1. What is PCB Trace Impedance?

PCB trace impedance is the opposition to alternating current (AC) in a printed circuit board trace. Proper impedance control is crucial for signal integrity in high-speed digital circuits and RF applications.

2. How Does the Calculator Work?

The calculator uses the impedance equation for microstrip traces:

Where:

• \( Z \) — Characteristic impedance (Ω)
• \( \epsilon_r \) — Dielectric constant of the substrate
• \( h \) — Height of dielectric (mm)
• \( w \) — Width of trace (mm)
• \( t \) — Thickness of trace (mm)

Explanation: The equation accounts for the relationship between trace geometry, substrate properties, and resulting impedance.

3. Importance of Impedance Calculation

Details: Proper impedance matching prevents signal reflections, reduces electromagnetic interference (EMI), and ensures reliable high-speed data transmission.

4. Using the Calculator

Tips: Enter dielectric constant, height, trace width and thickness in millimeters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is typical PCB trace impedance?
A: Common values are 50Ω for RF systems and 75Ω for video applications, though specific designs may require different values.

Q2: How accurate is this calculator?
A: This provides a good estimate for surface microstrip traces, but for precise designs use field solvers or manufacturer tools.

Q3: What affects trace impedance most?
A: The three main factors are trace width (inverse relationship), dielectric height (direct relationship), and dielectric constant (inverse relationship).

Q4: When is impedance control needed?
A: For signals with rise times less than ~4× the propagation delay along the trace length (typically >50MHz digital or any RF).

Q5: How to achieve target impedance?
A: Adjust trace width, use different dielectric materials, or modify stackup height. Often requires iteration.