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Heat distribution and dissipation has been an issue throughout the semiconductor industry, which has been addressed by polycrystalline diamond products that can be used in cutting and dressing optics, as well as thermal, electrochemical, and nuclear fusion applications. Polycrystalline chemical vapor deposition (CVD) synthetic diamond products endure tightly controlled growth conditions while being manufactured, and handle just as strict quality control procedures. Polycrystalline CVD diamond is the final result, and is a manufactured material featuring high consistency, with predictable properties and behavior required for cutting tool, wire drawing, and dressing applications.

Thermal management of semiconductor applications make it difficult to optimize performance, which is something Element Six has addressed and made significant progress with over the years. At IMS 2018, they showed how CVD crystalline diamond has been engineered for thermal management and helps overcome the aforementioned limitations by lowering gate junction temperatures, boosting power densities and efficiencies, and prolonging lifetimes. Each grade was designed to accommodate the needs of a specific application area, along with exploiting one or more unique properties of synthetic diamond.

These systems are being pushed by technology and economic factors to higher frequencies, voltages, and immediate operating temperatures, which resulted in CVD diamond heat distributors and GaN-on-diamond wafers seeing increased usage of thermal management for high-power semiconductor devices. Synthetic CVD diamond’s room temperature thermal conductivity can reach up to 2,000 W/mK, which is respectively five and ten times higher than copper and aluminum nitride.

Element Six demonstrated the differences in these properties by displaying a block of ice at their booth, and inserted three discs made of copper, aluminum, and CVD crystalline diamond. While the aluminum disc struggled to penetrate the ice and didn’t undergo any radical temperature changes, the copper disc sliced through the ice block, and instantly became hotter (heat generated from fingers of individual holding the disc). The CVD diamond disc on the other hand, not only cut through the ice block like butter, but became just as cold in less than a second after being applied onto the ice block.

Diamond transports heat equally as well in all three dimensions, making the material an effective heat spreader. Metallized diamond heat spreaders and GaN-on-diamond wafers are both capable of significantly lowering thermal resistance, and, in turn, the gate junction temperature of semiconductor devices, which results in higher power densities. There are specific steps in the test and assembly of packaged semiconductor devices that require temperatures to either be kept low enough for preventing device damage or remain constant across the entire package to optimize assembly quality.

Because metallized diamond head spreaders support both lateral and vertical heat at extremely fast rates, they can rapidly extract and evenly spread heat across hot devices. Another more technical example involves cooling devices during functional tests. Devices under test must operate under a test pattern without a heat sink attached, which may cause overheating. CVD diamond resolves this issue without resorting to active water impingement cooling. Another example uses diamond to quickly distribute heat across a substrate while a flip-chip die is bonded to it, making it possible to simultaneously apply the same amount of heat to every solder joint, ensuring high quality across an array of 1,000 solder joints.

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