10V ceramic cap at 95V DC ?
in [Design]
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From: Adam S on 1 Apr 2007 06:54 I was wondering what happens when you put too much voltage across a one of those low voltage multilayer ceramic capacitors. I took a 2.2uF 10V X7R in 1206 package, and applied 95V across it and nothing exciting happened. Leakage settled to 0.5uA after 2 minutes. Even after disconnecting for 1 minute the terminal voltage was around 60V+. The only thing I noticed was capacitance had dropped from 2.30uF to 1.85uF (at 0 VDC bias) after the test. However heating the capacitor with a soldering iron tip for a second , had restored it to its original 2.30uF. So what bad things are suppose to happen when you exceed the 10V spec. ?
From: Uwe Bonnes on 1 Apr 2007 09:45 Adam S <not.valid(a)nosuchaddress> wrote: > I was wondering what happens when you put too much voltage across a one > of those low voltage multilayer ceramic capacitors. I took a 2.2uF 10V > X7R in 1206 package, and applied 95V across it and nothing exciting > happened. Leakage settled to 0.5uA after 2 minutes. Even after > disconnecting for 1 minute the terminal voltage was around 60V+. The > only thing I noticed was capacitance had dropped from 2.30uF to 1.85uF > (at 0 VDC bias) after the test. However heating the capacitor with a > soldering iron tip for a second , had restored it to its original 2.30uF. > So what bad things are suppose to happen when you exceed the 10V spec. ? As you have seen - Polarization gets lost (perhaps recoverable) and more - Capacitance at that high voltage drops considerably - At some point in time or at some higher voltage the part will spark or something like that Bye -- Uwe Bonnes bon(a)elektron.ikp.physik.tu-darmstadt.de Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt --------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
From: colin on 1 Apr 2007 12:56 "Adam S" <not.valid(a)nosuchaddress> wrote in message news:460f8f69$0$9771$afc38c87(a)news.optusnet.com.au... >I was wondering what happens when you put too much voltage across a one of >those low voltage multilayer ceramic capacitors. I took a 2.2uF 10V X7R in >1206 package, and applied 95V across it and nothing exciting happened. >Leakage settled to 0.5uA after 2 minutes. Even after disconnecting for 1 >minute the terminal voltage was around 60V+. The only thing I noticed was >capacitance had dropped from 2.30uF to 1.85uF (at 0 VDC bias) after the >test. However heating the capacitor with a soldering iron tip for a second >, had restored it to its original 2.30uF. > > So what bad things are suppose to happen when you exceed the 10V spec. ? I was making a EFL inverter, it had some 1nf 1205 400v caps in the filter, when I was trying to get it to work ocassionaly the thing would resonate and get so excited sparks would jump acros the endcaps of the capacitors ! I was surprised the caps hadnt failed and gone short circuit, it was quite spectacular. Ive used some 10uf ceramic caps in a low leakage integrator application, I measured the total leakage in the circuit and it was the same as the leakage through the glass fiber pcb. theres probably good reason why the guaranteed specs are seemingly somewhat pessimistic. Colin =^.^=
From: Joerg on 1 Apr 2007 18:10 Adam S wrote: > I was wondering what happens when you put too much voltage across a one > of those low voltage multilayer ceramic capacitors. I took a 2.2uF 10V > X7R in 1206 package, and applied 95V across it and nothing exciting > happened. Leakage settled to 0.5uA after 2 minutes. Even after > disconnecting for 1 minute the terminal voltage was around 60V+. The > only thing I noticed was capacitance had dropped from 2.30uF to 1.85uF > (at 0 VDC bias) after the test. However heating the capacitor with a > soldering iron tip for a second , had restored it to its original 2.30uF. > > So what bad things are suppose to happen when you exceed the 10V spec. ? Be careful if that comes off a low impedance source. I have seen ceramic turn into bubbly green glass with a loud bang. -- Regards, Joerg http://www.analogconsultants.com
From: Ian on 2 Apr 2007 08:39
"Adam S" <not.valid(a)nosuchaddress> wrote in message news:460f8f69$0$9771$afc38c87(a)news.optusnet.com.au... >I was wondering what happens when you put too much voltage across a one of >those low voltage multilayer ceramic capacitors. I took a 2.2uF 10V X7R in >1206 package, and applied 95V across it and nothing exciting happened. >Leakage settled to 0.5uA after 2 minutes. Even after disconnecting for 1 >minute the terminal voltage was around 60V+. The only thing I noticed was >capacitance had dropped from 2.30uF to 1.85uF (at 0 VDC bias) after the >test. However heating the capacitor with a soldering iron tip for a second >, had restored it to its original 2.30uF. > > So what bad things are suppose to happen when you exceed the 10V spec. ? ISTR some information (AVX site?) saying that most ceramic caps will survive several times the rated voltage, it is just that a few per batch may not. Regards Ian |