What are the electrical properties of unidirectional polyimide film
Unidirectional polyimide (PI) film, as a special engineering material, has the core advantages of "high temperature resistance, high voltage resistance, and low loss" in electrical properties. Especially with the mechanical strength added by unidirectional orientation, its electrical stability and service reliability are outstanding, and it is widely suitable for aerospace, electronic power and ot
Unidirectional polyimide (PI) film, as a special engineering material, has the core advantages of "high temperature resistance, high voltage resistance, and low loss" in electrical properties. Especially with the mechanical strength added by unidirectional orientation, its electrical stability and service reliability are outstanding, and it is widely suitable for aerospace, electronic power and other fields. The following is a detailed analysis of its key electrical performance:
1、 Outstanding features of key electrical performance
1. High voltage resistance and excellent insulation strength
The dielectric strength of unidirectional PI film can reach 150-250 kV/mm, which is much higher than that of ordinary polyester (PET) film (about 100-150 kV/mm). Even in the scenario of thinning (such as below 25 μ m), it can still withstand high voltage impact and is suitable as an insulation material for high-voltage motors, transformers, or high-voltage line insulation layers for aerospace equipment.
The unidirectional orientation process makes the arrangement of film molecules more regular, with fewer internal defects (such as bubbles and impurities), strong breakdown voltage stability, and no insulation failure caused by local defects.
2. Low dielectric loss, suitable for high-frequency scenarios
The dielectric loss tangent is only 0.001-0.005, with minimal variation in high frequency (1kHz-1MHz) and wide temperature range (-200 ℃~260 ℃), low electrical energy loss, and no accelerated material aging caused by heat generation.
The relative dielectric constant (2.8-3.5) is stable and suitable as a substrate for high-frequency communication equipment, radar antennas, and flexible circuit boards (FPCs). It can reduce signal transmission delay and attenuation, ensuring signal integrity.
3. High resistivity, minimal leakage current
Volume resistivity ≥ 10 ¹⁶Ω· cm, surface resistivity ≥ 10 ¹⁵ Ω, high insulation resistance, negligible leakage current, can effectively isolate current, avoid short circuit or leakage risk, especially suitable for electronic component packaging with strict insulation reliability requirements (such as power modules, semiconductor devices).
Even in high temperature (above 200 ℃) or humid environments, the decrease in resistivity is small, and the insulation performance remains stable, without insulation failure caused by environmental changes.
4. Strong resistance to arc and corona aging
Arc resistance ≥ 120 seconds, able to resist the burning of high-voltage arcs, not easily carbonized or broken down, suitable for electrical equipment such as high-voltage switches and contactors that frequently switch on and off, and improve equipment service life.
The corona resistance life can reach 1000-5000 hours (under 10kV/mm conditions), far superior to traditional insulation materials. When used in a high-voltage corona environment for a long time, the dielectric performance deteriorates slowly, making it suitable as an insulation layer for stator windings of motors and generators to cope with long-term high temperature and high voltage conditions.
5. Wide temperature range electrical stability, suitable for extreme environments
The electrical performance remains stable within the range of -200 ℃~260 ℃, and the insulation performance will not decrease due to embrittlement at low temperatures. At high temperatures, the dielectric strength will not decrease or the loss will increase due to thermal aging. It is suitable for extreme environments such as aerospace (extreme temperature difference in space), nuclear industry (high temperature radiation), and deep-sea exploration (low temperature and high pressure).
Even after long-term use at 260 ℃ (for more than 1000 hours), key parameters such as dielectric strength and resistivity decay by no more than 10%, which is much better than other high-temperature resistant polymer films (such as polyetheretherketone (PEEK) film, with a long-term use temperature of ≤ 240 ℃).
2、 Electrical performance advantages reflected in application scenarios
Aerospace electronic equipment: As the insulation layer of high-voltage lines for satellites and rockets, as well as the substrate for radar antennas, it can withstand extreme temperature differences and high-voltage impacts, ensuring stable signal transmission;
High voltage motors/transformers: as insulation materials for stator windings and iron cores, high dielectric strength and corona resistance enhance the equipment's withstand voltage level and service life;
Flexible Circuit Board (FPC)/Rigid Circuit Board (PCB): Low dielectric loss and stable dielectric constant, suitable for high-frequency signal transmission, meeting the requirements of miniaturization and lightweighting of electronic devices;
Power semiconductor packaging: high resistivity and high temperature resistance, used as insulation pads for IGBT and SiC devices to isolate high voltage and high temperature, ensuring stable device operation;
New energy equipment: As an insulation material for photovoltaic inverters and wind power converters, it can withstand high temperature, high voltage, and frequent start stop electrical stress, improving equipment reliability.
3、 Precautions
The electrical properties of unidirectional PI thin films are positively correlated with thickness: the thicker the film, the higher the dielectric strength, but the dielectric constant and loss slightly increase. It is necessary to choose the appropriate thickness based on actual voltage and frequency requirements (common thicknesses: 12 μ m, 25 μ m, 50 μ m, 75 μ m);
Surface cleanliness has a significant impact on electrical performance: if there are impurities such as oil and dust on the surface of the film, it may cause a decrease in local breakdown voltage, and cleaning treatment is required before use;
The differences in formulas and production processes among different manufacturers can lead to slight fluctuations in electrical performance. When selecting, it is necessary to refer to the technical data sheet (TDS) of the specific brand.
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