Freudenberg advances thermal interface elastomers

Weinheim, Germany – Freudenberg Sealing Technologies (FST) has developed a silicone rubber material that combines seemingly incompatible properties such as heat conductivity and electrical insulation.

The injection mouldable elastomer adheres to widely used substrates like plastics, aluminium and copper and compensates for rough areas, said FST in a 27 June statement.

Currently used by several automotive manufacturers, the “thermal interface material” (TIM) has a thermal conductivity of 1.7 to two watts per metre and Kelvin.

For comparison, the thermal conductivity of air is 0.026, said the FST announcement.

To achieve the conductivity, FST said it mixed the elastomer with inorganic fillers from special non-conductive metal compounds.

In terms of electrical insulation, the material achieves a comparative tracking index (CTI) value of 600, placing it in “the best possible protection class for tracking resistance”.

According to FST, the dielectric strength of the silicone rubber is more than 10 kilovolts per millimeter.

“This means that the common test voltages of 2.4 to 4 kilovolts won’t pose any particular challenges for the material,” the seals manufacturer added.

The elastomer's hardness is around 35 Shore A and being injection-moulable makes it suitable for “a wide range of complex electrical applications,” said Armin Striefler of FST.

The feature, said the FST product and process developer, will provide an “important advantage” for efficient series processes.

“This also makes its use very flexible, since nearly all three-dimensional geometries are possible," he said.

Furthermore, the materials "always adhere optimally to the substrate – whether plastic or metal.” 

According to FST, the elastomer is currently being used by several automotive OEMs, including a ‘well-known’ car manufacturer which is using it in the charging port of electric vehicles.

The charging port features several components whose interaction is essential for the thermal management of the charging process, FST explained.

These include a circuit board with temperature sensors as well as measurement and control electronics for charging management - all secured inside a housing about the size of a hand.

FST said it manufactures the housing with injected elastomer and provides it to an automotive supplier.

The supplier then produces the module ready for installation by the automaker, which is using the part in “large numbers in series-produced vehicles”.