Abstract: A heat sink (4) intended for mounting along the edge (3) on an electrical circuit board (1) in order to cool heat-generating components (2) on the circuit board. The heat sink (4) is designed with on the one hand a longitudinal slot (5) for mounting on the circuit board (1) and on the other hand a mounting flange (6) located in substantially the same plane as the slot (5). The design of this mounting flange (6) means that a circuit board (1) provided with a heat sink (4) can be mounted in guide tracks or equivalent in the same manner as a circuit board (1) without heat sink (4). The design of the heat sink (4) also means that the same heat sink (4) can be used for different circuit boards (1) and different components (2).