Method and device for providing a plate heat exchanger (1) having a number of corrugated plates (2). Between the corrugated plates (2) first and second flow channels (7, 8) are arranged, which first flow channels (7), via first inlet openings (11) and first outlet openings (12), are connected essentially parallel to in-going and out-going junction channels (13, 14). The plates (2) are fitted to each other in pairs, forming cells (15) including an inner spacing element (16) welded to and between the plates, and outer spacing elements (17) welded to the plates (2) on the sides of the plates (2) facing away from each other, along at least two of the edge parts (3 6). The cells (15) are stacked against each other and joined together by welding of the outer spacing elements (17), and in that said in-going and out-going junction channels (13, 14) are welded to said first inlet openings (11) and first outlet openings (12) respectively.