Meet xMEMS, a challenger to AirJet’s radical solid-state chip cooling

If you had any doubts about silicon cooling chips being the wave of the future, this should help convince you: Now there are two companies operating in that space. xMEMS has announced the XMC-2400, a competitor to the Frore Systems AirJet that was announced less than two years ago.

What xMEMS is calling the xMEMS XMC-2400 µCooling chip isn’t a direct competitor to AirJet’s laptop processor coolers, though. For now, it’s aimed at smartphones and tablets, as well as SSDs. Nevertheless, that puts it on a collision course with Frore’s AirJet Mini Slim and its future roadmap. Meanwhile, xMEMS says it will scale up its teeny-tiny cooling chip into something larger and more robust.

Most cooling solutions for semiconductors are either passive — via heatsinks, which thermally conduct heat using metals like copper and aluminum — or active, typically using forced air via a blower to cool the chip. Active cooling is typically better at removing heat, but a fan, blower, or an array of heat pipes are both expensive and take up valuable space.

Micro-electromechanical systems (MEMS) feature the best of both worlds. They’re small, and can be easily connected to the outside of an existing chip. They’re also more effective than a passive cooling solution, as they use a vibrating membrane as a fan of sorts, sucking in cool air, pushing it across the heated surface of the chip package, and then pushing the hot air out through the system and from there outside of the device.

The argument is still the same: No matter how fast a chip might run, it can’t achieve its top speed for prolonged periods of time. These “turbo” modes typically last for seconds at most, which means that the speed of the chip isn’t the gating factor for chip performance, companies like xMEMS say. Cooling is.

“Each generation of processor, independent of a supplier [like] ARM, Intel, Nvidia, et cetera, improves the performance versus power equation,” said Mike Housholder, the vice president of marketing and business development at xMEMS “Yet, at a system level, we are never able to achieve the maximum performance specifications of the silicon for extended periods of time. This is always gated by system thermal dissipation. So, performance is no longer gated by the capabilities of the silicon.

“To sum it up, I see the thermal management challenge increasing, not decreasing,” Housholder said.

The introduction of the Frore Airjet was truly one of the most exciting announcements of 2022. Now xMEMS has its own take.

How is the XMC-2400 different than the Frore AirJet?

The difference in approach is apparent just from the photos: The smallest device Frore currently makes is the AirJet Mini Slim, with a 27.5mm x 41.5mm x 2.5mm footprint. Comparatively, the XMC-2400 is tiny: Just 9.26mm x 7.60mm x 1.08mm.

Why? Because xMEMS has been manufacturing MEMS devices for some time — but not for cooling. Instead, the XMC-2400 comes from the company’s legacy of building MEMS devices as speakers, inside tiny earbuds. A transition away from using MEMS membranes to produce sound to those that could cool a chip was a natural transition, according to Housholder.

xMEMS tech is featured in products like the Creative Aurvana Ace 2, in an advance that SoundGuys.com heralded as the audio version of the transition from hard drives to SSDs. Last November, xMEMS announced an ultrasonic transducer — normally pitched at above human hearing, but the company’s technology allowed it to generate audible sound. “So really, it’s the same piezo MEMS platform, but repurposed so instead of generating audible sound for music playing, it’s now generating airflow,” Housholder said.

Piezoelectronics can generate voltages when pressure is applied, or vice versa. In this case, the membrane is physically moving. “We’ve kind of had in the back of our mind, since the founding of the company, that once we could get to the sound from ultrasound technology that a cooling product could be an offshoot of that; that’s what we’re announcing” Housholder said.

“By playing with the frequencies of the ultrasound, we can tune it to audible sound or we can tune it to airflow,” Housholder added.

Like Frore’s AirJet, cool air is sucked in as the membrane vibrates in one direction, and is pushed against the heat spreader of the chip itself. That creates a cavity filled with relatively pressurized air, which is then pushed out through a release valve. The vents can be mounted in either the top or sides of the package. Housholder said that the XMC-2400 is bidirectional, so that you could have one XMC-2400 directly cooling a chip, while another is placed elsewhere in the system, near a vent, to assist pulling or pushing air outside of the system.

xMEMS’ advantage, according to Housholder, is efficiency: The company predicts it will move 39 cubic centimeters of air per second, via a single die, with 1,000Pa of back pressure. Each die includes an array of MEMS valves; in this case, the XMC-2400 includes a two-by-four array, for a total of eight. The company claims a general airflow-per-volume efficiency of 500, versus Frore’s 31.3. It’s also 1/39 the size of the AirJet Mini Slim, and draws one-tenth the power, between 20 to 30 milliwatts. Like the AirJet, the xMEMS chip generates essentially no noise.

The XMC-2400 is a two-chip solution; it will also include a control ASIC that will control the opening and closing of the valves. At this point, the MEMS chip itself is operational; the company has received the first revision of the control ASIC and it will be ready to go in a couple of months, Housholder said.

The future: Wait, cooling chiplets?!

Householder said that xMEMS intends to ship the XMC-2400 into smartphones — flagship smartphones, though potentially gaming phones as well. Since XMC-2400 is in pre-production, the company hasn’t yet announced any customers. xMEMS plans to sample the XMC-2400 to customers in the first quarter of 2025.

SSDs are also a target. “I think that we can address that now,” Householder said. “I think that market is probably well suited to our chips as they exist today.”

Currently, the company is fabricating its chips at both TSMC and Bosch, the latter being the top MEMS fab in the world, Housholder said. xMEMS has ways to scale its technology: increasing the number of valve arrays in each chip die, for one. xMEMS also showed off a demo where two XMC-2400s were working in concert to move a small fan. There’s no reason why xMEMS or a customer couldn’t have a number of the chips working in concert.

And Householder suggested another, more intriguing possibility: Thinking of the XMC-2400 or a derivative as a cooling chiplet, inside the SOC of a conventional microprocessor. That’s not out of the range of possibility, of course. Intel’s upcoming Lunar Lake chip, consisting of several chiplets, is made up of several chiplets manufactured by TSMC.

That would mean that the chip vendor would have to agree, and the SOC package would itself have to be vented. It’s also not clear by how much cooling would improve. “We’re certainly not the expert there,” Housholder said. “But again, I think that the possibility exists and we’re anxious to explore it.”

For now, the most important implication seems to be for SSDs, which will have not one but two potential active-cooling solutions in addition to their current commodity passive heatsinks. But as xMEMS iterates and physically expands its cooling solutions, more components inside a laptop, including the CPU, will have more options to choose from, too. The best news of all? It sounds like cooling chips aren’t just a fun concept. They’re a legitimate market.