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cost effective alternative to aluminum electrolytic capacitors

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robismyname

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current design utilizes UWT1E101MCL1GS, CAP 100UF 25V ELECT WT SMD x 3 (pretty large in value and real estate). The electrolytic are prone to failing some shock and vibe testing. Ceramics are an option but I am 85% sure that I will not have enough space on the board to get 300UF worth populated. I looked at Supercaps but they appear to be too costly.

Are there any alternatives to the aluminum electrolytic capacitors? Tantalum (a type of electrolytic)? Would a ceramic work with a different dielectric than NPO?
 

dick_freebird

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If you're down for shock and vibe, are you also faced with
the aerospace rules for ceramics (no dielectrics under 50V
makes "small" caps large...)?

Tantalums at lower voltages are pretty compact, I've not
had occasion to look at 25V ones. But I'd check out the
Kemet high-rel lines.
 

crutschow

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Tantalum is indeed a type of electrolytic and is more reliable than aluminum electrolytics, which is why they are uses in high reliability military and aerospace electronics whereas Al devices are never used. But, of course they are also more expensive than Al electrolytics.

NPO ceramic caps have the best temperature stability, but also are the least volume efficient. There are a number of other ceramic dielectrics that allow the fabrication of larger ceramic caps in a reasonable volume, and I have seen low voltage ones as large as 470µF, but they tend to be expensive.
 

robismyname

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i noticed that aluminum and tantalum capacitors have higher ESR than ceramic. Is it better to have more ESR? IS ESR related to Q factor?
 

dick_freebird

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Electrolytics particularly have a dismal ESL. ESR, not
great either due to the long spiral structure. ESR is
anti-Q.
 

dick_freebird

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Here's a blurb that came across my email-pile today:

High-Voltage Chip Capacitors

AVX Corporation (Greenville, SC) is expanding its award-
winning TCJ Series with two new high-voltage tantalum
polymer chip capacitors. AVX’s new surface mount,
tantalum polymer chip capacitors provide excellent
capacitance and low ESR for a broad range of high-
voltage applications, including telecommunications
equipment, base stations, switching hubs, router,
and line filters. Features include:

The maintaining of 20% recommended voltage
detracting (derating?).

Small case sizes (2924 for the 100V and 2917 for
the 125V) and low profiles.
 

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