A heat sink has a base plate to be clamped against a heat source and one or more heat pipes containing a phase change fluid. Each heat pipe has an elongated tubular evaporator fitted in a channel in the base plate, and a columnar condenser part perpendicular to the base plate forming a structural column for air heat exchange fins. The channel in the base plate is parallel to an edge. An additional channel or ridge is provided, also parallel to the edge, for receiving a clamp or spring clip to urge the base plate against the heat source. The base plate is inexpensively extruded with the parallel channels, ridges, etc., extending across the width of the base plate parallel to the edge. The heat sink has a minimum number of inexpensive parts yet is highly thermally efficient.