Forums

Where'd they go? (Gold electrolytics)

Started by Tim Wescott February 1, 2012
I realized yesterday that gold electrolytics seem to have disappeared 
from the market.

What do folks use when they need a really low-leakage capacitor?

-- 
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
Tim Wescott a écrit :
> I realized yesterday that gold electrolytics seem to have disappeared > from the market. > > What do folks use when they need a really low-leakage capacitor? >
I tend to use film caps when possible. Then tantalums (Joerg would say that when they leak you have a big sonic alarm). You can also use 2 electrolytics in series and bias the middle point with a high value resistor so that the cap on the side you want no leakage has no voltage across it. -- Thanks, Fred.
On Tue, 31 Jan 2012 23:50:43 -0600, Tim Wescott <tim@seemywebsite.com>
wrote:

>I realized yesterday that gold electrolytics seem to have disappeared >from the market. > >What do folks use when they need a really low-leakage capacitor?
Polymer aluminum caps are pretty good. Unlike wet caps, leakage is low and doesn't change much with voltage, right up to when they punch through and short. Tantalums are pretty good. But ceramics are available in 10's of uFs, too. -- John Larkin, President Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
On Wed, 01 Feb 2012 08:52:39 -0800, John Larkin wrote:

> On Tue, 31 Jan 2012 23:50:43 -0600, Tim Wescott <tim@seemywebsite.com> > wrote: > >>I realized yesterday that gold electrolytics seem to have disappeared >>from the market. >> >>What do folks use when they need a really low-leakage capacitor? > > Polymer aluminum caps are pretty good. Unlike wet caps, leakage is low > and doesn't change much with voltage, right up to when they punch > through and short. > > Tantalums are pretty good. > > But ceramics are available in 10's of uFs, too.
I was looking at the specifications for polymer aluminum electrolytics, and the specified leakage current wasn't any better than the specified leakage of a plain ol' aluminum electrolytic. Both my customer and I are a bit paranoid about counting on circuit elements beyond their rated parameters, so something that's rated to be low leakage would be a cool thing. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Tim Wescott <tim@seemywebsite.com> writes:

> On Wed, 01 Feb 2012 08:52:39 -0800, John Larkin wrote: > >> On Tue, 31 Jan 2012 23:50:43 -0600, Tim Wescott <tim@seemywebsite.com> >> wrote: >> >>>I realized yesterday that gold electrolytics seem to have disappeared >>>from the market. >>> >>>What do folks use when they need a really low-leakage capacitor? >> >> Polymer aluminum caps are pretty good. Unlike wet caps, leakage is low >> and doesn't change much with voltage, right up to when they punch >> through and short. >> >> Tantalums are pretty good. >> >> But ceramics are available in 10's of uFs, too. > > I was looking at the specifications for polymer aluminum electrolytics, > and the specified leakage current wasn't any better than the specified > leakage of a plain ol' aluminum electrolytic. Both my customer and I are > a bit paranoid about counting on circuit elements beyond their rated > parameters, so something that's rated to be low leakage would be a cool > thing.
Some of the supercapacitors are touted as "low leakage" but I don't know how they compare with other types. -- John Devereux
On Fri, 03 Feb 2012 05:52:20 +0000, John Devereux wrote:

> Tim Wescott <tim@seemywebsite.com> writes: > >> On Wed, 01 Feb 2012 08:52:39 -0800, John Larkin wrote: >> >>> On Tue, 31 Jan 2012 23:50:43 -0600, Tim Wescott <tim@seemywebsite.com> >>> wrote: >>> >>>>I realized yesterday that gold electrolytics seem to have disappeared >>>>from the market. >>>> >>>>What do folks use when they need a really low-leakage capacitor? >>> >>> Polymer aluminum caps are pretty good. Unlike wet caps, leakage is low >>> and doesn't change much with voltage, right up to when they punch >>> through and short. >>> >>> Tantalums are pretty good. >>> >>> But ceramics are available in 10's of uFs, too. >> >> I was looking at the specifications for polymer aluminum electrolytics, >> and the specified leakage current wasn't any better than the specified >> leakage of a plain ol' aluminum electrolytic. Both my customer and I >> are a bit paranoid about counting on circuit elements beyond their >> rated parameters, so something that's rated to be low leakage would be >> a cool thing. > > Some of the supercapacitors are touted as "low leakage" but I don't know > how they compare with other types.
Astonishingly high prices. A lithium coin cell costs as much as a few second's worth of capacitors... -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
Tim Wescott <tim@seemywebsite.please> writes:

> On Fri, 03 Feb 2012 05:52:20 +0000, John Devereux wrote: > >> Tim Wescott <tim@seemywebsite.com> writes: >> >>> On Wed, 01 Feb 2012 08:52:39 -0800, John Larkin wrote: >>> >>>> On Tue, 31 Jan 2012 23:50:43 -0600, Tim Wescott <tim@seemywebsite.com> >>>> wrote: >>>> >>>>>I realized yesterday that gold electrolytics seem to have disappeared >>>>>from the market. >>>>> >>>>>What do folks use when they need a really low-leakage capacitor? >>>> >>>> Polymer aluminum caps are pretty good. Unlike wet caps, leakage is low >>>> and doesn't change much with voltage, right up to when they punch >>>> through and short. >>>> >>>> Tantalums are pretty good. >>>> >>>> But ceramics are available in 10's of uFs, too. >>> >>> I was looking at the specifications for polymer aluminum electrolytics, >>> and the specified leakage current wasn't any better than the specified >>> leakage of a plain ol' aluminum electrolytic. Both my customer and I >>> are a bit paranoid about counting on circuit elements beyond their >>> rated parameters, so something that's rated to be low leakage would be >>> a cool thing. >> >> Some of the supercapacitors are touted as "low leakage" but I don't know >> how they compare with other types. > > Astonishingly high prices. > > A lithium coin cell costs as much as a few second's worth of capacitors...
Yes I have never seen the point of them either... -- John Devereux
On Tue, 31 Jan 2012 23:50:43 -0600, the renowned Tim Wescott
<tim@seemywebsite.com> wrote:

>I realized yesterday that gold electrolytics seem to have disappeared >from the market. > >What do folks use when they need a really low-leakage capacitor?
Generally, when I need a high value low leakage capacitor, I'll use a low-leakage aluminum electrolytic. Just because "gold" (wasn't that just Panasonic's trade name) caps have disappeared from Digikey doesn't mean they're generically gone. Many, if not most, of the e-cap makers catalog low leakage parts- but they are not necessarily stocked on this side of the Pacific. Mouser still stocks Nichicon low leakage e-caps, but you can get them in bulk from many GCA factories. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
On Fri, 03 Feb 2012 08:00:31 -0500, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

>On Tue, 31 Jan 2012 23:50:43 -0600, the renowned Tim Wescott ><tim@seemywebsite.com> wrote: > >>I realized yesterday that gold electrolytics seem to have disappeared >>from the market. >> >>What do folks use when they need a really low-leakage capacitor? > >Generally, when I need a high value low leakage capacitor, I'll use a >low-leakage aluminum electrolytic. Just because "gold" (wasn't that >just Panasonic's trade name) caps have disappeared from Digikey >doesn't mean they're generically gone. Many, if not most, of the e-cap >makers catalog low leakage parts- but they are not necessarily stocked >on this side of the Pacific. > >Mouser still stocks Nichicon low leakage e-caps, but you can get them >in bulk from many GCA factories. > > >Best regards, >Spehro Pefhany
You are correct. There never was a "gold" EL, as in some variant of what the industry originally engineered which used Gold. It was a trade name that was apparently quite successful. They got the Gold. What they sold was a technology they discovered and patented (and branded), which gave the yields he desires, but actual "Gold" in the caps would have made them considerably more expensive and I do not recall them being $10 or $20 each. So it was just a damn good name. But *that* may well be exactly what he is referring to, as he did not remove that vaguery from the query.
On Fri, 03 Feb 2012 05:38:55 -0800, Archimedes' Lever wrote:

> On Fri, 03 Feb 2012 08:00:31 -0500, Spehro Pefhany > <speffSNIP@interlogDOTyou.knowwhat> wrote: > >>On Tue, 31 Jan 2012 23:50:43 -0600, the renowned Tim Wescott >><tim@seemywebsite.com> wrote: >> >>>I realized yesterday that gold electrolytics seem to have disappeared >>>from the market. >>> >>>What do folks use when they need a really low-leakage capacitor? >> >>Generally, when I need a high value low leakage capacitor, I'll use a >>low-leakage aluminum electrolytic. Just because "gold" (wasn't that just >>Panasonic's trade name) caps have disappeared from Digikey doesn't mean >>they're generically gone. Many, if not most, of the e-cap makers catalog >>low leakage parts- but they are not necessarily stocked on this side of >>the Pacific. >> >>Mouser still stocks Nichicon low leakage e-caps, but you can get them in >>bulk from many GCA factories. >> >> >>Best regards, >>Spehro Pefhany > > You are correct. There never was a "gold" EL, as in some variant of > what the industry originally engineered which used Gold. It was a trade > name that was apparently quite successful. They got the Gold. > > What they sold was a technology they discovered and patented (and > branded), which gave the yields he desires, but actual "Gold" in the > caps would have made them considerably more expensive and I do not > recall them being $10 or $20 each. So it was just a damn good name. > > But *that* may well be exactly what he is referring to, as he did not > remove that vaguery from the query.
Hmm. I assumed that they were, indeed, using gold in the chemistry. IIRC the price would have been consistent with using a thin flash of gold on aluminum foil or plastic film. But, if it was just super-low-leakage aluminum caps, that's fine (assuming I can find them). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com