1. What is the JLCPCB Impedance Formula?

The JLCPCB impedance formula calculates the characteristic impedance of PCB traces based on the dielectric constant, trace dimensions, and substrate height. It's particularly useful for designing controlled impedance traces for high-speed circuits.

2. How Does the Calculator Work?

The calculator uses the JLCPCB impedance formula:

Where:

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

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

3. Importance of Impedance Calculation

Details: Accurate impedance calculation is crucial for high-speed PCB design to prevent signal reflections and ensure proper signal integrity.

4. Using the Calculator

Tips: Enter dielectric constant (typically 4.0-4.5 for FR4), substrate height, trace width, and trace thickness. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the typical impedance range for PCB traces?
A: Common values are 50Ω for single-ended and 100Ω for differential pairs, but specific requirements vary by application.

Q2: How accurate is this formula?
A: It provides a good estimate but for precise requirements, use field solvers or manufacturer-specific calculators.

Q3: What affects PCB trace impedance?
A: Trace width, thickness, substrate height, dielectric constant, and proximity to other traces/planes.

Q4: Can I use this for differential pairs?
A: No, this formula is for single-ended traces. Differential impedance requires additional considerations.

Q5: What's the typical dielectric constant for FR4?
A: Approximately 4.3 at 1GHz, but varies with frequency and specific material composition.