The heat exchanger plates have the section shown, with raised sections on the upper and lower faces in which run the flow pipes of one of the fluids. Notches are created on the longitudinal ends to allow these pipes to communicate, their supply and evacuation from a lateral face of the plate, whereas the other fluid enters and leaves via the longitudinal faces. The exchanger is therefore easier to make. The plates are manufactured by extrusions and only machined to create the notches.