FR-4 — density first
Epoxy-glass laminate gives the most routing per unit area: 1–38 layers, 0.075 mm trace and spacing, laser vias down to 0.1 mm and impedance control on any signal layer. Its limits are thermal and dielectric rather than mechanical.
Metal core — heat first
A thin dielectric on an aluminium base conducts heat away from the components. The trade-off is density: the conductive base and thin dielectric make plated through holes and multilayer routing impractical, so these boards are typically single or double sided.
Ceramic — stability first
Alumina and aluminium nitride tolerate higher temperatures and hold their dielectric properties far better than epoxy. They are fired rather than laminated, which changes the design rules: thinner conductors, laser-machined features and mostly single or double-sided circuits.
Choosing between them
Ask what fails first in the application. If it is routing density, stay on FR-4. If it is junction temperature, go metal core. If it is dielectric stability at temperature or at RF, ceramic is the answer.
