To improve coolant sealing or reduce the risks in the event of leakage for an electronic unit, e.g. an engine control unit, containing electric and/or electronic components which are disposed on an upper side of a thermally conductive electronic base plate and thermally coupled to the base plate, the base plate in turn being thermally coupled to a coolant passage, there is provided a particular configuration and arrangement of the components delimiting a coolant passage. Advantageously, the underside of the base plate can come into direct contact with a coolant (“direct cooling”). By making a ridge running in an annularly closed manner and being formed in one-piece with the base plate, coolant escaping from the coolant passage is prevented from passing directly to the underside of the base plate. Accordingly, the coolant passage may be sealed by a “double sealing arrangement” on the underside of the base plate.