Impedance Control and Reliable Results in Millimeter-Wave PCB Design

In high-speed and high-frequency PCB design, impedance control is a critical concern. This is especially true for millimeter-wave frequencies above 30 GHz, where even small variations in trace dimensions or dielectric properties can cause significant signal loss or reflection.

To achieve stable performance, designers must carefully engineer the PCB stack-up and trace geometry to meet precise impedance targets.

Our Challenge: Determining PCB Stack-Up and Line Width for Millimeter-Wave Signals

In a recent project, a customer approached us with a common concern:

"We need impedance control for signal lines in the millimeter-wave band, but we're unsure how to determine the optimal PCB stack-up and trace geometry."

Designing for millimeter-wave frequencies requires careful coordination of multiple factors:

• Material selection (dielectric constant, loss tangent)
• Layer structure (core thickness, prepreg configuration)
• Signal line width and spacing

These elements are tightly interrelated and cannot be decided in isolation. Achieving the desired impedance requires optimizing them as a complete system.

Our Approach: Optimization Based on Target Impedance and Number of Layers

To begin, we confirmed the target impedance (such as 50Ω or 100Ω differential) and the desired number of PCB layers. Using simulation tools, we explored the optimal stack-up and trace geometry combinations.

Key considerations included:

• Core material thickness
• Surface versus inner-layer routing
• Line width and process tolerances affecting impedance stability

After multiple rounds of verification, we proposed specific design values that met the customer's performance requirements.

Our Result: Achieving the Desired PCB Characteristics

After evaluating the manufactured PCB, the measured impedance matched the simulation results precisely. Signal transmission tests in the millimeter-wave band confirmed a significant improvement in signal quality. The customer was highly satisfied and expressed confidence in moving forward with their next product development.

Summary

Impedance control in millimeter-wave PCBs requires more than simply adjusting line width. Only through comprehensive optimization of material selection, layer structure, and routing design can you achieve the target characteristics. This case demonstrates the critical importance of thorough upfront design review and simulation.

We continue to support high-frequency and high-speed PCB development, helping our customers succeed in their product development.

Struggling with Impedance Control in Millimeter-Wave PCB Design? Let's Solve It Together.

If you're unsure how to determine the right layer structure, material stack-up, or signal line width to meet your target impedance, we're here to help. Upload your files here and let us optimize your PCB stack-up and signal line geometry for precise impedance control before signal integrity issues arise. Want to learn more? Download our PCB Design Guide for practical tips on routing strategies, decoupling techniques, and simulation workflows.