1. What is PCB Propagation Delay?

PCB propagation delay is the time it takes for an electrical signal to travel through a trace on a printed circuit board. It depends on the trace length and the dielectric constant of the PCB material.

2. How Does the Calculator Work?

The calculator uses the propagation delay equation:

Where:

• \( \text{length\_mm} \) — Trace length in millimeters
• \( \epsilon_r \) — Dielectric constant of the PCB material
• \( \text{delay\_ps} \) — Propagation delay in picoseconds

Explanation: The equation shows that delay increases with longer traces and higher dielectric constants. The constant 85 comes from the speed of light in vacuum and unit conversions.

3. Importance of Propagation Delay Calculation

Details: Accurate propagation delay calculation is crucial for high-speed digital design, signal integrity analysis, and timing-critical applications.

4. Using the Calculator

Tips: Enter trace length in millimeters and dielectric constant (typical values: FR4 ≈ 4.3, Rogers materials ≈ 2.2-10.2). All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: Why is propagation delay important?
A: It affects signal timing in high-speed circuits and can cause synchronization issues if not properly accounted for.

Q2: What are typical propagation delay values?
A: For FR4 (ε_r≈4.3), delay is about 67ps/cm. The exact value depends on the specific material.

Q3: How does dielectric constant affect delay?
A: Higher ε_r increases delay as signals travel slower through materials with higher permittivity.

Q4: Does trace width affect propagation delay?
A: Not significantly for typical PCB traces. The primary factors are length and dielectric constant.

Q5: How accurate is this calculation?
A: It provides a good estimate for typical PCB traces, but actual delay may vary slightly due to manufacturing variations.