The dielectric strength of thin film capacitors is one of their core parameters, which directly determines their voltage resistance and reliability.

Dielectric strength refers to the electric field strength that a dielectric material can withstand before breakdown, measured in volts per unit thickness（V/μ m or V/m). It reflects the quality of the material as an insulator, the higher the dielectric strength, the better the insulation performance. During testing, the film is usually placed between two poles and the voltage is gradually increased until breakdown occurs. The voltage value at this point is the breakdown voltage.

In terms of influencing factors, the dielectric strength and the material itself (such as polypropylene)PP、 The purity and density of polyester PET are closely related. Defects in manufacturing processes, such as pinholes and microcracks, can significantly reduce their value. In addition, environmental factors such as temperature and humidity can also affect its long-term stability.

In practical applications, to ensure safety, the working voltage is usually designed to be about half of the breakdown voltage. For example, silicon monoxide（The dielectric strength of SiO thin films is about 2 MV/cm, while that of silicon dioxide (SiO ₂) thin films can reach up to 10 MV/cm. When selecting, materials with appropriate dielectric strength should be matched according to circuit requirements such as voltage level and frequency.

The dielectric strength of thin film capacitors decreases with increasing temperature. This is because high temperature accelerates the aging of internal dielectric materials and increases electronic activity, leading to a decrease in insulation resistance and thus reducing its ability to withstand voltage. Therefore, when used in high-temperature environments, the operating voltage must be correspondingly reduced to ensure safety.

The voltage derating standard for thin film capacitors is usually recommended to beWhen the temperature is above 85 ℃, for every 1 ℃ increase, the rated voltage needs to be reduced by 1.3%. This means that in high-temperature environments, the actual operating voltage of capacitors must be correspondingly reduced to ensure their reliability and lifespan.

For example, a rated voltage isA 100V thin film capacitor can still operate at 100% rated voltage at 85 ℃; When the temperature rises to 86 ℃, its operating voltage should drop to 98.7V (100V × 98.7%); At 87 ℃, it is 97.4V, and so on.

The rated voltage of thin film capacitors decreases with increasing temperature, which is determined by their material properties. Therefore, when used in high-temperature environments, the voltage of capacitors must be reduced to ensure their reliability and lifespan.

Voltage derating standard:

It is usually recommended toWhen the temperature is above 85 ℃, for every 1 ℃ increase, the rated voltage needs to be reduced by 1.3%. For example, a thin film capacitor with a rated voltage of 100V can still operate at 100% rated voltage at 85 ℃; When the temperature rises to 86 ℃, its operating voltage should drop to 98.7V (100V × 98.7%); At 87 ℃, it is 97.4V, and so on.

Practical application suggestions:

Adequate margin: When selecting capacitors, their rated voltage should have sufficient margin to cope with the voltage derating requirements caused by temperature fluctuations.

Monitoring temperature rise: Under high-frequency or pulsed current conditions, capacitors will generate heat on their own, and it is necessary to ensure that their temperature rise does not exceed the allowable range (such as polypropylene capacitors allowing their temperature rise to be less than 5 ℃).