Enhancing suspension performance with 3-ply laminated load beam

A continuous increase in HDD storage capacity and density has driven suspension technology away from a traditional assembly of monolithic stainless steel. Several features such as dampers, partial etched structure, and microactuator have been incorporated into the suspension for higher resonance and shock performance. This paper focuses on an alternative material to enhance suspension performance via the use of 3 ply laminated load beam with a layer of polyimide sandwiched between two outer layers of stainless steel. The integral component of the three layers modifies structural stiffness and provides improvement in damping property to the load beam resonant frequencies. Ferric chloride etching was used to remove stainless steel outer layers whereas a specially configured reactive ion etcher was utilized to remove an exposed area of undesired polyimide. A reactive ion etching recipe was developed to ensure that the etching process does not affect the surface condition of stainless steel while maintaining a high etch rate and minimizing undercut. Resonance tests demonstrate nearly 2,000 Hz increase in sway frequency. Gram load reliability tests also reveal that the reduction in the number of weldments around the pre-load area minimizes stress distortion associated with each welded joint yielding higher stability in gram-load performance.