What are the thermal properties of bidirectional polyimide films
Bidirectional polyimide film (BOPI) has excellent and balanced thermal properties: long-term temperature resistance of 260-300 ℃, short-term peak value of 400-500 ℃, glass transition temperature Tg ≥ 250 ℃, thermal decomposition temperature ≥ 500 ℃, low thermal expansion coefficient, and stable size. It is a special polymer film with high heat resistance and low deformation.
Bidirectional polyimide film (BOPI) has excellent and balanced thermal properties: long-term temperature resistance of 260-300 ℃, short-term peak value of 400-500 ℃, glass transition temperature Tg ≥ 250 ℃, thermal decomposition temperature ≥ 500 ℃, low thermal expansion coefficient, and stable size. It is a special polymer film with high heat resistance and low deformation.
1、 Temperature tolerance range (core indicator)
Long term continuous use: -200 ℃~260 ℃ (H-class insulation, safe for long-term use above 180 ℃).
Short term tolerance (several minutes): 300-400 ℃, anaerobic environment can approach 500 ℃ for a short time.
Extreme temperature resistance: Not brittle at low temperatures up to -269 ℃ (liquid helium); It only decomposes significantly at temperatures above 500 ℃.
2、 Glass transition temperature Tg
Standard BOPI: 250-300 ℃; Special (such as diketone anhydride type) can reach 290-320 ℃.
Below Tg: stiff and dimensionally stable; Tg or above: gradually softening but still maintaining mechanical strength, without melting or flowing.
3、 Thermal decomposition temperature Td
Initial decomposition: ≥ 500 ℃ (nitrogen atmosphere); Aerobic environment is about 450 ℃.
5% weight loss temperature (T5%): 520-530 ℃, with thermal stability far exceeding that of most engineering plastics.
4、 Coefficient of thermal expansion CTE (critical dimensional stability)
After biaxial stretching: 10-20 ppm/℃ (10 ⁻⁶/℃), much lower than ordinary PI (30-50 ppm/℃) and general plastics.
Room temperature to 200 ℃ average: 15-25 ppm/℃; Match with copper foil (17 ppm/℃) and adapt to FPC process.
5、 Thermal shrinkage rate (high temperature process stability)
200℃/30min：≤0.5%； 300 ℃/10min: ≤ 1.0%.
Biaxially stretching arranges molecular chains in a regular manner, making them less prone to shrinkage and deformation at high temperatures, making them suitable for precision electronic processing.
6、 Thermal conductivity and flame retardancy
Thermal conductivity: pure PI about 0.2-0.3 W/m · K (adiabatic); Modification (with ceramic/graphite fillers) can achieve a thermal conductivity of 1.0-1.5 W/m · K.
Flame retardancy: UL94 V-0 grade, self extinguishing, no dripping, does not release toxic gases at high temperatures.
7、 Comparison with ordinary PI film (advantages)
Temperature resistance: Long term high of 20-40 ℃, short-term high of 50-100 ℃.
CTE: 30% to 60% lower, with more stable dimensions.
Heat shrinkage: reduced by more than 50%, resulting in higher process yield.
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