The friction stir welding is a process which made improvement in the light construction industries. The application of this new process lies in the capacity to assemble alloys of aluminium and more obviously with alloys which are not easily weldable alloys by the traditional processes. In our study, we centered the tests on the description of the significant parameters of process FSSW (friction stir spot welding) which will be at the origin of the realization of the weld bead. This experimental approach let us notice that the shape of the tool and in particular the pawn has a great influence on the mechanical resistance of the joint of welding. This is because of the heat gradients and mechanical undergone by material during welding. The importance of these phenomena depends on the same time on the nature of material and the choice on the parameters (geometry, positioning, tool rotating, penetration depth and the force applied of the pin and the shoulder).