Duh, chemical engineer question - I understand that you can make the
caps read correctly by baking them.   However, what happens when you
solder them on to the board - i.e., won't they "age" on the assembly
and then again function differently from caps just out of the 150C
oven?

Denny

On 7/18/18, John Maxwell <[log in to unmask]> wrote:
> At 150C the parts are above the Curie temperature
>
> Sent from my iPhone
>
>> On Jul 18, 2018, at 11:48 AM, John Maxwell <[log in to unmask]> wrote:
>>
>> 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
>>
>>
>> Sent from my iPhone
>>
>>> 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?
>>>>
>