Analysis of nickel cylindrical bump insertion into aluminium thin film for flip chip applications
This paper investigates the mechanical deformation and the electrical contact resistance of an electroplated Ni micro-cylinder called micro-insert inserted in an Al thin film. A modified nanoindentation apparatus is used to perform the experiments with 6?m, 8.5?m and 12.5?m diameters micro-inserts having the same 5?m height. Mechanical deformation of Ni micro-insert and Al film is described at different maximum loads corresponding to an equivalent stress of 0.8GPa, 1.6GPa and 3.2GPa. At equivalent stress less than 1.6GPa, Ni micro-insert exhibits an elastic deformation while at 3.2GPa it presents an elasticplastic deformation with a large amount of compression and penetration into micro-insert foundation. Visco-plastic deformation of Al film is noticed during hold at all maximum loads. Beside, Al creep parameters are extracted using a combined Maxwell/Kelvin-Voigt phenomenological model. Mechanical results are coupled to electrical contact resistance measurement.
nickel aluminium electrical contact resistance micro-insertion nanoindenter elasticplastic deformation creep