1. A method of manufacturing a printed circuit board comprising:a. forming an inner core structure having an inner core circuitry on at least one surface of the inner core structure;
b. applying a coverlay material over the inner core circuitry;
c. forming a printed circuit board stack up, wherein the printed circuit board stack up comprises the inner core structure, a dummy core, one or more non-conductive layers and one or more conductive layers, wherein the dummy core is a metal clad base material, wherein the dummy core is stacked on the coverlay material;
d. laminating the printed circuit board stack up, thereby forming a laminated stack;
e. forming a depth controlled rout from a surface of the laminated stack to the dummy core and around a perimeter of the dummy core, wherein a portion of the laminated stack within the perimeter of the rout and to a depth including the dummy core forms a laminated stack cap;
f. removing the laminated stack cap, thereby exposing the coverlay material and forming a flexible portion of the printed circuit board.