Fine actuator reaction force cancellation flexible suspension

Abstract

A head stack assembly (HSA) for a hard disk drive includes a carriage from which a plurality of arms extend, where the arms include outer arms 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 only carries one suspension assembly coupled with an inner side of the outer arm, wherein each suspension assembly includes a corresponding fine actuator. The HSA also includes a reverse suspension assembly coupled to an outer side of each outer arm, where each reverse suspension assembly includes a structurally flexible dummy load beam having a mass distribution and a stiffness distribution configured to mitigate a plurality of structural dynamic modes of an operating suspension assembly coupled to the inner side of the outer arm.

Description

Technical Field

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

[0002] A hard disk drive (HDD) is a non-volatile storage device that is housed in a protective housing and stores digitally encoded data on one or more circular magnetic disks with magnetic surfaces. When the HDD is in operation, each magnetic recording disk is rapidly rotated by a spindle system. Data is read from and written to the magnetic recording disks using read / write heads (or "transducers") positioned above specific locations on the disks by actuators. The read / write heads use magnetic fields to write data to and read data from the surfaces of the magnetic recording disks. The write head operates by running an electric current through its coils to generate a magnetic field. Electrical pulses are sent to the write head in different patterns of positive and negative currents. The current in the write head's coils generates a local magnetic field in the gap between the head and the disk, which in turn magnetizes a small area on the recording medium.

[0003] An HDD includes at least one head gimbal assembly (HGA), which typically includes a suspension assembly and a corresponding head slider mounted thereon and housing a read / write transducer (or "head"). Each slider is attached to the free end of the suspension assembly, which extends from a rigid arm cantilevered from an actuator. Several actuator arms can be combined to form a single movable unit, a head stack assembly (HSA), typically with a rotary pivot bearing system. The suspension assembly of a conventional HDD typically includes a relatively rigid load beam having a mounting plate at its base end, which is attached to the actuator arm and a flexure (or "gimbal" or "gimbal flexure") mounted at its free end. This flexure (or "gimbal" or "gimbal flexure") carries the slider and its read / write head. Positioned between the mounting plate and the functional end of the load beam is actually a "hinge" that has compliance in the perpendicular flexure direction (perpendicular to the disk surface). The hinge enables the load beam to suspend and load the slider and read / write head toward the rotating disk surface. The function of the flexure is thus to provide gimbal support for the slider, allowing it to pitch and roll (i.e., gimbal motion) to adjust its orientation.

[0004] In addition to the primary voice coil motor (VCM) actuator that provides relatively coarse positioning, increasing areal density (a measure of the amount of information bits that can be stored on a given area of the disk surface) has necessitated the development and implementation of secondary and even tertiary actuators (typically "fine actuators") for improving head positioning through relatively fine positioning. Some HDDs employ milliactuator designs or microactuator designs to provide second and / or third level actuation of the recording head to enable more precise positioning of the head relative to the recording track. Milliactuators can be broadly classified as actuators that move the entire front end of the suspension (e.g., load beam, flexure, and slider) and are typically used as second level actuators. Microactuators (or "microactuators") can be broadly classified as actuators that only move (e.g., rotate) the slider, thereby moving the slider relative to the suspension and load beam, or only move the read / write element relative to the slider body. A microactuator can be used alone in conjunction with a first-stage actuator (e.g., a VCM), or in conjunction with a first-stage actuator and a second-stage actuator (e.g., a milliactuator) for more precise head positioning. Unless otherwise specified, the terms "microactuator," "milliactuator," "secondary actuator," "tertiary actuator," "dual-stage actuator," "fine actuator," etc., as used herein, generally refer to a relatively finely positioned actuator (e.g., technically, a secondary or tertiary) used in conjunction with a relatively coarsely positioned primary actuator, such as a VCM actuator in the HDD context. Piezoelectric (PZT)-based transducers and capacitive micromachined transducers are two types of fine actuators that have been developed for use with HDD sliders.

[0005] Any approaches that may be described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, 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 DESCRIPTION OF THE DRAWINGS

[0006] Embodiments are illustrated by way of example and not limitation in the accompanying figures in which like references refer to similar elements and in which:

[0007] Figure 1 is a plan view illustrating a hard disk drive according to one embodiment;

[0008] Figure 2 is a perspective view illustrating an actuator assembly according to one embodiment;

[0009] Figure 3A is a plan view illustrating a hard disk drive suspension assembly coupled to an arm on the inside according to one embodiment;

[0010] Figure 3Bis a plan view illustrating a hard disk drive inverted suspension assembly coupled to an arm on an outboard side according to one embodiment;

[0011] Figure 3C is an example of a device mounted on a common arm according to one embodiment. Figure 3A Suspension components and Figure 3B A plan view of the reverse suspension assembly;

[0012] Figure 4A is a graph illustrating example frequency response functions according to one embodiment, including for a single conventional suspension assembly and a mirrored suspension assembly on a common arm;

[0013] Figure 4B is a graph illustrating an example frequency response function according to one embodiment, including for a single conventional suspension assembly and an inverted suspension assembly on a common arm;

[0014] Figure 4C is a graph illustrating example frequency response functions according to one embodiment, including for a single conventional suspension assembly and an inverted suspension assembly;

[0015] Figure 4D is a graph illustrating an example frequency response function according to one embodiment, including for a single conventional suspension assembly and an inverted suspension assembly on a common arm;

[0016] Figure 5A is a plan view illustrating a first example inverted suspension assembly according to one embodiment;

[0017] Figure 5B is a plan view illustrating a second example inverted suspension assembly according to one embodiment;

[0018] Figure 5C is a plan view illustrating a third example inverted suspension assembly according to one embodiment;

[0019] Figure 5D is a plan view illustrating a fourth example inverted suspension assembly according to one embodiment;

[0020] Figure 6 is a cross-sectional side view illustrating an example inverted suspension assembly having a non-uniform thickness according to one embodiment; and

[0021] Figure 7 is a flow chart illustrating a method of manufacturing a head stack assembly (HSA) according to one embodiment. DETAILED DESCRIPTION

[0022] Generally speaking, a method for eliminating fine actuator reaction forces of a suspension assembly of a head-gimbal assembly (HGA) for a hard disk drive (HDD) is described. In the following description, 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. However, it will be apparent that the embodiments of the invention described herein can be practiced without these specific details. In other cases, well-known structures and devices may be shown in block diagram form to avoid unnecessarily obscuring the embodiments of the invention described herein.

[0023] introduction

[0024] the term

[0025] Reference herein to "an embodiment," "one embodiment," etc., is intended to mean that a particular feature, structure, or characteristic being described is included in at least one embodiment of the present invention. However, instances of such phrases are not necessarily all referring to the same embodiment.

[0026] The term "substantially" should be understood to describe a feature that is mostly or nearly structured, constructed, dimensioned, etc., but in practice manufacturing tolerances, etc., result in situations where the structure, configuration, dimensions, etc. are not always or necessarily exactly as described. For example, describing a structure as "substantially vertical" would give the term its ordinary meaning, such that the sidewalls would be vertical for all practical purposes, but might not be at precisely 90 degrees throughout.

[0027] While terms such as "best," "optimize," "minimize," "maximize," "maximize," etc. may not have certain values associated with them, if such terms are used herein, it is intended that one of ordinary skill in the art will understand that such terms will include affecting a value, parameter, metric, etc., in a beneficial direction consistent with the present disclosure as a whole. For example, describing a value of something as "minimum" does not require that the value actually be equal to some theoretical minimum value (e.g., zero), but should be understood in a practical sense that the corresponding goal is to move the value in a beneficial direction toward the theoretical minimum value.

[0028] Scenario

[0029] Figure 2 is a perspective view illustrating an actuator assembly according to one embodiment. The actuator assembly 200 includes a carriage 201 (see, e.g., Figure 1 134) which is supported by a pivot bearing assembly (not shown here; see e.g. Figure 1 The pivot bearing assembly 152) is connected to the central pivot (not shown here; see e.g. Figure 1The actuator assembly 200 further includes a plurality of actuator arms 206 (see, for example, FIG. Figure 1 132), each of the plurality of actuator arms being coupled to a suspension assembly 208 (see, e.g., Figure 1 The front suspension 110c of FIG. 1 houses the read / write head 210 (see, e.g., FIG. Figure 1 The read / write head 110a of FIG. 1 is a magnetic read / write head 110b and generally includes a swaged base plate 208a, a load beam 208b (see, e.g. Figure 1 Each suspension assembly 208 is electrically connected to a flexible printed circuit (FPC) 212 connected to the carriage 201 via the suspension tail 208c.

[0030] Recall that in addition to the primary voice coil motor (VCM) actuator that provides relatively coarse positioning, fine actuators have also been developed and implemented to improve head positioning through relatively fine positioning. A hard disk drive (HDD) head stack assembly (HSA) typically includes multiple arms. The top and bottom arms of the HSA (also known as the outer arms) carry only one suspension with a head to read / write (R / W) data on the media surface. In contrast, the inner arms of the HSA carry two suspensions on each arm, i.e., one suspension with an upward-facing head to perform R / W on the bottom media surface of the upper disk, and the other suspension with a downward-facing head to perform 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 drive the upward-facing and downward-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 in the fine actuator transfer function (TF). The TF, also known as the frequency response function (FRF), expresses the dynamic characteristics of a structure in the frequency domain, with peaks at its resonant frequencies. The gain of these peaks is related to the damping of these resonances and how external forces are applied. This cancellation is effective for an inner arm carrying two suspensions, because the reaction forces from the two suspensions' fine actuators have the same amplitude but are out of phase, thus canceling each other. However, for an outer arm carrying only one suspension, there is no opposing suspension to finely actuate to achieve reaction force cancellation.

[0031] Because there is no reaction force cancellation on the outer arm, the reaction force from the outer arm responsively produces an additional resonance peak for the inner head when the fine actuators on all suspensions are driven in parallel. One solution is to use a demultiplexer ("demux") to finely drive the inner arm head independently of the outer arm head, at least one approach being described in U.S. Patent No. 11,482,254, the entire contents of which are incorporated herein by reference for all purposes as if fully set forth herein. Such a demux control circuit decouples the inner arm head from the outer arm head to achieve significantly more effective reaction force cancellation for the inner arm head, resulting in a better TF. However, the fine actuator TF of the outer head is still not as good as the fine actuator TF of the inner head because there is no reaction force cancellation in this scenario.

[0032] Flexible reverse suspension assembly

[0033] To address the aforementioned challenges associated with the performance of the outer head, as may be apparent in the expression of the corresponding FRF, according to one embodiment, a balanced (e.g., "reverse") fine actuator on an inverse suspension (e.g., "fake" suspension) assembly can be implemented on the outer arm to cancel the reaction forces to a single "real" suspension on such an arm. The balanced fine actuator operates out of phase with the suspension fine actuator on the same arm, and the structural dynamics of the corresponding reverse suspension are "tuned," e.g., judiciously configured as a flexible structure / component, to match the key suspension resonant frequencies and achieve optimal reaction force cancellation similar to or close to that of an inner arm with two suspensions.

[0034] Figure 3A is a plan view illustrating a hard drive suspension assembly coupled to an arm on the inside, according to one embodiment. As depicted, the suspension assembly 300 is coupled to the inside surface (lower surface in this top view) of the arm 302. The suspension assembly 300 includes a mounting plate 304, which is typically swaged to the arm 302, to which is connected a load beam 306, which is coupled to a bend 308, which typically runs the length of the suspension assembly 300 and terminates at a distal gimbal portion 308g (or "gimbal" or "gimbal bend") that carries the slider and its read / write head (not visible here; see, e.g., FIG. 1 ). Figure 1 1 and 2. The suspension assembly 300 further includes a slider 110b and a read / write head 110a. The suspension assembly 300 also includes a fine actuator 310, referred to herein as a milliactuator because it is configured to move a load beam 306. The fine actuator 310 is generally positioned between and coupled to the mounting plate 304 and the load beam 306. For the purposes of this description, the suspension assembly 300 is considered a "real," or working, or operational suspension.

[0035] Figure 4Ais a graph illustrating an example frequency response function for a single conventional suspension assembly and a mirrored suspension assembly on a common arm according to one embodiment. In this example, the solid line function (or signal) 401 represents the frequency response function of the suspension assembly mounted on the arm (see, e.g., Figure 3A The FRFs of the read and write nodes of the suspension assembly 300 (with the head) on the arm 302 of FIG. 1 , e.g., characterizing the head off-track response to the voltage input of the fine actuator 310, without any balancing suspension or counter suspension on the opposite side of the common arm (see, e.g., FIG. 2 ). Figure 3A ). As a non-limiting example for the context of the methods, techniques, and embodiments described herein, depicted here by function 401 as a series of peaks: (a) a torsional mode 401a near about 6.4 kHz; (b) a whole-arm (flat) rocking mode 401b near about 8.5 kHz; (c) an end-arm (torsional) rocking mode 401c near about 18.5 kHz; and (d) a torsional rocking mode 401d near about 29 kHz. These peaks are discussed in more detail below with reference to the corresponding opposing suspension assemblies. Here, the dashed function (or signal) 402 represents the FRF of the read and write nodes on the suspension assembly 300, where the mirrored suspension assemblies (with the heads) are mounted on opposite sides of a common arm, in response to a common voltage input to the corresponding fine actuators 310 on the two suspensions on the common arm.

[0036] Figure 3B is a plan view illustrating a hard disk drive inverted suspension assembly coupled to an arm on the outside, according to one embodiment. As depicted, the inverted suspension assembly 320 is coupled to the outer surface (the upper surface in this top view) of the arm 302. The inverted suspension assembly 320 includes a mounting plate 324, which is typically swaged to the arm 302, to which is connected a load beam 326, which is coupled to a flexure 328. Here, the flexure 328 only extends to the load beam 326 near the fine actuator 330 and does not terminate at the distal gimbal portion because the inverted suspension 320 does not carry a slider or read / write head. As mentioned, the suspension assembly 320 also includes a balanced fine actuator 330, referred to herein as a milli-actuator because it is configured to move the load beam 326. The balanced fine actuator 330 is typically positioned between the mounting plate 324 and the load beam 326 and coupled to the mounting plate and the load beam. For purposes of this description, the inverted suspension assembly 320 may be considered or referred to as a "dummy" suspension.

[0037] Figure 3C is an example of a device mounted on a common arm according to one embodiment. Figure 3A Suspension components and Figure 3B Refer to the corresponding Figures 3A to 3B Components of the suspension assembly 300 and the inverse suspension assembly 320 will be described. Figure 4B is a graph illustrating an example frequency response function according to one embodiment, including for a single conventional suspension assembly and an inverted suspension assembly on a common arm. In this example, the solid line function (or signal) 401 again represents the frequency response function of the conventional suspension assembly and the inverted suspension assembly mounted on the arm (see e.g. Figure 3A Here, dashed function (or signal) 403 represents the FRF of the read and write nodes on the suspension assembly 300, where the counter suspension assembly 320 is mounted on a common arm (e.g., Figure 3C on the opposite side of the arm 302) and in response to the fine actuator 310 and the balancing fine actuator 330 ( Figure 3B ). The control voltage applied to the fine actuator 310 of the suspension assembly 300 on the outer arm 302 is also applied to the fine actuator 330 of the counter suspension assembly 320 on the same arm 302. The fine actuator 330 of the counter suspension assembly 320 is designed to move the counter suspension assembly 320 in the opposite direction relative to the fine actuator 310 of the suspension assembly 300 on the same arm 302, so that their reaction forces on the arm are in opposite directions. Therefore, when the counter suspension is designed to match the dynamics of a real suspension (e.g., with a magnetic head), such opposing reaction forces are effectively cancelled. Notably, multiple structural modes of the (inner) suspension assembly 300 are effectively mitigated or cancelled by using the (outer) counter suspension assembly 320, for example, as depicted, the full arm (flat) rocking mode 401b, the end arm (torsional) rocking 401c, the torsional rocking 401d. Whereas signal 401 indicates three main peaks (eg, 401b to 401d ) reaching 30 kHz, signal 403 indicates only one main peak reaching 30 kHz, eg, at approximately 22 kHz.

[0038] An example signal 403 ( ) representing the FRF of the read / write node on the suspension assembly 300 and the counter suspension assembly 320 on the opposite side of the common arm is shown. Figure 4B ) and signal 402 ( ) representing the FRF of the mirror suspension assembly on the opposite side of the common arm from the read / write node on the suspension assembly 300. Figure 4A ), it is visually apparent that signal 403 matches signal 402 relatively closely. Although, the inverse suspension assembly 320 can be further optimized to more closely match the two structural dynamic functions, because Figures 4A to 4BThe graphs of are used herein for non-limiting explanatory purposes only. The key point is that an inverted suspension (or "balanced" suspension) assembly such as inverted suspension assembly 320 can be judiciously configured as a flexible structure / component (i.e., "tuned") in conjunction with a balanced fine actuator such as balanced fine actuator 330 operating out of phase with the suspension fine actuator 310 on the same arm 302 so that the structural dynamics of the inverted suspension assembly 320 substantially match the critical resonant frequency of the corresponding suspension assembly 300 to achieve optimal reaction force cancellation / mitigation for multiple modes similar to or approaching that of an inner arm with two suspensions. Furthermore, the cost of manufacturing an inverted suspension assembly such as inverted suspension assembly 320 can be significantly lower than a mirrored suspension assembly due, at least in part, to the absence of relatively expensive read / write heads and gimbal flexures.

[0039] Figure 4C is a graph illustrating an example frequency response function according to one embodiment, including for a single conventional suspension assembly and an inverted suspension assembly. Here, the illustrated frequency range extends beyond 30 kHz to show a fourth peak 440 at approximately 40 kHz. In this example, the solid line function (or signal) 404 represents the frequency response corresponding to the fine actuator mounted on the arm and responsive to the fine actuator (see, e.g., Figure 3A The FRF of a single conventional suspension assembly (with a magnetic head) is shown with respect to a voltage input to a fine actuator 310 of the arm. The alternating dashed line function (or signal) 405 represents the FRF corresponding to the voltage input to the fine actuator 310 mounted on the arm and responsive to the fine actuator (see, e.g., Figure 3B 330), and the fine dashed line function (or signal) 406 represents the FRF of a single trapezoidal inverted suspension assembly (without a head) corresponding to a voltage input to a fine actuator such as fine actuator 330, and the fine dashed line function (or signal) 406 represents the FRF of a single rectangular inverted suspension assembly (without a head) mounted on an arm and responsive to a voltage input to a fine actuator such as fine actuator 330. Figure 4C Four highlighted (ie, bracketed) peaks 410, 420, 430, and 440 corresponding to the structural dynamics of each respective individual suspension component are shown, with each peak occurring approximately around the same frequency as the other suspension components.

[0040] Figure 4D is a graph illustrating example frequency response functions according to one embodiment, including for a single conventional suspension assembly and an inverted suspension assembly on a common arm. Here, the illustrated frequency range also extends beyond 30 kHz. In this example, the solid line function (or signal) 404 again represents the FRF corresponding to a single conventional suspension assembly mounted on the arm and responsive to a voltage input from fine actuator 310, while the fine dashed line function (or signal) 407 represents the FRF corresponding to a single conventional suspension assembly mounted on the common arm and responsive to a voltage input from a fine actuator (e.g., including, for example, a fine actuator such as Figure 3BFRF of the conventional suspension assembly and the rectangular inverse suspension assembly with the voltage input of the fine actuator 330 (balanced fine inverse actuator). Figure 4D It is illustrated that while there are the aforementioned four main peaks 410 , 420 , 430 , and 440 up to 40 kHz corresponding to the structural dynamics of a single conventional suspension component, the example signal 407 representing the FRF corresponding to the conventional suspension component 300 , where the inverted suspension component 320 is on the opposite side of the common arm 302 , results in only one main peak 450 .

[0041] Example dummy load beam structure

[0042] In practice, the inverted suspension components (e.g. Figure 3B The precise structural configuration of the inverse suspension assembly 320) may vary from implementation to implementation, primarily based on the structural dynamics of the corresponding suspension assembly that is the target of such counterbalancing. According to one or more embodiments, a noteworthy structural attribute that may or should be considered is that a given "dummy" load beam (e.g., Figure 3B The mass distribution and / or stiffness distribution within the load beam 326 of the inverse suspension assembly 320 can thus be configured as a flexible structure rather than a simple rigid block (which does not deform or deforms only negligibly under physical forces) that is designed to be an equivalent mass driven by the pseudo fine actuator as the mass of the target relative HGA. Therefore, the inverse suspension assembly 320 can be designed to be in the presence of the fine actuator 310 ( Figure 3A ) force to counteract or reduce the corresponding suspension component 300 ( Figure 3A ) rather than just a single (e.g., low-frequency) structural mode / peak. Accordingly, a number of dummy load beam structural configurations were modeled and analyzed, and are presented below as non-limiting example configurations that can be optimized for mode mitigation / elimination by substantially matching the critical modes of a "real" operating suspension component.

[0043] Figure 5A is a plan view illustrating a first example inverted suspension assembly according to one embodiment. The inverted suspension assembly 500 is coupled to an arm (not shown here; see e.g. Figure 3B50). The inverted suspension assembly 500 includes a mounting plate 504 to which is connected a rectangular load beam 506 coupled to a flexure 508. Here, the flexure 508 also extends only to the load beam 506 proximate the fine actuator 510, since the inverted suspension assembly 500 does not carry a slider or a read / write head. For the purposes of this specification, the inverted suspension assembly 500 may be considered to be a "dummy" suspension including a "dummy" load beam 506 or referred to as a "dummy" suspension including the "dummy" load beam. For a rectangular structural body 506a similar to the rectangular structural body of the inverted suspension assembly 500, further including a rectangular cutout 506b originating from the body 506a, the optimization techniques considered include, but are not limited to, various adjustments to the length of the body 506a in the longitudinal direction (x-direction, along the long axis of the body 506a) and various adjustments to the length of the cutout 506b in the longitudinal direction. Similarly, various adjustments to the width of the body 506a in the lateral direction (y-direction, along the short axis of the body 506a) and / or the width of the cutout 506b may also be applied to optimize a reverse suspension assembly such as the reverse suspension assembly 500 to match the critical mode of the corresponding operating suspension assembly for mode cancellation / mitigation purposes.

[0044] Figure 5B is a plan view illustrating a second example inverted suspension assembly according to one embodiment. The inverted suspension assembly 520 is coupled to an arm (not shown here; see e.g. Figure 3B 302). The inverted suspension assembly 520 includes a mounting plate 524 to which is connected a trapezoidal load beam 526 coupled to a flexure 528. Here, the flexure 528 also extends only to the load beam 526 proximate the fine actuator 530, since the inverted suspension assembly 520 does not carry a slider or a read / write head. For the purposes of this specification, the inverted suspension assembly 520 may be considered to be a "dummy" suspension including a "dummy" load beam 526 or referred to as a "dummy" suspension including the "dummy" load beam. For a trapezoidal structural body 526a similar to the trapezoidal structural body of the inverted suspension assembly 520, further including a generally trapezoidal cutout 526b originating from the body 526a, the optimization techniques considered 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 also be applied to optimize a reverse suspension assembly such as the reverse suspension assembly 520 to match the critical mode of the corresponding operating suspension assembly for mode cancellation / mitigation purposes.

[0045] Figure 5C is a plan view illustrating a third example inverted suspension assembly according to one embodiment. Inverted suspension assembly 540 is coupled to an arm (not shown here; see e.g. Figure 3B ). The inverted suspension assembly 540 includes a mounting plate 544 to which is connected a rectangular load beam 546 coupled to a bend 548. Here, the bend 548 also extends only to the load beam 546 proximate the fine actuator 550, since the inverted suspension assembly 540 does not carry a slider or a read / write head. For the purposes of this specification, the inverted suspension assembly 540 may be considered to be a "dummy" suspension including a "dummy" load beam 546 or referred to as a "dummy" suspension including the "dummy" load beam. For a rectangular structural body 546a similar to the rectangular structural body of the inverted suspension assembly 540, further including a trapezoidal cutout 546b originating from the body 546a, the optimization techniques considered include, but are not limited to, various adjustments to the length of the body 546a in the longitudinal direction (x-direction, along the long axis of the body 546a) and various adjustments to the length of the cutout 546b in the longitudinal direction. Similarly, various adjustments to the width of the body 546a in the lateral direction (y-direction, along the short axis of the body 546a) and / or the relationship between the base and legs of the cutout 546b may also be applied to optimize a reverse suspension assembly such as the reverse suspension assembly 540 to match the critical mode of the corresponding operating suspension assembly for mode cancellation / mitigation purposes.

[0046] Figure 5D is a plan view illustrating a fourth example inverted suspension assembly according to one embodiment. The inverted suspension assembly 560 is coupled to an arm (not shown here; see e.g. Figure 3B). The inverted suspension assembly 560 includes a mounting plate 564 to which is connected a rectangular load beam 566 coupled to a flexure 568. Here, the flexure 568 also extends only to the load beam 566 proximate the fine actuator 570, since the inverted suspension assembly 560 does not carry a slider or a read / write head. For the purposes of this specification, the inverted suspension assembly 560 may be considered to be a "dummy" suspension including a "dummy" load beam 566 or referred to as a "dummy" suspension including the "dummy" load beam. For rectangular structural bodies 556a similar to the rectangular structural body of the inverted suspension assembly 560, further including a cutout 566b originating from at least one lateral side of the body 566a, the optimization techniques considered include, but are not limited to, various adjustments to the length of the body 566a in the longitudinal direction (x-direction, along the long axis of the body 566a) and various adjustments to the length of the cutout 566b in the longitudinal direction. Similarly, various adjustments to the width of the body 566a in the lateral direction (y-direction, along the short axis of the body 566a) and / or the width of the cut-out portion 566b can also be applied to optimize a reverse suspension assembly such as the reverse suspension assembly 560 to match the critical mode of the corresponding operating suspension assembly for mode cancellation / mitigation purposes.

[0047] Figure 6 is a cross-sectional side view illustrating an example inverted suspension assembly having a non-uniform thickness according to one embodiment. Figure 5A . The inverse suspension assembly 600 is coupled to an outer surface of an arm (not shown here). The inverse suspension assembly 600 includes a mounting plate 604, which is typically swaged to the arm, to which a load beam 606 is connected. The inverse suspension assembly 600 also includes a fine actuator (not visible here), referred to herein as a milliactuator, because it is configured to move the load beam 606. For the purposes of this specification, the inverse suspension assembly 600 may be considered to be or referred to as a "pseudo" suspension. At least according to the embodiment illustrated herein, the inverse suspension assembly 600 includes a load beam 606 having a non-uniform thickness. According to a related embodiment, the inverse suspension assembly 600 includes a load beam 606 having a first thickness t1 at a first portion p1 that structurally intersects with the mounting plate 604, and having a different second thickness t2 at a second portion p2 that extends away from the mounting plate 604. This embodiment illustrates the inverse suspension assembly 600 in addition to the reference embodiment. 5A to 5DIn addition to the described variations in the configuration and shape (e.g., rectangular, trapezoidal) of structural features (e.g., bodies, cutouts, cutouts) in the x-direction (longitudinal) and y-direction (lateral), the thickness of the load beam 606 may additionally and alternatively be varied in height (z-direction) for optimizing an inverted suspension assembly, such as the inverted suspension assembly 600, to match a critical mode of operation of a corresponding suspension assembly for mode cancellation / mitigation purposes. For purposes of example, a first thickness t1 at a first portion p1 of the load beam 606 that structurally interfaces with the mounting plate 604 is thinner than a second thickness t2 at a second portion p2 of the load beam 606 that extends away from the mounting plate 604. However, the locations at which the load beam 606 may transition from one thickness to another, as well as the number of different thicknesses and thickness transitions, may vary with the specific implementation, primarily based on the structural dynamics of the corresponding suspension assembly for which multi-mode counterbalancing is a goal. In Figure 6 , the second portion p2 of the load beam 606 is thickened from both the top and bottom surfaces (e.g., in the up-down direction) compared to the first portion p1. Alternatively, the second portion p2 of the load beam 606 may be thickened from only the top or bottom surface relative to p1 (e.g., in the up-down direction), such as to facilitate manufacturing.

[0048] Method for manufacturing a magnetic head gimbal assembly

[0049] Figure 7 is a flow chart illustrating a method of manufacturing a head stack assembly (HSA) according to one embodiment. Figure 7 The head stack assembly (HSA) is designed, constructed and intended to be implemented into a hard disk drive (HDD) (see, e.g. Figure 1 HDD 100).

[0050] At block 702, at least one suspension assembly including a corresponding fine actuator is coupled to each of a plurality of arms extending from a carriage. For example, a suspension assembly such as suspension assembly 300 ( Figure 3A 、 Figure 3C ) of the suspension assembly is coupled to the slave carriage (see e.g. Figure 2 The plurality of arms 302 ( Figure 3A 、 Figure 3C ) in each arm.

[0051] At block 704, an inverted suspension assembly including a fine actuator and a mass distribution and a stiffness distribution configured to mitigate a plurality of structural dynamic modes of a corresponding suspension assembly coupled to the same arm is coupled to each arm at the outer end of the carriage. For example, a corresponding fine actuator 330 ( Figure 3B )、510( Figure 5A )、530( Figure 5B )、550( Figure 5C )、570( Figure 5D ) such as the reverse suspension assembly 320 ( Figures 3B to 3C )、500( Figure 5A )、520( Figure 5B )、540( Figure 5C )、560( Figure 5D ) of the inverted suspension assembly coupled to a plurality of arms 302 ( Figures 3A to 3C ) in each arm.

[0052] According to the embodiments described herein, an inverted suspension (or "balanced" suspension) assembly can be judiciously configured as a flexible structure / component (i.e., "tuned"), incorporating a balanced fine actuator operating out of phase with a corresponding "real" suspension fine actuator on the same arm, such that the structural dynamics of the inverted suspension assembly substantially matches multiple key resonant frequencies of the corresponding suspension assembly to achieve optimal reaction force cancellation / mitigation of multiple structural dynamic modes. The cost of manufacturing an inverted suspension assembly can be significantly lower than that of a mirrored suspension assembly, at least in part due to the absence of relatively expensive read / write heads and gimbal flexures.

[0053] Physical Description of an Exemplary Operating Situation

[0054] Embodiments may be used in the context of a digital data storage device (DSD) such as a hard disk drive (HDD). Thus, according to one embodiment, Figure 1 A plan view illustrating a conventional HDD 100 is shown to help describe how a conventional HDD typically operates.

[0055] Figure 1 The functional arrangement of components of an HDD 100 is illustrated, including a slider 110b, which includes a magnetic read / write head 110a. Slider 110b and head 110a may be collectively referred to as a head slider. HDD 100 includes at least one head gimbal assembly (HGA) 110 having a 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. HDD 100 also includes at least one recording medium 120 rotatably mounted on a spindle 124 and a drive motor (not visible) attached to spindle 124 for rotating medium 120. Read / write head 110a (also referred to as a transducer) includes a write element and a read element for writing and reading information stored on medium 120 of HDD 100, respectively. A disk clamp 128 may be used to attach medium 120 or multiple disk media to spindle 124.

[0056] The HDD 100 also includes an arm 132 attached to the HGA 110, a carriage 134, and a voice coil motor (VCM) comprising an armature 136 containing a voice coil 140 attached to the carriage 134, and a stator 144 containing a voice coil magnet (not visible). The armature 136 of the VCM is attached to the carriage 134 and is configured to move the arm 132 and the portion of the HGA 110 that accesses the media 120, which are collectively mounted on a pivot shaft 148 with an interposed pivot bearing assembly 152. In the context of an HDD with multiple disks, the carriage 134 may be referred to as an "E-block" or comb because the carriage is arranged to carry an array of linked arms, giving it the appearance of comb teeth.

[0057] The assembly including a head gimbal assembly (e.g., HGA 110) having a flexure to which a head slider is coupled, an actuator arm (e.g., arm 132) and / or a 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 described. For example, an HSA may refer to an assembly that also includes electrical interconnect components. Generally speaking, an HSA is an assembly that is configured to move a head slider to access portions of a medium 120 for read and write operations.

[0058] Further references Figure 1 , electrical signals including write signals to the head 110a and read signals from the head (e.g., current to the voice coil 140 of the VCM) are transmitted by a flexible cable assembly (FCA) 156 (or "flexible cable", or "flexible printed circuit" (FPC)). The interconnect between the flexible cable 156 and the head 110a may include an arm electronics (AE) module 160, which may have an onboard preamplifier for the read signal and other read channel and write channel electronic components. The AE module 160 may be attached to the carriage 134 as shown. The flexible cable 156 can be coupled to an electrical connector block 164, which in some configurations provides electrical connectivity through electrical feedthroughs provided by the HDD housing 168. The HDD housing 168 (or "housing base" or "baseboard" or simply "base"), together with the HDD cover, provides a semi-sealed (or hermetically sealed, in some configurations) protective housing for the information storage components of the HDD 100.

[0059] Other electronic components, including a disk controller and servo electronics including a digital signal processor (DSP), provide electrical signals to the drive motor, the voice coil 140 of the VCM, and the head 110a of the HGA 110. The electrical signal provided to the drive motor causes the drive motor to rotate, thereby providing torque to the spindle 124, which in turn is transmitted to the medium 120 attached to the spindle 124. As a result, the medium 120 rotates in direction 172. The rotating medium 120 forms an air cushion that acts as an air bearing on which the air bearing surface (ABS) of the slider 110b rides, allowing the slider 110b to fly above the surface of the medium 120 without coming into contact with the thin magnetic recording layer that records information. Similarly, in HDDs that utilize a lighter-than-air gas (such as helium for non-limiting example), the rotating medium 120 forms an air cushion that acts as a gas or fluid bearing on which the slider 110b rides.

[0060] The electrical signal provided to the voice coil 140 of the VCM enables the head 110a of the HGA 110 to access the track 176 on which the information is recorded. As a result, the armature 136 of the VCM swings through an arc 180, which enables the head 110a of the HGA 110 to access the individual tracks on the medium 120. The information is stored in a plurality of radially nested tracks on the medium 120, which are arranged in sectors (such as sector 184) on the medium 120. Accordingly, each track is composed of a plurality of sectorized track portions (or "track sectors"), such as sectorized track portion 188. Each sectorized track portion 188 may include recorded information and a data header containing error correction code information and a servo burst signal pattern, such as an ABCD-servo burst signal pattern (which is information identifying the track 176). When accessing track 176, the read element of head 110a of HGA 110 reads a servo burst signal pattern that provides a position error signal (PES) to the servo electronics, which controls the electrical signal provided to the voice coil 140 of the VCM, thereby enabling head 110a to follow track 176. Upon finding track 176 and identifying a particular sectored track portion 188, head 110a either reads information from track 176 or writes information to track 176 according to instructions received by the disk controller from an external agent (e.g., a computer system's microprocessor).

[0061] The electronic architecture of an HDD includes multiple electronic components for performing their respective HDD operating functions, such as a hard disk controller (HDC), an interface controller, an arm electronic module, a data channel, a motor driver, a servo processor, a buffer memory, etc. Two or more of these components may be combined on a single integrated circuit board called a "system on a chip" (SOC). Several (if not all) of these electronic components are typically arranged on a printed circuit board that is coupled to the bottom side of the HDD, such as to the HDD housing 168.

[0062] This document refers to hard drives, such as Figure 1 The HDD 100 illustrated and described may include an information storage device sometimes referred to as a "hybrid drive." A hybrid drive generally refers to a storage device that combines the functionality of a conventional HDD (see, for example, HDD 100) with a solid-state storage device (SSD) (which is electrically erasable and programmable) that uses non-volatile memory, such as flash memory or other solid-state (e.g., integrated circuit) memory. Because the operation, management, and control of different types of storage media are generally different, the solid-state portion of the hybrid drive may include its own corresponding controller functionality, which may be integrated into a single controller along with the HDD functionality. The hybrid drive may be constructed and configured to operate and utilize the solid-state portion in a variety of ways, such as, by way of non-limiting example, using the solid-state memory as cache memory, for storing frequently accessed data, for storing I / O intensive data, and the like. Additionally, the hybrid drive may be constructed and configured to essentially function as two storage devices, a conventional HDD and an SSD, in a single housing, with one or more interfaces for host connection.

[0063] Extensions and replacements

[0064] In the foregoing description, embodiments of the present invention have been described with reference to a large number of specific details, which may vary according to different specific implementations. Therefore, various modifications and changes may be made thereto without departing from the broader spirit and scope of the embodiments. Therefore, the present invention and what the applicant intends to be the sole and exclusive indicator of the present invention are the set of claims issued by this patent application in the specific form in which such claims issue, including any subsequent corrections. Any definitions of terms contained in these claims expressly set forth herein shall determine the meaning of these terms as used in the claims. Thus, limitations, elements, characteristics, features, advantages or attributes that are not expressly cited in a claim should not limit the scope of this claim in any way. Therefore, this specification and drawings are to be regarded as illustrative rather than restrictive.

[0065] Furthermore, in this description, certain process steps may be shown in a particular order, and letters and alphanumeric labels may be used to identify certain steps. Unless expressly indicated otherwise in the specification, embodiments are not necessarily limited to any particular order of performing such steps. Specifically, these labels are used only to facilitate 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), comprising: a disk stack comprising a plurality of disk media rotatably mounted on a spindle; a plurality of head sliders, each head slider housing a read-write transducer configured to read from and write to 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; as well as 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 comprising an outer arm at each end of the disk stack and one or more inner arms between the outer arms, wherein each inner arm carries two suspension assemblies and each outer arm carries one suspension assembly, each suspension assembly including a corresponding fine actuator configured to move a corresponding head slider of the plurality of head sliders to access a portion of the corresponding disk media; and An inverted suspension assembly is coupled to a side of at least one outer arm opposite the corresponding suspension assembly, the inverted suspension assembly having a mass distribution and a stiffness distribution configured to resist a plurality of structural dynamic modes of the corresponding suspension assembly.

2. The HDD of claim 1 , wherein the inverted suspension assembly comprises a fine actuator configured to move a corresponding inverted load beam having a mass distribution and a stiffness distribution configured to resist the plurality of structural dynamic modes of the corresponding suspension assembly. 3 . The HDD of claim 2 , wherein the counter load beam includes a cutout starting from a body of the counter load beam. The HDD according to claim 2 , wherein the reverse load beam is configured as a flexible structure. 5 . The HDD of claim 4 , wherein the counter load beam includes a cutout starting from a body of the counter load beam.

6. The HDD of claim 2, wherein the control voltage of the fine actuator of each inverted suspension assembly is configured to drive the inverted load beam in a direction opposite to that of the corresponding suspension assembly. 7 . The HDD of claim 1 , wherein the inverted suspension assembly comprises an inverted load beam having a rectangular body and a cutout through the body. 8 . The HDD of claim 1 , wherein the inverted suspension assembly comprises an inverted load beam having a trapezoidal body and a cutout through the body.

9. The HDD of claim 1, wherein the inverted suspension assembly comprises an inverted load beam having a non-uniform thickness.

10. The HDD according to claim 9, wherein: The inverted suspension assembly further includes a base plate coupled to the outer arm, the inverted load beam coupled to the base plate, and The opposing load beam includes a first thickness at a first portion that structurally interfaces with the base plate and a second, different thickness at a second portion that extends away from the base plate.

11. A hard disk drive (HDD) head stack assembly (HSA), the hard disk drive (HDD) head stack assembly (HSA) comprising: a member for carrying a plurality of arms; a plurality of arms coupled to the load-bearing member, the plurality of arms comprising an outer arm at each end of the load-bearing member and one or more inner arms between the outer arms, wherein each inner arm carries two suspension assemblies, and each outer arm carries one suspension assembly coupled to an inner side of the outer arm, each suspension assembly including a corresponding fine actuator; as well as An inverted suspension assembly is coupled to the outboard side of each outer arm, each inverted suspension assembly having a mass distribution and a stiffness distribution configured to mitigate a plurality of structural dynamic modes of the suspension assembly coupled to the inboard side of the outer arm.

12. The HSA of claim 11 , wherein the inverted suspension assembly includes a fine actuator configured to move a corresponding inverted load beam having a mass distribution and a stiffness distribution configured to mitigate the plurality of structural dynamic modes of the suspension assembly coupled to the inboard side of the outer arm.

13. The HSA of claim 12, wherein the opposing load beam is a flexible structure.

14. The HSA of claim 12, wherein the control voltage of the fine actuator of each inverted suspension assembly is configured to drive the inverted load beam in a direction opposite to that of the corresponding suspension assembly.

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

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

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

18. The HSA of claim 11, wherein the inverted suspension assembly comprises an inverted load beam having a non-uniform thickness.

19. A hard disk drive comprising the HSA according to claim 11.

20. A method of manufacturing a head stack assembly (HSA), the method comprising: coupling at least one suspension assembly including a corresponding fine actuator to each arm of a plurality of arms extending from the carriage; as well as An inverted suspension assembly including a fine actuator and a mass and stiffness distribution configured to mitigate multiple structural dynamic modes of the corresponding suspension assembly coupled to the same arm is coupled to each arm at the outer end of the carriage.

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