Is there any special requirements/limitations to how 100Mbps Ethernet conductors can be connected to the PCB?

For instance in the design prompting the question I have a Ethernet connection entering the enclosure via a M12 panel mount (4-pin, D-coded), on the other side of the M12 are 4 conductors - these conductors need to be connected to the PCB holding the Ethernet PHY.

Can I put them into the board via a screw/spring loaded terminal? should I solder directly? Are there special connectors for this purpose that I have not yet stumbled across?


100Mbps Ethernet requires 100Ω differential pairs. This means the connectors and PCB traces need to be matched to 100Ω, if the connector doesn't support differential pairs there will be reflection and attenuation which degrade signal quality and lead to packet loss.

There are many panel mount connectors available such as this which are cheap and easy to use:

enter image description here


  • 2
    \$\begingroup\$ You can even find M12 D-Coded panel mount connectors with a pre-installed Cat5e/Cat6 cable terminated with a RJ45 8P8C connectors, which you would plug into the corresponding PCB 8P8C jack. \$\endgroup\$ – Charles Gervais May 13 at 18:18
  • \$\begingroup\$ If my only option is to connect the 4 conductors from the back of the M12 to the PCB what is the best solution? Directly solder? \$\endgroup\$ – IdTem May 14 at 8:12
  • \$\begingroup\$ Sure, see what kind of rates you get, I'd be interested to know. It's not the contact resistance that's the problem, it's the inductance and capacitance \$\endgroup\$ – Voltage Spike May 15 at 6:36

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.