Method for manufacturing a circuit board

A method for manufacturing a circuit board comprising:

• providing a first single-sided board and an insulating structure, wherein the first single-sided board is divided into a first base region and first folding regions connecting opposite sides of the first base region, the insulating structure comprises a first surface and two side surfaces connecting opposite sides of the first surface, the first single-sided board comprises a first metal layer and a first insulating layer stacked on the first metal layer;
• pressing the first single-sided board to the insulating structure with the first insulating layer facing the insulating structure, thereby forming a first laminated board, wherein the first base region is combined with the first surface, the first folding regions are respectively bent to the two side surfaces to be combined with the two side surfaces, the first insulating layer and the insulating structure combine to form a first dielectric layer;
• providing a second single-sided board and a third single-sided board, wherein the second single-sided board is divided into a second base region and second folding regions connecting opposite sides of the second base region, the second single-sided board comprises a second metal layer and a second insulating layer stacked on the second metal layer, the third single-sided board comprises a third metal layer and a third insulating layer stacked on the third metal layer, the third insulating layer comprises a top surface, a bottom surface facing away the top surface, and two side walls opposite to each other, each of the two side walls is connected to the top surface and the bottom surface, the third metal layer is combined with the bottom surface;
• pressing the second single-sided board to the third insulating layer with the second insulating layer facing the third insulating layer, thereby forming a second laminated board, wherein the second base region is combined with the top surface, the second folding regions are respectively bent to the two side walls to be combined with the two side walls, the second insulating layer and the third insulating layer combine to form a second dielectric layer;
• forming a first inner wiring layer by a portion of the second metal layer corresponding to the second base region of the second laminated board, and forming a second inner wiring layer by the third metal layer of the second laminated board, wherein the first inner wiring layer electrically connects to the second inner wiring layer;
• pressing one first laminated board, the second laminated board with the first inner wiring layer and the second inner wiring layer, and another first laminated board in that sequence to form an intermediate structure, wherein the first inner wiring layer is wrapped around by the second dielectric layer and the first dielectric layer of the one first laminated board, the second inner wiring layer is wrapped around by the second dielectric layer and the first dielectric layer of the another first laminated board;
• forming outer wiring layers by a portion of each of the first metal layers of the intermediate structure corresponding to the adjacent first base region, wherein the outer wiring layers electrically connect to the first inner wiring layer and the second inner wiring layer;
• forming covering films on surfaces of the outer wiring layers facing away from the first inner wiring layer, and forming at least one opening on each of the covering films to expose a portion of the outer wiring layers;
• forming electromagnetic interference shielding layers on the covering films, wherein the electromagnetic interference shielding layers infill the at least one opening on each of the covering films to electrically connect to the outer wiring layers.