Abstract: A method for production of a heat exchanger is disclosed, where a powder flux is applied in a process of soldering a heat exchanger core of aluminum. An annular groove is formed in a seat plate. Measures are taken for preventing wetting of the annular groove of the seat plate when sprayed with the water on the preassembled core, such that a non-corrosive flux would not adhere to the annular groove of the seat plate. Water is sprayed in the form of a mist on a preassembled heat exchanger core through plurality of spray nozzles. The annular grooves of the seat plates are thoroughly dried after the application of water for attaining a perfect absence of residual non-corrosive flux in the annular grooves of the seat plates. A non-corrosive flux powder is sprayed onto the preassembled heat exchanger core of aluminum with a powder spray gun. The non-corrosive flux is caused to adhere fast to the portion wetted with the water.