Standard of Excellence: The Role of Continuous Education in Enhancing Customer Experience
Global Sourcing Spotlight: Supplier Audits—Ensuring Compliance in Global Sourcing
Smart Automation: When It’s Time to Replace SMT Equipment
Pushing the Limits of PCB Impedance Control
July 9, 2024 | Alex Knowles, RoBATEstimated reading time: 1 minute
While we’ve long known the importance of impedance control in PCB design, with the increase in frequencies, the decrease in SNR (NRZ to PAM4), and the continual reduction in device size, the impact of signal integrity on poor impedance control of transmission lines is even more significant.
What Affects Impedance in a PCB?
Obviously, the critical elements include the design of trace width/separation, copper thickness, dielectric, stackup, glass weave, routing/snaking, and via placement. There are many helpful products to simulate and simplify this process, but theoretical simulation and experimental measurement are two different ballgames. Now we must look past our perfectly ideal design and get it manufactured.
All PCB fabricators have their own carefully guarded methods of modifying their process to achieve the desired controlled impedance specification. When you start considering the techniques and processes in PCB manufacturing, the list seems endless: etching, high layer counts, feature density, pressing, layer registration, material storage, and expansion/contraction. With so many contributing factors, who can blame them for playing their cards close to the vest?
Thus, how well can these manufacturing processes produce a match to the original design, and how well will the result match the theory? As Einstein said, “A theory is something nobody believes in except the person who made it. An experiment is something everybody believes, except the person who made it.”
To read this entire article, which appeared in the June 2024 issue of PCB007 Magazine, click here.
Share on:
Testimonial
"The I-Connect007 team is outstanding—kind, responsive, and a true marketing partner. Their design team created fresh, eye-catching ads, and their editorial support polished our content to let our brand shine. Thank you all! "
Sweeney Ng - CEE PCBSuggested Items
Beyond Design: Micro-ohm Power Delivery Network for AI-driven GPUs
11/18/2025 | Barry Olney -- Column: Beyond DesignThe evolution of modern processors, marked by faster edge transitions, reduced output impedance, and increasingly complex bus architectures, has significantly augmented the demands on PCB infrastructure. These challenges are compounded by AI-driven graphics processing units (GPUs), which require exceptionally high-power delivery at ultra-low operating voltages, placing greater stress on power integrity and layout design.
The Shaughnessy Report: Zee Plane! Zee Plane!
11/11/2025 | Andy Shaughnessy -- Column: The Shaughnessy ReportPlanes aren’t magic, but they are big time-savers. Without planes, designers would have to create thousands of traces to accomplish the same objectives. You can imagine the first time a designer thought about using a sheet of copper, asking, “Hey, why am I killing myself laying out all these traces? Can’t I just use this sheet of copper instead?”
November 2025 Design007 Magazine: Proper Plane Design
11/10/2025 | I-Connect007 Editorial TeamWithout planes, designers would have to create thousands of traces to accomplish the same objectives. Power planes provide low impedance and stable power to every component on the board, much like a large power bus. Ground planes stabilize reference voltage, improve thermal performance, and help preclude EMI issues. Power and ground plane design is often a battle of tradeoffs.
Everyone’s Talking About Power
11/06/2025 | Heidi Barnes, Keysight TechnologiesDelivering power to a digital load is an AC function, not DC. That simple statement may be obvious, but the implications of how electricity travels to an electronic load are complicated. Dynamic loads with rapidly changing currents create electric and magnetic fields that adhere to Maxwell’s equations. Ground can be misleading and is probably better used for describing where one grows potatoes and carrots. Electrical currents have “return paths,” and the energy is traveling in the fields between the power rail and the return path.
Beyond Design: The Fundamental Structure of Spectral Integrity
10/21/2025 | Barry Olney -- Column: Beyond DesignImpedance can be characterized in both the time and frequency domains. In the time domain, it influences how electromagnetic energy propagates through interconnects, affecting signal integrity and waveform fidelity. In the frequency domain, AC impedance determines how well the network can suppress noise and deliver clean power at a range of frequencies. AC impedance shapes how power rails respond to transient loads.