Ask Me Anything with Ethan Pierce


PCB West speaker Ethan Pierce will answer your IoT questions here. Start posting!

How does the design of a PCB differ when developing it for IoT applications compared to traditional applications?

It’s kind of a broad question but how do you address thermal management in IoT? How do you make sure that components operate within their specified temperature ranges?

Hello Ethan, how do you address thermal management when designing for IoT? Do you have best practices you can share?

I think it’d be interesting to get your opinion on testing and debugging. Considering the challenges associated with compact IoT devices, what do you think engineers should keep in mind to make sure their electronics won’t fail and specifically how would you recommend they’d test for performance?

I have kind of a complex question. How do you address EMI challenges in IoT? Trying to ensure reliability in a crowded wireless environment.

What are the key considerations in terms of size and form factor when designing a PCB for IoT devices with space constraints?

Hi Ethan. How do you optimize your boards for power efficiency in devices that need to operate on battery power for extended periods?

Ethan, do you recommend specific materials for IoT boards?

Thank you everyone for the great questions! Feel free to reach out via linkedin and mention this thread :slight_smile: !

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Designing PCBs for IoT applications involves unique considerations compared to traditional PCBs, focusing on compactness, energy efficiency, connectivity, and durability. Key aspects include:

  1. Compact Size: Utilizing high-density interconnect (HDI) technology to fit into small spaces.
  2. Low Power Consumption: Optimizing layout for energy efficiency and incorporating low-power components.
  3. Connectivity Features: Incorporating RF modules for wireless communication and ensuring minimal interference for stable connectivity.
  4. Environmental Durability: Using robust materials and protective coatings to withstand harsh conditions.
  5. Integrated Antennas: Carefully designing and positioning antennas to maintain optimal signal transmission.
  6. Sensor Integration: Precisely placing sensors to ensure accurate data collection without interference.
  7. EMI/EMC Management: Implementing strategies to mitigate electromagnetic interference and ensure compatibility.
  8. Multi-layer Designs: Employing multi-layer configurations to accommodate complex functionalities in a compact form.
  9. Software Integration: Ensuring seamless integration between the PCB hardware and device software/firmware.
  10. Cost-Effectiveness: Balancing design complexities with the need for mass production and affordability.

These considerations ensure IoT PCBs meet the specific demands of connectivity, miniaturization, and functionality required in the IoT ecosystem.

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@ravi.blore & @ishachandra27
You’ll need to explore the Thermal Design Engine

  1. Get your system architecture setup
    1. Setup your preliminary architecture of the device based on the power requirements of the system (20W, 5W) battery powered etc
  2. Work on your thermal power dissipation guesses
  3. Understand efficiency loses from your buck or boost regulators by calculating the power in vs power out and the efficiency curve in the datasheet
  4. For the other non power ICs in your design look up the “Theta JC” which will be in the datasheet this will give you the thermal information to find the power dissipation across all your chips
  5. Attempt to simulate the design using whatever tools you can with your mechanical team
  6. Build the physical systems
  7. Find out all your guesses were totally wrong from performing real life thermal testing with a lab or using thermal imaging cameras and external temp sensors and verifying the device operates within the require ranges. for many products the skin temp of the surface is a limitation that must be maintained.
  8. Go back to step 1 and revisit with your findings
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This is a loaded one and I’ve had many conversations with end customers and design teams over the years about this specific question:
Testing and debugging are critical stages in the development of compact IoT devices to ensure reliability and performance. Given the complexities and potential high costs associated with firmware issues, it’s crucial to adopt a thorough and proactive approach to testing. Here are some key points engineers should consider:

  1. Failsafe Bootloader/JTAG Access: Always ensure that there is a way to update or debug the device firmware post-manufacture. Designing the PCB with accessible pinouts for a failsafe bootloader or JTAG connection is essential. These connections may be discreet or under a seal to maintain the device’s aesthetic or functional integrity, but they should allow for firmware updates and debugging. This is crucial to avoid scenarios where a device becomes a ‘brick’ due to firmware issues, which can be costly.
  2. Manufacturing Considerations: Think about the entire lifecycle of the device, including the manufacturing process. It’s important to design with the assembly and post-assembly processes in mind, ensuring devices can be easily flashed or reprogrammed as needed without disassembly. This consideration can save significant costs and time in the production phase.
  3. Graceful Failure Modes: Accept that no electronic device is immune to failure, but focus on designing systems that fail gracefully. Implement watchdog timers, error handling routines, and safe states that the device can revert to in case of a malfunction. Testing for and designing around these edge cases ensures that the device can still operate under partial functionality, which can be critical for certain applications.
  4. Lifecycle Testing: Employ hardware-accelerated lifecycle testing to simulate extended use and environmental conditions, such as temperature variations, humidity, vibration, and shock. This helps identify potential points of failure and areas for improvement, ensuring the device’s longevity and reliability.
  5. User Testing: Getting the device into the hands of end-users early in the development process can provide invaluable insights into real-world usage, uncovering issues that may not be evident in the lab. This feedback can guide further development and testing efforts to ensure the device meets user needs and expectations.
  6. Performance Testing: Evaluate the device’s performance under various conditions and workloads to ensure it meets the required specifications. This includes testing for power consumption, processing speed, wireless connectivity range and stability, sensor accuracy, and response times. Use specialized testing equipment and software to simulate real-world scenarios and measure performance metrics.
  7. Security Testing: With IoT devices often being part of larger networks, security is paramount. Conduct vulnerability assessments and penetration testing to identify potential security weaknesses in the device and its communication protocols.
  8. Power saving: modes for your processors or microcontrollers will need to be considered. There are usually issues with processors entering and exiting power states. Best advice is to do some kind of user black box testing and observe if the device can successfully enter its expected power state and power consumption.
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Addressing EMI (Electromagnetic Interference) challenges in IoT devices, especially to ensure reliability in crowded wireless environments, involves a multifaceted approach. Here are some strategies to mitigate EMI and enhance the device’s performance and reliability:

  1. PCB Layout Design:
  2. Shielding and Filtering:
    • Shielding: Use metal shields over highly sensitive or noisy components to contain or block electromagnetic fields. This is especially useful for RF components and high-speed processors. just make sure you understand what the metal shields connecto toy
    • Connectors: Connectors will need to be ground 360 degrees around the entire connector so when connectors mate the signal is guided through that cable and not to the outside world. This is difficult with plastic connectors and connector interfaces that lack 360 degree coverage like RJ45 connectors.
    • Filters: Implement EMI filters on power supply lines and I/O ports to block unwanted high-frequency noise. Common-mode chokes and ferrite beads are effective in suppressing EMI on cables and traces.
  3. Component Placement:
    • Component Placement: Place noisy components away from sensitive areas. Isolate analog and digital sections as much as possible, and consider the orientation of components to minimize coupling. Keep switching traces as close to the IC as possible and make sure they have their return path.
  4. Wireless Communication Considerations:
    • Frequency Selection: Operate wireless communications in less congested frequency bands when possible. 2.4GHz is very congested if you can operate on 5GHz that’s better but more power consumption. Also if you can use something like LTE Cat-M. There is a lot of benefit there
    • Antenna Design and Placement: Design or select antennas that have directional properties to minimize interference with other devices. Place antennas away from metal objects and other antennas to avoid detuning and coupling. Also work with your Antenna vendor they have design services to help you optimize the design
  5. Use of Technology and Protocols:
    • Robust Communication Protocols: Implement protocols with error detection and correction capabilities to enhance data integrity in noisy environments. We are at the mercy of other devices and must comply with regulatory rules. or even on 2.4GHz if you can use another protocol like thread that’s more resilient to congestion. LoRa may also be an option
  6. Regulatory Compliance and Testing:
    1. Pre-compliance Testing: Perform EMI pre-compliance testing during the development phase to identify and address potential issues early. This is going to help you figure out if you pass before spending the money to do the actual certification
    2. Certification: Ensure the device meets relevant EMI/EMC regulatory standards for the intended markets, such as FCC (Federal Communications Commission) in the USA or CE (Conformité Européenne) in Europe.

When designing PCBs for space-constrained IoT devices, essential considerations include:

  1. Use Case: Design according to the device’s functionality and environment, influencing component choice and layout.
  2. Power Requirements: Aim for energy efficiency and consider the power supply design to ensure operational longevity within small spaces. Attempt to get devices to operate at the lowest compatible voltages as this reduces power consumption. 1.8V, 3.3V, 5V are some options. Also can you thermally operate the device in specified space.
  3. Sensors: Account for the type, quantity, and placement of sensors, ensuring they fit within the form factor without performance compromise. This is critical for your application whether its a gyroscope/accelerometer or an optical color sensor that needs to observe something in your device
  4. Wireless Interfaces: Chip antennas vs microstrip antennas based on your space constraints and complexity
  5. Stackup: Carefully plan the PCB stackup, as the number of layers and their configuration can significantly impact the board’s ability to accommodate complex circuits in limited space, affecting both routing density and electromagnetic performance. Cost wise a 2 or 4 layer board may be the cheapest but the most performance and space dense board can be 6 or 8 layers.

Leveraging multi-function ICs, using HDI technology for tighter layouts, and addressing thermal management are also crucial to integrating complex functionalities into restricted spaces while ensuring performance and reliability.

Certainly, here’s a formatted version of your response:

From experience, there are a few things to consider:

  • Leakage Current: Examine the leakage current for every device in your power path. Specifically, TVS (Transient Voltage Suppression) diodes can introduce substantial leakage current. It’s crucial to pay attention to your alternate parts as well, as these can significantly impact your battery life, potentially being the difference between 5nA and 500nA being consumed by a device.
  • Power Saving Modes: The power-saving modes for your processors or microcontrollers need careful consideration. It’s common to encounter issues with processors entering and exiting power states. The best advice is to conduct some kind of user black box testing to observe if the device can successfully enter its expected power state and achieve the anticipated power consumption.
  • Power Source Chemistry: The choice of your power source’s chemistry is vital. Li-ion (Lithium-ion) batteries, for instance, are not ideal for extended use applications due to their self-discharge rate. Instead, consider LiSoC (Lithium Thionyl Chloride) batteries or Hybrid Lithium Capacitors for long-term power scenarios, as they tend to offer better performance in such applications.

When designing boards for IoT applications, choosing the right materials is crucial to meet the specific needs of these devices, such as durability, performance, and cost-effectiveness. I would say these are the two most common materials for IoT boards and Sierra Circuits has these available!

FR-4: This is the most standard material used for PCBs, known for its good balance of cost, durability, and electrical properties. FR-4 is suitable for a wide range of IoT applications, especially where high performance is not the primary requirement.

Flex PCB Materials: Polyimide materials are used for flexible PCBs, which are advantageous for IoT devices requiring bending or folding to fit into compact or irregular spaces. Flex PCBs are also useful for dynamic applications where the PCB needs to flex during use.

Copper: In terms of the copper using 0.5oz copper may be better than 1oz copper depending on your application because of the etching control you’ll get over 1oz copper for impedance controlled nets.

Impedance Control: High-speed signals are sensitive to impedance variations, and impedance control is crucial for maintaining signal integrity. 0.5oz copper allows for finer control over impedance, as the thickness of the copper layer directly affects the trace width required to achieve a specific impedance. Thinner copper layers like 0.5oz can result in narrower trace widths, which is beneficial for high-density, high-speed designs.

You’ll need to define your stackup to better understand your material selection. If you don’t know where to start with a 4 Layer FR4 prototyping board with through hole vias. If you need more guidance here sierra circuits will get you going with their stackup designer!

For component placement, are you saying that components will radiate/couple more in one direction than in the other? Is there some semi-standard notation to look for in data sheets? (e.g., “radiates at 1.7MHz in the long direction, and 2.29MHz regardless of direction”?)