A heat exchanger with plates comprising at least a first and second plate (10, 20) arranged parallel across from one another and a covering element, called cover, each of the first and second plates (10, 20) having a fluid circulation circuit (100, 200), the fluid circulation circuit of the first plate being formed in the face of the first plate across from the second plate, the second plate pressing on the first plate, and the fluid circulation circuit of the second plate being formed in the face of the second plate across from the cover, the cover pressing on the second plate, each circulation circuit comprising: - a fluid inlet (E1, E2) and a fluid outlet (S1, S2) separate from one another; - between said inlet (E1, E2) and outlet (S1, S2) of each circulation circuit (100, 200), at least one portion, called ladder, comprising two parallel channels (B1, B2) separated from one another, respectively called first end rung and second end rung, and two other channels, respectively called first upright and second upright, which extend in a direction substantially perpendicular to the rungs (B1, B2), the first upright connecting the ends of the rungs (B1, B2) situated on a same side, called first side, to one another, and the second upright connecting the ends of the rungs situated on the other side, called second side, to one another; and in that each circuit comprises at least one additional ladder, preferably two additional ladders, forming a group of ladders (GECH1) with said ladder, the ladders of said groups (GECH1) being distributed in a direction substantially parallel to the rungs, and in that said first uprights of the ladders of said group of ladders (GECH) are connected to one another, on the side of the group, called third side, defined by said first end rungs, by a channel, called first group channel, which extends in a direction substantially parallel to the rungs, and in that said second uprights of the ladders (ECH1, ECH2) of said group of ladders (GECH) are connected to one another, on the side of the group, called fourth side, defined by said second end rungs, by a channel, called second group channel, which extends in a direction substantially parallel to the rungs; and characterized in that each circuit comprises at least one additional group of ladders (GECH2), and preferably two additional groups of ladders, forming, with said group of ladders (GECH1), a ladder group assembly, the groups of ladders of said assembly being distributed in a direction substantially parallel to the first and second uprights (M1, M2), and in that said first group channels of the groups of ladders of said group assembly are connected to one another by a channel, called first assembly channel, that extends in a direction substantially parallel to the uprights, and in that said second group channels of the groups of ladders of said group assembly are connected to one another by a channel, called second assembly channel, that extends in a direction substantially parallel to the uprights. - a fluid inlet (E1, E2) and a fluid outlet (S1, S2) separate from one another; - between said inlet (E1, E2) and outlet (S1, S2) of each circulation circuit (100, 200), at least one portion, called ladder, comprising two parallel channels (B1, B2) separated from one another, respectively called first end rung and second end rung, and two other channels, respectively called first upright and second upright, which extend in a direction substantially perpendicular to the rungs (B1, B2), the first upright connecting the ends of the rungs (B1, B2) situated on a same side, called first side, to one another, and the second upright connecting the ends of the rungs situated on the other side, called second side, to one another;