A heat sink includes a first heat dispensing unit including multiple heat dispensing plates between which chips are clamped. A base board is connected on a top of the first heat dispensing unit and two engaging portions are connected to two ends of the base board. A second heat dispensing unit is fixed on a top of the base board. Two clamps connect the base board to the first heat dispensing unit. The second heat dispensing unit can be a fan, a water-cooling unit or an aluminum extruding member.