Fine actuator reaction force cancellation flexible suspension

Abstract

To provide a high-precision hard disk drive suspension assembly for a surface density increase.SOLUTION: A suspension assembly 300 includes a carriage from which multiple arms extend, where the arms include an outer arm 302 at each end of the carriage; and inner arms between the outer arms, such that each inner arm carries two suspension assemblies and each outer arm carries only one suspension assembly coupled with an inner side of the outer arm, with each suspension assembly including a corresponding fine actuator 310 and a counter-suspension assembly coupled to an outer side of each outer arm, where each counter-suspension assembly includes a structurally flexible dummy load beam having a mass distribution and a stiffness distribution configured to mitigate multiple structural dynamics modes of the operating suspension assembly coupled to the inner side of the outer arm.SELECTED DRAWING: Figure 3A

Description

[Technical Field]

[0001] Embodiments of the present invention may relate generally to hard disk drives, and more particularly to a flexible suspension assembly for precision actuator reaction force cancellation. [Background technology]

[0002] A hard disk drive (HDD) is a non-volatile storage device that stores digitally encoded data on one or more circular disks with magnetic surfaces housed in a protective enclosure. When an HDD is in operation, each magnetic-recording disk is rapidly spun by a spindle system. Data is read from and written to the magnetic-recording disk using a read-write head (or "transducer") positioned over specific locations on the disk by an actuator. The read-write head uses a magnetic field to write data to and read data from the surface of the magnetic-recording disk. The write head functions by generating a magnetic field using current flowing through the write head's coil. Electrical pulses are sent to the write head with different patterns of positive and negative current. The current in the write head's coil generates a localized magnetic field across the gap between the head and the magnetic disk, which in turn magnetizes small areas on the recording medium.

[0003] HDDs generally include at least one head gimbal assembly (HGA), which houses the read / write transducers (or "heads"), including a suspension assembly and corresponding head sliders mounted thereon. Each slider is attached to the free end of the suspension assembly, which is cantilevered from a rigid arm of an actuator. Several actuator arms may be combined to form a single movable unit, typically a head stack assembly (HSA) with a rotating pivot bearing system. A conventional HDD suspension assembly typically includes a relatively rigid load beam with a mounting plate at its proximal end that is attached to an actuator arm, the free end of which carries a flexure (or "gimbal" or "gimbal flexure") that supports the slider and its read-write head. A flexible "hinge" is effectively located between the mount plate and the working end of the load beam in the vertical bending direction (perpendicular to the disk surface). The hinge allows the load beam to suspend and load the slider and read-write head toward the rotating disk surface. The function of the flexure, in turn, is to provide gimbal support for the slider so that it can rock (i.e., gimbal) back and forth to adjust its orientation.

[0004] Increases in areal density (a measure of the number of information bits that can be stored in a given area of ​​the disk surface) have led to the necessary development and implementation of secondary and even tertiary actuators (commonly referred to as "precision actuators") for improved head positioning through relatively fine positioning, in addition to primary voice coil motor (VCM) actuators, which provide relatively coarse positioning. Some HDDs use milli-actuator or micro-actuator designs to provide second-stage and / or third-stage actuation of the recording head to enable more accurate positioning of the head relative to the recording track. A milli-actuator may be broadly classified as an actuator that moves the entire front end of the suspension, e.g., the load beam, flexure, and slider, and is typically used as a second-stage actuator. A micro-actuator (or "microactuator") may be broadly classified as an actuator that moves (e.g., rotates) only the slider, either moving the slider relative to the suspension and load beam or moving only the read-write element relative to the slider body. A microactuator may be used in combination with only a first-stage actuator (e.g., a VCM) or in combination with a first-stage actuator and a second-stage actuator (e.g., a milli-actuator) for more precise head positioning. Unless otherwise indicated, the terms "microactuator," "milli-actuator," "secondary actuator," "tertiary actuator," "dual stage actuator," "fine actuator," and the like, as used herein, refer to a relatively fine positioning actuator (e.g., technically either secondary or tertiary) used in combination with a primary relatively coarse positioning actuator, such as a VCM actuator in the context of an HDD.Piezoelectric (PZT) based transducers and capacitive micromachined transducers are two types of precision actuators that have been developed for use with HDD sliders.

[0005] Any approach described in this section is an approach that could be pursued, but not necessarily a method that has been previously conceived or pursued. Thus, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section. [Brief explanation of the drawings]

[0006] Embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements and in which: [Figure 1] 1 is a plan view illustrating a hard disk drive according to an embodiment. [Figure 2] FIG. 1 is a perspective view illustrating an actuator assembly according to an embodiment. [Figure 3A] 1 is a top view illustrating a hard disk drive suspension assembly coupled to an inner arm according to an embodiment. FIG. [Figure 3B] FIG. 2 is a top view illustrating an opposed suspension assembly for a hard disk drive coupled to an outer arm according to an embodiment. [Figure 3C] 3B is a top view illustrating the suspension assembly of FIG. 3A and the opposing suspension assembly of FIG. 3B mounted on a shared arm, according to an embodiment. [Figure 4A] 1 is a graph illustrating an example frequency response function including a single conventional suspension assembly and a mirror suspension assembly on a shared arm, according to an embodiment. [Figure 4B]1 is a graph illustrating an example frequency response function including a single conventional suspension assembly and an opposed suspension assembly on a shared arm, according to an embodiment. [Figure 4C] 1 is a graph illustrating an example frequency response function including a single conventional suspension assembly and an opposed suspension assembly, according to an embodiment. [Figure 4D] 1 is a graph illustrating an example frequency response function including a single conventional suspension assembly and an opposed suspension assembly on a shared arm, according to an embodiment. [Figure 5A] FIG. 1 is a top view illustrating a first exemplary opposed suspension assembly, according to an embodiment. [Figure 5B] FIG. 10 is a plan view illustrating a second exemplary opposed suspension assembly, according to an embodiment. [Figure 5C] FIG. 10 is a plan view illustrating a third exemplary opposed suspension assembly, according to an embodiment. [Figure 5D] FIG. 10 is a plan view illustrating a fourth exemplary opposed suspension assembly, according to an embodiment. [Figure 6] 1 is a cross-sectional side view illustrating an exemplary opposed suspension assembly having a non-uniform thickness, according to an embodiment. [Figure 7] FIG. 1 is a flow diagram illustrating a method of manufacturing a head stack assembly (HSA) according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Generally, a precision actuator reaction force cancellation approach for a suspension assembly of a head gimbal assembly (HGA) for a hard disk drive (HDD) is described. In the following specification, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention described herein. It will be apparent, however, that the embodiments of the invention described herein may be practiced without these specific details. In other instances, well-known structures and devices may be shown in block diagram form in order to avoid unnecessarily obscuring the embodiments of the invention described herein.

[0008] introduction term References herein to "an embodiment," "one embodiment," etc. are intended to mean that the particular feature, structure, or characteristic being described is included in at least one embodiment of the invention. However, instances of such phrases do not necessarily all refer to the same embodiment.

[0009] It will be understood that the term "substantially" describes features that are largely or approximately structured, configured, dimensioned, etc., although manufacturing tolerances and the like may result in situations where, in practice, the structure, configuration, dimensions, etc. are not always or necessarily precisely as described. For example, if one were to describe a structure as "substantially vertical," the term would be assigned its obvious meaning, such that the sidewalls are, for all practical purposes, vertical, but may not be at exactly 90 degrees.

[0010] Terms such as "optimal," "optimize," "minimal," "minimize," "maximal," "maximize," and the like may not have specific values ​​associated with them, but when such terms are used herein, it is intended that one of ordinary skill in the art will understand that such terms include influencing values, parameters, metrics, and the like in a beneficial direction consistent with the entirety of this disclosure. For example, describing something as "minimal" does not require that the value actually be equal to a theoretical minimum (e.g., zero), but should be understood in a practical sense in that the corresponding goal would be to move the value in a beneficial direction toward the theoretical minimum.

[0011] context 2 is a perspective view showing an actuator assembly according to one embodiment. The actuator assembly 200 comprises a carriage 201 (see, for example, carriage 134 in FIG. 1) rotatably coupled to a central pivot shaft (not shown here, see, for example, pivot shaft 148 in FIG. 1) by a pivot bearing assembly (not shown here, see, for example, pivot bearing assembly 152 in FIG. 1) and is pivotally driven by a voice coil motor (VCM), whose voice coil 204 is shown here. Actuator assembly 200 further includes a plurality of actuator arms 206 (see, e.g., arm 132 in FIG. 1), each of which houses a read-write head 210 (see, e.g., read-write head 110a in FIG. 1) and is typically coupled to a suspension assembly 208 (e.g., lead suspension 110c in FIG. 1), which includes a swaged base plate 208a, a load beam 208b (see, e.g., load beam 110d in FIG. 1), and a suspension tail 208c. Each suspension assembly 208 is electrically connected by the suspension tail 208c to a flexible printed circuit (FPC) 212 coupled to carriage 201.

[0012] Recall that in addition to primary voice coil motor (VCM) actuators, which provide relatively coarse positioning, precision actuators have been developed and implemented for improved head positioning through relatively fine positioning. A hard disk drive (HDD) head stack assembly (HSA) typically includes multiple arms. The upper and lower arms of an HSA, also referred to as outer arms, support only one suspension with a head for reading / writing (Read / Write, R / W) data on the media surface. In contrast, the inner arms of an HSA support two suspensions on each arm: one suspension with an upward-facing head for R / W data on the bottom media surface of the upper disk, and the other suspension with a downward-facing head for R / W data on the top media surface of the adjacent lower disk. For suspensions integrated with PZT actuators, it is often beneficial to finely actuate the upper and lower-facing suspensions in opposite directions (out of phase) so that the reaction forces induced on the common arm are canceled. This results in better performance with fewer resonance peaks than in the precision actuator Transfer Function (TF). The Frequency Response Function (FRF), also known as the Frequency Response Function (FRF), is used to represent the dynamic characteristics of a structure in the frequency domain with peaks at its resonant frequencies and the damping and gain of those peaks related to how external forces are applied. This cancellation works for the inner arm, which supports two suspensions, because the reaction forces from the two suspension precision actuators are the same amplitude but out of phase, thus canceling each other. However, there is no counter-suspension to the fine drive for reaction force cancellation for the outer arm, which supports only one suspension.

[0013] Due to the absence of reaction force cancellation on the outer arms, when precision actuators on all suspensions are driven in parallel, the reaction forces from the outer arms respond by generating an extra resonance peak on the inner head. One solution is to use a demultiplexer ("demux") to finely drive the inner arm head separately from the outer arm head; at least one approach is described in U.S. Pat. No. 11,482,254, the entire contents of which are incorporated by reference herein as if fully set forth herein. Such a demux control circuit decouples the inner arm head from the outer arm head, achieving significantly more effective reaction force cancellation for the inner arm head, resulting in better TF. However, the precision actuator TF of the outer head is not as good as the precision actuator TF of the inner head due to the lack of reaction force cancellation in that situation.

[0014] Flexible Opposed Suspension Assembly To address the aforementioned challenges associated with outer head performance, as may be evident in the representation of the corresponding FRFs, according to one embodiment, a counter (e.g., "counter") precision actuator on an opposing suspension (e.g., "dummy" suspension) assembly may be implemented on the outer arm to cancel the reaction forces relative to a single "real" suspension on such arm. The counter precision actuator is operated out of phase with the suspension precision actuator on the same arm, and the structural dynamics of the corresponding opposing suspension are "tuned," e.g., intelligently configured as a flexible structure / component, to match dominant suspension resonant frequencies and achieve optimal reaction force cancellation similar to or close to that of an inner arm with two suspensions.

[0015] 3A is a plan view illustrating a hard disk drive suspension assembly coupled to an inner arm, according to one embodiment. As shown, the suspension assembly 300 is coupled to the inner surface (the underside in this top view) of the arm 302. The suspension assembly 300 typically includes a mount plate 304 swaged to the arm 302, to which a load beam 306 is connected, which is generally coupled to a flexure 308 extending the length of the suspension assembly 300 and terminating in a distal gimbal portion 308g (or "gimbal" or "gimbal flexure") that supports the slider and its read-write head (not visible here; see, e.g., slider 110b and read-write head 110a in FIG. 1). The suspension assembly 300 further includes a precision actuator 310, referred to herein as a milliactuator, configured to move the load beam 306. The precision actuator 310 is generally positioned between and coupled to the mount plate 304 and the load beam 306. For purposes of this description, the suspension assembly 300 is considered to be the "actual" suspension or working or operating suspension.

[0016] 4A is a graph illustrating an example frequency response function including a single conventional suspension assembly and a mirror suspension assembly on a shared arm, according to one embodiment. In this example, the solid function (or signal) 401 represents the FRF of a read-write node on the suspension assembly 300 (with the head) mounted on the arm (see, e.g., arm 302 in FIG. 3A ), characterizing the head off-track response to a voltage input of the precision actuator 310, for example, without any counterbalance or counter suspension on the other side of the shared arm (see, e.g., FIG. 3A ). As a non-limiting example in the context of the approaches, techniques, and embodiments described herein, shown here by function 401 are the following series of peaks: (a) a torsion mode 401a near approximately 6.4 kHz, (b) a whole-arm (flat) sway mode 401b near approximately 8.5 kHz, (c) an end-arm (twist) sway mode 401c near approximately 18.5 kHz, and (d) a twist sway mode 401d near approximately 29 kHz. These peaks are described in more detail below with reference to corresponding opposing suspension assemblies. Here, dashed function (or signal) 402 represents the FRF of a read-write node on suspension assembly 300 with a mirror suspension assembly (with heads) mounted on opposite sides of a shared arm in response to a common voltage input to respective precision actuators, such as precision actuators 310 on both suspensions on the shared arm.

[0017] FIG. 3B is a plan view illustrating an opposed suspension assembly for a hard disk drive coupled to an outer arm, according to one embodiment. As shown, the opposed suspension assembly 320 is coupled to the outer surface (top surface in this plan view) of the arm 302. The opposed suspension assembly 320 typically includes a mount plate 324 swaged to the arm 302, to which is connected a load beam 326 coupled to a flexure 328. Here, the flexure 328 only extends to the load beam 326 near the precision actuator 330 and does not terminate in a distal gimbal portion because the opposed suspension 320 does not support a slider or read-write head. As mentioned above, the opposed suspension assembly 320 further includes a balanced precision actuator 330, referred to herein as a milliactuator, configured to move the load beam 326. The balanced precision actuator 330 is generally positioned between and coupled to the mount plate 324 and the load beam 326. For purposes of this description, the opposed suspension assembly 320 may be considered or referred to as a "dummy" suspension.

[0018] FIG. 3C is a plan view illustrating the suspension assembly of FIG. 3A and the opposed suspension assembly of FIG. 3B mounted on a shared arm, according to one embodiment. See FIGS. 3A-3B for a description of the components of suspension assembly 300 and opposed suspension assembly 320, respectively. FIG. 4B is a graph illustrating an example frequency response function including a single conventional suspension assembly and opposed suspension assemblies on a shared arm, according to one embodiment. In this example, solid function (or signal) 401 again represents the FRF of the read-write node on suspension assembly 300 mounted on an arm (e.g., see arm 302 in FIG. 3A ) and responsive to a voltage input of precision actuator 310. Here, dashed function (or signal) 403 represents the FRF of the read-write node on suspension assembly 300 with opposed suspension assembly 320 mounted on the opposite side of the shared arm (e.g., arm 302 in FIG. 3C ) and responsive to a common voltage of precision actuator 310 and balanced precision actuator 330 ( FIG. 3B ). The control voltage to the precision actuator 310 of the suspension assembly 300 on the outer arm 302 is also applied to the precision actuator 330 of the opposing suspension assembly 320 on the same arm 302. The precision actuator 330 of the opposing suspension assembly 320 is designed to move the opposing suspension assembly 320 in an opposite direction relative to the precision actuator 310 of the suspension assembly 300 on the same arm 302, thereby causing their reaction forces on the arm to be in opposite directions. Therefore, these opposing reaction forces are effectively canceled when the opposing suspension is designed to match the dynamics of the actual suspension (e.g., head). It is noted that multiple structural modes of the (inner) suspension assembly 300 are effectively mitigated or canceled by the use of the (outer) opposing suspension assembly 320, such as whole arm (flat) sway mode 401b, end arm (twist) sway 401c, and twist sway 401d, as shown.Signal 401 exhibits three major peaks (eg, 401b-401d) relative to 30 kHz, whereas signal 403 exhibits only one major peak relative to 30 kHz, eg, about 22 kHz.

[0019] When comparing example signal 403 ( FIG. 4B ) representing the FRF of a read-write node on a suspension assembly 300 having an opposed suspension assembly 320 on the opposite side of the shared arm with signal 402 ( FIG. 4A ) representing the FRF of a read-write node on a suspension assembly 300 having a mirrored suspension assembly on the opposite side of the shared arm, it is visually apparent that signal 403 matches signal 402 relatively closely. However, opposed suspension assembly 320 may be further optimized to more closely match the two structural characteristic functions, as the graphs of FIGS. 4A-4B serve here merely for non-limiting illustrative purposes. Importantly, an opposed suspension (or "balancing" suspension) assembly, such as opposed suspension assembly 320, along with a balanced precision actuator, such as balanced precision actuator 330, operating out of phase with suspension precision actuator 310 on the same arm 302, can be judiciously configured (i.e., "tuned") as a flexible structure / component so that the structural characteristics of opposed suspension assembly 320 can be substantially matched to the dominant resonant frequencies of the corresponding suspension assembly 300 to achieve optimal multi-mode reaction force cancellation / mitigation similar to or close to that of an inner arm having two suspensions. Furthermore, the cost to manufacture an opposed suspension assembly, such as opposed suspension assembly 320, can be significantly lower than a mirror suspension assembly, due at least in part to the absence of relatively expensive read-write heads and gimbal flexures.

[0020] 4C is a graph illustrating an example frequency response function including a single conventional suspension assembly and an opposed suspension assembly, according to one embodiment. Here, the illustrated frequency range extends beyond 30 kHz and exhibits a fourth peak 440 near 40 kHz. In this example, solid line function (or signal) 404 represents the FRF corresponding to a single conventional suspension assembly (with a head) mounted on an arm and responsive to a voltage input of a precision actuator (see, e.g., precision actuator 310 in FIG. 3A ), alternating dashed line function (or signal) 405 represents the FRF corresponding to a single trapezoidal opposed suspension assembly (without a head) mounted on an arm and responsive to a voltage input of a corresponding precision actuator (see, e.g., precision actuator 330 in FIG. 3B ), and fine dashed line function (or signal) 406 represents the FRF corresponding to a single rectangular opposed suspension assembly (without a head) mounted on an arm and responsive to a voltage input of a precision actuator, such as precision actuator 330. FIG. 4C shows that there are four highlighted (i.e., bracketed) peaks 410, 420, 430, and 440 corresponding to the structural characteristics of each respective single suspension assembly, each occurring around the same frequency as the other suspension assemblies.

[0021] 4D is a graph illustrating an example frequency response function including a single conventional suspension assembly and an opposed suspension assembly on a shared arm, according to one embodiment. Again, the illustrated frequency range extends beyond 30 kHz. In this example, the solid line function (or signal) 404 again corresponds to a single conventional suspension assembly mounted on the arm and represents the FRF responsive to the voltage input of precision actuator 310, while the fine dashed line function (or signal) 407 corresponds to a conventional suspension assembly and a rectangular opposed suspension assembly mounted on the shared arm and represents the FRF responsive to the voltage input of each precision actuator (e.g., including a balanced precision opposed actuator, such as precision actuator 330 of FIG. 3B ). FIG. 4D illustrates that while the four aforementioned dominant peaks 410, 420, 430, and 440-40 kHz corresponding to the structural characteristics of a single conventional suspension assembly are present, an exemplary signal 407 representing an FRF corresponding to a conventional suspension assembly 300 with an opposing suspension assembly 320 on the opposite side of the shared arm 302 only results in one dominant peak 450.

[0022] Example of dummy load beam structure In practice, the exact structural configuration of an opposing suspension assembly (e.g., opposing suspension assembly 320 of FIG. 3B ) may vary from implementation to implementation, largely based on the structural characteristics of the corresponding suspension assembly that is the subject of such opposing balancing. According to one or more embodiments, a notable structural attribute that may or should be considered is the distribution of mass and / or stiffness within a given “dummy” load beam (e.g., load beam 326 of FIG. 3B ). Accordingly, opposing suspension assembly 320 may be configured as a flexible structure, rather than a simple rigid mass (that does not deform, or deforms negligibly, under physical forces), designed as an equivalent mass driven by a dummy precision actuator as the mass of the opposing HGA of interest. As a result, opposing suspension assembly 320 may be designed to counteract or mitigate multiple structural modes of the corresponding suspension assembly 300 ( FIG. 3A ) under the force of precision actuator 310 ( FIG. 3A ), rather than just a single (e.g., low-frequency) structural mode / peak. Accordingly, several dummy load beam structural configurations were modeled and analyzed and are presented below as non-limiting example configurations that can be optimized for modal mitigation / cancellation by substantially matching the principal modes of a "real" operating suspension assembly.

[0023] 5A is a plan view illustrating a first exemplary opposed suspension assembly, according to an embodiment. The opposed suspension assembly 500 is coupled to an outer surface of an arm (not shown here; see, for example, arm 302 in FIG. 3B ). The opposed suspension assembly 500 includes a mounting plate 504 to which is connected a rectangular load beam 506 coupled to a flexure 508. Again, because the opposed suspension assembly 500 does not support a slider or read-write head, the flexure 508 extends only to the load beam 506 near a precision actuator 510. For purposes of this description, the opposed suspension assembly 500 may be considered or referred to as a “dummy” suspension including the “dummy” load beam 506. For a rectangular structural body 506a similar to that of the opposed suspension assembly 500, further comprising a rectangular cutout portion 506b from the body 506a, contemplated optimization techniques include, but are not limited to, various adjustments to the length of the body 506a in the longitudinal direction (x-direction along the major axis of the body 506a) and various adjustments to the length of the cutout portion 506b in the longitudinal direction. Similarly, various adjustments to the width of the body 506a and / or the cutout portion 506b in the lateral direction (y-direction along the minor axis of the body 506a) may be applied in optimizing an opposed suspension assembly, such as opposed suspension assembly 500, to match the dominant modes of motion of the corresponding suspension assembly for mode cancellation / mitigation purposes.

[0024] FIG. 5B is a plan view illustrating a second exemplary opposed suspension assembly, according to an embodiment. Opposed suspension assembly 520 is coupled to an outer surface of an arm (not shown here; see, for example, arm 302 in FIG. 3B ). Opposed suspension assembly 520 includes a mount plate 524 to which is connected a trapezoidal load beam 526 coupled to a flexure 528. Again, because opposed suspension assembly 520 does not support a slider or read-write head, flexure 528 extends only to load beam 526 near precision actuator 530. For purposes of this description, opposed suspension assembly 520 may be considered or referred to as a “dummy” suspension including “dummy” load beam 526. For a trapezoidal structural body 526a similar to that of opposed suspension assembly 520, further comprising a large trapezoidal cutout 526b from the body 526a, contemplated optimization techniques include, but are not limited to, various adjustments to the length of the body 526a in the longitudinal direction (x-direction along the long axis of the body 526a) and various adjustments to the length of the cutout 526b in the longitudinal direction. Similarly, various adjustments to the width of the body 526a in the lateral direction (y-direction along the short axis of the body 526a), the relationship between the base and legs of the body 506a, the width of the cutout 526b, and / or the relationship between the base and legs of the cutout 526b may be applied in optimizing an opposed suspension assembly, such as opposed suspension assembly 520, to match the dominant modes of operation of the corresponding suspension assembly for mode cancellation / mitigation purposes.

[0025] 5C is a plan view illustrating a third exemplary opposed suspension assembly, according to an embodiment. Opposed suspension assembly 540 is coupled to an outer surface of an arm (not shown here; see, for example, arm 302 in FIG. 3B ). Opposed suspension assembly 540 includes a mounting plate 544 to which is connected a rectangular load beam 546 coupled to a flexure 548. Again, because opposed suspension assembly 540 does not support a slider or read-write head, flexure 548 extends only to load beam 546 near precision actuator 550. For purposes of this description, opposed suspension assembly 540 may be considered or referred to as a “dummy” suspension including “dummy” load beam 546. For a rectangular structural body 546a similar to that of opposed suspension assembly 540, further comprising a trapezoidal cutout portion 546b from the body 546a, contemplated optimization techniques include, but are not limited to, various adjustments to the length of the body 546a in the longitudinal direction (x-direction along the major axis of the body 546a) and various adjustments to the length of the cutout portion 546b in the longitudinal direction. Similarly, various adjustments to the width of the body 546a in the lateral direction (y-direction along the minor axis of the body 546a) and / or the relationship between the base and legs of the cutout portion 546b may be applied in optimizing an opposed suspension assembly, such as opposed suspension assembly 540, to match the principal modes of motion of the corresponding suspension assembly for mode cancellation / mitigation purposes.

[0026] 5D is a plan view illustrating a fourth exemplary opposed suspension assembly, according to an embodiment. Opposed suspension assembly 560 is coupled to an outer surface of an arm (not shown here; see, for example, arm 302 in FIG. 3B ). Opposed suspension assembly 560 includes a mounting plate 564 to which is connected a rectangular load beam 566 coupled to a flexure 568. Again, because opposed suspension assembly 560 does not support a slider or read-write head, flexure 568 extends only to load beam 566 near precision actuator 570. For purposes of this description, opposed suspension assembly 560 may be considered or referred to as a “dummy” suspension including “dummy” load beam 566. For a rectangular structural body 566a similar to that of opposed suspension assembly 560, further comprising a cutout 566b from at least one side of the body 556a, contemplated optimization techniques include, but are not limited to, various adjustments to the length of the body 566a in the longitudinal direction (x-direction along the major axis of the body 566a) and various adjustments to the length of the cutout(s) 566b in the longitudinal direction. Similarly, various adjustments to the width of the body 566a and / or the cutout(s) 566b in the lateral direction (y-direction along the minor axis of the body 566a) may be applied in optimizing an opposed suspension assembly, such as opposed suspension assembly 560, to match the principal modes of motion of the corresponding suspension assembly for mode cancellation / mitigation purposes.

[0027] FIG. 6 is a cross-sectional side view illustrating an exemplary opposed suspension assembly having a non-uniform thickness, according to one embodiment. For the location of section 6-6, refer to FIG. 5A. The opposed suspension assembly 600 is coupled (not shown) to an outer surface of an arm (not shown). The opposed suspension assembly 600 typically includes a mounting plate 604 swaged to the arm, to which a load beam 606 is connected. The opposed suspension assembly 600 further includes a precision actuator (not visible), referred to herein as a milliactuator, configured to move the load beam 606. For purposes of this description, the opposed suspension assembly 600 may be considered or referred to as a "dummy" suspension. According to at least the embodiments shown herein, the opposed suspension assembly 600 includes a load beam 606 having a non-uniform thickness. According to a related embodiment, an opposed suspension assembly 600 includes a load beam 606 having a first thickness t1 at a first portion p1 that structurally interfaces with a mount plate 604 and a different second thickness t2 at a second portion p2 that extends away from the mount plate 604. This embodiment illustrates that in addition to varying the configuration of structural features (e.g., body, cutout, notch) and shapes (e.g., rectangular, trapezoidal) in the x-direction (longitudinal) and y-directions (lateral), as described with reference to FIGS. 5A-5D , the thickness of the load beam 606 can additionally and alternatively be varied in height (z-direction) to optimize opposed suspension assemblies, such as opposed suspension assembly 600, to match the dominant modes of motion of the corresponding suspension assembly for mode cancellation / mitigation purposes. For illustrative purposes, the first thickness t1 at the first portion p1 of the load beam 606 that structurally interfaces with the mount plate 604 is less than the second thickness t2 at the second portion p2 of the load beam 606 that extends away from the mount plate 604.However, the locations where the load beam 606 may transition from one thickness to another, as well as the number of different thicknesses and thickness transitions, may vary from implementation to implementation, based primarily on the structural characteristics of the corresponding suspension assembly that is subject to multi-mode counterbalance. In FIG. 6, the second portion p2 of the load beam 606 is thicker from both the top and bottom surfaces (e.g., in both the upward and downward directions) than the first portion p1. Alternatively, the second portion p2 of the load beam 606 may be thicker only from the top or bottom surface (e.g., in either the upward or downward direction) relative to p1, such as for ease of manufacturing.

[0028] Method for manufacturing a head gimbal assembly 7 is a flow diagram illustrating a method of manufacturing a head stack assembly (HSA) according to one embodiment. The head stack assembly (HSA) assembled, manufactured, and produced according to the method of FIG. 7 is designed, configured, and intended for implementation in a hard disk drive (HDD) (see, for example, HDD 100 in FIG. 1).

[0029] At least one suspension assembly including a corresponding precision actuator is coupled to each of a plurality of arms extending from the carriage in block 702. For example, a suspension assembly such as suspension assembly 300 (FIGS. 3A and 3C) including a corresponding precision actuator 310 is coupled to each of a plurality of arms 302 (FIGS. 3A and 3C) extending from the carriage (see, for example, carriage 201 in FIG. 2).

[0030] At block 704, an opposing suspension assembly is coupled to each arm on the outer end of the carriage, the opposing suspension assembly having a precision actuator and a mass and stiffness distribution configured to mitigate multiple structural characteristic modes of a corresponding suspension assembly coupled to the same arm. For example, an opposing suspension assembly such as opposing suspension assembly 320 (FIGS. 3B-3C), 500 (FIGS. 5A), 520 (FIGS. 5B), 540 (FIGS. 5C), or 560 (FIG. 5D) with a corresponding precision actuator 330 (FIG. 3B), 510 (FIGS. 5A), 530 (FIGS. 5B), 550 (FIGS. 5C), or 570 (FIGS. 5D) is coupled to each of the multiple arms 302 (FIGS. 3A-3C).

[0031] In view of the embodiments described herein, an opposed suspension (or "balanced" suspension) assembly may be judiciously configured (i.e., "tuned") as a flexible structure / component, with a balanced precision actuator operating out of phase with a corresponding "real" suspension precision actuator on the same arm, so that the structural characteristics of the opposed suspension assembly may be substantially matched with multiple dominant resonant frequencies of the corresponding suspension assembly to achieve optimal reaction force cancellation / mitigation of multiple structural characteristic modes. The cost to manufacture an opposed suspension assembly may be significantly lower than a mirror suspension assembly, due at least in part to the absence of relatively expensive read-write heads and gimbal flexures.

[0032] Illustrative physical description of the operating context Embodiments may be used in the context of a digital data storage device (DSD), such as a hard disk drive (HDD). Accordingly, according to embodiments, a plan view illustrating a conventional HDD 100 is shown in FIG. 1 to help describe how a conventional HDD typically operates.

[0033] 1 shows the functional layout of components of a HDD 100, including a slider 110b that includes a magnetic read-write head 110a. Collectively, the slider 110b and head 110a may be referred to as a head-slider. The HDD 100 includes at least one head gimbal assembly (HGA) 110 that includes the head-slider, a lead suspension 110c typically attached to the head-slider via a flexure, and a load beam 110d attached to the lead suspension 110c. The HDD 100 also includes at least one recording medium 120 rotatably mounted on a spindle 124 and a drive motor (not visible) attached to the spindle 124 for rotating the medium 120. The read-write head 110a, which may also be referred to as a transducer, includes a write element and a read element for writing and reading information stored on the medium 120 of the HDD 100, respectively. The medium 120 or multiple disk media may be secured to the spindle 124 with a disk clamp 128 .

[0034] HDD 100 further includes an arm 132 attached to HGA 110, a carriage 134, and a voice coil motor (VCM) including an armature 136 including a voice coil 140 attached to carriage 134, and a stator 144 including a voice coil magnet (not shown). The VCM's armature 136 is attached to carriage 134 and configured to move arm 132 and HGA 110 to access portions of media 120, all collectively mounted on a pivot shaft 148 with an intervening pivot bearing assembly 152. In HDDs with multiple disks, carriage 134 may be referred to as an "E-block" or comb because the carriage is arranged to carry an array of interlocking arms that give the carriage the appearance of a comb.

[0035] An assembly comprising a head gimbal assembly (e.g., HGA 110), including a flexure to which a head slider is coupled, an actuator arm (e.g., arm 132) and / or load beam to which the flexure is coupled, and an actuator (e.g., VCM) to which the actuator arm is coupled, may be collectively referred to as a head stack assembly (HSA). However, an HSA may include more or fewer components than those listed. For example, an HSA may refer to an assembly that further includes electrical interconnection components. In general, an HSA is an assembly configured to move a head slider to access portions of medium 120 for read and write operations.

[0036] With further reference to FIG. 1 , electrical signals including write signals to and read signals from head 110 a (e.g., current to the voice coil 140 of the VCM) are transmitted by a Flexible Cable Assembly (FCA) 156 (or “flex cable,” or “Flexible Printed Circuit” (FPC)). The interconnection between flex cable 156 and head 110 a may include an Arm-Electronics (AE) module 160, which may have an on-board preamplifier for the read signal and other read channel and write channel electronic components. AE module 160 may be mounted to carriage 134, as shown. Flex cable 156 may, in some configurations, be coupled to an electrical connector block 164, which provides electrical communication through an electrical feedthrough provided by HDD housing 168. The HDD housing 168 (or "enclosure base," or "baseplate," or simply "base"), together with the HDD cover, provides a semi-sealed (or, in some configurations, hermetically sealed) protective enclosure for the information storage components of the HDD 100.

[0037] A disk controller including a digital signal processor (DSP) and other electronic components including servo electronics provide electrical signals to the drive motor, the voice coil 140 of the VCM, and the head 110a of the HGA 110. The electrical signals provided to the drive motor enable the drive motor to rotate, providing torque to the spindle 124, which is then transmitted to the medium 120 attached to the spindle 124. As a result, the medium 120 rotates in a direction 172. The rotating medium 120 forms a cushion of air that acts as an air bearing on which the air-bearing surface (ABS) of the slider 110b rides so that the slider 110b flies above the surface of the medium 120 without contacting the thin magnetic recording layer on which the information is recorded. Similarly, in HDDs utilizing a lighter-than-air gas such as helium, as a non-limiting example, the rotating media 120 creates a cushion of gas on which the slider 110b rides, acting as a gas or fluid bearing.

[0038] An electrical signal provided to the voice coil 140 of the VCM enables the head 110a of the HGA 110 to access tracks 176 where information is to be recorded. Thus, the armature 136 of the VCM swings through an arc 180, enabling the head 110a of the HGA 110 to access various tracks on the medium 120. Information is stored on the medium 120 in multiple radially nested tracks arranged in sectors on the medium 120, such as sector 184. Correspondingly, each track is made up of multiple sectored track portions (or "track sectors"), such as sectored track portion 188. Each sectored track portion 188 may include the recorded information and a header that includes error correction code information and a servo burst signal pattern, such as an ABCD servo burst signal pattern, that identifies the track 176. When accessing track 176, the read element of head 110a of HGA 110 reads the servo burst signal pattern, which provides a position-error-signal (PES) to the servo electronics, which in turn controls the electrical signal provided to the voice coil 140 of the VCM, thereby enabling head 110a to follow track 176. Upon locating track 176 and identifying a particular sectored track portion 188, head 110a reads information from track 176 or writes information to track 176 in response to instructions received by a disk controller from an external agent, e.g., a microprocessor in a computer system.

[0039] The electronic architecture of an HDD includes numerous electronic components, such as a hard disk controller (HDC), interface controller, arm electronics module, data channel, motor drivers, servo processor, buffer memory, etc., each performing its own respective function for the operation of the HDD. Two or more of these components may be combined on a single integrated circuit board, referred to as a "system on a chip" ("SOC"). Some, if not all, of these electronic components are typically located on a printed circuit board that is coupled to the bottom side of the HDD, such as HDD housing 168.

[0040] References herein to hard disk drives, such as HDD 100 shown and described with reference to FIG. 1, may encompass information storage devices sometimes referred to as “hybrid drives.” A hybrid drive generally refers to a storage device that has the functionality of both a traditional HDD (see, e.g., HDD 100) combined with a solid-state storage device (SSD), which uses non-volatile memory such as electrically erasable and programmable flash or other solid-state (e.g., integrated circuit) memory. Because the operation, management, and control of different types of storage media are typically different, the solid-state portion of a hybrid drive may include its own corresponding controller functionality, or the controller functionality may be integrated into a single controller along with the HDD functionality. A hybrid drive may be designed and configured to operate and utilize the solid-state portion in several ways, such as by using the solid-state memory as cache memory to store frequently accessed data, to store I / O (Input / Output) intensive data, etc., as non-limiting examples. Additionally, a hybrid drive may be essentially designed and configured as two storage devices in a single enclosure, i.e., a traditional HDD and an SSD, with either one or multiple interfaces for host connection.

[0041] Extensions and Substitutes In the foregoing description, embodiments of the present invention have been described with reference to numerous specific details that may vary from implementation to implementation. Accordingly, various modifications and changes may be made without departing from the broader spirit and scope of the embodiments. Thus, the sole and exclusive reference to the invention, and what applicants intend to be the invention, is the set of claims issuing from this application, and the particular form from which such claims originate, including any subsequent amendments. The definitions expressly set forth herein for terms contained in such claims shall control the meaning of those terms as used in the claims. Therefore, no limitation, element, property, feature, advantage, or attribute not expressly recited in a claim should in any way limit the scope of such claim. The specification and drawings are hereby to be regarded in an illustrative, and not restrictive, sense.

[0042] It should be noted that certain process steps may be described herein in a particular order, and alphabetic and alphanumeric symbols may be used to identify certain steps. Unless otherwise specified herein, embodiments are not necessarily limited to any particular order of performing such steps. In particular, symbols are used merely for convenient identification of steps, and are not intended to specify or require a particular order of performing such steps.

Claims

1. A hard disk drive (HDD), a disk stack including a plurality of disk media rotatably mounted on a spindle; a plurality of head sliders, each housing a read-write transducer configured to read from and write to disk media of the plurality of disk media; a first stage actuator configured to move the plurality of head sliders to access portions of the plurality of disk media; a head stack assembly (HSA) coupled to the actuator, the HSA comprising: a carriage coupled to the actuator; a plurality of arms coupled to the carriage, the plurality of arms including an outer arm at each end of the disk stack and one or more inner arms between the outer arms, each inner arm supporting two suspension assemblies, each outer arm supporting one suspension assembly, each suspension assembly including a corresponding precision actuator configured to move a corresponding head slider of the plurality of head sliders to access a corresponding portion of the disk media; a head stack assembly (HSA) including an opposing suspension assembly coupled to a side of at least one outer arm that faces a corresponding suspension assembly, the opposing suspension assembly having a mass distribution and stiffness distribution configured to face multiple structural characteristic modes of the corresponding suspension assembly.

2. 2. The HDD of claim 1, wherein the opposing suspension assemblies comprise precision actuators configured to move corresponding opposing load beams having mass and stiffness distributions configured to counter the plurality of structural characteristic modes of the corresponding suspension assemblies.

3. The HDD of claim 2 , wherein the opposing load beam includes a cutout portion from a body of the opposing load beam.

4. The HDD of claim 2 , wherein the opposing load beams are configured as flexible structures.

5. The HDD of claim 4 , wherein the opposing load beam includes a cutout portion from a body of the opposing load beam.

6. 3. The HDD of claim 2, wherein the control voltage of the precision actuator of each opposing suspension assembly is configured to drive the opposing load beam in an opposite direction from the corresponding suspension assembly.

7. 10. The HDD of claim 1, wherein the opposed suspension assembly includes an opposed load beam including a rectangular body and a cutout portion extending through the body.

8. 10. The HDD of claim 1, wherein the opposed suspension assembly includes an opposed load beam including a trapezoidal body and a cutout portion extending through the body.

9. 10. The HDD of claim 1, wherein the opposed suspension assemblies include opposed load beams having non-uniform thicknesses.

10. the opposing suspension assembly further comprising a base plate coupled to the outer arm and to which the opposing load beam is coupled; 10. The HDD of claim 9, wherein the opposing load beams have a first thickness at a first portion that structurally joins the base plate and a second, different thickness at a second portion that extends away from the base plate.

11. 1. A head stack assembly (HSA) for a hard disk drive (HDD), comprising: means for supporting a plurality of arms; a plurality of arms coupled to the means for supporting, the plurality of arms including an outer arm at each end of the means for supporting and one or more inner arms between the outer arms, each inner arm supporting two suspension assemblies and each outer arm supporting one suspension assembly coupled inwardly of the outer arms, each suspension assembly having a corresponding precision actuator; A head stack assembly (HSA) for a hard disk drive (HDD), comprising: an opposed suspension assembly coupled to the outside of each outer arm, each opposed suspension assembly having a mass distribution and stiffness distribution configured to mitigate multiple structural characteristic modes of the suspension assembly coupled to the inside of the outer arm.

12. 12. The HSA of claim 11, wherein the opposing suspension assembly comprises a precision actuator configured to move a corresponding opposing load beam having a mass and stiffness distribution configured to mitigate the plurality of structural characteristic modes of the suspension assembly coupled to the inner side of the outer arm.

13. The HSA of claim 12 wherein the opposing load beams are flexible structures.

14. 13. The HSA of claim 12, wherein the control voltage of the precision actuator of each opposing suspension assembly is configured to drive the opposing load beam in an opposite direction from the corresponding suspension assembly.

15. The HSA of claim 11 , wherein the opposed suspension assembly includes an opposed load beam having a rectangular body and a cutout portion extending through the body.

16. The HSA of claim 11 , wherein the opposed suspension assembly includes an opposed load beam having a trapezoidal body and a cutout portion extending through the body.

17. 12. The HSA of claim 11, wherein the opposed suspension assembly includes an opposed load beam having a rectangular body and a notch from each side of the body.

18. The HSA of claim 11 , wherein the opposed suspension assembly includes opposed load beams having a non-uniform thickness.

19. A hard disk drive comprising the HSA of claim 11.

20. 1. A method of manufacturing a head stack assembly (HSA), the method comprising: coupling at least one suspension assembly having a corresponding precision actuator to each of a plurality of arms extending from the carriage; and coupling to each arm of the outer end of the carriage an opposing suspension assembly having a precision actuator and a mass and stiffness distribution configured to mitigate multiple structural characteristic modes of the corresponding suspension assembly coupled to the same arm.

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