The Silicone Thermal Pad TO-3P1 (22mm x 18mm) is an electrically isolating, thermally conductive interface pad designed for mounting medium-to-large power semiconductor packages (such as TO-3P1, TO-247, TO-218, and TOP-3) securely to metal heatsinks. Manufactured from high-grade silicone rubber reinforced with a tear-resistant fiberglass mesh substrate, these pre-cut pads deliver high dielectric breakdown isolation to prevent electrical shorting while filling microscopic surface voids to enhance heat dissipation. Supplied in a bulk 1000-piece pack, they are ideal for high-volume manufacturing, automated assembly lines, electronic repair benches, and power supply fabrication.

Specifications

• Product Type: Thermally Conductive Electrical Insulator Pad
• Compatible Packages: TO-3P1 
• Dimensions: 22mm (Length) x 18mm (Width)
• Thickness: 0.3mm (±0.05mm)
• Mounting Hole: Pre-punched ~3.5mm center mounting screw hole
• Material: High-Grade Silicone Elastomer with Woven Fiberglass Core Reinforcement
• Thermal Conductivity: 1.2 W/m·K to 1.5 W/m·K
• Dielectric Breakdown Voltage: ≥ 4.0 kV AC (4000V)
• Volume Resistivity: ≥ 1.0 × 10¹² Ω·cm
• Operating Temperature Range: -50°C to +200°C
• Flammability Rating: UL94 V-0 equivalent flame retardant
• Pack Quantity: 1000 Pieces (Full Bulk Pack)

Features

• High Dielectric Breakdown Resistance (4kV+): Safely isolates high-voltage transistor tabs (IGBTs, MOSFETs, rectifiers) from grounded heatsinks, preventing short circuits and electrical hazards.
• Fiberglass Reinforced Core: Resists puncture, tearing, and elongation under mechanical screw clamping pressure or over sharp heatsink burrs.
• Pre-Cut 22x18mm Geometry: Precision stamped with a centered screw hole for fast, drop-in assembly without the need for manual trimming.
• Wide Thermal Stability (-50°C to +200°C): Maintains elasticity and thermal interface properties without drying out, cracking, or degrading over extended operating cycles.
• Clean Dry-Mount Alternative: Offers a clean, mess-free alternative to thermal grease alone, reducing production time and cleanup on assembly lines.

Common Applications

• Power Semiconductor Mounting: Thermal isolation for TO-3P1 / TO-247 MOSFETs, IGBTs, BJT power transistors, and SCRs/Thyristors.
• Switch-Mode Power Supplies (SMPS): Primary switching bridge transistors and secondary ultra-fast rectifier heatsink isolation.
• Solar Inverters & UPS Systems: Insulating high-voltage power switching stages mounted to shared aluminum chassis heatsinks.
• Motor Drives & EV Controllers: Power module mounting in industrial BLDC, stepper, and DC motor speed controllers.
• Audio Power Amplifiers: Direct mounting of high-power Class-AB and Class-D output transistors to shared amplifier heatsinks.

Usage Tips

• Surface Preparation: Clean the heatsink surface and the transistor mounting tab thoroughly to remove dust, burrs, and grease residues before placement.
• Insulating Shoulder Washer: Always pair with a nylon or plastic insulating bushing/shoulder washer for the mounting screw to prevent electrical contact between the metal screw and the semiconductor tab.
• Clamping Torque: Tighten mounting screws evenly (recommended 0.5 to 0.8 N·m) to establish firm thermal contact without over-compressing or piercing the pad.
• Optional Thermal Compound: For maximum thermal performance in ultra-high-power circuits, a micro-thin film of thermal grease can be applied to both sides of the pad to minimize interface thermal resistance.