Plate heat exchanger comprising - a plurality of modules formed of two metal plates (10, 20), each plate comprising a peripheral zone (19, 29), at least one inlet funnel (11, 21), at least one outlet funnel (12, 22) and an inner serrated zone comprising ridges (13, 23) and cavities (14, 24), said cavities (14, 24) and said peripheral zone being located in a lower plane, said inlet funnels (11, 21) and said outlet funnels (12, 22) raising from said peripheral zone (19, 29) to an upper plane parallel to said lower plane, said ridges (13, 23) being located in an intermediate plane parallel to said planes (P1, P2) and positioned between said planes (P1, P2), two plates (10, 20) constituting a module bearing, on the one hand, at the level of said peripheral zones (19, 29) and on the other hand, at the level of the bearing points of said cavities (14, 24), at least one inlet conduit being formed by said inlet funnels (11, 21) of each plate (10, 20) and at least one outlet conduit being formed by said outlet funnels (12, 22) of each plate (10, 20), the directions of said cavities (14, 24) and of said ridges (13, 23) of each plate (10, 20) forming a first angle β with the circulation direction of the fluids circulating in said exchanger, the directions of said cavities (14, 24) and of said ridges (13, 23) of two adjacent plates (10, 20) forming a second non-zero angle θ between them, said modules being stacked such that two adjacent modules bear at the level of said inlet funnels (11, 21) and said outlet funnels (12, 22), a first non-zero distance separating said ridges (13, 23) of said two adjacent plates (10, 20) of two adjacent modules, - a casing equipped with walls inside which are housed said modules, an inlet and an outlet of said exchanger being arranged in said casing, - a first cavity constituted by the inner space of each module, a first fluid being able to circulate in said first cavities between each inlet conduit and each outlet conduit, - a second cavity constituted by the space located between two adjacent modules and by the space between each extreme module and a wall of said casing, a second fluid being able to circulate in said second cavities between an inlet and an outlet of said exchanger, and - a third cavity constituted by the space located between said peripheral zones (19, 29) of said modules and said walls, characterised in that a flexible zone is integrated around each inlet funnel (11, 21) or each outlet funnel (12, 22), said flexible zone comprising at least one radial wave starting on said upper plane and being between said upper plane and said lower plane. - a plurality of modules formed of two metal plates (10, 20), each plate comprising a peripheral zone (19, 29), at least one inlet funnel (11, 21), at least one outlet funnel (12, 22) and an inner serrated zone comprising ridges (13, 23) and cavities (14, 24), said cavities (14, 24) and said peripheral zone being located in a lower plane, said inlet funnels (11, 21) and said outlet funnels (12, 22) raising from said peripheral zone (19, 29) to an upper plane parallel to said lower plane, said ridges (13, 23) being located in an intermediate plane parallel to said planes (P1, P2) and positioned between said planes (P1, P2), two plates (10, 20) constituting a module bearing, on the one hand, at the level of said peripheral zones (19, 29) and on the other hand, at the level of the bearing points of said cavities (14, 24), at least one inlet conduit being formed by said inlet funnels (11, 21) of each plate (10, 20) and at least one outlet conduit being formed by said outlet funnels (12, 22) of each plate (10, 20), the directions of said cavities (14, 24) and of said ridges (13, 23) of each plate (10, 20) forming a first angle β with the circulation direction of the fluids circulating in said exchanger, the directions of said cavities (14, 24) and of said ridges (13, 23) of two adjacent plates (10, 20) forming a second non-zero angle θ between them, said modules being stacked such that two adjacent modules bear at the level of said inlet funnels (11, 21) and said outlet funnels (12, 22), a first non-zero distance separating said ridges (13, 23) of said two adjacent plates (10, 20) of two adjacent modules, - a casing equipped with walls inside which are housed said modules, an inlet and an outlet of said exchanger being arranged in said casing, - a first cavity constituted by the inner space of each module, a first fluid being able to circulate in said first cavities between each inlet conduit and each outlet conduit, - a second cavity constituted by the space located between two adjacent modules and by the space between each extreme module and a wall of said casing, a second fluid being able to circulate in said second cavities between an inlet and an outlet of said exchanger, and - a third cavity constituted by the space located between said peripheral zones (19, 29) of said modules and said walls,