The Silicone Thermal Pad TO-220 18x13mm (Pack Approx. 10pcs) is a high-grade, pre-cut thermally conductive elastomeric insulating sheet designed for power semiconductor mounting. Sized at 18mm x 13mm with a pre-punched mounting hole tailored for standard TO-220, TO-220F, and SIP-3 semiconductor packages, these pads provide electrical insulation and low thermal resistance between high-voltage power transistor metal tabs and metal heatsinks. Manufactured from a silicone rubber matrix reinforced with an internal woven glass-fiber mesh, they deliver a dielectric breakdown strength of over 4kV to 6kV, thermal conductivity of 1.2 W/m·K to 1.5 W/m·K, and high resistance to puncture and tearing. They provide a clean, dry, and reliable alternative to messy thermal paste and fragile mica washers in prototyping, repairs, and small-batch production runs.

Specifications

• Product Name / Model: TO-220 Silicone Thermal Insulating Pad (Pre-Cut Sheet)
• Quantity: Approximately 10 Pieces per Retail Pack
• Target Package Standard: TO-220 
• Dimensions: 18mm (Length) x 13mm (Width) ±0.2mm
• Pad Thickness: 0.30mm (Standard range: 0.28mm to 0.32mm)
• Mounting Hole Diameter: Standard Ø 3.0mm to 3.5mm center hole (matches standard M3 screw hardware)
• Base Material: Thermally Conductive Silicone Rubber filled with Ceramic Micro-Fillers (Alumina / Boron Nitride)
• Reinforcement: Embedded Woven Fiberglass Mesh Core
• Thermal Conductivity: 1.2 W/m·K to 1.5 W/m·K (ASTM D5470)
• Thermal Resistance / Impedance (Rth): ~0.45°C·in²/W to 0.65°C·in²/W (at 50 psi contact pressure)
• Dielectric Breakdown Voltage: ≥ 4.0 kV AC / ≥ 6.0 kV DC (ASTM D149)
• Volume Resistivity: ≥ 1.0 × 10¹² Ω·cm (ASTM D257)
• Hardness (Shore A): 70 to 80 Shore A (ASTM D2240)
• Flammability Rating: UL 94 V-0 flame retardant compliant
• Tensile Strength: ≥ 8.0 MPa
• Continuous Operating Temperature: -60°C to +200°C (Intermittent peaks up to +250°C)
• Color Profile: Standard Industrial Blue / Grey

Features

• High Dielectric Isolation: Delivers electrical isolation exceeding 4kV, safely preventing electrical shorts between live transistor collector/drain tabs and grounded aluminum heatsinks.
• Fiberglass Mesh Reinforcement: Integrated woven fiberglass core prevents tearing, stretching, and mechanical puncture from metal burrs during high-torque mounting.
• Clean & Dry Application: Completely eliminates the mess, outgassing, and drying-out issues associated with liquid thermal pastes and grease compounds.
• Pre-Punched Precise Fit: Sized at 18x13mm with an integrated M3 mounting hole for quick, tool-free alignment during prototyping and bench repair work.
• Surface Micro-Conformability: Soft elastomeric silicone fills microscopic surface air gaps and roughness between the transistor tab and heatsink under moderate clamp pressure.
• Broad Temperature Stability: Retains flexible elastomeric sealing and heat transfer efficiency from sub-zero -60°C conditions up to +200°C continuous operation.

Common Applications

• Switch-Mode Power Supplies (SMPS): Electrical isolation and thermal conduction for primary MOSFETs, PFC switches, and fast-recovery output diodes mounted to shared heatsinks.
• Linear & Switching Voltage Regulators: Heatsink mounting for LM78xx, LM79xx, LM317, and LDO regulators in TO-220 packaging.
• Audio Power Amplifiers: Isolated mounting for complementary NPN/PNP output transistors (e.g., TIP31C/TIP32C, TIP41C/TIP42C, BD139/BD140).
• Motor Drivers & H-Bridge Inverters: Thermal dissipation for power MOSFETs and IGBTs in robotics and DIY motor control modules.
• Electronics Prototyping & Repair: Essential bench supply for servicing power supplies, laboratory bench equipment, and audio gear.

Usage Tips

• Use Insulating Step Bushings: When mounting metal-tab TO-220 transistors (where the tab is electrically connected to Collector or Drain), always use a nylon or polyphenylene sulfide (PPS) **TO-220 insulating step-washer (bushing)** on the M3 screw to prevent shorts through the screw threads.
• Inspect Heatsink Surfaces: Ensure heatsink mounting faces are deburred, clean, and free of drilling debris before placement; sharp metal particles can puncture the pad and breach dielectric isolation.
• Optimal Mounting Torque: Tighten mounting screws to a recommended torque of **0.45 N·m to 0.60 N·m** (4 to 5 in-lbs). Avoid excessive torque that could distort the tab or crush the pad.
• Do Not Apply Additional Thermal Paste: Silicone thermal pads are designed for dry installation; applying wet paste between the pad and heatsink creates unnecessary boundary layers and attracts dust.