Testing High Capacitance MLCC’s


#1

Most LCR meters are incapable of testing high value MLCC’s due to their internal impedance. The impedance of all MLCC’s 1.0uF and higher is so low at 1KHz that the supplied current of the meter is essentially drained, in-turn dropping the specified voltage to basically 0 Volts so the capacitor never sees the required voltage. This can be verified by measuring the voltage across the capacitor while it’s under test with a true RMS meter. If the voltage is less than 0.4Vrms, the capacitance reading will be low every time.

Some mid-range LCR meters have an impedance matching capability ALC (Automatic Level Control) Function. This allows the meter to decrease its own impedance until it’s lower than the device under test. However, in the case of most high value MLCC’s, this alone is not enough. With these caps, an amplifier unit is necessary to increase the current through the capacitor until the voltage across it reaches the pre-set level (.5Vrms – 1Vrms). We have an Agilent 4284A machine here at Digi-Key and it has both of these capabilities.

There could also be an issue of aging with these caps, however you want to ensure that you are testing them correctly before trying to correct any aging issue.

Here is a excellent article from Steve Maloy that also talks about aging with the MLCCs.
http://www.digikey.com/en/articles/techzone/2016/jun/what-is-the-capacitance-of-this-capacitor

We also have another great article from Mark Waldrip and Richard Tse at TDK that dives into Capacitance Measurement
http://www.digikey.com/en/pdf/t/tdk/capacitance-measurement

An LCR meter is a meter or electronic test equipment used to measure the inductance (L), capacitance (C), and resistance (R) of an electronic components.

See also:
MLCC Common failure issue: Flex Cracking post
Why ceramic capacitors may seem out of spec but aren’t


#2

Also from TDK this is a great video showing high capacitance measurement and techniques https://www.digikey.com/en/videos/t/tdk/high-capacitance-capacitor-measurement-tutorial-by-tdk .