Hello ,so far i was looking at PCB as dielectric and copper on both side like a sandwich.
How is it different in the sinkpad technology?
Suppose i want to calculate 50 Ohm impedance calculation with er=4.1 dielectrics.
Thanks.

https://www.luxendi.com/en-gb/sinkp...kPADtm is a thermal,medium to high power LEDs.

 

Did you read the article that you provided the link for? It answers your question.

The SinkPAD material is meant for LED designs, not RF designs.

With that said, if you are wanting to use this SinkPAD, or any other material (like Al Core or Copper Core), you would need to contact the material manufacturer and obtain their datasheet that documents all of the parameters including er (dielectric constant). There is more than er that will affect the 50 ohm calculation.