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
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.
On Wed, 6 Sep 2006 17:53:21 +0800, "Alan Rutlidge" markings. Just deep orange in colour.
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.
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.
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
"Alan Rutlidge" markings. Just deep orange in colour.
???
dessicant tape and 65% relative humidity seem contradictory.
Bye. Jasen
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".
Exactly. The inclusion of the word "while" separates the storage requirements for the loose items and the tape-and-reel components.
Hi Guys,
Thanks for your valuable comments and contribution to the thread. Appreciated.
Cheers, Alan
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
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