The low-capacity MLCC of the temperature compensation type is larger or smaller than the nominal value when the capacitance is measured.
The process is explained using the following steps.
The capacitance of a 1 pF MLCC was measured while changing the distance between the terminals of the test fixture during the OPEN correction.
As a result, when the distance between the terminals during the OPEN correction is greater than the L dimension of the MLCC being measured, the capacitance increases, and decreases when it is smaller.
Set the distance between the fixture terminals during OPEN correction to the same value as the L dimension of the chip being measured.
If OPEN correction is performed when the distance between the fixture terminals is long, the fixture stray capacitance during correction will be smaller than the capacitance during the actual measurement.
If the zero point correction is performed when the distance between the fixture terminals differs from the dimensions of the MLCC being measured, the stray capacitance of the fixture itself will not be accurately corrected to zero.
When the distance between the terminals during OPEN correction is smaller than the L dimension of the MLCC, the stray capacitance of the fixture is corrected to the zero point at a distance greater than reality, so the post-correction measurement result will decrease.
Conversely, if the distance between the terminals is set to greater than the L dimension of the MLCC, the post-correction measurement result will increase.
The variation in the distance between the terminals during OPEN correction is greater when using a tweezer-type of fixture (Ex. Agilent16334) than it is when using an insertion-type of fixture (Ex. Agilent16034).
Compared to the insertion-type of fixture, the tweezer-type has a measuring terminal tip with a larger surface area (S in formula 1), so the fluctuation in the capacitance measurement value increases according to the difference in the distance between the terminals.