THERMALLY CONDUCTIVE GREASE

Thermal greases are very commonly used thermally conductive materials.

The liquid or paste-like greases based on silicone or non-silicone polymers fill unavoidable air pockets caused by roughnesses and convex or concave unevennesses between the power component and the heat sink.

As a result, they enable more efficient heat transfer by minimising thermal contact resistance, with the layer thickness (bondline) being very thin in the two-digit micrometre range.

The composition of thermal greases depends on the application. To achieve high thermal conductivities (1 to 8 W/mK and more) they are filled with thermally conductive particles such as ceramic powders like zinc oxide, boron nitride or aluminium oxide or metal powders, silver particles or carbon, graphite flakes.

Their disadvantage is that they are permanently fluid (viscosities of 10 and 10,000 mPas at densities of 2 to 4 g/cm³) and can only be applied in a process-safe manner with great effort, e.g. by automated stencil printing. The risk of smearing and pump-out due to heat-changing geometries (micropumping due to CTE mismatch) during operation is high.

The use in applications that are mechanically exposed to shock and vibration is critical from the risk point of view of a robust design.

They are particularly suitable for stationary applications, e.g. in lap tops, PCs, graphics cards, game consoles, computer mainboards, CPU coolers, heat spreaders, heat pipes in electronic devices in telecommunications, power electronics or consumer electronics.