FR4 PCB Substrate Sourcing From China
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FR4 is the default glass-epoxy laminate behind most PCBs sourced from China — cheap, well understood, and fine up to a few GHz, but its dielectric loss makes it the wrong choice above roughly 5-10 GHz. For RF, mmWave, or controlled-impedance designs, Chinese fabs move to Rogers 4003C/4350B, PTFE, or polyimide, each carrying a real cost multiplier over baseline FR4. Knowing where FR4 stops being adequate is the difference between a board that hits spec and one that quietly loses signal.
When you source FR4, the grade matters — Tg (glass transition temperature) of 130 vs 150-170°C affects reliability through reflow and in hot environments, so specify it rather than accepting generic FR4. A common pitfall is letting a fab substitute a low-Tg material on a board that sees lead-free reflow or high operating temperatures.
Wiki (1)
FAQ
When is FR4 not good enough?
Above roughly 5-10 GHz, FR4's dielectric loss and loosely controlled Dk degrade RF performance. For high-frequency, mmWave, or tight impedance designs, switch to Rogers, PTFE, or another low-loss laminate.
What FR4 Tg should I specify?
Specify high-Tg FR4 (150-170°C) for boards that go through lead-free reflow or run hot; standard Tg 130°C is fine for low-stress consumer boards. Stating it prevents the fab from quietly using cheaper low-Tg material.
How much more does Rogers cost than FR4?
High-frequency laminates like Rogers carry a meaningful cost multiplier over FR4, often several times the bare-board material cost. Many designs use a hybrid stack-up, putting the costly laminate only on the RF layers.
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