Is dielectric constant of prepreg same to that of core in PCB?

Thread Starter

Dong-gyu Jang

Joined Jun 26, 2015

My PCB is stacked layer - core (doubled-side PCB) - stacked layer so 4 layers. There is prepreg between 1st layer and 2nd layer (also between 3rd and 4th layer).

I know dielectric constant of core which is normally 4.6 If it is FR-4. However, what is dielectric constant of prepreg?

My ground plane is 2nd layer so knowledge of this is important to make impedance-matched microstrip.

Some article said it is same to the core but is it normally true?