Basic questions

When do you need to start caring about matched net lengths etc?

100Mz to 200Mz is a good handwavy guide (but not necessarily!)

How much propagation delay is added by PCB traces?

1nS of propagation delay is added to a signal for every 150mm / 6″ of PCB trace.

Dielectric constant

Varies between PCB’s.

FR4 PCB is typically 4 to 4.5

RF applications, DDR4 memory boards, high speed FPGA boards might choose to use a special exotic (expensive) PCB laminate material with a lower dielectric constant, e.g. those available from

We benefit hugely from resources on the web so we decided we should try and give back some of our knowledge and resources to the community by opening up many of our company’s internal notes and libraries through mini sites like this. We hope you find the site helpful.
Please feel free to comment if you can add help to this page or point out issues and solutions you have found, but please note that we do not provide support on this site. If you need help with a problem please use one of the many online forums.


Your email address will not be published.