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'[EE]Overvoltage on Ceramic Capacitors.'
2010\02\22@135225 by Funny NYPD

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For  most of the electrolytic capacitor, they cannot be used  when application voltage is higher than the rated voltage. For ceramic Capacitors, they won't be damaged if the application voltage is higher but doesn't go above 1K Volts~a few Kilo-volts.

Anyone has a info how capacitor changes vs. voltage when lower voltage ceramic cap is used at a higher voltage application? Or it is just useless due to capacitor reduced too much?

Funny N.
Au Group Electronics, http://www.AuElectronics.com
http://www.AuElectronics.com/products
http://augroups.blogspot.com/



     

2010\02\22@140618 by Marcel Duchamp

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On 2/22/2010 10:52 AM, Funny NYPD wrote:
> For  most of the electrolytic capacitor, they cannot be used  when
> application voltage is higher than the rated voltage. For ceramic
> Capacitors, they won't be damaged if the application voltage is
> higher but doesn't go above 1K Volts~a few Kilo-volts.
>

Where did you get that idea?  Voltage ratings are not "optional"...

2010\02\22@143347 by Richard Prosser

picon face
Funny N,

I don't think you can generalise to this extent. It may be true for
some caps - but it certainly isn't true for others. And I'm not sure
how you can tell beforehand.

My take would be that even when the cap is not going to be damaged,
the voltage limit relates to where the cap is likely to fail
specification.

RP

On 23 February 2010 06:52, Funny NYPD <spam_OUTfunnynypdTakeThisOuTspamyahoo.com> wrote:
{Quote hidden}

>

2010\02\22@144750 by Spehro Pefhany

picon face
At 02:06 PM 22/02/2010, you wrote:
>On 2/22/2010 10:52 AM, Funny NYPD wrote:
> > For  most of the electrolytic capacitor, they cannot be used  when
> > application voltage is higher than the rated voltage. For ceramic
> > Capacitors, they won't be damaged if the application voltage is
> > higher but doesn't go above 1K Volts~a few Kilo-volts.
> >
>
>Where did you get that idea?  Voltage ratings are not "optional"...

Ceramic caps don't generally need to be DE-RATED by much compared to other
types for higher reliability, but you shouldn't exceed the maximum voltage.

You seem to be thinking of voltage coefficient, which can indeed be
awful on types such as Y5V (40% loss at rated voltage), but temperature
effects are even worse if you need to operate over a wide range (they
virtually cease to exist electrically at 90 or 100C), and there are also
pronounced aging effects for most types (even the relatively stable X7R/X5R).

http://www.johansondielectrics.com/technical-notes/product-training/basics-of-ceramic-chip-capacitors.html

Unfortunately, NP0/C0G caps are still prohibitively expensive in larger
capacitances such as 0.22uF.


>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
.....speffKILLspamspam@spam@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com



2010\02\22@153840 by Herbert Graf

picon face
On Mon, 2010-02-22 at 11:06 -0800, Marcel Duchamp wrote:
> On 2/22/2010 10:52 AM, Funny NYPD wrote:
> > For  most of the electrolytic capacitor, they cannot be used  when
> > application voltage is higher than the rated voltage. For ceramic
> > Capacitors, they won't be damaged if the application voltage is
> > higher but doesn't go above 1K Volts~a few Kilo-volts.
> >
>
> Where did you get that idea?  Voltage ratings are not "optional"...

Agreed. Perhaps what he was referring to is ceramic caps are more
"forgiving" if you get close to the max. Tantalums tend to explode
pretty much right at their rated maximum.

TTYL

2010\02\22@155613 by Spehro Pefhany

picon face
At 03:36 PM 22/02/2010, you wrote:
>On Mon, 2010-02-22 at 11:06 -0800, Marcel Duchamp wrote:
> > On 2/22/2010 10:52 AM, Funny NYPD wrote:
> > > For  most of the electrolytic capacitor, they cannot be used  when
> > > application voltage is higher than the rated voltage. For ceramic
> > > Capacitors, they won't be damaged if the application voltage is
> > > higher but doesn't go above 1K Volts~a few Kilo-volts.
> > >
> >
> > Where did you get that idea?  Voltage ratings are not "optional"...
>
>Agreed. Perhaps what he was referring to is ceramic caps are more
>"forgiving" if you get close to the max. Tantalums tend to explode
>pretty much right at their rated maximum.
>
>TTYL

Well before that, even, if you do it right (it's advisable to de-rate 2:1 or
even 3:1 for some applications with current surges).

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspamKILLspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com



2010\02\22@161720 by Funny NYPD

picon face
Check out page 11 of 16 in the following presentation (Breakdown voltage comparison):
http://dkc1.digikey.com/ca/en/tod/Murata/HighCapMultiCeramicCap/HighCap_Multilayer_Ceramic_Caps.html

On page 12 of 16, it claims the cap is heavily affected by DC bias voltage.

On the last page, one summary is: a 100UF MLCC ceramic cap can replace 470 uf Tan cap.


Funny N.
Au Group Electronics, http://www.AuElectronics.com
http://www.AuElectronics.com/products
http://augroups.blogspot.com/




________________________________
From: Herbert Graf <.....hkgrafKILLspamspam.....gmail.com>
To: Microcontroller discussion list - Public. <EraseMEpiclistspam_OUTspamTakeThisOuTmit.edu>
Sent: Mon, February 22, 2010 3:36:54 PM
Subject: Re: [EE]Overvoltage on Ceramic Capacitors.

On Mon, 2010-02-22 at 11:06 -0800, Marcel Duchamp wrote:
> On 2/22/2010 10:52 AM, Funny NYPD wrote:
> > For  most of the electrolytic capacitor, they cannot be used  when
> > application voltage is higher than the rated voltage. For ceramic
> > Capacitors, they won't be damaged if the application voltage is
> > higher but doesn't go above 1K Volts~a few Kilo-volts.
> >
>
> Where did you get that idea?  Voltage ratings are not "optional"...

Agreed. Perhaps what he was referring to is ceramic caps are more
"forgiving" if you get close to the max. Tantalums tend to explode
pretty much right at their rated maximum.

TTYL

2010\02\22@163931 by Sean Breheny

face picon face
MLCC capacitors do indeed decrease capacitance a fair amount as you
increase the DC bias. As an example, I've used some  1210 size, 100V
2.2uF MLCC caps which, at 50V, show only about 1.6uF capacitance. I
think these have X5R dielectric.

I don't think that they mean that a 100uF MLCC can exactly replace a
470uF Tantalum cap. They mean that, in many circuits, a 470uF tantalum
is often spec'd to get a certain minimum ESR and a lower capacitance
could be acceptable if the ESR were low enough. A 100uF MLCC could
easily have only 5 milliohm ESR, which is about 10x lower than a
similarly-sized Tantalum.

Sean


On Mon, Feb 22, 2010 at 4:17 PM, Funny NYPD <funnynypdspamspam_OUTyahoo.com> wrote:
{Quote hidden}

>

2010\02\23@081932 by Russell McMahon

face picon face
> > Tantalums tend to explode
>> pretty much right at their rated maximum.

> Well before that, even, if you do it right (it's advisable to de-rate 2:1 or
> even 3:1 for some applications with current surges).

Solid (not wet electrolytic) aluminum caps have about the same
advantages as Tantalum but without Tantalums charming flaw.

Tantalum caps are made by sintering a mass of Tantalum particles
together, attaching a wire and then creating an oxide layer on the
outside of the sintered mass. An outside electrode is then added over
the oxide and ther very large surface area of the particles and the
very thin oxide layer provide superb capacitance density. The voltage
rating is related to oxide thickness. typically its very very very
very thin by any normal standards. Being thin, if it's punctured the
hole width to depth ratio is large for even a "snmall" puncture.

What typically happens with Tantalums is that the voltage level
exceeds the "punch through" voltage of the insulating oxide layer and
a small non healing conduction path forms. If the circuit is low
energy enough the capacitor may be walking wounded but still walking.
However, if there is substantial energy available the break through
becomes increasingly severe and a very low resistance is offered to
the available energy to have fun with.

The important point is that the excess voltage can either come from
general over voltage or from a small spike or from ripple. The
tolerances are very fine and the failure is catastrophic. So, the 2:1
or 3:1 recommended overrating is to keep spikes etc below the rated
voltage. If the spike comes from eg inductive ringing and if the
capacitance is small enough relative to the capacitance or if the wind
is blowing south east and it's a bank holiday (let alone dead fish
being waved) then the spike may 'reach up" from very low levels.

Once it starts there is no going back.

Solutions

- Never use tantalum caps
- Ensure supply never exceeds cap voltage rating
- Never use tantalum caps
- Ensure spikes do not exceed etc
- Never use tantalum caps
- Use only on low energy circuits
- Never use tantalum caps
- Use solid Aluminum caps which are as good but don't have the problems
- Never use tantalum caps
- Never use tantalum caps

Also - Never use tantalum caps
But, the world does, and they are extremely good at what they are good at.
In low energy circuits they are superb
If you get paid at good rates for callouts and for distance and for
weekends then by all means use tantalum caps.
Otherwise ...


          Russell

2010\02\23@083553 by Funny NYPD

picon face
>Use solid Aluminum caps which are as good but don't have the problems
what's the cost and size on solid aluminum caps?, e.g. "10uF, 25V", or "47uF, 35V"?

Funny N.
Au Group Electronics, http://www.AuElectronics.com
http://www.AuElectronics.com/products
http://augroups.blogspot.com/




________________________________
From: Russell McMahon <RemoveMEapptechnzTakeThisOuTspamgmail.com>
To: Microcontroller discussion list - Public. <spamBeGonepiclistspamBeGonespammit.edu>
Sent: Tue, February 23, 2010 8:19:11 AM
Subject: Re: [EE]Overvoltage on Ceramic Capacitors.

> > Tantalums tend to explode
>> pretty much right at their rated maximum.

> Well before that, even, if you do it right (it's advisable to de-rate 2:1 or
> even 3:1 for some applications with current surges).

Solid (not wet electrolytic) aluminum caps have about the same
advantages as Tantalum but without Tantalums charming flaw.

Tantalum caps are made by sintering a mass of Tantalum particles
together, attaching a wire and then creating an oxide layer on the
outside of the sintered mass. An outside electrode is then added over
the oxide and ther very large surface area of the particles and the
very thin oxide layer provide superb capacitance density. The voltage
rating is related to oxide thickness. typically its very very very
very thin by any normal standards. Being thin, if it's punctured the
hole width to depth ratio is large for even a "snmall" puncture.

What typically happens with Tantalums is that the voltage level
exceeds the "punch through" voltage of the insulating oxide layer and
a small non healing conduction path forms. If the circuit is low
energy enough the capacitor may be walking wounded but still walking.
However, if there is substantial energy available the break through
becomes increasingly severe and a very low resistance is offered to
the available energy to have fun with.

The important point is that the excess voltage can either come from
general over voltage or from a small spike or from ripple. The
tolerances are very fine and the failure is catastrophic. So, the 2:1
or 3:1 recommended overrating is to keep spikes etc below the rated
voltage. If the spike comes from eg inductive ringing and if the
capacitance is small enough relative to the capacitance or if the wind
is blowing south east and it's a bank holiday (let alone dead fish
being waved) then the spike may 'reach up" from very low levels.

Once it starts there is no going back.

Solutions

- Never use tantalum caps
- Ensure supply never exceeds cap voltage rating
- Never use tantalum caps
- Ensure spikes do not exceed etc
- Never use tantalum caps
- Use only on low energy circuits
- Never use tantalum caps
- Use solid Aluminum caps which are as good but don't have the problems
- Never use tantalum caps
- Never use tantalum caps

Also - Never use tantalum caps
But, the world does, and they are extremely good at what they are good at.
In low energy circuits they are superb
If you get paid at good rates for callouts and for distance and for
weekends then by all means use tantalum caps.
Otherwise ...


          Russell

2010\02\23@103857 by Russell McMahon

face picon face
> >Use solid Aluminum caps which are as good but don't have the problems
> what's the cost and size on solid aluminum caps?, e.g. "10uF, 25V", or "47uF, 35V"?

My recollection is that size and costare similar to tantaum.
A quick look at Digikey suggests otherwise BUT I doubt that what I am
seeing there is representative.

A look through a suppliers list who sells them in volume would tell you.



  R
.

2010\02\23@105912 by graham foulkes

picon face
Hi
I agree. Tantalums have, in my experience only one advantage, size to
capacitance ratio. When you take into consideration that most circuitry has
lots of spare 'hidden' real estate (space that is unused) then it does not
make sense to put in higher priced, less reliable components. Distributing
the capacitance around in smaller units is invariably a better option. We
will not get into the arguments about the strategic problems of sourcing
raw tantalum ores, D.R.C. (Congo), coltan wars etc.

On Tue, Feb 23, 2010 at 10:38 AM, Russell McMahon <TakeThisOuTapptechnzEraseMEspamspam_OUTgmail.com>wrote:

{Quote hidden}

> -

2010\02\24@091131 by Philip Pemberton

face
flavicon
face
Spehro Pefhany wrote:
> Well before that, even, if you do it right (it's advisable to de-rate 2:1 or
> even 3:1 for some applications with current surges).

I usually try for a 2:1 over-rating on tantalum capacitors anyway. That
is, if I'm putting one on a 5V rail, I'll spec a 10V part instead of a
6.3V part. I do pretty much the same thing with aluminium electrolytics,
but with those it's generally easier and cheaper to get relatively high
voltage parts (25V seems to be more or less the standard these days).

The theory is that it'll last longer as it's being run further away from
its design specs. It probably doesn't work out as well as I think it
does, but it's always nice to have a safety margin.

--
Phil.
RemoveMEpiclistspamTakeThisOuTphilpem.me.uk
http://www.philpem.me.uk/

2010\02\24@095028 by Isaac Marino Bavaresco

flavicon
face
Em 24/2/2010 11:11, Philip Pemberton escreveu:
> Spehro Pefhany wrote:
>  
>> Well before that, even, if you do it right (it's advisable to de-rate 2:1 or
>> even 3:1 for some applications with current surges).
>>    
> I usually try for a 2:1 over-rating on tantalum capacitors anyway. That
> is, if I'm putting one on a 5V rail, I'll spec a 10V part instead of a
> 6.3V part. I do pretty much the same thing with aluminium electrolytics,
> but with those it's generally easier and cheaper to get relatively high
> voltage parts (25V seems to be more or less the standard these days).
>
> The theory is that it'll last longer as it's being run further away from
> its design specs. It probably doesn't work out as well as I think it
> does, but it's always nice to have a safety margin.
>  

It is not advisable to run aluminum electrolytic capacitors at voltages
too low relatively to their rated voltage (eg. running a 100V capacitor
at 5V), because the dielectric layer is formed and recomposed
(electrolytically) by the leakage current.

It is reported that electrolytic capacitors stored for prolonged periods
without power may lose their isolation, becoming short-circuited or
having very high leakage currents. In this case, some manufacturers
recommend to "renew" the capacitor's dielectric before assembling, by
subjecting them for some time to a voltage level with current limiting
(e.g. series resistor).

Equipment stored for very long periods of time may get damaged
(capacitors may leak or explode) when the power is re-applied.


Best regards,

Isaac

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