In modern electronic design, ensuring PCB signal integrity has become an increasingly challenging task. The growth of the Internet of Things (IoT) and Artificial Intelligence (AI) has driven demands for both miniaturization and high performance—two seemingly contradictory requirements. As chips become smaller, their functionality increases—creating the perfect conditions for interference.
Although overcoming this challenge may be difficult, it is not impossible. By following a few best practices, you can still ensure the functionality of your PCB.
1. Choosing the Right Materials
Ensuring signal integrity begins with material selection. From components to the substrate, all materials must be chosen to minimize signal loss while also being able to withstand potentially harsh operating conditions.
Typically, PCB materials should have a low dielectric constant to prevent high-frequency interference. It’s also important to consider how these materials will perform in the final application environment, as certain conditions could affect their properties. For example, high humidity can cause some polymers to absorb moisture, which in turn increases their relative dielectric constant.
Recent research has paved the way for breakthroughs in this area. Now, some advanced polymers can achieve dissipation factors as low as 0.001 at 10GHz. However, note that the highest-performing materials in this category may be difficult to acquire, potentially raising the cost of the device.
2. Minimizing Trace Lengths and Widths
Another strategy to prevent signal loss is to keep trace lengths small. The wider the trace, the less space there is on the substrate, leading to a higher potential for interference. Similarly, longer traces increase the conductive area, thereby increasing the risk of crosstalk.
Placing interconnected components close together helps minimize trace length. Thinking vertically rather than horizontally can also have a similar effect, as upward traces may be shorter than lateral traces. Additionally, 3D printing circuits instead of relying on traditional manufacturing could be a viable option, as 3D printers can print directly onto the substrate without needing to create slots, resulting in smaller widths.
It’s also important to consider the size of the return path, not just the individual trace. Keeping the return path and signal trace close together, and avoiding branching wherever possible, will help maintain signal integrity.
3. Reducing Noise with Grounding and Decoupling
As PCBs become more complex, proper grounding becomes increasingly important. While single-point grounding may be sufficient for low-frequency applications, modern devices typically require larger, multipoint ground planes.
Using dedicated ground layers provides a simple method for signal separation, preventing electromagnetic interference (EMI). This also facilitates built-in thermal management by providing a uniform current distribution across the board. When using this approach, you may need to separate DC and AC or analog and digital signal grounds, but it’s important to avoid split grounding, as this can negatively affect signal integrity.
Likewise, decoupling capacitors should be used effectively. For best results, place them close to the signal source, just before the signal connects to the ground plane. In high-frequency applications, you may need to pair decoupling capacitors with resistors.
4. Managing Temperature
Thermal management is another crucial strategy for maintaining PCB signal integrity. In today's market, it's challenging to use bulky heat sinks due to the small size of devices.
Using materials with low thermal conductivity helps, especially when your PCB houses high-power components in tight spaces. You don’t necessarily have to rely on heat sinks; you can create thermal vias to dissipate heat away from sensitive areas. Additionally, increasing the spacing between high-power components will improve thermal performance.
Even if the device is too small to fit a fan, leave enough room for airflow across the PCB. Placing high-heat components near the end of the circuit board, close to vents, will maximize the benefits of this design. Thermal insulators and conductive pads might also be an option.
5. Shielding Against Electromagnetic Interference (EMI)
High-frequency PCBs also require EMI shielding. While decoupling and grounding will reduce EMI around the circuit, they are not sufficient on their own to maintain signal integrity in sensitive applications. Devices operating in environments with other communication technologies may require more robust EMI protection.
One of the most important considerations in EMI shielding is the material of the shield. High-conductivity metal mesh is commonly used in the industry and is cost-effective, but it may not be suitable for smaller devices. In such cases, elastomers or foam insulation materials may offer better alternatives.
In some cases, you may need to filter EMI rather than completely shield it. Single-phase filters are typically used in consumer electronics, but high-power devices (especially those used in extreme environments) may require three-phase filters.
6. Thorough Testing of the Design
No matter how carefully you address these factors, you must test the design before finalizing it. This includes both simulations and physical trials.
Many modern digital design platforms include EMI, thermal management, and impedance simulators. Analyzing these three aspects will give you the most comprehensive view of your PCB design’s performance. Keep in mind that you should also leave room for tolerance, as the final application of the device may introduce real-world conditions that affect signals but are not captured in simulations.
Some markets also require extensive physical testing. For example, military-grade devices must undergo MIL-STD-810 testing, which exposes devices to direct sunlight, extreme temperatures, physical shocks, and other stresses to verify their integrity. You may need to collaborate with third-party testing organizations to perform such evaluations, but they can offer valuable insights into how your design performs in real-world conditions.
7. Leveraging Artificial Intelligence
Considering all these factors may seem overwhelming. However, you can leverage new technologies to make the process easier. AI design tools are becoming more prevalent, and they can highlight inefficiencies or potential areas for improvement that manual designs might overlook.
With AI, some companies have increased chip performance by 14% in just 10 days while reducing power consumption. Achieving this improvement through traditional methods would require more time and expensive testing.
However, keep in mind that AI is not perfect. It needs to be thoroughly trained to produce reliable results, and it can still make errors. Therefore, after using AI tools to optimize your design, you should still verify the PCB signal integrity. Nevertheless, AI can save you time and help you find better ways to refine your layout.
Increasing Demands for PCB Signal Integrity
As end-users seek to use more powerful devices in a wider range of operating environments, PCB signal integrity will become more important—but also more challenging to maintain. In this trend, adaptability is key. By following these seven best practices and staying abreast of material and resource innovations, you can ensure that your PCB designs remain as reliable as possible. At PCBYES, we provide one-stop PCB services, from design to PCBA assembly. We specialize in PCB manufacturing, PCBA, high-density boards, advanced circuit boards, SMT placement, and more.
