Ceramic CapacitorPrecautions for measuring the capacitance of chip multilayer ceramic capacitors

Do any of the following problems occur when measuring the capacitance of chip multilayer ceramic capacitors (hereinafter, "MLCC")?

Let's resolve these problems!!

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.

The high-capacity MLCC of the high dielectric constant type capacitor is smaller than the nominal value when the capacitance is measured.

The process is explained using the following steps.

Measured electrostatic capacity of high-capacity and non high-capacity in the state of ALC (Automatic Level Control ) ON/OFF ,the results are as follows.

⇒When measuring the high capacity capacitance, the measurement result was smaller compared to when the ALC was turned ON only when the ALC was OFF.

The results of measuring the voltage with a tester in each case are as follows.
In a high capacity MLCC measurement, the measurement voltage does not meet the standard conditions when the ALC is OFF.

The capacitance C is expressed as

When the capacitance C increases, Zc decreases.
In addition, the measurement voltage Vc in the measurement circuit can be expressed as

Therefore, the measurement voltage Vc decreases when Zc drops.

If the measurement voltage is less than the standard measurement voltage, perform the following steps

To measure the measurement voltage, apply the tester to each of the measuring terminals during the MLCC measurement as shown in the photograph below.

The main component of high dielectric constant type capacitor is barium titanate (BaTiO3).
This series of capacitors with static capacity over time and become smaller phenomenon. This phenomenon is called the aging characteristics of electrostatic capacity.

BaTiO3 system is shown in Figure 1,it is such a cubic when the temperature above the Curie point.

When the BaTiO3 ceramic capacitor is heated above the Curie point, the crystal structure is converted from tetragonal to cubic. When the temperature is below the Curie point, the crystal structure is converted from cubic to tetragonal.（Figure 2）
In a word, when the fine structure of the crystal is heated to the temperature above the Curie point, it will recover to the initial state, and the aging will start again.

Due to the reduced electrostatic capacity of aging, the heating process in the installation works of your company can be recovered.

The electrostatic capacity of the high dielectric constant type capacitor is measured as a reference value after 24 hours of heat treatment at 125℃ or higher, the logarithm of the relationship of the linear decline between time. Please refer to the following examples of electrostatic capacity aging characteristics of our products.