Joining of similar or dissimilar materials with a thickness in the range of micrometers and sub micrometers is of
great interest for a number of applications in, e.g., micro technology, photovoltaic and thin-film technology. A
laser micro joining process using 25 ns long KrF excimer laser pulses for joining thin films and foils is
demonstrated. Metal films of silver, aluminium, copper, molybdenum and titanium with thicknesses down to
500 nm deposited on polyimide substrates were used for bonding to a 12.5 μm thick silver foil. The laser
fluencies used for joining of the foil to the metal films are in the range of 3.5 J/cm2. The laser-induced joints
were investigated by SEM (scanning electron microscope), optical microscopy, and a tensile strength tester.
The shear stress calculated from the tensile force measurements and considering the laser-exposed area to be the
bonding area is 0.5 N/mm2 for silver/aluminium bonds. The tensile strength is not only determined by the bond
between the metal films but also by the adhesion of the thin film to the substrate. Synergetic effects lead to bond
formation comprising of thermal, mechanical, and chemical processes.