The insulation resistance of ceramic chip capacitor is the resistance value measured in pure DC state, and the larger the value, the better. Generally, the insulation resistance of high-frequency ceramic chip capacitors is above 5X10, and under strict requirements, it must be above 1X101oΩ. Generally, the insulation resistance of low-frequency ceramic patch capacitors is greater than 1X10Ω.
The insulation resistance of ceramic patch capacitor is formed by connecting the bulk resistance of dielectric and the surface resistance of capacitor in parallel. The bulk resistance of dielectric is related to the properties of dielectric material itself, but the surface resistance depends on the surface moisture and surface pollution of capacitor. Under the condition that the surface of ceramic chip capacitor is not polluted, the insulation resistance of ceramic chip capacitor is equal to the bulk resistance of ceramic medium.
As the charging current of the capacitor decreases with time, only after the capacitor is connected to the DC power supply Upc for a long time can its current eliminate the interference of the charging current and decrease to a stable value I determined only by the bulk resistance of the dielectric material and the surface resistance of the capacitor. Strictly speaking, only the resistance value calculated with this current stability value is the real insulation resistance value.
However, it takes time to wait for the arrival of this current stable value. Without waiting for this current stable value, the measured insulation resistance value will produce great errors. Therefore, the time for measuring the insulation resistance value is uniformly specified, that is, the resistance value measured when the DC voltage is applied for 1min at the normal temperature of 20.5 C.. This regulation has been recognized by most manufacturers including our country.
