Rigid Flexible Circuit (rigid-flex circuit board) is a circuit board combined of Rigid circuit board and Flexible circuit board, selectively interconnected by an epoxy pre-preg bonding film, and electronically connected with the plated through hole (PTH) and via, almost like a multi-layer flex circuit.
Areas to be designed as rigid where extra support is needed, and designed as flexible where the corners and areas require extra space and flexibility, so it can enjoy the advantage of both rigid boards such as rigidness & flatness and flexible circuits such as flexibility & bendability. Rigid-flex circuits provide higher component density and better quality control.
Normally, the rigid parts made of FR4 PCB will have one layer to multi-layers, and on outer layers most of the FR4 PCB, will have one layer to multilayers, and on outer layers in most of the time. The vital part is the flexible circuit that connected the Rigid PCB, it can be one layer or multi-layers too. Now Best Technology can manufacture rigid-flex circuits over 50 layers.