A method includes providing a first metal sheet and a second metal sheet, printing a plurality of channels on the first metal sheet, bonding the first metal sheet and the second metal sheet to each other to obtain a fin body, bending a first portion of the fin body to be transverse to a second portion of the fin body, separating the first metal sheet and the second metal sheet from each other to form the plurality of channels, introducing working fluid in the plurality of channels, and sealing the first metal sheet and the second metal sheet.