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Connect the Dots: IoT is Changing How We Design PCBs

"It's technology that helps you sleep, not keeps you up. It tells you when you've had enough. It gives you space to create or draw or write or learn, not refresh just one more time." — Tim Cook, CEO of Apple

The Internet of Things (IoT) is everywhere now—purpose-driven technology that improves lives by making technology work for people, not the other way around. With nationwide 5G wireless capacity rapidly expanding, the demand for and deployment of IoT products is exploding. Households increasingly rely on networked smart appliances. Traditional watches have largely been replaced by fitness trackers, and more of us get our weather reports by asking Alexa than watching the local TV weatherperson.

Demand growth is fueled by business as well as consumers, with pandemic-accelerated healthcare and industrial machinery applications leading the way. IoT devices of every stripe will continue to improve and add functionality while also becoming smaller, lighter, and faster.

Pressure to create innovative solutions for these devices puts the PCB designer at the epicenter of IoT.

It’s Time to Broaden our PCB Design Horizons
Designing boards for these devices will take a lot of skill on the part of the PCB designer, as well as a willingness to learn new tricks. Device memory, CPU, and wireless circuitry can often fit onto a system-on-a-chip (SoC) component in the assembly, but chip designs will have to accommodate other critical components packed into a small layout.

Using the same old tech to design boards for IoT will get tougher and tougher. There are packaging technologies available to help designers create boards small enough in thickness and diameter to accommodate the needs of smaller IoT devices. Three-dimensional integrated circuits can help reduce power consumption on a smaller design footprint. Multi-chip modules allow multiple integrated circuits to function as one—potentially reducing cost of the board while improving performance.

Designing PCBs for IoT also requires thinking about how the end-product is manufactured and put to use. For many IoT devices, PCBs are often embedded in other materials and must be flexible. That means your board design will likely feature newer materials like plastic, mesh, and flexible copper.

To move ahead, designers need to adhere to sound, established design methodology as well as tools that elevate their performance. Using more advanced PCB design tools will help designers respond to the demand for IoT devices.

Best Practices for PCB Designers on IoT Projects
John McMillian’s 2017 whitepaper^[1] remains the gold standard for IoT board design. Keep the seven design aspects laid out in that paper top of mind and it will help meet the challenges associated with IoT devices. We encourage you to download the paper and keep it on hand for reference. In the meantime, here is our take on McMillan’s seven keys to IoT PCB design:

1. Know your design domains. IoT designs with multi-chip modules integrate analog-to-digital, micro-electrical mechanical systems (MEMS), and radio to make them function as one. The more experience you have with these types of circuit design, the more easily you can create a PCB for IoT that meets your functionality requirements.
2. Stay focused on design constraints. Often, the nature of IoT devices puts limits on size and weight that trickle down to your design. If you are adding connectivity to a well-established product, for example, that can really be a challenge for the PCB layout. New versions of established IoT devices need to do everything the last model did, plus more, without getting any larger or heavier.
3. Broaden your component vocabulary. Before you begin to design in earnest, make sure you are familiar with all the components that create functionality for data flow, device display, and Wi-Fi connectivity. You will be building your design around these components, so the more familiar you are with them, the better.
4. Your schematic needs to convey the design’s intent. This includes issues such as physical constraints, cost considerations, and component availability. Keep this in mind as you create the bill of materials (BOM). Remember to verify part footprint sizes and height above the board as part of that investigation, especially on a highly constrained design. 
5. Test early and test often using all the tools available to you. Model-based design and testing tools will allow you to test, simulate, and verify the design’s functionality. Use them. This is how you catch problems and make changes before a prototype build. 
6. Learn the critical elements of board layout. Your CAD tool should allow you to visualize the board in its enclosure before you deal with routing and tracing. Using both 2D and 3D views for verification of things like flex circuit bends, you can more easily design within the device constraints.
7. Validate your design. Use your relationship with a PCB manufacturer and assembly partner to make sure your design will work. They will be able to provide feedback that will increase yields and reliability, as well as improve cost competitiveness.       

The future of IoT is just around the corner. Expand and hone your design skills today, and perhaps be part of creating the next Alexa or Fitbit tomorrow.

References

1. 7 Design Aspects of IoT PCB Designs—Siemens EDA (pads.com)

This column originally appeared in the March 2021 issue of Design007 Magazine.