무료 온라인 PCB 임피던스 계산기

50Ω은 동축 케이블의 고출력 처리 능력(30Ω)과 최저 신호 감쇠(77Ω) 사이의 역사적 타협점입니다. 전력 전송 효율과 실용적인 제조 공차의 균형을 맞추기 때문에 RF 및 고속 디지털 인터페이스의 표준이 되었습니다.

Dk affects impedance and signal velocity - higher Dk means narrower traces for 50Ω and slower signals. Df determines dielectric loss at high frequencies. For signals above 5Gbps, choose materials with Df < 0.01 (like Megtron 6) instead of standard FR-4 (Df ≈ 0.02).

At high frequencies (>1GHz), current flows mainly on the conductor surface. At 10GHz, skin depth is only 0.66μm in copper. This increases AC resistance and loss. Use smooth (HVLP) copper and consider wider traces for high-frequency designs.

Standard tolerance is ±10% for most digital signals. For critical RF applications, ±5% may be required but increases cost. Always consider that impedance varies with temperature (approximately +0.1%/°C for FR-4) and manufacturing process variations.

Vias add inductance (typically 0.5-1.5nH) and capacitance, causing impedance discontinuity. For high-speed signals: use smaller drill sizes (8-10mil), back-drill stubs, add ground vias nearby, and minimize via count in critical paths.

Use differential pairs for: high-speed serial links (>1Gbps), long traces (>6 inches), noisy environments, or when crossing between boards. Benefits include better noise immunity, lower EMI, and the ability to use lower voltage swings.