PI Heating Element: Everything You Should Know

In today’s electronics, maintaining precise and stable temperatures is vital. From batteries and sensors to aerospace instruments, reliable heating control can determine the performance and lifespan of a product. That’s where PI heating film, also known as polyimide heaters, have become a game changer.

These thin, flexible heaters combine advanced materials with fine circuit design, bringing both efficiency and durability to temperature control. Whether used in portable devices or industrial systems, a well-engineered polyimide heating film ensures smooth, consistent heat without adding bulk.

Let’s dive deep into what makes these heaters so special — their materials, design principles, working voltage, power density, and how manufacturers like Danyu electronics bring them to life with precision process control.

What Is a PI Heating Film?

A PI heating film is a thin, flexible heater made from polyimide (PI) as the insulating layer and a metallic conductor as the heating element. The conductor is etched or printed between two PI layers, forming a compact heating circuit.

Because polyimide has excellent thermal stability, mechanical strength, and chemical resistance, it can work under high temperatures — typically up to 150°C for long-term operation and short bursts up to 200°C when needed.

Compared with silicone or PET-based heaters, a PI heating film stands out for its thinness and precision. It’s commonly used in batteries, cameras, sensors, aerospace instruments, and medical devices, where compactness and reliability are essential.

What Materials Are Used in PI Heating Film?

The performance of any polyimide heater begins with its materials. The conductor layer — which generates the heat — is typically made from high-resistance alloys or copper-based metals.

Common conductor choices include:

• Copper (12–35µm): Excellent conductivity, used for fine line widths below 0.25mm.
• Brass (50µm): Stable resistance, easy to process, suitable for general applications.
• Stainless Steel 304 (30–50µm): Corrosion-resistant and durable, widely used in medium-power designs.
• FeCrAl (30–50µm): High resistance, ideal for heaters requiring higher working voltages.
• Cu-Ni (white copper, 50µm): Offers good uniformity and long service life.

The choice of conductor depends on the target resistance, power level, and line width requirements. For ultra-fine circuit designs (line width below 0.25mm), copper becomes the only feasible option due to its etching precision.

How Does the Conductor Design Affect Performance?

The conductor’s pattern determines the heat distribution, temperature rise rate, and energy efficiency. Designers adjust line width, spacing, and thickness to achieve a balance between resistance and power.

For example:

• A 1.5oz copper foil can achieve line widths as narrow as 0.08–0.09mm, with compensation of about 0.05mm for etching.
• FeCrAl conductors, on the other hand, need wider tracks — around 0.2mm — because of their higher resistance.

A single-layer conductor design is often preferred since it’s easier to control resistance and heat uniformity. For higher power density or dual-voltage systems, multilayer structures can be customized.

At Danyu electronics, the conductor pattern is precisely formed through chemical etching, followed by AOI (Automated Optical Inspection) to guarantee every line meets the target width and spacing tolerance.

What Are the Common Thickness and Adhesive Options?

The total thickness of a PI heating film depends on the polyimide base and adhesive layers. Common configurations include:

• 25µm PI + 25µm adhesive
• 50µm PI + 25µm adhesive
• 13µm PI + 15µm adhesive
• 13µm PI + 25µm adhesive

Standard finished thickness is usually around 0.13mm, but when applied to battery heating, a 0.2mm design is recommended for better mechanical protection.

For bonding and mounting, adhesive tapes play a key role. Frequently used ones include 3M 467, 3M 468, and Crown 513. These can handle up to 150°C continuous operation. If odor or high temperature resistance is a concern, 3M 9077 — a high-grade, substrate-based adhesive — is preferred.

How to Choose the Right Voltage and Power Density?

The working voltage of PI heaters ranges from 3.7V to 220V, depending on size and design. Smaller heaters usually run on low voltage (3.7V–24V) for safe portable applications, while larger ones may use 110V or 220V to reduce current draw.

Power density — the power generated per unit area — directly influences heating speed and temperature. Standard PI heaters operate at 1.2W/cm² (dry heating). Small heaters with proper control can reach up to 3W/cm², but a temperature controller is required. For transparent or low-temperature heaters, the working density is much lower, usually below 1W/cm².

Although higher power density means faster heating, it also increases the risk of overheating. So, the heater design should always match the application’s heat dissipation capability.

How Is Temperature Controlled in PI Heating Film?

Precise temperature management defines the reliability of any heating element. PI heaters offer multiple control options depending on the system’s sophistication:

1. Thermostat Switch:

Simple and cost-effective. It cuts off power when the preset temperature is reached and reactivates once the temperature drops.

2. Thermistor or K-type Thermocouple:

Used with electronic controllers for real-time feedback. Enables stable, long-term temperature regulation with digital or dial-based control.

3. Resistive Control:

Some designs integrate a three-level switch to change resistance and modify heating power — low, medium, and high.

4. Fuse Protection:

In high-reliability products, dual protection is used — a temperature controller and a fuse (either single-use or resettable) — to prevent runaway heating.

Temperature uniformity also depends on surface bonding. To improve evenness, aluminum foils can be added for heat spreading, while thermal insulation pads are used when heat retention is required.

Testing and Reliability of Polyimide Heaters

Each PI heating film undergoes strict reliability testing to confirm performance under real-world conditions. Common procedures include:

• Dielectric Strength: AC1200V, 5mA for 60s, with no breakdown.
• Insulation Resistance: DC1000V, >100MΩ.
• Thermal Shock: Cycling between -25°C and +125°C for four hours per cycle without damage.
• Wire Pull Test: Verified based on wire gauge and tensile standard.
• High Temperature and Humidity Test: 60°C / 95% RH for 240 hours, ensuring no delamination or resistance drift.

Mass production lots are also subjected to 100% resistance testing, often using low-resistance test racks. For smaller runs, resistance is measured manually with multimeters or bridges.

Practical Design and Usage Considerations

1. Proper handling and installation are essential for long service life. A few golden rules:
2. Never operate above rated voltage, as temperature rises sharply with excess voltage.
3. Avoid tearing, folding, or piercing the film.
4. For high-voltage products, maintain insulation integrity — no scratches or punctures on the protective layer.
5. When mounting, keep the bonding surface flat to ensure uniform heat transfer and prevent localized overheating.
6. If thermal sensors are used, their position can be freely designed depending on the heating zone.

How does Danyu Electronics Assist You?

At Danyu electronics, we go beyond manufacturing — we deliver heating solutions that are tailored to your exact needs. Here’s why customers choose us for their custom polyimide flexible heater projects:

• We can print your company logo or identification marks directly on the heater surface or packaging to strengthen your brand identity.
• Every order is handled with care from start to finish. We respond to all inquiries within 24 hours to keep your project moving.
• Whether you order a single prototype or a large production batch, you’ll receive the same high level of quality and service.
• We support all major shipping methods and maintain short lead times. Typical production is completed within 3–5 days, depending on quantity.
• All heaters come with a standard 1-year warranty, ensuring peace of mind for your purchase.
• Our engineering team offers complimentary support in heater design to create the most effective thermal solution for your application.
• We can produce heaters in any size, shape, voltage, or wattage according to your specifications.

Whether you need a heater for battery packs, optical sensors, or industrial modules, Best Technology delivers precision-manufactured PI heating films designed for stability, reliability, and long-term performance. For custom inquiries or design consultations, contact us at sales@best-heaters.com.

FAQs About PI Heating Films

1. What’s the typical working temperature of a PI heating film?

Standard PI heaters operate up to 130°C continuously and can handle short-term peaks of 150°C.

2. Can PI heating films be made in transparent form?

Yes. Transparent versions use conductive films instead of metal foils and can reach sizes up to 580mm × 2000mm.

3. How is resistance tolerance controlled during production?

Single-layer heaters maintain ±5% tolerance, while dual-layer designs follow ±10%.

4. Can PI heaters heat up faster with higher power density?

They can, but beyond 1.2W/cm², additional temperature control is necessary to prevent overheating.

5. What’s the standard thickness of a PI heating film?

Typically around 0.13mm, but can be customized up to 0.2mm for applications like battery heating.