Several big trends have converged to make the Internet of Things possible:
- Wireless networking technologies such as Wi-Fi and 4G LTE have continually improved and become viable alternatives to wired connections like Ethernet. According to 2014 estimates from Cisco, Wi-Fi and cellular will account for more traffic than wired Internet as soon as 2018. In 2013, wired still led 56 percent to 41 percent.
- Devices such as the Nest thermostat and the Philips Hue lightbulbs have demonstrated how connectivity can be extended to many new and more compact device types. Smartphones were one of the first usable ways to access the Internet without having to rely on a laptop or desktop. Now applications can be pulled up from a smartwatch or deeply woven into the activities of connected home appliances.
- Printed electronics have evolved to become flexible and suitable for a variety of form factors. Flex PCB and High-Density Interconnect (HDI) PCBs enable the manufacturing of sophisticated wearables ranging from medical implants and hearing aids to fitness trackers and augmented reality heads-up displays. These boards provide excellent design freedom (i.e., they can be formed into many shapes), high copper tensile strength, and are suitable for harsh environments.
These three trends have enabled the IoT and also driven up demand for flex and HDI PCBs in particular. Let's look at bit more in depth about why these types of PCBs will play a central part in the IoT.
The IoT opportunity for Flex and HDI PCBs
Tens of billions of new devices will be connected to IP networks as the IoT spreads, and many of them will need PCBs that can fit into tight spaces while still delivering high performance. IT research firm Gartner has estimated that by 2020, up to 26 billion devices could be connected to the Internet.
Providing flexibility for wearable applications
Applications for IoT devices such as wearables put unique demands on PCBs. For example, a circuit board within a fitness tracker would likely be subject to frequent flexing and other forms of dynamic stress. Device makers have responded by exploring options like flex PCBs and HDI PCBs.
One specific approach, described in the June 2015 of The PCB Magazine, would be to connect multiple PCBs by using elastic copper conductors. Each board would have its own surface mount components, while the entire creation would be contained within an elastomeric material to ensure a stretchable system.
This level of flexibility builds on the potential already demonstrated by flex PCBs in applications such as medical devices, aerospace equipment, and cars. With something like a hearing aid, a flex PCB enables components such as batteries, microphones, and digital signal processors to be mounted in one small package. In a car, a flex PCB can greatly simplify an otherwise complicated wiring harness and also provide effective resistance within the harsh environment under the hood.
Where HDI fits into the IoT
HDI allows for dense component placement and more versatile routing in a PCB. The main benefit of HDI is that it reduces drill to copper. Using blind and buried vias allows designers to avoid denser areas of the board, which in turn means the denser circuitry is routed cleaner.
Compared with traditional PCBs, HDI PCBs have tinier trace widths and superior wiring density. They achieve these advantages through the use of technologies such as buried vias, blind vias, and stacked microvias.
Another note on microvias: Their extremely small pad size, as described in a 2014 EE Times article by Pi Zhang of Nuvation Engineering, helps to boost channel routing width. Layer reduction is possible since through-holes may be replaced with microvias, allowing signal layers along with their corresponding reference planes to be eliminated. It's the PCB version of hitting two birds with one stone.
The future of PCB design for the IoT
Combining flex and HDI PCB technologies can ensure that the circuit boards powering the IoT are sufficiently small and high-performing to power a wide variety of devices. They can help drive down the number of wiring connectors, minimize space and weight, and improve PCB reliability through the reduction of things such as thermal stress.
Sierra Circuits is an experienced manufacturer of PCBs, including flex and HDI. Our capabilities in HDI include sequential lamination and laser microvias. Find out more on our main HDI PCB page.