Tantalum caps - how long is the shelf life?

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Just wondering if any here have any personal experiences or useful
information about the shelf life of tantalum capacitors, specifically resin
dipped types.  Had quite a few (maybe 20 years old) NOS go s/c when
subjected to approximately 60% of the rated d.c. voltage.
Have they deteriorated over time or could they just be from a bad batch?
Unfortunately I don't know who the manufacturer was as there are no brand
markings.  Just deep orange in colour.

Cheers,
Alan



Re: Tantalum caps - how long is the shelf life?


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Yep they just die with age, no bad batches needed. There are modern
low leakage electrolytics that can directly replace them for most
apps, they at least can dry out and go open circuit.

Re: Tantalum caps - how long is the shelf life?


On Wed, 6 Sep 2006 17:53:21 +0800, "Alan Rutlidge"

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I don't have any experience with long term storage of solid tantalums
but here is what Vishay say in their FAQ sheet.

Q. What are the recommended storage conditions for solid tantalum
capacitors?
A. Vishay recommends that solid tantalum capacitors be vacuum-sealed
with desiccant tape and reels be stored at 40 °C with 65% relative
humidity.

I haven't found any info about what may happen if these conditions are
not used but the high storage temperature in a vacuum seal seems to
suggest that they readily absorb moisture. It is not hard to imagine
how they might react when put to use after 20 years storage if they
have absorbed moisture.

Re: Tantalum caps - how long is the shelf life?


On Wed, 06 Sep 2006 11:12:34 GMT, Ross Herbert

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I meant the loose capacitors must be stored in a vacuum seal container
with dessicant while tape and reels must be stored at 40 deg C at
specified humidity.

Re: Tantalum caps - how long is the shelf life?


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???

 dessicant tape and 65% relative humidity seem contradictory.


Bye.
   Jasen

Re: Tantalum caps - how long is the shelf life?



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Pretty sure they're separate:
"I meant the loose capacitors must be stored in a vacuum seal container with
dessicant" ===while==== "tape and reels must be stored at 40 deg C at
specified humidity".





Re: Tantalum caps - how long is the shelf life?



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Exactly. The inclusion of the word "while" separates the storage
requirements for the loose items and the tape-and-reel components.

Re: Tantalum caps - how long is the shelf life? - Thanks guys



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Hi Guys,

Thanks for your valuable comments and contribution to the thread.
Appreciated.

Cheers,
Alan



Re: Tantalum caps - how long is the shelf life? - Thanks guys


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also check solderability, which deteriorates over time. poke a lead into
a solder pot. The solder should wick up the leg. If it doesnt wick up,
the component wont solder very well. If it in fact pushes down (the
exact opposite of wicking up) then the soldering will be extremely bad.

Cheers
Terry

Re: Tantalum caps - how long is the shelf life?


Hi,
as they are so old, they were manufactured before the moisture barrier
became standard within the tant cap build.

No moisture barrier means ingress of mositure, which  allows migration of
the silver into the manganese dioxide allowing a short to develop.

Modern tants dont have this problem.

Also, older tants that are under bias don't suffer the silver ion migration.

Don't know of any other storage issues with tants.

Cheers
Greg



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