Electronic – What happened to electrolytic capacitors in the 21st century


We can sometimes see decades-old capacitors (such as ones made in the USSR) still working. They are bigger and heavier, but durable and not desiccating. Modern aluminium capacitors serve for about 11 years, if you are lucky, then become dry and quietly fail. I remember early 2000s devices where capacitors failed after 3–4 years of service, and not necessarily low-end devices (one example is E-TECH ICE-200 cable modem worth ∼ 240 USD in 2000). A repair due to failed electrolytic capacitors became a commonplace, something uncharacteristic for 1980s.

Was this 1990s degradation caused by cheap mass production? Or by poorly-tested technologies related to miniaturization? Or many manufacturers just didn’t care?

It appears that the trend is by now reversed, and recent capacitors are a bit better than the ones from 1994–2002. Can experts confirm it?

Best Answer

There was a period of time where lots of capacitors were made with a dodgy electrolyte, especially by some large Taiwanese manufacturers. The capacitors looked OK in a wide variety of tests when new, but they didn't age well. Because it took a few years for the capacitors to fail, and the high failure rate to become known, an awful lot of them had been produced and built into things before people realised there was a problem. It then took a few more years to for the things to leave circulation.

Exactly why these manufacturers had electrolyte problems is not completely clear. They were using new, water based electrolytes which had been developed in Japan and worked very well. Presumably the cheaper manufacturers had missed something or cut some corners while reproducing (or ripping off) the Japanese research.

The type of capacitor affected was cheap, large capacitance, low ESR capacitors. These are the kind of thing that appears in huge numbers of consumer devices, so the problem became known in the wider community. Plus, the failure mode of these capacitors was rupture and venting, so it was easy for even people unfamiliar with electronics to see which component was at fault when their motherboard stopped working.

Wikipedia has an article about it: Capacitor Plague