By BizLED Bureau
April 8, 2015: With high demand for LEDs for high-end applications, manufacturers are facing various challenges with thermal management.
Despite being energy-efficient, when compared to incandescent lights, LEDs waste about 70% of the electrical energy as heat. To save this energy, the heat needs to be conducted away from the LED, and maintain a safe operating temperature. An LED when overheated, cuts down its lifespan as well as its efficiency and color quality.
Currently, the thermal management technologies that are being used by the manufacturers restrict the speed at which LED light can penetrate into high-powered application areas. These thermal management technologies fail to deliver the technical performance required for various applications. However, some big companies are trying to find a solution to this problem to make the whole process cost-effective.
A thermal substrate requires excellent electrical isolation and thermal conductivity. However, this characteristics restricts the choice of materials. Traditionally, aluminum nitride (AIN) has been used to do thermal management in chip on board (COB) LEDs and high power LEDs.
However, aluminum nitride has its own limitations. It requires carbonthermal reduction of aluminum oxide or direct nitridation of aluminum. It also requires high temperatures. This makes it very expensive. It is also very brittle, and its size is small.
Hence, manufacturers are looking for better options other than using aluminum.
UK-based Cambridge Nanotherm has developed a new approach of growing thin films of ceramic (mainly Alumina, Al2O3) on metal substrates.
It has patented the electrochemical process to create a dielectric on the surface of aluminum, which produces a composite substrate that has thermal properties that are cost effective.
The new method turns the surface of an aluminum sheet into a dielectric nanoceramic layer. As a result, 30 to 60 nanometers of crystals are formed. As nanoceramic is formed by a conversion process, it has a robust link between the dielectric and the aluminum. This leads to a uniform layer of ceramic, which is a dielectric as well.
The nanoceramic dielectric layer is just 3 microns thick, making the thermal path between the LED chip and the aluminum very small. This in turn results in high thermal conductivity.
The nanoceramic layer can be developed on 3D shapes as well, which will make vias development very easy. With this process, holes can also be drilled in the aluminum sheet very easily and ceramic dielectric gets deposited uniformly on the surface of these holes.
The thermal conductivity of nanoceramic dielectric layer is about 7.2 W/mK and it has a dielectric measure of about 50 V/um. For COB LEDs, the finished product needs a thermal conductivity of 152 W/mK.
The process by Cambridge Nanotherm also cuts down cost, ultimately bringing down the cost of LED products. The nanoceramic substrates can also be processed with the help of standard PCB manufacturing facilities.
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