Maker Pro
Maker Pro

Super capacitor phone battery

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Joined
Jan 21, 2010
Messages
25,510
Capacitors with liquid electrolytes suffer from drying out, and sometimes just leakage. In some cases a component like this will fail if just left sitting around unused. Elevated temperatures make it worse. The specifications of some capacitors give a lifetime at their rated maximums -- and I've seen it as low as 500 hours.

Small multi-layer ceramic capacitors can be damaged by flexation of the board they're mounted on.

Film capacitors can accumulate damage (generally caused by voltage spikes).

A designer will choose a capacitor that should last the "lifetime" of the product. Depending on the manufacturer, the "lifetime" may be the warranty period or even less...
 

hevans1944

Hop - AC8NS
Jun 21, 2012
4,878
Joined
Jun 21, 2012
Messages
4,878
I'd like to hear your opinions on why capacitors are so relatively unreliable.
Well, it is all relative. Electronics in general has become more reliable, and that means the components have become more reliable too. Capacitors seem uncomplicated... two leads attached to two electrodes and a dielectric in between. What could be simpler and more reliable? Well, howsabout a coil of stiff wire? Inductors are pretty reliable. Howsabout a thin film of conductive material vapor-deposited on a ceramic substrate? Thin-film resistors are pretty reliable. There are a lot of components more reliable than capacitors, some by design and some by happenstance. Problem with capacitors is they come in a plethora of types, styles, lead attachments, dielectrics, and packaging. There is a lot of room for failure built into in the construction methods. Electrolytic capacitors are the worst. Even dry-slug tantalum capacitors have failures greater than, say, polypropylene capacitors of similar electrical specifications because their technology is more complicated. SMD capacitors may turn out to be the most reliable, but there isn't enough "history" to reliably assert that they are. For my money, I pick dipped mica followed by just about any plastic dielectric, followed by dry tantalum as my "go to" capacitors for reliability. YM(or km)MD.
 

kpatz

Feb 24, 2014
334
Joined
Feb 24, 2014
Messages
334
Electrolytic capacitors have a finite lifespan, since they can dry out over time. This is why vintage electronics often need to be recapped during a restoration.

In more recent years, with the "manufacture as cheaply as possible" mentality, many devices have cheap capacitors (often from China) which can fail quickly. There was also an espionage case a few years ago where a new, unfinished capacitor formula was stolen and used to manufacture cheap knockoff capacitors used in a lot of devices from TVs to computer motherboards. Because the formula was incomplete and flawed, many of these caps failed prematurely, leading to a large number of devices failing prematurely.
 
Top