A microchannel heat exchanger (800) is manufactured by bonding a first sheet (802a) of material and a second sheet (802b) of material in a first connection pattern for integral formation of a core portion (801) and a manifold portion (808) for the first and second sheets (802a, 802b) of material. A third sheet (802c) of material is then superposed on to the second sheet (802b) of material and bonded in a second connection pattern to the second sheet of material for integral formation of the core portion (801) and the manifold portion (808) for the second and third sheets (802b, 802c) of material. The second and third sheets (802b, 802c) of material are bonded without bonding the second sheet (802b) of the material to the first sheet (802a) of material. The core portion (801) and the manifold portion (808) of the heat exchanger (800) are thus integrally created. The interstices between the first, second, and third sheets (802a, 802b, 802c) of material are then expanded to create fluid flow channels (806). This method can also be used to create a heat sink. The bonding method may be a form of laser welding where an opaque sheet absorbs the laser energy and the heat conducts through the top sheet to the sheet immediately below, but does not cause bonding with subsequent sheets below.