Patent attributes
A method of measuring a thickness of a ball bonded to a pad is disclosed. The method includes: taking an image of the pad and the ball at each step position through an image taking means being shifted in a vertical direction at predetermined step intervals; obtaining luminance variations at an edge portion of the pad in each taken image to determine an in-focus height of the pad based on an image taking height position at which the taken image has the largest luminance variation at the edge portion of the pad; obtaining luminance variations on an upper surface of the ball in each taken image to determine an in-focus height of the upper surface of the ball based on an image taking height position at which the taken image has the largest luminance variation on the upper surface of the ball; and calculating the thickness of the ball by finding a difference between the obtained in-focus heights of the pad and the upper surface of the ball.
