Comparison of four common dielectric materials for film capacitors

Film capacitors are often used in input filter circuits due to the following characteristics of film capacitors:
Advantages of film capacitors over other types of capacitors:
1. lower parasitic effects.
2. very stable over temperature and frequency
3. high ripple current resistance
4. self-healing properties

When special safety requirements are mandatory, this feature ensures high reliability throughout the product process chain. Other technologies can make reliable capacitors though. However, other problems may occur after manufacturing, e.g. during PCB or device installation. In addition, the failure mode of film capacitors is a drop in capacitance or an open circuit mode, which makes them ideal for applications where safety and reliability are required.
The characteristics of film capacitors, however, can vary from one dielectric material to another. Comprehensive comparison
Film capacitors of different dielectric types vary in their temperature resistance performance as well as their performance in high frequency applications. Understanding the strengths and weaknesses of each film material will allow you to better find the right film capacitor for your project.

Film capacitors, 4 common dielectric materials:
Polyester (PET):
- Polyester film is one of the main materials for film capacitors, with excellent insulating and mechanical properties.
- It also has excellent properties such as high temperature resistance and chemical corrosion resistance, and can be used in a wide range of industrial and electronic fields.
- Polyester capacitors are also known as Mylar capacitors or polyester capacitors.
Polypropylene (PP):
- Polypropylene film is another common film capacitor material that is more stable at high temperatures and resistant to chemical corrosion than polyester film.
- This material is widely used in high-temperature operating environments and in certain high-performance electronic devices, such as electrical regulators, computer motherboards, and aerospace instruments.
- Polypropylene capacitors are also known as CBB capacitors.
Polystyrene (PS):
- Polystyrene film capacitors have low dielectric loss and high insulation resistance, but have a large temperature coefficient and are suitable for high frequency circuits.
Polycarbonate (PC):
- Polycarbonate is also a dielectric material for film capacitors, with excellent performance characteristics.
Comparison of four dielectric material properties:

Material Properties PP PET PEN PPS
Advantages High current and voltage stability in a specific temperature and frequency range High capacitance density, high operating temperature High capacitance density, high operating temperature Very stable, precision tolerances, high operating temperature
Limitations High temperature not suitable High frequency not suitable High frequency not suitable High cost
Applications AC and DC High Power, Pulse, X&Y EMI Suppression DC and AC Low Power, Bypass, Isolation, Coupling and Decoupling, Timing and Filters DC Low Power, Bypass, Isolation, Coupling and Decoupling, Timing and Filters DC Low Power, High Temperature, Timing, Filters, Oscillating Circuits
Dielectric Materials Summary of Characteristics
PET Most common film capacitor. Resistant to high and low temperatures, low cost.
PEN High capacitance density, high operating temperature.
PPS Good heat resistance and thermal characteristics, but high cost.
PP High insulation resistance, low tanδ (loss) for high currents, but slightly lower thermal resistance.

Film capacitors have been used as X and Y capacitors in EMI filters for many years and are used in a large number of industrial and consumer applications. Understanding the characteristics of film capacitors made of different materials will help you find the right film capacitor faster.