Thermal Interface Materials: Gap Fillers, Pads and Pastes vs. Potting Compound
Electronics get hot – and that heat needs to be dissipated in a controlled manner. Thermal interface materials (TIMs) bridge the air gap between the component and the heatsink. This article compares gap fillers, pads, pastes, and thermally conductive potting compounds.
To the point: Which TIM for which application?
Thermal paste for thin, defined gaps (CPU/heatsink). Thermal pads for reproducible, medium gaps in series production. Dispensable gap filler for variable, larger gaps and automated manufacturing. Thermally conductive potting compound when additional protection and fixation are required. The decisive factors are gap size, heat flow, and process parameters (λ) as specified in the datasheet.
A comparison of TIM types
| TIM | gap | Strength | process |
|---|---|---|---|
| thermal paste | very thin | best gap filling thin | manual/dispensable |
| thermal pad | defined/medium | reproducible, clean | Components |
| Gap Filler | variable/large | Automatable, adaptable | dispensable (1K/2K) |
| Thermally conductive potting compound | entire cavity | Protection + Heat Dissipation | potting |
Guideline values – the specific suitability depends on the product and application and must be checked in the respective technical data sheet.
What matters
- Gap size and tolerance: determines paste/pad/gap filler.
- Heat flow: required thermal conductivity (λ).
- Contact pressure: Pads require defined pressure.
- Process: Manual assembly, assembly or dispensing system.
- Additional function: heat dissipation only or also protection/fixation.
Gap filler in the series
Dispensable gap fillers combine good gap matching with automation capabilities and are therefore widely used in e-mobility and electronics manufacturing. Pot life, abrasiveness (pump wear), and dispensing accuracy are relevant factors for processing.
When protection is added
If the assembly also needs to be protected against moisture, vibration and media, a thermally conductive potting compound often a better choice than a pure TIM.
λ is not everything
Thermal conductivity (λ) is important, but the actual thermal resistance also depends on layer thickness and bonding. A thin, continuous gap with medium λ can dissipate heat more effectively than a thick layer with high λ. The goal is always to minimize thermal resistance.
Processing in series production
Filled thermal interface materials (TIMs) are abrasive and can cause wear on dispensing systems. Pump selection, service life, pot life, and reproducible dispensing quantity are crucial. Thermal pads offer advantages in terms of clean and quick installation, while gap fillers are suitable for variable gaps.
Frequently Asked Questions
Paste, pad or gap filler – which should I use?
Paste for very thin gaps, pad for defined medium gaps in the series, gap filler for variable or larger gaps and automation.
Do I need to apply pressure?
Pads require defined pressure for good contact. Dispensable materials adapt to the geometry.
When is a thermally conductive potting compound preferable?
When protection against moisture, vibration and media is required in addition to heat dissipation.
Sources and technical basis
The information is based on manufacturer data sheets and recognized principles of thermal management. Thermal conductivity (λ), gap behavior, and suitability are product-dependent and can be found in the respective technical data sheet.
How SILITECH supports
Tell us the gap dimensions, heat flow and process – we will recommend a suitable TIM or thermally conductive potting compound and provide the data sheets.
