imec Saves Time and Money with New 3D Printed Chip Cooling Solution

One of the world’s top research and innovation hubs in nanoelectronics and digital technologies is imec, headquartered in Leuven, Belgium with additional offices in Japan and India and distributed R&D groups in the US, Taiwan, China, the Netherlands, and at multiple Flemish universities.

A few years ago, the company used inkjet printing to output a transistor logic board with nearly 3,400 circuits, and is well known for its 2015 collaborative project resulting in a 3D printed EEG headset for the purposes of brain-computer interfacing.

The company creates innovation in applications ranging from healthcare, education, and smart cities to mobility, logistics, manufacturing, and energy, thanks to its excellent infrastructure and local and global partner network. Now, imec has turned its attention to efficient cooling solutions…which, if you’re living through a July heat wave like I am at the moment, sounds great. However, I’m not talking about a 3D printed fan, but rather an impingement-based solution for cooling chips at the package level.

The company recently announced that for the first time, it’s demonstrated a cost-effective, 3D printed cooling solution for chips, which is quite an achievement in a world of growing cooling demands for 3D chips and systems.

More and more, high-performance electronic systems are having to learn how to deal with increasing cooling demands. It would be the most efficient to introduce direct cooling on the chip backside, but unfortunately, most existing direct cooling microchannel solutions end up creating a temperature gradient across the surface of the chip.

Typically, conventional solutions combine heat exchangers, which are bonded to heat spreaders and attached to the back of a chip to achieve cooling. All of these parts are connected through thermal interface materials (TIM), which make a strong, fixed thermal resistance; adding more efficient cooling solutions will not overcome this resistance.

An impingement-based cooler with distributed coolant outlets, like the 3D printed one imec has created, is the optimal chip cooling solution, as it places the cooling liquid directly in contact with the chip, spraying liquid perpendicular to the surface of the chip. This helps all of the liquid on the surface is the same temperature, in addition to lowering the amount of contact between the chip and the coolant. But, most of these coolers are not cheap, because they’re silicon-based, and their use processes and nozzle diameters not working with the chip packaging process flow doesn’t help in keeping costs down.

imec’s new impingement chip cooler is more cost-effective, as it uses polymers rather than expensive silicon. The cooler is also a pretty familiar object, as Herman Oprins, a senior engineer at imec, explained:

“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.”

The cooler’s 3D printed nozzles, made with high-resolution SLA technology, are only 300µm and match the heat map, as 3D printing gives companies the ability to customize pattern designs for these types of objects, in addition to producing complex internal structures. Additionally, production costs and time were decreased because 3D printing makes it possible to fabricate the entire structure in just one part, instead of several.

The 3D printed impingement chip cooler has a higher cooling efficiency – according to imec, the chip has “a temperature increase of less than 15°C per 100W/cm2 for a coolant flow rate of 1 l/min.” Due to its smart internal cooler design, the device has a pressure drop as low as 0.3 bar, and the impingement chip cooler is also much smaller than other solutions; imec says it actually matches the chip package’s footprint, which allows for much more efficient cooling and even a package reduction. The cost-effective chip cooler also performs better than benchmark conventional cooling solutions, which have thermal interface materials that cause temperature increases of 20-50°C.

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