There are a number of rigid plate designs on the same side/both sides, but they also support laser drilling of microporous holes, hollow plates, heavy copper up to 30 ounces, sheet welded disc, microwave and RF plates, up to 58 layers, and other technologies.

multilayered rigidity of the highest order
A solution for managing the fullness of heat and signals, using coins and voids
FR4 / polyimide / high-speed / special material
mixed solutions for microwave/ RF applications
HDI micro through hole - blind hole, buried hole, crisscrossing hole and embrasure
capsule with epoxy resin and copper gate
fast rotating support
heat control
heavy copper
controllable resistance
large PCB size