Thermal Gap Fillers
Compliant Gap-Filling Thermal Interface Pads
Thermal gap fillers are compliant elastomeric pads, typically formulated from a silicone elastomer base with aluminum oxide or boron nitride fillers, designed to bridge 0.5 mm to 5 mm clearances between equipment and thermal mounting surfaces. These interfaces accommodate manufacturing tolerances and deliver thermal conductivities of 1 to 6 W/mK under low compression forces that prevent excessive preload on sensitive components. For lunar systems, gap fillers must maintain thermal performance across the full temperature range, satisfy ASTM E595 and NASA SP-R-0022A outgassing requirements in vacuum, and resist long-term compression set that degrades contact effectiveness over decades.
Compliant pads filling variable gaps between equipment and thermal mounting surfaces
Purpose
Accommodate manufacturing tolerances while maintaining thermal contact across gaps
Context
Child of L2-TCS-INTF in the Active Thermal Control System
Principles
- ▸Compliant elastomeric pads compress to fill gaps from 0.5mm to 5mm
- ▸Thermal conductivity of 1-6 W/mK depending on filler loading (Al2O3, BN)
- ▸Self-adhesive versions simplify assembly and prevent pad migration
- ▸Low compression force prevents excessive preload on sensitive components
Typical implementations
- ▸Bergquist/Henkel Gap Pad 5000S35 (5 W/mK thermal conductivity)
- ▸Laird Technologies Tflex gap fillers
- ▸3M Thermally Conductive Interface Pad 5590H
- ▸Fujipoly SARCON thermal gap fillers
Lunar considerations
- ▸Outgassing must meet ASTM E595 / NASA SP-R-0022A requirements
- ▸Long-term compression set reduces gap filler effectiveness over decades
- ▸Must maintain thermal performance across full temperature range
Specifications
Functional
| primary function | Compliant pads filling variable gaps between equipment and thermal mounting surfaces |
Physical
| materials | Silicone elastomer base, Al2O3 thermally conductive filler, Fiberglass reinforcement |
Interfaces
Provides
- Gap-tolerant thermal coupling for equipment mounting
Requires
- Replacement gap filler materials
Cite this entry
Lunar Ark Codex. "Thermal Gap Fillers" (L3-TCS-INTF-GAP). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-TCS-INTF-GAP
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.