Developing phase-shifting micro moire interferometry using phase shifter with rough resolution and by shifting specimen grating

Abstract

In this research, phase shifting method is used to modify PEMI (portable engineering moire interferometer) into micro moire interferometer which can measure displacement field with highly improved sensitivity. Apart from existing micro moire technique, a low cost and less precise translation stage with rough resolution (10 /spl mu/m resolution) is adapted for the phase shifter. Moreover, specimen grating instead of reference grating is phase shifted and again the cost is outstandingly reduced. Least square algorithm and other image processing schemes, such as FFT filtering and fringe enhancement technique, are applied to minimize the errors induced by lowering the cost. To verify the newly constructed micro moire technique, displacement fields of flip chip package with ACA interconnection and wafer level chip size package were measured. In case of flip chip package, microscopic local displacement fields such as ACA layer and underfilled area were obtained with increased sensitivity. For chip size package, displacement field of a solder ball with 400 /spl mu/m diameter was acquired with predominantly elevated sensitivity of 26 nm per fringe.