Power transistors and diodes in TO-220 packages generate significant heat during operation, and their exposed metal tab is often electrically live. Mounting the tab directly against a heat sink or chassis without adequate insulation can create a short-circuit or leakage risk, so engineers typically need to solve heat dissipation and electrical isolation at the same time when designing cooling for these components.
How the Heat Conductive Silicone Cap Addresses Both Cooling and Insulation
Lixing Compound Material’s Heat Conductive Silicone Cap is a silicone sleeve designed specifically for TO-220 series packages. It fits directly over the component body, providing a thermal conduction path and an electrical insulation layer between the component and the heat sink or enclosure in a single part. Compared to a traditional mica sheet plus separate insulating pad, the one-piece cap simplifies installation and reduces the risk of misalignment or a cracked mica sheet during assembly.
Material Mechanism: Thermally Conductive Filler in a Silicone Matrix
Per published data, the series uses a silicone base loaded with thermally conductive filler to form a heat conduction path, with thermal conductivity of 0.8 to 1.0 W/m-K (per ASTM D5470). The silicone matrix’s inherent polymer insulation properties also give the cap a dielectric strength greater than 4KV (per ASTM D149), forming a stable electrical barrier between the component and the heat sink. Hardness is Shore A 70 ± 5 (per ASTM D2240), giving the cap enough resilience and conformability to fit snugly over the component body.
Core Technical Points
- Operating temperature range of -40°C to +180°C (per GB/T 3512-2014), covering the working range of most industrial power supply and power conversion applications.
- Rated UL 94 V-0 / V-1 for flame resistance and ROHS compliant, suitable for electronics subject to fire-safety and environmental regulations.
- Tensile strength greater than 20 Kgf/cm² and elongation greater than 160% (both per ASTM D412), giving the material a degree of mechanical tolerance during fitting and removal.
Industrial Applications
These caps are primarily used on TO-220 packaged diodes, transistors, and other power components, commonly seen in power supplies, motor drives, and industrial controllers where both cooling and insulation are required. Replacing a mica-sheet-plus-pad stack with a Heat Conductive Silicone Cap can also help simplify assembly on the production line.
Selection Reminder
Standard sizes cover TO-220A, TO-220B, TO-220C, TP-3PA, and TP-3PB packages, each with different length, width, height, and thickness dimensions. Confirm the exact package dimensions against the specification table before selecting a size to avoid a poor fit. Custom sizes, colors, or physical parameters are also available for non-standard packages.
Conclusion
For TO-220 power component designs that need to address cooling and insulation together, the Heat Conductive Silicone Cap offers a one-piece approach. Confirm the appropriate part number with your supplier based on your application’s voltage, temperature, and package dimensions before implementation.
Tags: Heat Conductive Silicone Cap, TO-220, Thermal Management, Power Electronics, Silicone Insulation
