A method of joining a metal and a plastic member, a method of joining a CFRP member and a plastic member, a method of joining a metal and a CFRP member through a plastic member, in particular a method of joining members able to join members by a faster joining speed and able to give a joined member excellent in joining strength are provided. A method of joining a metal and a plastic member by overlaying a metal and a plastic member and joining them by firing a laser beam from the plastic member side, comprising overlaying the plastic member and glass through which the laser beam will pass on the metal in that order and firing the laser beam from the plastic member side through the glass at a joining location where the metal and the plastic member are overlaid to join them by a joining speed of 0.5 m to 5.0 m/min.

A laser welding method and system for joining portions of first and second workpieces of thermoplastic material that is partially permeable to a laser beam but absorbs radiation from the laser beam. The first and second workpieces, which are made of material that absorbs radiation from a laser beam, are clamped together. A mask is placed on a first surface of the first workpiece, the first surface being opposite the surface engaging the second workpiece. The mask is impermeable to a laser beam and forms a slot for passing a laser beam to the portion of the first surface of the upper workpiece exposed by the slot, so that heating and melting of the material of the workpieces is limited to the width of the slot. A laser beam is directed onto the slot and moved in a manner to illuminate the slot to melt and join the workpieces.

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.

A welded joint between at least one metal material element and at least one thermoplastic material element is obtained by pressing the elements against each other while applying heat. Contact surfaces of the metal material, which are in contact with the thermoplastic material, are provided with uneven surface portions having a distribution of asperities. With heat applied, the thermoplastic material fills spaces between these asperities and maintains this configuration after subsequent cooling, thereby improving strength of the joint. The uneven surface portions are obtained in a preliminary forming step of the metal material in a press mould, which is configured with a forming surface for generating the uneven surface portions by mechanical deformation and/or with a device for guiding a laser or electron beam. By this technique, hybrid components are obtained made of one or more elements of metal material between which a shaped component of thermoplastic material is interposed.