Are rough surfaces on PCBs impacting high-frequency signals?

Printed-circuit boards (PCBs) are an integral part of most electronic devices today, and as PCBs become smaller, electronics engineers must remain aware of the tiny defects that can affect how these components function, especially when they involve high-frequency signals. Surface roughness may seem minor, but it can significantly affect PCB performance, including impedance and signal transmission. What should electronics engineers know about it, and how can they minimize this issue?

Path length

Rough PCB surfaces increase the signal’s path length. This is due to the skin effect, which occurs because high-frequency electrical signals are more likely to flow along a conductor’s outer surface instead of through its core. A longer path length can also increase resistance and cause energy loss.

Engineers can reduce these issues by choosing the appropriate surface finishes for different PCB parts. Immersion silver is a good choice for balancing performance and affordability, although it must be handled carefully to prevent tarnishing.

Electroless nickel immersion gold offers a flat and smooth surface with a gold layer that promotes excellent solderability and conductivity and a nickel layer that offers oxidation protection. This surface finish minimizes signal distortion, making it a popular option for microwave and radio-frequency applications.

Although immersion tin features a smooth surface, it has lower corrosion resistance than other options, making it less frequently selected for high-frequency PCBs. Because hard gold has good conductivity and resists wear, engineers often use it in high-frequency applications, such as on contact points and connectors. This approach minimizes signal loss and increases overall durability.

If you plan to outsource finishing or other manufacturing steps to a specialty provider, consider choosing one with extensive experience and the equipment and expertise needed for your PCB design.

For example, in 2024, PCB company OKI Circuit Technology created an ultra-high, multilayer PCB line. This expansion boosted its capacity potential by approximately 1.4× while also helping the company cater to customers with smaller orders. The company has also invested in numerous enhancements that increase its precision and equip it to meet the needs of next-generation communications, robotics, and semiconductors.

Signal integrity

Rough surfaces compromise signal integrity and can cause parasitic capacitance. This issue can also increase crosstalk if it results in uneven electromagnetic field distribution. Smoother surfaces enable faster signal speeds while preventing distortion and delays.

Because surface roughness is one of many factors that can interfere with signal integrity, electronics engineers should scrutinize all design aspects to find other potential culprits. Some companies offer specialized tools to make the task easier.

One provider sells software that uses artificial intelligence to assess proposed designs. Users can also check trace path routing by studying cross-sectional diagrams that show various layers, identifying potential issues more quickly.

Component placement and PCB layout configurations can affect signal integrity, so designers should consider those aspects before assuming rough surfaces have degraded performance. Digital twins and similar tools allow engineers and product designers to experiment with various layouts before committing to a final PCB layout. Keeping a log of all design changes also allows engineers to revert to previous iterations if newer versions worsen signal integrity.

If companies notice ongoing signal integrity problems or other challenges, examining the individual industrial processes may highlight the causes. This usually starts with data collection because the information provides a baseline. Once companies begin tracking trends, they can discover the most effective ways to tighten quality control and meet other goals that improve PCB performance.

Tailored assistance

If electronics engineers conclude that rough surfaces are among the primary contributors to signal issues in their high-frequency PCBs, they can then address the problem by partnering with third-party providers that understand the complexities of finishing small parts. These companies can detail the various finish types available and provide pricing and lead times, depending on the unit order of PCBs.

Companies that need PCB finishing for prototypes or small production runs may request manual processes. Skilled technicians use tools and magnification on parts with complex geometries or other characteristics that make them unsuitable for mechanical methods.

Controlled combustion, electrolytic action, and vibratory containers are some of the other options for finishing small parts through non-manual means. Specialist finishers can examine the PCB designs and recommend the best strategies to achieve consistent smoothness with maximum efficiency.

Because many manufacturers have high-volume finishing needs, some startups have emerged to fill the need while supporting producers’ automation efforts. Augmentus is one example, focusing on physical AI to scale automated surface finishing for high-mix environments. The company has built a fully autonomous system for today’s factory floors. In July 2025, the company secured $11 million in a Series A+ funding round to scale for high-mix, complex robotic surface finishing and welding.

Augmentus views surface finishing as one of the most challenging problems in automation, but the company believes its technology will break new ground. Although it is too early to know how this option and others like it may change PCB production, automated processes could offer better repeatability, making surface roughness less problematic.

Ongoing awareness

Because surface roughness can negatively affect high-frequency PCB signals, engineers should explore numerous ways to address it effectively. Considering this issue early in the design process and selecting appropriate finishes are proactive steps for strengthening component quality control.

About the author

Emily Newton is a technical writer and the editor-in-chief of Revolutionized. She enjoys researching and writing about how technology is changing the industrial sector.

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