Material Charge five times faster with diamond membranes

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Researchers from Fraunhofer USA have developed ultra-thin nanomembranes made of synthetic diamond that can be integrated into electronic components. The nanomembranes can reduce the local heat load by up to ten times, thus increasing the driving performance and lifespan of electric vehicles.

The thermal conductivity of diamond is four to five times higher than that of copper, making the material particularly interesting for cooling power electronics in e-mobility, photovoltaics, or storage systems. So far, heat sinks made of copper or aluminum plates increase the heat-dissipating surface of a heat-producing component, thereby preventing damage from overheating.

Reduce the local heat load of electronic components by tenfold

Scientists from Fraunhofer USA Inc., Center Midwest CMW in East Lansing, Michigan, an independent foreign branch of the Fraunhofer Society, have now developed nanomembranes made of synthetic diamond that are thinner than a human hair. The flexible material can be directly integrated into electronic components. Here, it cools the power electronics in electric vehicles, which, for example, transmit traction energy from the battery to the electric motor, converting the current from direct to alternating current in the process.

According to the scientists, the flexible, electrically insulating nanomembranes could reduce the local thermal load on electronic components such as current regulators in electric motors by tenfold. Energy efficiency, lifespan, and driving performance of electric vehicles are significantly improved as a result. Another advantage: In the charging infrastructure, the diamond membranes contribute to a charging speed that is five times higher.

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Diamond membrane replaces insulating intermediate layer

Normally, a copper layer mounted under the component improves the heat flow. Between the copper and the component, there is an electrically insulating oxide or nitride layer, which, however, conducts heat poorly. "We want to replace this intermediate layer with our diamond nanomembrane, which conducts heat to the copper highly effectively, as diamond can be processed into conductive paths," says Dr. Matthias Mühle, head of the Diamond Technologies group at Fraunhofer USA Center Midwest CMW. "Since our membrane is flexible and freestanding, it can be positioned as desired on the component or the copper, or directly integrated into the cooling circuit."

Freestanding, smooth diamond can be heated to 80 degrees Celsius

For this purpose, Mühle and his team grow the polycrystalline diamond nanomembrane on a separate silicon wafer. Then, they detach it, turn it over, and etch away the backside of the diamond layer. This process creates a freestanding, smooth diamond that can be heated to a low temperature of 80 degrees Celsius and subsequently placed on the component. "Through the heat treatment, the micrometer-thick membrane automatically bonds with the electronic component. The diamond is then no longer freestanding but integrated into the system," explains Mühle.

The nanomembrane can be realized on a wafer scale (4 inches and more), making it suitable for industrial applications. The development has already been filed for patent. Application tests with inverters and transformers in fields such as electromobility or telecommunications are set to start within this year.