Dispensing Thermally Conductive Paste
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Thermally conductive pastes are 1K or 2K paste media with a concentration of conductive fillers. They improve the transmission of heat between two objects, such as between a circuit board and a heat sink, thus helping to prevent drops in performance and faults. These materials are often also described as gap fillers. Usually they are one or two component potting compounds based on silicone, epoxy or polyurethane. Including additives or fillers specifically changes the properties of thermally conductive pastes and adapts them to the particular application.
When using conductive potting materials, their specific thermal conductivity coefficient λ plays an important role. It is often simply described as thermal conductivity or thermal conductance. This value (unit: W/(m?K)) describes the ability of a material to transfer thermal energy by way of thermal conductance. The higher the thermal conductivity, the greater the heat transfer per unit of time.
Thermally conductive pastes are used in the automotive industry, in the electronics and electrical industries and in many other sectors. Particularly in recent years there has been a disproportionately high and significant increase in the use of these materials. This is attributed, among other things, to the establishment of new or rapid improvement in proven technologies. Examples of this include LED technology and the encapsulation of batteries for electric mobility. Thermal management is also steadily growing in importance due to the increasing miniaturization of electronic components in all industries.
The thermal conductivity of thermally conductive pastes is established using special fillers such as aluminum oxide, silver or boron nitride. These fillers, which can take the form of irregular fragments, spheres or cubes, often have very high levels of hardness as well as sharp-edged profiles. Therefore, when choosing systems to be used for preparing and dispensing thermally conductive pastes, a compatible system design is absolutely essential. Otherwise the user risks paying high maintenance and repair costs.
Thermally conductive adhesives work on two fronts: While thermally conductive pastes are dispensed to thermally connect two components, thermally conductive adhesives connect components thermally and mechanically. Compared to thermally conductive pastes, the specific thermal conductivity of these adhesives is usually lower. To ensure that the dual role of the material is effective, it is necessary to adjust the filler quantity precisely to the substrate. A higher proportion of filler for improving thermally conductive properties would result in the immediate degradation of the adhesive properties. Conversely, a higher proportion of adhesive runs the risk of the connection loosening due to the effects of temperature.
Selecting the right dispensing system is critical to achieving optimum results when applying thermal interface materials. While gear pump dispensers are not suitable for these types of highly filled and paste-like materials, piston-type dispensing systems offer distinct advantages due to their robustness and high precision during the mixing process.