Tantalum Caps

[richie00boy]

OK, I did a search but could only find information pertaining to how they were an environmental disaster. Just before I write them off completely, can people confirm if they dry out like aluminium electrolytic caps? Also, do they generally have lower ESR and ESL than the equivalent electro?

[Mr Evil]

They don't dry out. They do have lower ESR and ESL. If you're thinking of using them to get high frequency impedance down, then consider paralleling a small, high-quality capacitor with a normal electrolytic instead.

Yes, they are an environmental and social disaster, and some people report poor reliability, but they are useful if you need a large capacitance in a physically small package.

[jcx]

i think the recommendation to use tants dates from the 80's or earlier, probably just has been propagated since without critical examination

tant's sintered powder construction probably offered lower esl than older Al electros but smt caps cut this to next to nothing for any cap - ceramic 4.7uF 0805 caps are available today (as much C as commonly recommended tant values) - vias & layout will be a bigger component of L than the cap, lots more if you're still building with thru-hole DIPs like most diyers - where esl really matters ceramic smt caps with the terminals on the long side of the chip are used

closer analysis of paralleled cap resonaces suggest that some esr may be desirable to dampen impedance peaks between the self resonant freqs of the caps - some op amp app notes specifically recommend Al electros over tants for this reason - solid polymer Al electrolytics may even have "too low" an esr for this damping effect

[richie00boy]

Thanks both. The drying out of electros was really my main concern. I already use parallel caps to get better HF performance and this is really not an issue to me.

I try to be nice to the environment and the people within where possible, so I think I will boycott tants purely on that reason.

[Stocker]

My engineer pal boycotts them for a different reason: they don't dry out (being a dry material), but they break down and usually fail short-circuit.

[richwalters]

Originally posted by richie00boy


I try to be nice to the environment and the people within where possible, so I think I will boycott tants purely on that reason.

Umm ..Hi there.....Over the years I've worked in R&D labs for major corporations....the price for 1 million off rules the day....unfortunately electronics as you rightly mentioned is a dirty business.........lead free solder is taking an awful long debut.....capacitors are gradually becoming cleaner....
-> Do you use a mobile phone ? No I don't have a mobile phone...(who else doesn't).....those who have and are electronic engineers claim their faim to be good to the environment are in an illusion. The same with modern cars. You will find tants in everyone's pants ....everywhere.

richj

[gmarsh]

If you need big capacitance in a small package, and environmental issues outweight cost issues, check out MLCC capacitors.

Almost every ceramic cap manufacturer in existance manufacturers a 47uF, 6.3V, X5R-dieletric MLCC in a 1210 case. You'll need a B-case tantalum to get the same density, and the 1210 is almost exactly the same size. A MLCC's ESL/ESR will completely blow tantalum away, their reliability is fantasitc, and they can handle tens of amps.

A few companies (Murata, NIC and Panasonic, I know for sure) make X5R/100uF/6.3V/1210 capacitors.

And they're getting cheaper by day - switching regulators in commodity bricks and point of load converters invariably use MLCC's for everything, and this market is growing fast right now. It wouldn't surprise me if consumer computer motherboards start using these soon instead of electrolytics...