Capacitor shelf life or expiry date?

[slybunda]

do capacitors have a limited life even if just kept in a box in storage?

[stj]

Re: Capacitor shelf life or expiry date?

only electrolytics - because they have liquid sealed in them

[PeteS in CA]

Re: Capacitor shelf life or expiry date?

It may take years or decades, but as stj posted, electrolytics can dry out sitting on a shelf or in something electronic that is not powered on for those years.

Electrolytics that are not used for quite a few months (a year or two?) can also have the aluminum oxide dielectric thin, so that they can no longer withstand their full rated voltage. This thread discusses the process of re-forming the dielectric layer, https://www.badcaps.net/forum/showthread.php?t=50530 .

I apologize for being vague about timing, but electrolytic capacitors don't have a "Best If Used By" date.

[slybunda]

Re: Capacitor shelf life or expiry date?

good info there to read up on. didnt realize caps could degrade when not used.

[stj]

Re: Capacitor shelf life or expiry date?

the electrolyte is sealed in with a rubber bung - it can harden and degrade too.
there have been attempts to improve this, but i dont know if they helped because i never see the capa i'm about to mention unused.

an american company in the 80's put epoxy over the end of the cap to cover the rubber seal,
the japanese made some with a plastic case and an epoxy seal instead of the rubber,
and the soviets used a plastic bung with a rubber washer and crimped the can over it.

what i can say is none of those ideas stop them aging inside stuff.

so now you know more than you wanted to know

[andrewsawesomr]

Re: Capacitor shelf life or expiry date?

The rule of thumb I've heard is to not store electrolytic capacitors for more than 5 years, but I'm not sure how true that is

[PeteS in CA]

Re: Capacitor shelf life or expiry date?

...
an american company in the 80's put epoxy over the end of the cap to cover the rubber seal,
the japanese made some with a plastic case and an epoxy seal instead of the rubber,
...

I remember seeing some larger US-made caps with epoxy end seals (Sprague 676D and 677D? And Mallory's near-equivalent?). Nippon Chemicon's RZ and RZA series had epoxy end seals. But I only saw new parts of these types, not parts that had sat unused on a shelf for 10 years. I think that the fact that epoxy end seal parts are uncommon (some Vishay 678D parts are available with epoxy end seal) suggests that either it was ineffective or the cost-benefit ratio made it economically marginal.