The invention relates to a method for producing a heat exchanger, wherein at least one microchannel, placed within a plate having an upper face and a lower face and precisely arranged between said upper face and lower face is obtained by making a groove on the upper face of the plate, said groove extending between an open extremity facing on the upper face and a blind extremity placed inside the plate, and machining the blind extremity of the groove to create a volume of a suitable size to house a tube inserted in the microchannel, said tube being fixed inside the microchannel by generating an interference between the tube and the microchannel. The invention relates also to a heat exchanger obtained by such method.