An extruded aluminum heat sink for semiconductor rectifiers and having substantially identical right- and left-hand fin sections joined by an integral transverse horizontal web so that the heat sink is symmetrical about a vertical plane through the web. Each fin section has a relatively thick trunk portion that is tapered in thickness in a direction laterally outwardly from the web. A plurality of integral fins are disposed angularly to the trunk portion and project upwardly and downwardly therefrom so that the tips of the fins define a rectangular transverse configuration. Integral with each fin section adjacent the web is a mounting leg that projects downwardly and has an outwardly turned flange at its lower end for mounting the heat sink on a support such as a copper bus bar.