Several parameters like slider shape (e.g. crown, camber and twist), Air bearing surface tolerances (e.g. etch depths and rail shapes), suspension parameters (e.g. static attitude and gram load) and HDD tolerances (e.g. disk and suspension stacking and relative orientations of these stacks) affect the slider flying heights. It would be very expensive to control each one of these to get a tight control of the flying height in a high volume manufacturing environment. It is therefore highly desirable to have a method that adjusts the flying height to the desired value after most of the manufacturing steps have been done. This is intended to be one time factory adjustment.

Since flying height depends significantly on the suspension preload (also called Gram Load), an adjust of gram load provides a way of adjusting flying height. The method needs to be precise and non-contaminating. Our research has shown that this may be accomplished using laser radiation.

As explained below the decreasing the gram load involves, annealing the stress in the hinge area of the suspension. The gram load increase is accomplished by the laser induced bending of the hinge. The later method is also used by us for adjusting static attitude of the slider. In this case bending is induced in the flexure of the suspension.

These technologies are expected to play an important role as we approach higher areal densities requiring low flying or contact recording.