Choosing Substrates for High-Frequency PCBs
Above roughly 1 GHz, standard FR-4 losses start to bite. The effective dielectric constant shifts with frequency, and a careless stack-up turns your 50-ohm line into something else entirely.
Why Dk and Df matter
Dielectric constant (Dk) sets your impedance; dissipation factor (Df) sets your loss. A 0.1 swing in Dk moves impedance several percent β enough to fail a spec.
Material tiers
Rogers, Panasonic Megtron and Taconic serve RF and automotive radar; mid-loss FR-4 fills the cost-sensitive middle. Match the grade to the budget, not the hype.
Practical selection
Fix your Dk/Df target from the simulation, then ask the laminate mill for the actual lot data. Design in margin for supplier variation.
Key Takeaways
Key Takeaways
- Match material grade to frequency, not to marketing.
- Request real lot Dk/Df data from the laminate supplier.
- Build margin for supplier-to-supplier variation.
