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Capacitors (electrolytics, specifically) explode if you put reverse voltage or excessive voltage to them. How does this happen? Aren't electrolytics just two metal films with a seperator and doused in some electrolyte? What is the mechanism behind this explosion?

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    \$\begingroup\$ Insufficient research - Google shows lots of references. Question should be closed. \$\endgroup\$ May 17, 2015 at 15:14
  • \$\begingroup\$ @LeonHeller I've re-researched this just now, and I cannot find anything relating to the mechanism behind capacitor explosion. There are a lot of sites explaining the triggers (reverse voltage, high voltage), but nothing I could find related to the physical cause behind the failure. \$\endgroup\$
    – 0xDBFB7
    May 17, 2015 at 15:24
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    \$\begingroup\$ I found this in about 10 secs: industrial.panasonic.com/lecs/www-data/pdf/ABA0000/… \$\endgroup\$ May 17, 2015 at 15:39
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    \$\begingroup\$ Not an answer because I don't know enough about the actual chemistry: When you bias an electrolytic in the wrong polarity current begins to flow. Flowing current means energy is delivered to the part. That means the part will heat up. Many materials, when heated up, undergo a phase change (for example water evaporating into steam). Often this phase change results in the volume of the material changing. I'm guessing that the electrolyte in the exploding capacitor is one of those materials. \$\endgroup\$
    – The Photon
    May 17, 2015 at 15:41
  • \$\begingroup\$ It could also be that the electrolyte simply catches fire when overheated, and the exhaust gases blow up the case. \$\endgroup\$
    – The Photon
    May 17, 2015 at 15:46

1 Answer 1

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The electrolyte in an aluminum electrolytic capacitor is conductive, but a thin layer of aluminum oxide on the anode acts as a dielectric. Applying more than about 1.6V of reverse voltage strips the dielectric of its oxygen atoms causing the capacitor to become a near short circuit. Current flowing through the capacitor generates heat which eventually boils the electrolyte. The electrolyte vapor then expands, in time rupturing the case of the capacitor.

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