Engineers clamor for ever-smaller sensors

With its myriad benefits, the Internet of Things (IoT) holds great promise, usually touted for the world-changing impact the applications will have. But for the engineers who are on the front lines developing the miniature sensors, components, and systems that make up these devices, it’s kind of, well, a nightmare.

Pete Smith, Senior Manager Product Knowledge for TE Sensor Solutions, has been in the sensor industry long enough to “know where all the bodies are buried.” He says that he cannot remember a time when the pressure has been as great as it now to reduce the size of sensors, and it’s being driven in large part by the IoT.

“You remember the size of the first Motorola phone? They called it the brick, because it was the size of a brick. And in retrospect, it really didn’t have very many features,” said Smith. “With the evolution of the technology, everything is getting smaller now and more feature-rich. Designers are suddenly realizing that they don’t have the room for all these sensors to do what they want to do with their product, and so they are coming to us to help them figure something out.”

That’s good for companies like TE Connectivity, because as every engineer knows smart companies are driven not by cool ideas, but by customers and what customers want.

The perfect sensor, Smith said (presumably tongue-in-cheek), is one that consumes no space and no power. But since that’s not yet feasible, the company is doing the next best thing: Making sensors smaller by developing multi-sensor modules that feature more than one sensing capability in a single package and reducing the size of the packaging itself.

As an example, Smith pointed to an altimeter his company makes that is used in drone technology. “It’s in a tiny little package that measures only 3 x 3 x 2 mm, you can put 8 of them on your thumb nail,” he said.

TE Connectivity altimeter MS5839

The package contains a pressure sensor that measures atmospheric pressure, from which altitude information can be derived, and a microcontroller that processes the signals from the sensing elements and digitizes the data. “We were even able to throw in a temperature sensor without making the package any bigger,” Smith notes.

Not only are the sensors inside getting smaller, but the packaging that surrounds it is likewise shrinking. But as packaging gets smaller, it tends to be less robust and there is a limit to how thin the walls get before structural integrity is impacted.  

“The challenge is that at the same time customers want smaller packages, they are also asking for more robust products, which isn’t surprising because many IoT applications require sensors—which can be very delicate--be put into unfriendly places,” explained Smith.  

As an example, Smith pointed to an application where the company’s altimeter has to be exposed to the outside environment, which means it is exposed to everything else in the atmosphere—from dust and pollen, to water, rain, and snow. It’s a cruel world.

Requirements like this have led to a migration away from standard, off-the-shelf polymers to the use of more exotic materials such as filled polymers or titanium, which are both strong and lightweight, for packaging. In some cases, the material might also be called upon to perform double duty—for example if the electronics need electromagnetic shielding, the packaging might be designed to provide both structural integrity and EMI protection.

Smith said that kind of creative thinking has been central to the sensor design work he has done over the years. “Many years ago, when I was a product development engineer, the engineering department had an edict that in order to get efficiency gains, every component had to do two things,” he said.

TE Connectivity TSYS03 temperature sensor

TE Connectivity's smallest sensor is only slightly smaller than your average ladybug.

As for just how miniature can sensors can get, Smith is confident engineers will come up with more clever innovations. But a limiting factor today may surprise you: Smith noted that if you take a miniature sensor that is typically mounted to a PCB and turn it upside down, you’ll note that the solder pads are generally one of the larger parts of the assembly now.

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