Diamonds Dissipate Heat from Radio Frequency Devices

Diamond absorbs heat more readily than any other material at room temperature. And a subsidiary of the diamond giant De Beers is aiming to exploit that ability to whisk away heat from electronics.

The company, Element Six, released last week its latest grade of synthetic diamond for thermal management applications. The new product exhibits a thermal conductivity up to 700 W/mK, three times more effective at spreading heat equally from hot spots in RF power amplifiers and other electronics than alternative ceramic products.

Thomas Obeloer, business development manager at Element Six, said in a statement that Diafilm ETC700 delivered high thermal conductivity “far surpassing the performance of competing materials such as copper or ceramics." It is the lowest of six grades in the company’s Diafilm product line, which range up to 2000 W/mK.

Element Six, which also sells artificial diamonds for laser optics and industrial drills, has touted its heat spreading materials for over a decade. But recreating diamond, which is formed naturally through billions of years of heat and pressure, is not cheap. The high manufacturing costs have kept it in a few high-performance markets.

In telecommunications and other wireless products, a thin slab of synthetic diamond is soldered between the chip and the substrate. The thermal resistance increases as the separation between the layers goes down. Like other heat spreaders, the diamond is typically coated with metal to improve the interface between the diamond and the chip.

But the Diafilm ETC700 is capable of conducting electricity without the metal coating – usually a combination of titanium, platinum, and gold – resulting in reduced frequency-dependent conductive losses.

Element Six’s diamonds are made through chemical vapor deposition, a process normally used in manufacturing semiconductors in thin films. The diamonds usually paired with RF and microwave products are polycrystalline. The single-crystal diamond has better thermal conductivity but it is used primarily in laser optics.

The market for diamond heat spreaders has a few bright spots. Raytheon has tested it as a substrate material in electronic warfare systems, with tests showing a three-fold increase in power density from gallium nitride chips. At least one company, Akash Systems, is using diamond as a substrate for its wireless amplifiers – to be used in communications satellites.

The new Diafilm product exhibits a large “conduction cross-section” that enables better RF performance by improving the ground-plane isolation. Its high bulk thermal conductivity “reduces capacitive coupling between ground planes at low frequencies, and reduces conductive losses at higher frequencies,” Element Six said in a statement.

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