Application Case of Dowsil™ CN-8760 Thermally Conductive Encapsulant in Industrial Power Module

As industrial power modules develop towards high power density and miniaturization, their thermal dissipation challenges are becoming increasingly severe. Efficient and reliable thermally conductive potting materials have become the key to ensuring the long-term stable operation of modules. Dow's Dowsil™ CN-8760 Thermally Conductive Encapsulant, with its excellent thermal conductivity, convenient processability, and reliable electrical insulation properties, has become an ideal choice for such applications. This case study details its successful application in a new industrial inverter power module.

Dowsil™ CN-8760 is a two-part, 1:1 mix ratio thermally conductive encapsulant that cures at either room temperature or with heat to form a dark gray elastomer. Its core advantage lies in balancing excellent processing performance with reliable material properties.

• Moderate Thermal Conductivity: With a thermal conductivity of 0.66 W/mK, it effectively conducts heat generated by power devices (such as IGBTs, MOSFETs), reducing chip junction temperature and enhancing the module's power cycling capability and service life.

• Low viscosity, good flowability: Mixed viscosity is 2,850 cP, offering good flowability to fully fill the complex internal structures and small gaps of the module, encapsulating components and pins, and reducing air entrapment.
• Long working time: At 25°C, the pot life of the mixed material is as long as 120 minutes, providing ample processing window for manual dispensing or automated production line operations.
• Multiple curing options: Supports room temperature curing (25°C) and can also be heat-accelerated (e.g., 40 minutes at 50°C) to meet different production cycle requirements.

• Excellent electrical insulation: Volume resistivity >1E16 ohm*cm, dielectric strength up to 33 kV/mm, providing reliable insulation protection for high-voltage circuits.
• Flexible elastomer: Cured Shore A hardness is 52, forming a soft elastomer that effectively buffers stress caused by temperature cycling or mechanical vibration, protecting sensitive components and solder joints.
• High-reliability certification: UL 94 V-0 flame classification certified, meeting the safety requirements for material flame retardancy in industrial equipment.

• Ease of Repair: Unlike rigid potting materials, the cured silicone rubber elastomer can be cut and peeled with a sharp blade, facilitating rework, repair, or component replacement of defective modules, significantly reducing scrap costs.

Industrial inverters are the core of motor drives. The power modules inside integrate multiple high-voltage, high-current switching devices, generating significant heat and often operating in environments with vibration and electrical interference. The requirements for potting materials are extremely stringent.

• Thermal conduction and heat spreading: Dowsil™ CN-8760 is potted inside the power module housing, tightly encapsulating heat-generating components such as IGBTs and diodes. Its thermal conduction network quickly transfers heat from point heat sources throughout the potting compound, which is then dissipated to the external heatsink via the module's metal substrate or housing, effectively reducing the hotspot temperature of critical components. Tests show that under the same operating conditions, modules potted with CN-8760 have a core IGBT junction temperature approximately 15-20°C lower than un-potted modules or those using ordinary thermal grease, significantly improving the module's overload capability and long-term reliability.

• Moisture and dust proof: Cures to form a dense elastomer, completely sealing the module interior, preventing the ingress of moisture, dust, and corrosive gases. It meets IP67 and above protection等级 requirements, suitable for harsh industrial environments (e.g., textile, mining, outdoor cabinets).
• Insulation and voltage withstand: High dielectric strength and volume resistivity ensure safe isolation between the internal high-voltage busbar (up to several thousand volts) and low-voltage signal lines or metal housing within the module, preventing tracking and breakdown, and ensuring system safety.
• Mechanical buffering and vibration damping: The soft elastomeric texture absorbs and disperses mechanical stress from equipment operation vibration or external impact, protecting fragile parts such as chips, bond wires, and solder joints, improving the module's durability in vibrating environments.

• Suitable for automated production: The 1:1 mix ratio is robust against mixing ratio errors, suitable for automatic metering, mixing, and dispensing equipment, ensuring batch consistency. The long pot life avoids the risk of premature gelation of the material on the production line.
• Reduces overall cost: No need for high-temperature, long-duration curing, saving energy and time. Excellent repairability reduces the overall module scrap rate due to a small number of defects, offering a more advantageous overall cost of use.

In this application for an industrial inverter power module, Dowsil™ CN-8760 Thermally Conductive Encapsulant successfully addressed the thermal dissipation challenge under high heat flux density, while also providing excellent electrical insulation, environmental protection, and mechanical buffering. Its flexible processability (long pot life, optional room temperature/heat cure) perfectly matches modern automated production lines, and its repairability offers great convenience for production and after-sales maintenance. This material not only enhances the power density, reliability, and service life of the end product but also helps manufacturers optimize production efficiency and cost. For various electronic devices requiring both thermal management and protection, such as power modules, adapters, sensors, and electric control units, Dowsil™ CN-8760 is a reliable high-performance potting solution.