Abstract: A composite board for heat dissipation, comprises two or three or more flat boards connected together through welding/bonding. There are multiple pipes formed between the flat boards for the heat dissipation liquid passing through. The heat dissipation liquid is controlled by a water pump. The electronic elements that generate heat contact the composite board directly or indirectly. A circuit is formed on at least one of the surfaces of the composite board, and the electronic elements are welded to the circuit. Thus, the heat in the case and the circuit board used in a computer, especially a notebook computer, may be dissipated more efficiently, available spaces may be increased, and the heat dissipation of airflow may be facilitated.