Polyimide (PI) tape is prized not only for its heat resistance but also for its excellent electrical insulation properties. One of the most important metrics for assessing insulation performance is dielectric strength—a key parameter for engineers in electronics, electrical, and aerospace industries.

1) What Is Dielectric Strength?
Dielectric strength refers to the maximum electric field a material can withstand without electrical breakdown.
• Unit: Typically measured in kilovolts per millimeter (kV/mm) or volts per micron (V/μm).
• Meaning: A higher dielectric strength means the material is better at resisting electrical current leakage or breakdown under high voltage.
For PI tape, dielectric strength is largely determined by the polyimide film and adhesive systemused.

2) Typical Dielectric Strength of PI Tape
• Standard PI Film: ~100–200 kV/mm
• PI Tape with Silicone Adhesive: 6–10 kV (for typical tape thickness of 25–50 μm)
• High-Performance PI Tape: Can exceed 12 kV for special insulation applications
These values can vary depending on film thickness, adhesive composition, and testing conditions.

3) How to Evaluate Dielectric Strength
Industry standards such as ASTM D149 or IEC 60243 are used for testing:
1. Sample Preparation – PI tape samples are cut to a specified size.
2. Electrode Setup – The tape is placed between two electrodes.
3. Voltage Application – Voltage is gradually increased until breakdown occurs.
4. Calculation – Dielectric strength = Breakdown Voltage ÷ Thickness of material.
Example: If a 50 μm tape breaks down at 7.5 kV, its dielectric strength is 150 kV/mm.

4) Factors Affecting Dielectric Strength
• Moisture Absorption: Water reduces insulation capacity.
• Surface Defects: Scratches or dust can trigger early breakdown.
• Temperature: High temperatures can lower dielectric strength over time.
• Aging: Prolonged exposure to UV, ozone, or chemicals can degrade performance.

5) Why It Matters
For applications such as motor windings, transformer insulation, and PCB masking, selecting PI tape with the right dielectric strength ensures electrical safety, long service life, and compliance with industry standards.

Conclusion
Dielectric strength is a critical parameter for evaluating PI tape’s insulation performance. By understanding the voltage limits and proper testing methods, engineers can choose the right tape to handle the electrical demands of their projects.
