Why is the capacitance value of chip capacitors low? This is the reason!

1. The influence of measurement instrument differences on measurement results

Large-capacity capacitors (usually above 1UF) are more likely to have low capacitance when measuring. The main reason for this phenomenon is that the actual voltage applied to both ends of the capacitor cannot reach the voltage required by the test conditions. This is because The test voltage at both ends of the capacitor is inconsistent with the set voltage actually displayed due to the internal impedance divider of the instrument. In order to minimize the error of the measurement results, we recommend to adjust the instrument and try to adjust the set voltage of the instrument with the voltage measured on both ends of the capacitor as much as possible, so that the actual output voltage on the capacitor under test is consistent.

Countermeasures: The influence of measurement instrument differences on the measurement results. Countermeasures:

When measuring the capacitance value, adjust the instrument and adjust the set voltage of the instrument and the voltage measured on both ends of the product as much as possible, so that the voltage actually loaded on the object under test is consistent with the output voltage.

2. The influence of test conditions on measurement results

First consider the measurement conditions. For chip capacitors with different capacitance values, different test conditions will be used to measure the capacitance values. The main difference is the setting of the test voltage and the setting of the test frequency. The following table shows the different capacitances. Value measurement conditions:

Capacitance AC voltage frequency

Capacity>10μF 1.0±0.2Vrms 120Hz

1000pF<Capacity≦10μF 1.0±0.2Vrms 1kHz

Capacity≦ 1000pF 1.0± 0.2Vrms 1MHz

Solution: For capacitors with different capacitance values, different test voltages and test frequencies will be used to measure their capacitance values.

3. Measure the impact of environmental conditions on the measurement results

SMD ceramic capacitors (X7R/X5R/Y5V) series products are called non-temperature-compensating components, that is, under different working temperature environments, the capacitance will change significantly. Under different working temperatures, the nominal capacitance The difference between the capacitance value and the actual capacitance value. For example, the test capacity at 40°C will be nearly 20% lower than the test capacity at 25°C. It can be seen that when the external environment temperature is relatively high, the test value of the capacitance value will be significantly lower. We usually recommend placing it in an environment of 20°C for a period of time, so that the material is in a stable test environment before performing the capacitance test.

Solution: Put the product in an environment of 20℃ for a period of time, so that the material can be tested in a more stable test environment.

4. Material aging of MLCC products

Material aging refers to the phenomenon that the capacitance value of the capacitor decreases with time. This occurs in all material products that use ferroelectric materials as dielectric materials, which is a natural and inevitable phenomenon. The reason is that the internal crystal structure changes with temperature and time, resulting in a decrease in capacitance, which is a reversible phenomenon. When the aging material is applied for a period of time higher than the Curie temperature of the material (recommended conditions for the restoration of the capacitance value is 150 ℃/1 hour), when the ambient temperature returns to room temperature (placed at room temperature 25 ℃ for 24 hours), the material The molecular structure of will return to its original state. The material will then begin another cycle of aging, and the capacitance of the chip capacitor will return to within the normal specifications.

Solution: high-temperature baking: place the product with low test capacity in an ambient temperature of 150℃ and bake it for 1 hour. Then put it at room temperature 25℃ for 24 hours, and then test, the capacitance value will return to the normal specification range; or after immersing the product with low test capacity in a tin furnace or reflow soldering, perform the test again, the capacitance value will be restored To within the normal specification range.