A heat sink for dissipating heat from an electric unit, the heat sink including a cooling channel, a first cooling wall arranged on a side of the cooling channel facing the electric unit, and a coolant feed and discharge which are both fluidically connected to the cooling channel configured for supplying and discharging cooling liquid. The heat sink is configured such that the electric unit can be mechanically and thermally connected to the first cooling wall and the heat sink can be releasably secured to a cooling unit including a first fluid port and a second fluid port. The heat sink is further configured such that when the heat sink is secured to the cooling unit, a fluid-tight seal is simultaneously created between a first and second fluidic connection, and the heat sink can be mechanically fixedly connected to the electric unit.