the loss of the dielectric material, the capacitor will short circuit, and with sufficient short circuit current, the electrolyte will rapidly heat up and either leak or cause the capacitor to burst, often in spectacularly dramatic fashion.
...

Modern capacitors have a safety valve, typically either a scored section of the can, or a specially designed end seal to vent the hot gas/liquid, but ruptures can still be dramatic. An electrolytic can withstand a reverse bias for a short period, but will conduct significant current and not act as a very good capacitor. Most will survive with no reverse DC bias or with only AC voltage, but circuits should be designed so that there is not a constant reverse bias for any significant amount of time.​

Purely electrolytic capacitors could possibly explode; however, for tantalum type polarized capacitor, does it belong to electrolytic type? Can it possible explode?



Bob

 

[ckshivaram]

Tantalum capacitors possess very low electrical leakage, (high leakage resistance), and will retain a charge for a long duration, they are also more tolerant of harsh, hot operating environments unlike standard aluminium electrolytic capacitors. Tantalum capacitors are relatively expensive, particularly the military grades, they are not particularly tolerant of heavy charge and discharge currents, particularly of a repetitive nature and their effective series resistance, ESR, is quite high when compared to aluminium electrolytics. As with all electrolytic capacitors, correct polarity must be observed otherwise the capacitor will depolarize and the dielectric oxide layer will be reduced back to the metal, reducing the resistance of the device and causing it to become very hot and possibly explode. Tantalum capacitors are less prone to "drying out", causing a decrease in capacitance as is often the case with aluminium electrolytic capacitors particularly when used in hot environments. They maintain their designed capacitance under such conditions over long periods of time, (decades).

In some low-power, battery-operated systems, a tantalum capacitor may be the cause of excessive current. The usual suspect is ESD damage to a CMOS device.

However there have been several recent cases where a plastic encapsulated, surface mounted, tantalum capacitor was the source of the excessive current.

 

[andre_luis]

hi Bob,

I already witnessed a little smoke eruption when I polarized one device with excessive voltage much greater than nominal specified value.
But, I´m not sure if we could truly classify that occurrence like a concrete explosion.

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[BradtheRad]

I had a couple of electrolytics burst when I accidentally subjected a circuit to overvoltage. The metal housings flew upward at dangerous speed. Bits of brown cardboard littered the area.

 

[betwixt]

Having used many, many thousands, possibly millions of tantalum capacitors - yes they most certainly do explode! They behave more like fragmentation bombs than the "phut" of wet electrolytics. They look more like a firework display than a bang and puff of smoke.

Brian.

 

[andre_luis]

...They behave more like fragmentation bombs than the "phut" of wet electrolytics. They look more like a firework display than a bang and puff of smoke...

I had not realized that I should feel lucky to have survived to that experience with no more trauma.

:lol:

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[liteon]

They do explode specially when there is voltage surge or voltage applied to them is greater than their rated voltage,tantalums are very prone to voltage surge and can not survive in such condition as a results may explode immediately. So if it happens to you expect a super heated piece of epoxy flying towards your face at supersonic speed, ouch!permanent scar in the cheek.(why you were not wearing a helmet when trying to fool around those tantalums) LOL.

 

[hobbss]

I agree with Brian -- I have witnessed tantalum capacitors explode several times. Note, they will explode in two conditions. The first is if they are put on backwards (i.e., the polarization is reversed). In my experience, this tends to be less "explosive" -- at least the capacitor itself. They just tend to short, and if used for decoupling, can cause problems if your power supply is not correctly fused/breakered. The second condition is over-voltage. These explosions can be pretty spectacular. I had one on the bottom side of a board on 1" standoffs. It blew, jetted a little flame (as the tantalum burned?), and melted the veneer on my desk. The trick here is to define exactly what "over-voltage" is. You should always read the datasheets, but a general rule of thumb is to derate the capacitor by at least 50% (some people say 66%) when used in low impedance circuits (i.e., acting as the output capacitor of a voltage regulator). This derating suggestion is not an exaggeration or an ultra-conservative rule. I made the mistake of using 25V tant caps on a 15V regulator circuit -- after the third one blew, I gave up and switched to 35V caps.

Edit: Surprisingly, tantalum capacitors are much more popular in the United States and in east Asia. Traditional electrolytics are far more prevalent in Europe. Part of that is due to political reasons (read up on where tantalum comes from). I also believe part of that is just due to what design engineers are taught in school.