The Silicone Thermal Pad TO-220 18x13mm (Full Pack 1000pcs) is a high-grade, pre-cut thermally conductive elastomeric insulating sheet engineered for power semiconductor mounting. Specifically sized at 18mm x 13mm with a pre-punched mounting hole to match standard TO-220, TO-220F, and SIP-3 packages, these pads provide electrical insulation and low thermal resistance between high-voltage power transistor metal tabs and metal heatsinks. Made from silicone rubber substrate reinforced with glass fiber (fiberglass 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 tear resistance. They serve as a clean, reliable alternative to messy thermal grease and fragile mica insulators in switch-mode power supplies, audio amplifiers, motor drives, and industrial power electronics.

Specifications

• Product Name / Model: TO-220 Silicone Thermal Insulating Pad (Pre-Cut Sheet)
• Quantity: 1000 Pieces per Bulk 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 M3 screw dimensions)
• 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: Provides electrical breakdown protection above 4kV, safely isolating high-voltage transistor collector/drain tabs from grounded metal chassis.
• Fiberglass Mesh Reinforcement: Internal woven glass-fiber core resists tearing, puncture from burrs, and mechanical cut-through during high-torque screw mounting.
• Clean & Dry Installation: Eliminates the mess, migration, and drying-out issues associated with traditional white thermal paste/grease application.
• Pre-Punched Precise Fit: Pre-cut 18x13mm dimensions with a centered M3 mounting hole ensure quick, tool-free alignment on high-volume production and assembly lines.
• Surface Micro-Conformability: Soft silicone matrix compresses under clamp pressure to fill microscopic air voids and surface imperfections between the transistor tab and heatsink.
• Wide Thermal Stability: Maintains elastomeric elasticity and thermal transfer properties from sub-zero -60°C environments up to +200°C continuous industrial heat.

Common Applications

• Switch-Mode Power Supplies (SMPS): Isolating primary-side MOSFETs, PFC transistors, and secondary fast-recovery rectifiers from shared aluminum extrusion heatsinks.
• Linear & Switching Voltage Regulators: Mounting LM78xx, LM79xx, LM317, and LDO regulators in TO-220 packages to metal chassis walls.
• High-Power Audio Amplifiers: Isolating complementary NPN/PNP output transistors (e.g., TIP41C/42C, 2SC5200 small-format) on shared audio heatsink rails.
• Motor Speed Controllers & Inverters: Thermal mounting for H-bridge MOSFETs and IGBTs in BLDC/DC motor driver modules.
• Solar Inverters & UPS Power Stages: Electrical safety isolation for high-voltage DC-DC booster switches.

Usage Tips

• Use Insulating Bushings/Washers: For metal-tab TO-220 packages (where the tab connects internally to Drain/Collector), always use a nylon or polyphenylene sulfide (PPS) **TO-220 insulating step-washer (bushing)** on the M3 screw to prevent electrical shorts through the screw threads.
• Check Heatsink Surface Finish: Ensure the heatsink surface is free of metal burrs, sharp drilling swarf, and deep scratches before placing the pad; sharp debris can pierce the pad and cause dielectric breakdown.
• Apply Proper Mounting Torque: Tighten mounting screws to a recommended torque of **0.45 N·m to 0.60 N·m** (4 to 5 in-lbs). Over-tightening can crush the pad or strip the screw, while under-tightening leaves thermal air gaps.
• No Extra Paste Needed: Do not apply wet thermal grease on top of silicone pads; doing so adds unnecessary thermal boundary layers and attracts dust without improving thermal conductivity.