BERGQUIST GAP PAD TGP 3500ULM Highly Conformable Ultra-Low Modulus Thermally Conductive Gap Filler (formerly GAP PAD 3500ULM)
BERGQUIST GAP PAD TGP 3500ULM is an extremely soft, ultra-low modulus gap filling material with 3.5 W/(m·K) thermal conductivity, engineered for high-performance applications that require extremely low assembly stress. At 70 Shore 000 with a Young’s modulus of just 27.5 kPa (4 psi), the pad conforms to rough or uneven surfaces at very low pressure, delivering thermal impedance of 0.5 °C·in²/W at 0.040″/10% deflection with dielectric breakdown voltage greater than 5,000 VAC. Offered with or without fiberglass at 0.508 to 3.175 mm thickness across an operating range of -60°C to +200°C, with UL 94 V-0 flammability.
Key Properties
- Thermal Conductivity: 3.5 W/(m·K) (ASTM D5470)
- Thermal Impedance @ 0.040 in, 10% Deflection: 0.5 °C·in²/W
- Hardness: 70 Shore 000 (ASTM D2240)
- Young’s Modulus: 27.5 kPa (4 psi)
- Dielectric Breakdown Voltage: > 5,000 VAC (ASTM D149)
- Operating Temperature Range: -60°C to +200°C
- Thickness: 0.508 to 3.175 mm
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- Specifications
- Applications
- General Info
- FAQs
Physical Properties
| Property | Value | Test Method |
| Technology | Silicone | — |
| Appearance | Gray | — |
| Reinforcement Carrier | Fiberglass or no fiberglass | — |
| Thickness | 0.508 to 3.175 mm | ASTM D374 |
| Inherent Surface Tack | 2 (higher tack one side) | — |
| Operating Temperature Range | -60°C to +200°C | — |
| Hardness, Shore 000 (30-sec delay @ 125 mil) | 70 | ASTM D2240 |
| Heat Capacity | 1.0 J/g·K | ASTM E1269 |
| Density (bulk rubber) | 3.1 g/cc | ASTM D792 |
Mechanical Properties
| Property | Value | Test Method |
| Young’s Modulus | 27.5 kPa (4 psi) | — |
Thermal Properties
| Property | Value | Test Method |
| Thermal Conductivity | 3.5 W/(m·K) | ASTM D5470 |
| Thermal Impedance @ 0.040 in, 10% Deflection | 0.5 °C·in²/W | ASTM D5470 |
| Thermal Impedance @ 0.040 in, 20% Deflection | 0.44 °C·in²/W | ASTM D5470 |
| Thermal Impedance @ 0.040 in, 30% Deflection | 0.39 °C·in²/W | ASTM D5470 |
Electrical Properties
| Property | Value | Test Method |
| Dielectric Breakdown Voltage | > 5,000 VAC | ASTM D149 |
| Dielectric Constant @ 1,000 Hz (min. at 20 mil) | 6.0 | ASTM D150 |
| Volume Resistivity | 1 × 10¹⁰ ohm·meter | ASTM D257 |
Flame & Fire Performance
| Property | Value | Test Method |
| Flammability | V-0 | UL 94 |
Storage
| Property | Value | Test Method |
| Shelf Life (Optimal Storage) | 12 months at 25°C (±3), 50% RH (±10) | — |
Compliance
- UL 94 — Compliant (V-0)
- Consumer electronics gap filling
- ASIC and DSP package thermal management
- Telecommunications equipment thermal interface
- PC and notebook thermal pads
- Fragile packages and low-force clip mounts where assembly stress must be minimal
Common industries: consumer electronics, computing, and telecommunications hardware.
BERGQUIST GAP PAD TGP 3500ULM is an extremely soft, ultra-low modulus (ULM) gap filling material with 3.5 W/(m·K) thermal conductivity. The material offers exceptional thermal performance at low pressures due to a unique 3.5 W/m·K filler package and an ultra-low modulus resin formulation, and it is well suited for high-performance applications that require extremely low assembly stress.
The pad maintains a conformable nature that allows excellent interfacing and wet-out, even on surfaces with high roughness or topography. It is offered with and without fiberglass reinforcement, has higher natural inherent tack on one side (eliminating thermally impeding adhesive layers), and a top side with minimal tack for ease of handling. It is supplied with protective liners on both sides.
Physical performance includes 70 Shore 000 hardness (30-second delay at 125 mil), 3.1 g/cc density, 1.0 J/g·K heat capacity and a Young’s modulus of only 27.5 kPa (4 psi). Electrically, dielectric breakdown voltage is greater than 5,000 VAC, dielectric constant at 1,000 Hz is 6.0 (minimum value at 20 mil), and volume resistivity is 1 × 10¹⁰ ohm-meter.
Thermally, the material delivers 3.5 W/(m·K) thermal conductivity per ASTM D5470, with thermal impedance at 0.040 in of 0.5, 0.44 and 0.39 °C·in²/W at 10%, 20% and 30% deflection, across an operating temperature range of -60°C to +200°C. Available in sheet form or die-cut parts at thicknesses from 0.508 to 3.175 mm. Shelf life is 12 months at 25°C (±3) and 50% RH (±10).
Compliant with UL 94 V-0 (flame retardancy) and the listed ASTM test methods: ASTM D374, D2240, D792, D149, D150, D257, D5470, and E1269.
What differentiates GAP PAD TGP 3500ULM from TGP 3000ULM and TGP 3000?
All three are silicone gap fillers in the 3 W/m·K class, but TGP 3500ULM is both the highest-conductivity (3.5 W/m·K) and the softest of the group. Its Young's modulus of 27.5 kPa compares with 105 kPa for TGP 3000ULM and 180 kPa for TGP 3000, and it is measured on the Shore 000 scale (70 Shore 000) rather than Shore 00. It is offered with or without fiberglass and has higher tack on one side only. Choose TGP 3500ULM when the assembly can tolerate almost no compression force; choose TGP 3000ULM for thicker gaps (up to 4.0 mm) and higher dielectric strength; choose TGP 3000 where tear resistance and handling robustness matter most.
Why does ultra-low modulus matter in a gap filler?
A gap pad is compressed to reach the real gap in the assembly, and the force it pushes back with is transferred to the component, the solder joints and the housing. A low-modulus pad reaches the same deflection at a much lower stress, so thin BGAs, ceramic packages, clip-mounted heat sinks and thin-wall enclosures are not bowed or over-stressed. At 27.5 kPa, TGP 3500ULM is among the lowest-stress gap fillers in the Bergquist line while still delivering 3.5 W/(m·K).
What is the operating temperature range for GAP PAD TGP 3500ULM?
The operating temperature range is -60°C to +200°C.
Is GAP PAD TGP 3500ULM suitable for flame-rated electronics environments?
Yes. The material is rated UL 94 V-0 for flammability, making it suitable for consumer electronics, computing and telecommunications assemblies that require a flame-retardant thermal gap filler.
How should GAP PAD TGP 3500ULM be specified?
Specify grade (BERGQUIST GAP PAD TGP 3500ULM), thickness (within 0.508 to 3.175 mm), fiberglass or non-fiberglass construction, part geometry (sheet or die-cut), inherent tack configuration (higher tack side orientation), the target deflection or compression force, dielectric and thermal impedance requirements, UL 94 V-0 flame rating, operating temperature range, and finished format.
