US-12620413-B2 - Profile shape control for gimbal assembly

US12620413B2US 12620413 B2US12620413 B2US 12620413B2US-12620413-B2

Abstract

A suspension assembly having a load beam that includes a lower surface, proximal end terminating in a hinge, a distal end, and a sag bend between the proximal end and the distal end. A base plate includes a distal end connected to the hinge. A gimbal includes a base portion that includes middle struts where proximal ends of the middle struts are welded to the load beam at locations adjacent the sag bend, and a distal end welded to the distal end of the load beam. When the middle struts are positioned in a neutral position, a gap G between an upper surface of the middle struts and a plane defined by the lower surface of the load beam does not exceed 10 μm for any point along the middle struts that are within a distance D of 0.5 mm from the sag bend.

Inventors

Jeffry S. Bennin
Kuen Chee Ee
Long Zhang

Assignees

MAGNECOMP CORPORATION

Dates

Publication Date: 20260505
Application Date: 20241206

Claims (8)

1 . A suspension assembly comprising: a load beam including a lower surface, a proximal end terminating in a hinge, a distal end, and a sag bend between the proximal end and the distal end; a base plate including a distal end connected to the hinge; and a gimbal comprising: a base portion that includes middle struts, wherein proximal ends of the middle struts are welded to the load beam at locations adjacent the sag bend, and a distal end welded to the distal end of the load beam, wherein when the middle struts are positioned in a neutral position, a gap G between an upper surface of the middle struts and a plane defined by the lower surface of the load beam does not exceed 10 μm for any point along the middle struts that are within a distance D of 0.5 mm from the sag bend.
2 . The suspension assembly of claim 1 , further comprising: a slider mounted to the gimbal.
3 . The suspension assembly of claim 1 , further comprising: channels formed in the lower surface of the load beam, wherein each of the channels extends along and is aligned with one of the middle struts.
4 . The suspension assembly of claim 1 , further comprising: openings formed in the lower surface of the load beam, wherein each of the openings extends along and is aligned with one of the middle struts.
5 . The suspension assembly of claim 4 , wherein: the load beam has a thickness T; the load beam includes rails that extend from edges of the load beam; and the openings extend into the rails by a distance D 1 that is between 1 and 3 times the thickness T of the load beam.
6 . The suspension assembly of claim 1 , wherein the load beam further comprises: holes formed through the load beam adjacent to the sag bend; and tabs extending into the holes; wherein the proximal ends of the middle struts are welded to the tabs.
7 . The suspension assembly of claim 1 , wherein the load beam further comprises: holes formed through the load beam adjacent to the sag bend, wherein the sag bend extends across the holes.
8 . The suspension assembly of claim 1 , wherein the load beam further comprises: holes formed through the load beam adjacent to the sag bend, wherein the sag bend extends along edges of the holes.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of, and priority to, U.S. Provisional Application No. 63/608,576 filed on Dec. 11, 2023, which is hereby incorporated by reference in its entirety. FIELD OF THE INVENTION The present disclosure relates to hard disk drives, and more particularly to a suspension assembly for hard disk drives. BACKGROUND OF THE INVENTION A hard disk drive (HDD) is a non-volatile storage device that stores digitally encoded data on one or more circular disks having magnetic surfaces. In operation, each disk spins rapidly. Data is read from and written to the disk using a read-write head that is positioned over a specific data track or location on the disk surface by a suspension assembly, which in turn is attached to the arm of the head stack assembly, which is rotated by a voice coil motor or actuator integral to the head stack assembly. Keeping the read-write head stable, and aligned with a targeted data track upon the disk surface defines the primary function of the suspension assembly during hard disk drive operation. Optimized suspension assembly design and manufacture can minimize the effects of mechanical, thermal, and other off-track disturbances which can degrade the performance of the hard disk drive. The suspension assembly includes a load beam. In operation, the actuator positions the distal end of the load beam over the desired portion of the disk (e.g., one of the circular tracks on the disk surface). A gimbal assembly (also referred to as a head gimbal assembly or a flexure) is mounted to the distal end of the load beam. The gimbal assembly includes components such as a slider containing the read-write head and PZT devices (piezoelectric devices) that rotate a portion of the gimbal assembly for fine positioning of the slider (as opposed to more coarse positioning of the slider by the actuator). The pressure caused by air viscosity between the slider and the spinning disk causes the slider to hover over (in close proximity to) the surface of the disk. While the load beam is relatively stiff, particularly in the lateral axis, the gimbal assembly is more flexible so that the slider can pitch and roll as it floats over the disk surface in order to maintain its operational distance immediately over the disk surface. Dynamic load conditions within the hard drive sourced from the rotating disk, actuator positioning, enclosure cooling fans, discrete shock loading, etc. can induce large vibrational responses in the drive and suspension assembly system. Resonance is the vibrational response in both frequency and magnitude of a system resulting from external excitation imparted into the system. A mathematical transfer function can be created relating the loading excitation conditions into the systems (or input) to the resonance or vibrational response (or output). The transfer function, termed a Forced Resonance Frequency function, visualizes the location and magnitude of multiple natural or modal frequencies, denoting high energy conditions in the system represented by a collection of wave-like structural motions called mode shapes. The primary mode shapes of the suspension assembly system include load beam first bending, load beam first torsion, load beam second bending, load beam second torsion, and load beam sway etc., which are similarly represented by gimbal assembly mode shapes including gimbal first torsion, gimbal second torsion, gimbal sway, etc. Suspension assembly design factors, such as material types, material thicknesses, part length, mass, rail geometry, spring-rate, gimbal geometry, etc. all play a factor in determining the natural frequencies of a suspension assembly. An optimized suspension assembly design can either minimize the magnitude of the resonance response of each modal frequency, or increase the frequency of the resonance, and in support of optimizing the system performance of the hard disk drive. FIG. 1 illustrates a portion of a head stack assembly 1, while FIGS. 2-3 illustrate a head suspension assembly 2, which includes a load beam 4 terminating at a proximal end with a hinge 6 that is connected to a baseplate 8. A head gimbal assembly 11, containing the slider 14 with the read/write head and gimbal 10, is mounted to the distal end of the load beam 4. The baseplate 8 is connected to an actuator arm 12 of the head stack assembly 1 (FIG. 1), which is rotated by an integral actuator (not shown). As best shown in FIG. 2, head gimbal assembly 11 comprises a gimbal 10 of thin components of layered sheet metal (e.g., stainless steel) and polymer (e.g., polyimide) on which the slider 14 is mounted (e.g., by adhesive). A circuit 16 (i.e., electrical traces) extends along the load beam 4 and head gimbal assembly 11 for electrical signal communication to and from the read/write head and PZT's. The gimbal 10 can be attached to the load beam 4 by three welds 18, 20, 22. These welds can be spot welds between the load beam 4 and th