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Locking in security at the IoT PCB level

The electronics manufacturing services provider designing and assembling IoT printed circuit boards must have a comprehensive understanding of today’s electronics that contribute to an IoT device’s security.

Certainly, a great number of software vendors are supporting the IoT products businesses with their versions of security software. However, from a hardware point of view, chipmakers are going down that same road and also providing software support. Many name-brand microcontroller (µC), microprocessor (µP), system-on-a-chip (SoC) and field-programmable gate array (FPGA) vendors have embedded security circuitry in their chips.

In both cases — software and hardware — it’s important for the electronics manufacturing services (EMS) provider to keep up to date on the latest security technologies so it can work together with the IoT product customer to assure that the final product has top-notch security embedded in it. It’s equally important that OEM IoT product customers collaborate with EMS providers to closely investigate and analyze the many design and assembly tradeoffs involved in producing that product.

From a hardware point of view, in a lot of cases, the µP and its vast processing power may be overkill in an IoT device application. Here’s where a µC with the right level of processing power at a cost-effective price comes in handy.

An example of today’s offerings is the ARM Cortex-M µC. It’s supported by the company’s mbed operating system, software specifically designed for IoT devices. According to ARM literature, it “brings a comprehensive suite of security elements and connectivity making creation and deployment of IoT solutions possible at scale.”

This ARM µC is just one of many similar products on the market today for IoT applications. Therefore, it’s important for both OEMs and partner EMS providers to fully understand all the specifications and, most importantly, the nuances a specific IoT µC presents.

From a broad perspective, there are several key IoT design considerations to take into account, too many to detail in this small space. However, suffice it to say that the first question you have to ask yourself is: Does your IoT application require the more powerful µP with embedded security, a security co-processor linked up with a conventional µP, a less powerful µC, a SoC or an FPGA, each with embedded security?

This question is especially apropos simply due to the limited IoT rigid board real estate. And, by the way, the rigid portion of an IoT’s circuitry is where this heavier device or devices must be placed for stability. In some cases, auxiliary components — including through-hole devices — associated with the µC can be placed on the flex circuit side. However, given a choice, it is best to have it placed on the rigid section of the rigid-flex board.

As far as device packaging, the most often used for these devices include micro BGAs, CSPs and QFNs. Micro BGAs, for example, measure in the range of 13 x 13 millimeters or 33/64 x 33/64 inches, or basically ½ x ½ inch to a larger 35 x 35 mm or 1 3/8 x 1 3/8 inches. CSP and QFN packaging have similarly small measurements. You have to consider how much area you have on the rigid circuitry to properly place it along with associated devices.

The µC’s processing power generates a certain amount of heat that must be dissipated from a small area of real estate in IoT devices. The µC also draws a certain amount of current. To save battery power in an IoT product, it’s best to select a µC that requires the smallest amount of current possible to run the application’s required electrical functionality.

Protocols also have to be part of the consideration mix for both the IoT product OEM and the EMS provider. Protocols like Zigbee, Bluetooth, USB, Laura and others have different hardware devices and different security requirements.

If it’s Bluetooth, embedding security will require a different architecture type versus Zigbee versus Laura. If it’s a military IoT application, slight compromises may need to be made on the power side to make the IoT product is more robust since it will be used in harsh conditions.

Here I’ve touched on several important IoT PCB design and assembly points associated with embedded security. There are numerous other considerations that can best be answered once IoT product customers collaborate in depth with their EMS providers.

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