A method of manufacturing a plate heat exchanger, the method comprising the steps of:
(1) Stamping a plate, forming at least one protrusion in the form of a hollow truncated cone in each plate; (2)cleaning the surface of the plate; A plate assembly is formed by continuously mounting a protruding part of a plate into a corresponding opening of an adjacent plate, wherein a specific clearance is maintained between the adjacent surfaces of the plate to form a passage through the heat carrier
(3)Further, a solder paste compound solution based on copper hydrogencarbonate and a nickel salt is prepared, and the plate assembly is immersed in the solder paste compound solution; thereafter, the applied solder paste compound solution is dried. Subsequently, the plate assembly is placed in a high temperature straight-through furnace, a protective medium containing free hydrogen is provided in the high temperature straight-through furnace; two temperature zones are provided along the moving path of the plate assembly, wherein the plate is in the first temperature zone The assembly is annealed and a copper based alloy is used in the second temperature zone to weld and cover the panel assembly. The method is capable of producing a high quality plate heat exchanger which is corrosion resistant and has a seal in the welded area, thereby ensuring a long life.