High dielectric constant ceramic capacitors all exhibit aging due to the crystal structure changing from ferroelectric (tetragonal or diamond) to paraelectric (cubic) structures. Higher the dielectric constant (k) and the thinner the dielectric the more rapidly the parts age or lose capacitance.

John


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> On Jul 18, 2018, at 11:10 AM, Guy Ramsey <[log in to unmask]> wrote:
> 
> Well, I'll Be.  I cooked them at 150C for an hour and they measure 100uF
> I learned something today.
> 
>> On Wed, Jul 18, 2018 at 8:08 AM <[log in to unmask]> wrote:
>> 
>> Guy,
>> 
>> Read this and try putting the parts through their Curie point and test
>> them again.  We have seen this on some parts here.
>> 
>> https://www.johansondielectrics.com/ceramic-capacitor-aging-made-simple
>> 
>> Drew
>> 
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
>> Sent: Wednesday, July 18, 2018 7:00 AM
>> To: [log in to unmask]
>> Subject: [TN] capacitor measurement
>> 
>> I got pulled into a Receiving Inspection problem. Our test instrument, an
>> old HP 4192A impedance meter, and a newer Instek 6020 tell us that our X5R
>> capacitors are out of spec.
>> A 100uF, 10%, 6.3V capacitor measures between 25% and 30% below the
>> nominal value.  The instruments have Kelvin probes and are zero calibrated
>> at frequrency, 120Hz the test waveform is 500mV rms.
>> Does anyone have any advise?
>>