Inputs
- Structure type
- Dk
- Dielectric height
- Trace width
- Copper thickness
- Pair spacing
FPC / PCB Engineering Calculator
PCB Impedance Calculator: Microstrip, Stripline & Differential Pair
Estimate PCB impedance for microstrip, stripline and differential pairs from Dk, dielectric height, copper thickness and trace width.
How to use the PCB Impedance Calculator / Impedance Planner
This PCB impedance calculator gives an early routing estimate for line width, dielectric height and Dk. Production controlled impedance should be validated with a field solver and test coupon.
Simplified microstrip / stripline estimate
Formula: Z0 is estimated from dielectric constant, dielectric height, trace width and copper thickness
- Dk: dielectric constant of the material system.
- H: dielectric height between trace and reference plane.
- W: trace width.
- T: copper thickness correction.
Formula Basis
- Formula basis: simplified transmission-line approximations for early microstrip and stripline planning.
- Reference: IPC lists IPC-2141 for controlled impedance circuit boards and high-speed logic design guidance. https://www.ipc.org/ipc-design-standards
- Engineering note: final controlled impedance should be validated by a field solver, factory stack-up and impedance coupon measurement.
Example
With Dk 3.4, 0.05 mm dielectric height, 0.1 mm width and 0.5 oz copper, the tool gives an early single-ended impedance estimate.
Outputs
- Single-ended impedance estimate
- Differential impedance estimate
Engineering Notes
- FPC materials often have different Dk and adhesive effects from rigid FR-4 boards.
- Copper roughness, solder mask, coverlay and adhesive can shift actual impedance.
- Use this planner to narrow the starting point before factory simulation.
Validation Checks
- Controlled impedance target
- Layer reference plane
- Differential pair spacing
- Coupon validation
Related Manufacturing Process
- Stack-up Design - Total thickness, dielectric spacing, symmetry, controlled impedance
- Circuit Layout - Trace width, spacing, bend-zone routing, differential pair spacing
- Electrical Test - Open / short, resistance, voltage drop, impedance coupon
Related Calculators
- PCB Trace Width Current Calculator - Estimate PCB trace width and current capacity from copper thickness and temperature rise.
- Creepage and Clearance / Voltage Spacing Calculator - Estimate creepage and clearance spacing from a user-defined voltage rule before formal standard review.
- PCB Power / Trace Resistance Calculator - Estimate PCB power loss, voltage drop and conductor resistance from trace geometry and current.
FAQ
Why is this called a planner?
Because simplified equations are useful for direction, not final release data. Production impedance needs a validated stack-up and field solver.
Can coverlay affect impedance?
Yes. Coverlay and adhesive can alter the effective dielectric environment, especially for FPC microstrip structures.