How to Testing Cermaic Capacitors?

[[email protected]]

hello,
I heard that Ceramic Capacitors rarely fail nevertheless how can one be
sure? Is there a way to test them to know if they are good? Is it
important to test these or not? Any help would be appreciated!

 

[crazy frog]

ive never tested them before but
thay can shortout sumtimes.
had a shorted one in a rotel amp
in the phono stage on the power
rail, it took out a fuse, i have hered
that if you apply to much heat soldering
them thay can short as well.

 

[Ed /:-}]

ceramics are known to have a problem with high resistance instead of infinite ohms, tolerance on some are really wide, temp stability -v- cap is shocking

 

[Franc Zabkar]

hello,
I heard that Ceramic Capacitors rarely fail nevertheless how can one be
sure? Is there a way to test them to know if they are good? Is it
important to test these or not? Any help would be appreciated!

I've seen S/C, low capacitance, and temperature drift problems. To
test for the latter, measure the capacitance while subjecting the cap
to a hair dryer or spray freeze.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

 

[The Real Andy]

hello,
I heard that Ceramic Capacitors rarely fail nevertheless how can one be

You heard wrong.

sure? Is there a way to test them to know if they are good? Is it
important to test these or not? Any help would be appreciated!

If in doubt, replace them.

 

[Terry Given]

I've seen S/C, low capacitance, and temperature drift problems. To
test for the latter, measure the capacitance while subjecting the cap
to a hair dryer or spray freeze.

-- Franc Zabkar

I have seen quite a few short-circuit "little blue" 100nF bypass caps.
When there is a few hundred on a board to pick from, this can be less
than fun to fix.

all Z5U and Y5V dielectric caps will "fail" the freeze-spray/hair dryer
test, because the dielectrics themselves have seriously ratshit
performance over temperature. see the first graph of:

http://www.avxcorp.com/docs/catalogs/cy5v.pdf

Z5U are even worse with temperature.

The 2nd graph is interesting too - capacitance *plummets* with rising
Vdc above 10%. Any more than 40% Vrated and capacitance has dropped to
about 1/10 its rated value!

Cheers
Terry

 

[Phil Allison]

<[email protected]

hello,
I heard that Ceramic Capacitors rarely fail nevertheless how can one be
sure? Is there a way to test them to know if they are good? Is it
important to test these or not? Any help would be appreciated!

** On 5 volt rail digital stuff, ceramics sometimes go short - especially
tiny blue monolithics - and pull the supply rail right down.

My favourite trick is to substitute a 5 volt, 6 amp bench DC supply and
*smoke the sucker* out.




......... Phil

 

[Franc Zabkar]

I have seen quite a few short-circuit "little blue" 100nF bypass caps.
When there is a few hundred on a board to pick from, this can be less
than fun to fix.

all Z5U and Y5V dielectric caps will "fail" the freeze-spray/hair dryer
test, because the dielectrics themselves have seriously ratshit
performance over temperature. see the first graph of:

http://www.avxcorp.com/docs/catalogs/cy5v.pdf

Z5U are even worse with temperature.

The 2nd graph is interesting too - capacitance *plummets* with rising
Vdc above 10%. Any more than 40% Vrated and capacitance has dropped to
about 1/10 its rated value!

Cheers
Terry

I take your point. The capacitor failures that I verified with a heat
test were in horizontal oscillators. I recall one in a 13" IBM
monitor, others were in high end CADCAM systems. I believe they were
NPO types which should have been relatively stable. Another common
choice for this type of application used to be silvered mica. I had
drift problems with those also.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.