Hole connecting layer manufacturing method, circuit board manufacturing method and circuit board

A method of manufacturing a hole connecting layer, the hole connecting layer being arranged between two adjacent sub-boards in at least two sub-boards stacked in sequence from top to bottom, the method comprising:

• attaching a first insulating dielectric layer for pressing and filling glue to a side of one of the sub-boards facing adjacent another sub-board;
• pressing and curing the first insulating dielectric layer located on the sub-board;
• attaching a second insulating dielectric layer for pressing and filling glue on the first insulating dielectric layer after pressing and curing, wherein a side of the second insulating dielectric layer away from the first insulating dielectric layer is configured to be bonded to the adjacent another sub-board;
• manufacturing a first receiving hole in the first insulating dielectric layer, and manufacturing a second receiving hole in the second insulating dielectric layer, wherein the first receiving hole and the second receiving hole are arranged oppositely up and down;
• and filling a conductive medium in the first receiving hole and the second receiving hole to complete the manufacture of the hole connecting layer, wherein each sub-board is electrically connected to the adjacent another sub-board through the conductive medium;
• wherein a diameter of the first receiving hole gradually increases, and a minimum diameter of the first receiving hole is less than a diameter of a conductive via hole of two adjacent sub-boards, a diameter of the second receiving hole gradually increases, a minimum diameter of the second receiving hole is equal to a maximum diameter of the first receiving hole, and a maximum diameter of the second receiving hole is equal to the diameter of the conductive via hole of the two adjacent sub-boards.