MANUFACTURING – PCB & ELECTRONIC MANUFACTURING CALCULATOR
Pcb Impedance Controlled
A precise tool.
What is the Pcb Impedance Controlled & How does it work?
Controlled impedance traces ensure signal integrity at high frequencies by keeping the characteristic impedance constant along the route.
For a typical microstrip on a FRβ4 substrate the characteristic impedance can be approximated by the quasiβstatic formula:
Z_0 \approx \frac{87}{\sqrt{\varepsilon_r+1.41}} \ln\left(\frac{5.98h}{0.8w + t}\right)
Z0 = characteristic impedance (Ξ©)
h = dielectric thickness (mm)
w = trace width (mm)
t = copper thickness (mm)
\varepsilon_r = relative dielectric constant
h = dielectric thickness (mm)
w = trace width (mm)
t = copper thickness (mm)
\varepsilon_r = relative dielectric constant
Designers adjust the trace width, dielectric thickness, and copper thickness to meet the target impedance while considering manufacturability, loss, and spacing constraints.
Parameters
Result
β
Frequently Asked Questions
What is the purpose of controlled impedance traces on a PCB?
Controlled impedance traces ensure that the characteristic impedance remains constant along the route, maintaining signal integrity at high frequencies.
How do I calculate the characteristic impedance of a microstrip trace?
Use the formula Z0 β 87 / β(Ξ΅r + 1.41) ln(5.98h / (0.8w + t)), where Ξ΅r is the relative dielectric constant, h is the dielectric thickness, w is the trace width, and t is the copper thickness.
What does the term 'quasi-static formula' mean in this context?
The quasi-static formula is an approximation used to calculate the characteristic impedance of a microstrip trace under certain conditions, ignoring high-frequency effects.
Why is the copper thickness (t) important in the impedance calculation?
Copper thickness affects the overall resistance and thus influences the characteristic impedance of the trace.
What is the role of the relative dielectric constant (Ξ΅r) in this formula?
The relative dielectric constant represents how much the substrate material affects the electric field, impacting the calculated impedance.
Can this calculator be used for all types of PCB traces?
This formula is specifically for microstrip traces on FR-4 substrates. Other trace types or materials may require different formulas.
How does the dielectric thickness (h) affect the impedance calculation?
A thicker dielectric results in lower characteristic impedance, while a thinner dielectric increases it.
Results are for informational purposes only and do not constitute professional advice.