polyester film capacitor (CL series, PET dielectric) and CBB polypropylene film capacitor (PP dielectric) are the two most widely used film capacitors in the industry. Both are non-polar metallized film capacitors with self-healing property. The difference of dielectric materials causes different loss, high-frequency performance, temperature stability, size and cost. Engineers should compare pros and cons according to circuit conditions for proper selection.

polyester film capacitor pros and cons: Its advantages include high dielectric constant, smaller size under same capacitance and voltage, good heat resistance and low raw material cost. It fits low-frequency projects with tight budget and limited PCB space. Its disadvantages are high dissipation factor, fast loss rise with frequency, poor capacitance stability and large dielectric absorption. It heats up easily under high-frequency pulse and large current, so it is only for medium-low frequency coupling, bypass and general filtering.

CBB polypropylene capacitor pros and cons: It has ultra-low dissipation factor, outstanding high-frequency performance, tiny capacitance temperature drift, low dielectric absorption, strong pulse resistance and high insulation resistance. It works stably in switching power supplies, inverters, resonant circuits and X2 safety capacitor circuits. Its main disadvantage is low dielectric constant, so it has larger size and higher cost than polyester capacitor with the same parameters.

weidy CBB capacitor summarizes the selection rules: polyester film capacitor is preferred for low-frequency, cost-sensitive and space-limited schemes. CBB capacitor must be adopted for high-frequency switching, high ripple, pulse absorption and high stability requirements. Random replacement is forbidden. Polyester film cannot be used for safety certified capacitors; only PP material can make X2 safety capacitors. For circuits between low and high frequency, sample comparison tests are recommended to find the best cost-effective solution.