Controlled Impedance PCBs are becoming common nowadays due to the increase in the demand of high speed Video, USB Interface, Ethernet interface and wireless communications. Controlled impedance boards have been manufactured since the early 80s but with the increase in the sophistication of modern electronics the requirement of precision manufacturing with tight tolerance has increased.
We need controlled impedance because the function of a wire or trace is to transfer signal power. Maximum signal power is achieved with matching impedance. The same considerations apply to signal transfer through traces on a PCB. When board traces carry high frequency signals, care must be taken to design traces matching the impedance of the driver and receiver devices. The longer the trace or the higher the frequencies, the higher the need to control the trace impedance.
Which factors determine the impedance in PCBs?
The Following factors determine the impedance of electronic circuits;
- Height of Trace (T1)
- Width of Trace at the top (W2)
- Width of the trace at bottom (W1)
- Distance of other copper features on the same signal layer or different layer (H1)
- Dielectric constant of PCB Material (Er1)
The impedance value calculation can be complex but fortunately for available computer programs PCB design engineers can attain PCB design criteria very quickly.
The most typical impedances we see from our customers are 50, 75 and 100 ohms. The typical tolerance is +/- 10%. However, we have seen some boards with requirements of +/- 5%.
Nujay is your go to when in need of controlled impedance PCBs, we’ve partnered with the experts. Our strategic alliances with PCB factories who produce controlled impedance boards on a regular basis with high quality raw materials and highly controlled processes allow us to be confident in supplying you the best PCBs. We’d love to help build your existing or new PCBs which require controlled Impedance.