Thermal gap filler pads are more than just silicone sheets. Inside many of them are carriers—thin films, fabrics, or reinforced layers that determine how a pad handles, compresses, insulates, and transfers heat. Understanding carriers helps you select the right pad for your application and avoid costly mistakes.
One golden rule: never remove carriers. They are engineered into the thermal gap filler pad to provide strength, insulation, or controlled thickness. Stripping them away compromises both thermal and mechanical performance.
1. Film Carriers
PET (Polyethylene Terephthalate)
- Typical Thickness: ~12–50 µm (0.012–0.05 mm); common around 25 µm.
- Advantages: Low-cost, easy to die-cut, strong dielectric properties.
- Limits: Stable only to ~100–120 °C.
- Best for: Consumer devices and telecom hardware.
PEN (Polyethylene Naphthalate)
- Typical Thickness: .001’’ ~
- Advantages: Higher thermal stability (~120–150 °C), tougher than PET.
- Trade-off: More expensive, not extreme high-temp.
- Best for: Warmer, humid environments.
Kapton (Polyimide)
- Typical Thickness: 12.5–50 µm are most common, with 25 µm widely used in gap pads.
- Advantages: Handles ~200–260 °C, excellent dielectric performance.
- Trade-off: Costlier, slightly stiffer.
- Best for: High-reliability power electronics and aerospace.
Thermally Conductive Polyimide (Chomerics-style)
- Typical Thickness: ~25–50 µm.
- Advantages: Adds lateral thermal spreading while insulating.
- Best for: Hot-spot management without switching to metal foils.
2. Fabric (Fiberglass) Reinforcement
Fiberglass Inside (internal scrim)
- Typical Thickness: The scrim itself is ~50–100 µm, but embedded so it barely adds to overall thickness.
- Pros: Improves strength, prevents tearing, ensures dimensional stability.
- Cons: Slightly reduces compressibility and increases thermal resistance.
Fiberglass Outside (surface cloth)
- Typical Thickness: Cloth layer ~100–150 µm on one or both sides.
- Pros: High wear resistance under clips or screws.
- Cons: Reduces surface conformability.
3. Fabric-Reinforced Thermal Pads
Sil-Pad (Henkel/Bergquist)
- Fabric Layer Thickness: Reinforcing fiberglass fabric typically ~0.007-0.009’’ Sil-Pad layer
- Strengths: High dielectric strength, reliable under screw loads.
- Use Case: Power modules and TO packages.
TG-ALC (T-Global)
- Carrier Thickness: Fabric-reinforced silicone carrier 0.5mm to 2.5mm, depending on the version.
- Overall Pad Thickness: Ultra-thin options around 0.5mm to 2.5mm.
- Strengths: Non-tacky surface, strong handling, dielectric >4 kV/mm, thermal conductivity ~5 W/m·K.
- Best for: High-density electronics needing both reinforcement and ease of assembly.
4. Metal-Foil Carriers
Aluminum Carrier Pads (Chomerics)
- Foil Thickness: Typically .005’’ thickness with a transparent blue PET liner that SHOULD be removed before assembly.
- Advantages: Spreads heat laterally, tough under clamp loads.
- Trade-offs: Stiffer; requires good dielectric isolation; possible corrosion concerns.
- Best for: High-power devices needing spreading across uneven hot spots. Typically included in products such as A579, THERM-A-GAP PAD60A
5. When Reinforcement Works Against You
- Low-pressure assemblies: Carriers may prevent pads from conforming properly.
- Uneven stacks: Rigid carriers can bridge low components, creating air gaps.
- Added thermal resistance: Fabrics interrupt silicone pathways.
- Stress under cycling: Rigid films or foils may delaminate under extreme temperature swings.
Quick Thickness Snapshot
| Carrier Type | Typical Thickness Range | Notes |
| PET | 12–50 µm (common 25 µm) | Cheap, good for low-temp use |
| PEN | 25–50 µm | More robust than PET |
| Kapton (Polyimide) | 25–50 µm (common 25 µm) | High-temp, excellent dielectric- usually thermally conductive Kapton (polyimide) |
| Thermally Conductive Polyimide | 25–50 µm | Adds modest spreading |
| Fiberglass Inside Scrim | 50–100 µm | Embedded, minimal stack impact |
| Fiberglass Outside Cloth | 100–150 µm | Adds wear resistance |
| Sil-Pad Fabric | 75–125 µm | Found in GPVOUS, GPVOS, GPVO Gap Pads |
| TG-ALC Fabric Carrier | 0.5mm to 2.5mm | Found in T-Global TG-A6200LC pads |
| Aluminum Foil Carrier | .005’’ | For spreading & durability, and adding durable adhesive, specified by “A” in products such as PAD60A, Therm-A-Gap A579 |
More Information on Carriers
Carriers are critical to how a thermal pad behaves under load, heat, and assembly. Their thickness—often just tens of microns—can decide whether your design succeeds or struggles with handling, conformity, or insulation. Always specify the carrier as part of your pad design, and remember: don’t remove carriers. Carriers and liners are different. NEDC does custom die cutting, and waterjet cutitng for customers.