A heat dissipation device includes a casing forming a receptacle for receiving and retaining a fan module and a finned structure that includes spaced fins to define channels through air flows for primary exchange of heat with the heat dissipation device. The heat dissipation device further includes a thermally conductive surface cover board that is mounted to the casing to at least partly cover an air entrance that is defined in the casing to allow air to be drawn into the casing by the fan module. The surface cover board defines air passages through which air is conducted into the casing. Heat is exchanged with the air when the airflow passes through the surface cover board. Thus, the heat dissipation device features twice heat exchange with airflow and thus enhanced heat removal rate by simply adding the surface cover board to the casing and without significant modification of the existing heat dissipation device.