imec announced it has demonstrated — for the first time — a low-cost, impingement-based solution for cooling ICs at the package level. imec’s impingement cooler achieves high cooling efficiency, with a chip temperature increase of less than 15°C per 100 W/cm² for a coolant flow rate of 1 l/min.

This is an important innovation to tackle the ever-increasing cooling demands of high performance 3D chips and systems.

Problem Statement

High performance electronic systems are coping with increasing cooling demands. Conventional solutions realize cooling through combining heat exchangers bonded to heat spreaders that are attached to the chip backside. These are all interconnected with thermal interface materials (TIM) that create a fixed thermal resistance that can’t be overcome by introducing more efficient cooling solutions. Direct cooling on the chip backside would be more efficient, but current direct cooling microchannel solutions create a temperature gradient across the chip surface.

The ideal chip cooler is an impingement-based cooler with distributed coolant outlets. It puts the cooling liquid in direct contact with the chip and sprays the liquid perpendicular to the chip surface. This ensures that all the liquid on the chip surface has the same temperature and reduces the contact time between coolant and chip. However, current impingement coolers have the drawback that they are silicon-based and expensive or their nozzle diameters and processes are not compatible with the chip packaging process flow.

imec Solution

imec developed a new impingement chip cooler that uses polymers, instead of silicon, to achieve cost-effective fabrication. imec’s solution features nozzles of only 300 µm, made by high-resolution stereolithography 3D printing. The use of 3D printing allows customization of the nozzle pattern design to match the heat map and the fabrication of complex internal structures. 3D printing also enables efficient printing of the whole structure in one part, reducing production cost and time.

imec’s impingement cooler achieves high cooling efficiency, with a chip temperature increase of less than 15°C per 100 W/cm² for a coolant flow rate of 1 l/min. It features a pressure drop as low as 0.3 bar, due to the smart internal cooler design. It outperforms benchmark conventional cooling solutions, where the thermal interface materials alone cause a 20°C to 50°C temperature increase. In addition to its high efficiency and cost-effective fabrication, imec’s cooling solution is much smaller compared to existing solutions, matching the footprint of the chip package, which enables chip package reduction and more efficient cooling.

“Our new impingement chip cooler is actually a 3D printed ‘showerhead’ that sprays the cooling liquid directly onto the bare chip. 3D prototyping has improved in resolution, making it available for realizing microfluidic systems such as our chip cooler. 3D printing enables an application-specific design, instead of using a standard design.” — Herman Oprins, senior engineer at imec