Startup’s Innovation Quickly Cools Down Mobile Devices

Jetcool’s heat sinks can fit on a chip and are more efficient than current methods

3 min read
Image of chip on blue background
Photo: Jetcool Technologies Inc.

Image of chip on blue backgroundJetcool’s heat sink can be embedded within the substrate, be part of the baseplate, or be a modular add-on.Photo: JETCOOL Technologies Inc

THE INSTITUTEAs electronics get smaller and more powerful, they are generating more heat. One challenge for manufacturers is finding a way to cool down their creations without affecting performance.

Current methods to prevent overheating include fans, aluminum heat sinks, and liquid-cooled cold plates. A heat sink has a thermal conductor to disperse the heat. As devices get smaller and hotter, their heat sinks are getting larger.

Mechanical engineer Bernie Malouin, founder of the startup Jetcool Technologies, says making bigger heat spreaders is a backward approach. His team came up with a different way: a technology they call microconvective cooling, which uses small jets of fluid. Jetcool’s heat sink can be embedded within the substrate, be part of the baseplate, or be a modular add-on.

Jetcool, based in Littleton, Mass., was named Next Top Startup at a competition held during the IEEE International Microwave Symposium (IMS) in June. The company also won the event’s Audience Choice Award.

“Why develop smaller and smaller devices just to saddle them with larger and larger heat sinks?” Malouin says. “It just didn’t make sense to me. Jetcool uses small heat sinks that are essentially the same size as the device itself. On top of that, our approach provides 10 times better cooling than other methods such as microchannels, cold plates, or air cooling.”

MINIATURE JETS

Instead of spreading the heat, Jetcool’s small jets of high-velocity fluid are aimed directly at the surface to remove the heat right where it’s generated. The jets are built into the silicon substrate, integrating cooling into the processor chip. Its solution integrates seamlessly with almost all of today’s liquid-cooling infrastructure, requiring only industry-standard pressures and flow rates.

What’s more, Malouin says, Jetcool heat sinks are lightweight, don’t use thermal epoxies or pastes, and eliminate the need for metal heat sinks. The miniature cooling modules can be added during chip fabrication or to an existing component at the packaging stage, he says.

Jetcool’s on-chip microconvective cooling could be used in the motor drives of electric vehicle power systems, the laser diodes that are part of defense systems, and the performance processors powering data centers.

Several prototypes are being piloted, and Malouin said he expects to start selling products next year.

MINIATURIZATION MOVEMENT

Malouin has nine U.S. patent applications pending. Some of his technology has been licensed from his former employer, MIT Lincoln Laboratory, in Lexington, Mass., where for eight years he worked in its mechanical engineering and thermal engineering group. That’s where he and Jetcool’s technology director, Jordan Mizerak, first met and came up with their idea, which was based on technology the team had been perfecting for five years.

“At Lincoln Laboratory, we observed this trend in miniaturization that was happening all around us,” Malouin says. “Innovations were being built upon more powerful devices in smaller and smaller packages. We saw power density was really going through the roof, and that’s the problem we worked to solve. The company is very young, but our technology has actually been fairly well proven.”

The startup is currently self-funded, but Malouin envisions a seed round early next year to expand the pilot project. In addition to Malouin and Mizerak, there’s only one other employee, but Jetcool is looking to hire people who “want to help reshape the future of electronics cooling,” Malouin says.

HIGH-VALUE RECOGNITION

Malouin says the IMS provided a great forum for him to network with other startups, get feedback about his product, and better understand customers’ needs. Just as important, he adds, was that IEEE and the IMS brought small and large companies under one roof.

“Large organizations provide a fairly unique vector to turn new technologies into real products,” he says. “I think building relationships between startups and large companies is really key, and that’s something that IEEE and the IMS do very well.

“Being named the Next Top Startup has brought a lot of recognition to us and our technology. From our viewpoint, the competition was a tremendous success and something of high value to the startup community. We hope it continues in the future, because the event was well received by everyone.”

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The Inner Beauty of Basic Electronics

Open Circuits showcases the surprising complexity of passive components

5 min read
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A photo of a high-stability film resistor with the letters "MIS" in yellow.
All photos by Eric Schlaepfer & Windell H. Oskay
Blue

Eric Schlaepfer was trying to fix a broken piece of test equipment when he came across the cause of the problem—a troubled tantalum capacitor. The component had somehow shorted out, and he wanted to know why. So he polished it down for a look inside. He never found the source of the short, but he and his collaborator, Windell H. Oskay, discovered something even better: a breathtaking hidden world inside electronics. What followed were hours and hours of polishing, cleaning, and photography that resulted in Open Circuits: The Inner Beauty of Electronic Components (No Starch Press, 2022), an excerpt of which follows. As the authors write, everything about these components is deliberately designed to meet specific technical needs, but that design leads to “accidental beauty: the emergent aesthetics of things you were never expected to see.”

From a book that spans the wide world of electronics, what we at IEEE Spectrum found surprisingly compelling were the insides of things we don’t spend much time thinking about, passive components. Transistors, LEDs, and other semiconductors may be where the action is, but the simple physics of resistors, capacitors, and inductors have their own sort of splendor.

High-Stability Film Resistor

A photo of a high-stability film resistor with the letters "MIS" in yellow.

All photos by Eric Schlaepfer & Windell H. Oskay

This high-stability film resistor, about 4 millimeters in diameter, is made in much the same way as its inexpensive carbon-film cousin, but with exacting precision. A ceramic rod is coated with a fine layer of resistive film (thin metal, metal oxide, or carbon) and then a perfectly uniform helical groove is machined into the film.

Instead of coating the resistor with an epoxy, it’s hermetically sealed in a lustrous little glass envelope. This makes the resistor more robust, ideal for specialized cases such as precision reference instrumentation, where long-term stability of the resistor is critical. The glass envelope provides better isolation against moisture and other environmental changes than standard coatings like epoxy.

15-Turn Trimmer Potentiometer

A photo of a blue chip
A photo of a blue chip on a circuit board.

It takes 15 rotations of an adjustment screw to move a 15-turn trimmer potentiometer from one end of its resistive range to the other. Circuits that need to be adjusted with fine resolution control use this type of trimmer pot instead of the single-turn variety.

The resistive element in this trimmer is a strip of cermet—a composite of ceramic and metal—silk-screened on a white ceramic substrate. Screen-printed metal links each end of the strip to the connecting wires. It’s a flattened, linear version of the horseshoe-shaped resistive element in single-turn trimmers.

Turning the adjustment screw moves a plastic slider along a track. The wiper is a spring finger, a spring-loaded metal contact, attached to the slider. It makes contact between a metal strip and the selected point on the strip of resistive film.

Ceramic Disc Capacitor

A cutaway of a Ceramic Disc Capacitor
A photo of a Ceramic Disc Capacitor

Capacitors are fundamental electronic components that store energy in the form of static electricity. They’re used in countless ways, including for bulk energy storage, to smooth out electronic signals, and as computer memory cells. The simplest capacitor consists of two parallel metal plates with a gap between them, but capacitors can take many forms so long as there are two conductive surfaces, called electrodes, separated by an insulator.

A ceramic disc capacitor is a low-cost capacitor that is frequently found in appliances and toys. Its insulator is a ceramic disc, and its two parallel plates are extremely thin metal coatings that are evaporated or sputtered onto the disc’s outer surfaces. Connecting wires are attached using solder, and the whole assembly is dipped into a porous coating material that dries hard and protects the capacitor from damage.

Film Capacitor

An image of a cut away of a capacitor
A photo of a green capacitor.

Film capacitors are frequently found in high-quality audio equipment, such as headphone amplifiers, record players, graphic equalizers, and radio tuners. Their key feature is that the dielectric material is a plastic film, such as polyester or polypropylene.

The metal electrodes of this film capacitor are vacuum-deposited on the surfaces of long strips of plastic film. After the leads are attached, the films are rolled up and dipped into an epoxy that binds the assembly together. Then the completed assembly is dipped in a tough outer coating and marked with its value.

Other types of film capacitors are made by stacking flat layers of metallized plastic film, rather than rolling up layers of film.

Dipped Tantalum Capacitor

A photo of a cutaway of a Dipped Tantalum Capacitor

At the core of this capacitor is a porous pellet of tantalum metal. The pellet is made from tantalum powder and sintered, or compressed at a high temperature, into a dense, spongelike solid.

Just like a kitchen sponge, the resulting pellet has a high surface area per unit volume. The pellet is then anodized, creating an insulating oxide layer with an equally high surface area. This process packs a lot of capacitance into a compact device, using spongelike geometry rather than the stacked or rolled layers that most other capacitors use.

The device’s positive terminal, or anode, is connected directly to the tantalum metal. The negative terminal, or cathode, is formed by a thin layer of conductive manganese dioxide coating the pellet.

Axial Inductor

An image of a cutaway of a Axial Inductor
A photo of a collection of cut wires

Inductors are fundamental electronic components that store energy in the form of a magnetic field. They’re used, for example, in some types of power supplies to convert between voltages by alternately storing and releasing energy. This energy-efficient design helps maximize the battery life of cellphones and other portable electronics.

Inductors typically consist of a coil of insulated wire wrapped around a core of magnetic material like iron or ferrite, a ceramic filled with iron oxide. Current flowing around the core produces a magnetic field that acts as a sort of flywheel for current, smoothing out changes in the current as it flows through the inductor.

This axial inductor has a number of turns of varnished copper wire wrapped around a ferrite form and soldered to copper leads on its two ends. It has several layers of protection: a clear varnish over the windings, a light-green coating around the solder joints, and a striking green outer coating to protect the whole component and provide a surface for the colorful stripes that indicate its inductance value.

Power Supply Transformer

A photo of a collection of cut wires
A photo of a yellow element on a circuit board.

This transformer has multiple sets of windings and is used in a power supply to create multiple output AC voltages from a single AC input such as a wall outlet.

The small wires nearer the center are “high impedance” turns of magnet wire. These windings carry a higher voltage but a lower current. They’re protected by several layers of tape, a copper-foil electrostatic shield, and more tape.

The outer “low impedance” windings are made with thicker insulated wire and fewer turns. They handle a lower voltage but a higher current.

All of the windings are wrapped around a black plastic bobbin. Two pieces of ferrite ceramic are bonded together to form the magnetic core at the heart of the transformer.

This article appears in the February 2023 print issue.

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