Electronic Components & Devices

Design

Climatic factors

Operating temperature

Any operating temperature should not exceed the upper category temperature.
It is necessary to select a capacitor whose rated temperature is higher than the operating temperature.
Also it is recommended to consider the temperature distribution in equipment and seasonal temperature variable factor.

Problem due to exceeding the rated temperature range

When the capacitor is used at a temperature above the upper category temperature, insulation resistance of the capacitor may deteriorate and cause rapid current increase and a short circuit.

  • ・Factors of temperature rise
    1. (1) Ambient temperature
      1. ① Outside temperature of equipment
      2. ② Inside temperature of equipment due to heat accumulation
      3. ③ Radiation heat from heating components such as Power transistors, PTC thermistors, etc., around the capacitor.
      4. ④ Thermal conduction through the pattern of printed wiring board.

Problem due to self-heating of the capacitor

The surface temperature of the capacitor shall be the upper category temperature (maximum operating temperature) or less, including self-heating. (See Applied voltage and self-heating temperature)

  • ・Self-heating
    1. (1) Due to ESR of capacitor by AC current
      Special attention to high frequency circuits because of self-heating of the capacitor due to ESR by AC current.
    2. (2) Due to ESR of the capacitor by rapid charging/discharging
    3. (3) Due to exceeding the rated voltage
      When using a capacitor in a circuit which causes self-heating, confirm that the surface temperature rise of the capacitor is less than or equal to 20°C, and also that the temperature is at or below the upper category temperature of the capacitor. (See Applied voltage and self-heating temperature)

Consult us before using a capacitor in equipment which requires a very high degree of reliability, such as medical equipment, aerospace applications or nuclear equipment.

Malfunctions of medical, space, nuclear (power plant) or other vital equipment may endanger human life or have serious consequences for society.
Capacitors to be used in the equipment mentioned above need to be specially designed for obtaining higher reliability than those for general purpose.

Safety Application Guide for Multilayer Ceramic Chip Capacitors All Lists

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