Material, not marketing
FR-4 uses epoxy-glass with a dielectric constant that varies with frequency and temperature. High-frequency laminates — PTFE-based or hydrocarbon-ceramic — keep Dk and Df far more stable, which is what an RF front end needs.
What changes in the build
- Lamination — different temperature and pressure cycles; some materials need specialised bonding layers.
- Drilling and plating — PTFE is softer and more prone to smear; hole preparation changes.
- Surface finish — some finishes interact badly with PTFE; ENIG or a specified alternative is chosen deliberately.
- Lead time — material availability matters as much as the process itself.
When the switch pays
The break-even is not a frequency number; it is the loss budget. If the design still closes its link budget with FR-4 at the target frequency and distance, the cheaper substrate stays. Once insertion loss or phase stability dominates, the high-frequency laminate is the only way to meet the specification.
We build hybrid stackups when only the RF layers need the specialised material, which keeps cost proportional to where the performance is needed.
