3D-printed copper plate could transform data centre cooling

US and Japanese researchers have developed technology that cools computer chips more efficiently than existing methods. Their research has been published in the Cell Press journal Cell Reports Physical Science.

The team of mechanical engineers used a mathematical algorithm and advanced 3D printing method to produce pure copper cold plates that outperformed conventional cold plates and required less energy to run. If used to cool an entire data centre, the technology would contribute only about 1.1% of the centre’s total energy usage compared to more than 30% for conventional air-cooling methods, the researchers estimated.

“Cooling is the bottleneck in computer-chip design,” said first author Behnood Bazmi, a mechanical engineer at the University of Illinois Urbana-Champaign, USA. “By bridging the gap between computational design and manufacturing capability, our approach provides a pathway for more energy-efficient liquid cooling of chips and other electronics.”

Computer chips are becoming increasingly high powered, which means they produce more heat. This, combined with the increase in data centres, is putting a strain on the energy grid; by 2028, it’s predicted that data centres will consume up to 12% of the national grid load in the United States (and up to 11% of Australia’s electricity consumption by 2035).

For the past 40–50 years, computer chips have been cooled by circulating air, but air is no longer sufficient to dissipate the heat produced by modern chips. Liquid direct-to-chip cooling could offer a more effective solution, the researchers said.

Direct-to-chip cooling systems consist of a cold plate that is attached to a computer chip. These cold plates have tightly packed metal ‘fins’ that project out into the cooling liquid to maximise the surface area that is in contact with the coolant. Some direct-to-chip liquid cooling systems are already commercially available, but those systems prioritise manufacturing cost over performance, according to the researchers. In this study, they aimed to optimise fin design to produce cold plates with maximal cooling ability.

The team used a technique called topology optimisation to design fins with an optimal shape. From a simple rectangular starting design, topology optimisation uses a mathematical algorithm to gradually alter the fin’s shape. For each iteration in fin design, the algorithm estimates the cooling capability and the amount of power that would be needed to pump coolant past the fins.

“Topology optimisation ends up converging on a design which is optimal in maximising thermal performance and minimising pumping power,” said senior author and mechanical engineer Nenad Miljkovic, from the University of Illinois Urbana-Champaign.

The fins produced by the team were much more jagged and complex in shape than conventional fins, which are usually simple rectangles, cones or cylinders. Because this design would be too difficult to manufacture using conventional techniques, the team collaborated with a company called Fabric8 to use an advanced manufacturing method called electrochemical additive manufacturing (ECAM) to produce copper cold plates with the optimised fins. Rather than melting copper, ECAM relies on electrochemical plating to deposit copper and build the fins up, layer by layer, from bottom to top.

Pure copper has a high thermal conductivity, but it’s difficult to 3D print, so most cold plates are made of an aluminium alloy (AlSiMg) or stainless steel, which are not optimal for heat transfer.

“ECAM can manufacture pure copper parts with very fine detail — down to 30 to 50 micrometres: less than the width of a human hair,” Miljkovic said.

When the cooling performance of an individual copper cold plate with optimised fins was compared to cold plates with conventional rectangular fins, the team found that the optimised plate delivered up to 32% better cooling and reduced pressure drop (less effort to push fluid through the cold plate) by up to 68% while maintaining the same cooling performance. At the level of an entire data centre, this would translate into significant energy savings compared to both air-cooling and commercially available liquid-cooling systems, the researchers said.

For example, a data centre with 1 gigawatt of computing power consumes about 550 megawatts to run an air-cooling system. This means it consumes a total of 1.55 GW in energy, with 1 GW used for functions such as ChatGPT, searches and storage, and the remaining 550 MW for cooling. “With our cold plates, data centres would only need to use 11 megawatts for cooling instead of 550 megawatts,” Miljkovic said.

The researchers said their technology could be scaled to design optimised cooling systems for other electronics and non-electronic applications. “Our workflow can be applied to a wide range of cooling challenges across different length scales,” Bazmi said.

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