HK1163919A - Suspension assembly having a microactuator grounded to a flexure - Google Patents

Description

Suspension assembly with micro-actuator grounded to flexure

Technical Field

Background

Information storage devices are used in computers or other consumer electronic devices to retrieve and/or store data. Magnetic hard disk drives are examples of information storage devices that include one or more heads that can read and write, but other information storage devices may also include heads-sometimes including heads that cannot write. For convenience, all heads that are capable of reading are referred to herein as "read heads," regardless of the other devices and functions that the read heads are capable of performing (e.g., write, fly height control, touch down detection, landing control, etc.).

In modern hard disk drive devices, each read head is a sub-component of a Head Gimbal Assembly (HGA). The read head typically includes a slider and a read/write transducer. The read/write transducer typically includes a magnetoresistive read element (e.g., a so-called giant magnetoresistive read element or a tunneling magnetoresistive read element) and an inductive write structure that includes a flat coil deposited by lithography and a yoke structure having a pole tip directed toward the disk medium.

The HGA also typically includes a suspension assembly including a mounting plate, a load beam, and a laminated flexure that carries electrical signals to and from the read head. The read head is typically bonded to the tongue component of the laminated flexure. Further, an HGA is a sub-component of a Head Stack Assembly (HSA) that typically includes a plurality of HGAs, a rotary actuator, and a flexible cable. The mounting plate of each suspension assembly is attached to the arm of the rotary actuator (e.g., by forging), and each laminated flexure includes a flexure tail that is electrically connected to the flex cable of the HAS (e.g., by solder bonding).

Modern laminated flexures typically comprise conductive copper traces separated from a stainless steel support layer by a polyimide dielectric layer. Enabling signals to/from the heads to reach the flex cable on the actuator body, each HGA flexure includes a flexure tail that extends along the actuator arm away from the heads and ultimately attaches to the flex cable adjacent the actuator body. That is, the flexure includes conductive traces that are electrically connected to a plurality of conductive pads on the head and extend from adjacent the head to terminate at electrical connection points at the flexure tail.

The position of the HSA relative to the rotating disk in the disk drive, and hence the position of the read head relative to the data tracks on the disk, is actively controlled by a rotary actuator, which is typically driven by a Voice Coil Motor (VCM). In particular, the current conducted through the coil of the VCM applies a torque to the rotary actuator, enabling the read head to seek and follow the desired data track on the rotating disk.

However, the industry trend toward increasing areal data densities requires that the spacing between data tracks on the disk be greatly reduced. Furthermore, disk drive performance requirements, particularly with respect to the time required to access desired data, do not allow for a reduction in the rotational speed of the disk. In fact, for many disk drive applications, the rotational speed has increased significantly. The result of these trends is a need for increased bandwidth for servo control of the position of the read head relative to the data tracks on the rotating disk.

One solution that has been proposed in the art to increase the servo bandwidth of a disk drive is dual-stage actuation. Under the concept of dual-stage actuation, a rotary actuator driven by the VCM is used as a coarse actuator (for large adjustments of the position of the HAS relative to the disk), while a so-called "microactuator" with a larger bandwidth but with a smaller stroke (stroke) is used as a fine actuator (for smaller adjustments of the read head position). Various microactuator designs have been proposed in the art for dual stage actuation in disk drive applications. Some of these designs use one or more piezoelectric microactuators attached to a stainless steel component of the suspension assembly (e.g., the mounting plate or extension thereof, and/or the load beam or extension thereof, and/or an intermediate stainless steel element connecting the mounting plate to the load beam)

However, if the microactuator is electrically connected to the stainless steel surface of the suspension assembly (e.g., for grounding), the electrochemical reaction may cause an oxide layer to be generated on the stainless steel at the connection location. The oxide layer may be insulating, thus interfering with the desired conductivity and may be exacerbated by thermal and wet conditions. Over time, the expected response of the micro-actuator to the applied signal may become small, resulting in reduced or impaired performance of the information storage device and/or data loss.

Accordingly, there is a need in the field of information processing devices to improve the design of a suspension assembly integrated with a micro-actuator by improving the grounding of the micro-actuator.

Drawings

FIG. 1 is a top view of a disk drive that can include an embodiment of the present invention.

FIG. 2 is a bottom perspective view of a Head Gimbal Assembly (HGA).

FIG. 3 is a top view of a portion of an HGA according to one embodiment of the present invention.

FIG. 4 is a bottom view of a portion of an HGA according to one embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating epoxy extending through a mounting plate and through a hole of a flexure to ground to the flexure according to one embodiment of the invention.

FIG. 6 is a cross-sectional view illustrating epoxy extending through the flexure to ground to the flexure according to one embodiment of the invention.

FIG. 7 is a cross-sectional view illustrating epoxy extending through a mounting plate and to a flexure according to one embodiment of the invention, and particularly illustrating an air gap.

FIG. 8 is a schematic diagram of a flexure metal layer including an air gap according to one embodiment of the present invention.

FIG. 9 is a schematic view of a bottom portion of a load beam including an air gap according to one embodiment of the present invention.

Detailed Description

FIG. 1 is a top view of a disk drive 100 that can include an embodiment of the present invention. The disk drive 100 includes a disk drive base 102. The disc drive 100 also includes a pivot 106 rotatably mounted on the disc drive base 102 for rotating the disc 104 mounted on the pivot 106. The rotation of the disks 104 establishes an air flow through an optional recirculation filter 108. In some embodiments, the disk drive 100 may have only a single disk 104, or alternatively, two or more disks.

The disc drive 100 also includes a rotary coarse actuator 110 rotatably mounted on the disc drive base 102. The rotary coarse actuator 110 includes an actuator arm 114 that supports a Head Gimbal Assembly (HGA) 118. The voice coil motor 112 rotates the actuator 110 through a limited range of angles so that the HGA 118 may be desirably positioned relative to one or more tracks of information on the disk 104. Preferably, each disk surface of disk drive 100 will include one HGA 118, but low density (populated) disk drives using fewer HGAs are also contemplated. In the non-operational state, the HGA may rest on the ramp 120, for example, to avoid contact with the non-rotating disk 104. The electrical signals to/from the HGA 118 are carried to other driver electronics, in part via a flex cable (not shown) and a flex cable mount 116.

FIG. 2 is a bottom perspective view of HGA 200. Referring again to FIG. 2, the HGA 200 includes a load beam 202 and a read head 210 for reading data from and writing data to a disk (e.g., disk 104). The read head 210 includes a slider substrate having an air bearing surface (to which the marks 210 are directed) and an opposite top surface (not visible in the view of FIG. 2). The slider substrate preferably comprises AlTiC, but other ceramic materials or silicon may be used. The slider substrate of the read head 210 also includes a trailing face 212 that includes a read/write transducer (too small to be physically shown in the view of FIG. 2, but disposed on the trailing face 212). In certain embodiments, the read/write transducer is preferably an inductive magnetic write transducer combined with a magnetoresistive read transducer. The purpose of the load beam 202 is to provide limited vertical compliance to the read head 210 to follow vertical undulations of the disk surface as the disk (e.g., disk 104 of FIG. 1) rotates, and to preload the air bearing surface of the read head 210 against the disk surface with a preload force commonly referred to as a "gram load".

In the embodiment of FIG. 2, the HGA 200 also includes a laminated flexure 204 attached to the load beam 202. The laminated flexure 204 includes a tongue 206 having a read head engaging surface. The head 210 is attached to the read head engaging surface of the tongue 206 of the laminated flexure 204. Since the read head 210 partially obscures the tongue 206, only a portion of the tongue 206 is visible in the view of FIG. 2. A first use of the laminated flexure 204 is to provide compliance to the head 210 to follow pitch and roll angular (pitch and roll angular) undulations of the disk surface as the disk (e.g., disk 104) rotates, while limiting relative motion between the read head 210 and the load beam 202 in the lateral direction and about the yaw axis. A second purpose of the laminated flexure 204 is to provide multiple electrical paths to facilitate signal transmission to/from the read head 210. For the second use, the laminated flexure 204 includes a plurality of conductive traces 218 defined in a conductive (e.g., copper) sub-layer of the laminated flexure 204. The conductive traces 218 are separated from a support layer (e.g., stainless steel) by a dielectric layer (e.g., polyimide).

In the embodiment of fig. 2, the load beam 202 includes hinge plates 222 and 224 and is attached to the mounting plate 220 via the hinge plates 222 and 224 and the microactuator mounting structure 300. These parts may be made of stainless steel and may be attached to each other by a number of spot welds, for example. Alternatively, the load beam 202 may have an integral hinge plate area without being assembled using separate hinge plate components, such that the load beam 202 and its hinge plates would be a single component with material continuity. In another alternative, the microactuator mounting structure 300 may also be an integral element of the mounting plate 220.

The load beam 202 with the hinge plates 222, 224 (if present), the microactuator mounting structure 300, and the mounting plate 220 may together be referred to as a "suspension assembly". Thus, the mounting plate 220 may also be referred to as a suspension assembly mounting plate 220. In certain preferred embodiments, the suspension assembly mounting plate 220 includes a swage boss (shock boss)226 to facilitate attachment of the suspension assembly to an actuator arm (e.g., actuator arm 114). In this case, the suspension assembly mounting plate 220 may also be referred to as a "forged mounting plate". Note that after the laminate flexure 204 is attached to the load beam 202, the laminate flexure 204 may be considered to also be a "suspension assembly".

FIG. 3 is a top view of a portion of an HGA according to one embodiment of the present invention. The suspension assembly 300 of the HGA includes a mounting plate 304. Mounting plate 304 may include a forging station 305 to assist in attaching the mounting plate suspension assembly to an actuator arm (e.g., actuator arm 114). Mounting plate 304 may have a through-hole 306 extending from the top 307 of mounting plate 304 to the bottom of the mounting plate. As will be described, in one embodiment, the micro-actuator mounting structures (340, 342) are formed in the mounting plate 304 and the micro-actuators (312, 313) may be mounted in the micro-actuator mounting structures 304. Epoxy 329 can be mounted to the micro-actuator and can extend through-hole 306 to bond to the flexure, with epoxy 329 extending through the flexure's opening to the flexure's ground trace so that the micro-actuator is grounded to the flexure.

In particular, the mounting plate 304 may include a pair of generally square micro-actuator mounting structures 340 and 342 formed in the mounting plate 304. The microactuators 312 and 313 may each be mounted in a microactuator mounting structure 340 and 342, respectively. As is known in the art, micro-actuators are commonly used to position the read head. Additionally, epoxy lines 330 and 332 of epoxy 329 can each be bonded to the microactuator and can extend through the through-holes 306 to bond to the flexure, with the epoxy 329 extending through the opening of the flexure to the gold-plated ground trace of the flexure, so that the microactuator is grounded to the flexure. One skilled in the art will appreciate that a single micro-actuator may be mounted to the mounting plate, a pair of micro-actuators may be mounted to the mounting plate, or any suitable number of micro-actuators may be mounted to the mounting plate.

Referring to FIG. 4, which is a bottom view of a portion of an HGA according to one embodiment of the present invention, through-hole 306 extends from top 307 of mounting plate 304 to bottom 309 of mounting plate 304. Further, as seen from the bottom 309 of the mounting plate 304, the flexure 204 is attached to the bottom 309 of the mounting plate 304 and the flexure 204 is coupled to the micro-actuators 312 and 313. As described in more detail below, the flexure 204 may include a metal layer, an insulator layer, a trace layer including ground traces, and openings that extend through the metal layer and insulator layer to gold plated ground traces of the flexure.

Thus, in one embodiment, a pair of epoxy lines 330 and 332 of epoxy 329 can be bonded to micro-actuators 312 and 313 and can extend through-holes 306 to bond to flexures 204. Specifically, as described in more detail below, the epoxy 329 can extend through the opening of the flexure to the flexure's ground trace, such that the microactuators 312 and 312 are grounded to the flexure 204.

In one embodiment, micro-actuators 312 and 313 are Piezoelectric (PZT) micro-actuators. The piezoelectric microactuators 312 and 313 may be gold (Au) plated. Further, in one embodiment, the epoxy 329 may include silver (Ag) and be conductive. However, it should be understood that any kind of suitable epoxy or solder that is electrically conductive may be utilized.

Referring now to fig. 5, fig. 5 illustrates a cross-sectional view 500 of epoxy extending through a hole of a flexure through a mounting plate to ground to the flexure according to one embodiment of the invention. Specifically, referring to fig. 5, epoxy 502 extends through-hole 503 of mounting plate 504 and through load beam 506 to extend through opening 507 of the flexure, specifically through steel layer 508 and insulator layer 512 of the flexure to bond to gold plated 520 copper layer 514 of the flexure, which is a ground trace. Thus, the microactuators 312 and 313 are grounded to the gold plated ground traces of the flexure's copper layer 514 through the epoxy 502.

Referring also to fig. 6, fig. 6 illustrates a cross-sectional view 600 of the epoxy 502 extending through the flexure 204 to ground to the flexure 204, in accordance with one embodiment of the present invention. As described above, in one embodiment, the metal layer 508 of the flexure 204 may be stainless steel and the insulator layer 512 may be polyimide. In addition, as shown in FIG. 6, the flexure 204 may include a gold plated 520 copper layer 514 that includes a ground trace. As previously described, the copper layer 514 of the flexure 204 may include a plurality of conductive traces and a ground trace. In addition, the ground trace of the copper layer 514 may be grounded to the steel layer 508 through a via 519. In addition, as previously described, with reference to the function of the flexure 204, the read head is typically electrically connected to one or more of the plurality of conductive traces of the copper layer 514.

Thus, in one embodiment, the Ag epoxy 502 may be used to ground the micro-actuator by extending from the micro-actuator through a through hole of the mounting plate 504 and through the opening 507 of the flexure 204 to extend through the steel layer 508 and the insulator layer 512 of the flexure 204 to ground to the ground trace of the exposed gold plated 502 copper layer 514 of the flexure. Thus, by simply extending the epoxy through the through-hole of the mounting plate, the micro-actuator is directly grounded to the ground trace of the flexure. This has the advantage of solving the problems associated with and to this end of using current flexure cables with steel micro-actuators currently bonded to mounting plates, without additional cost or design/process changes.

Additional embodiments are described below as bleeding air so that the epoxy can flow down more easily to contact the gold plated copper layer more easily. Fig. 7 is a cross-sectional view 700 illustrating an epoxy 502 extending through a mounting plate 504 and into a flexure, particularly illustrating an air gap, according to another embodiment of the invention. In this embodiment, epoxy 502 extends through mounting plate 504, load beam 506, steel layer 508, and insulator layer 512 to gold plated 520 copper layer 514. However, the present embodiment includes air holes or gaps 710 formed in the gold plated 520 copper layer 514 to allow air flow. In one embodiment, there is a cap 702 that may be formed of a thin insulator material. By having air holes, the air is vented so that the epoxy 502 can flow down more easily to contact the gold plated 520 copper layer 514 more easily. Without air holes, air bubbles may form, preventing the epoxy from covering and contacting the gold plated copper layer more completely.

Turning to fig. 8, a schematic diagram of a flexure metal layer 800 is shown. In particular, fig. 8 illustrates a gap 802 that may be formed in the metal layer 508 of the flexure 204 adjacent to the metal load beam layer 506 to allow air flow. Referring to fig. 9, a schematic view of the bottom of a load beam 900 is illustrated. As seen in fig. 9, the metal load beam layer 506 may include a gap 902 to vent air. These additional embodiments help the air vent so that the epoxy can flow down more easily to contact the gold plated copper layer more easily, as previously described.

In the foregoing specification, the invention has been described with reference to specific exemplary embodiments, but those skilled in the art will recognize that the invention is not limited to these embodiments. It is contemplated that various features and aspects of the invention may be used separately or in combination and may be used in different environments or applications. The specification and drawings are, accordingly, to be regarded in an illustrative and exemplary rather than a restrictive sense. "including," "comprising," and "having" are intended to be open-ended terms.

Claims (24)

1. A disk drive comprising:

a pivot attached to the disk drive base;

a disk mounted on the pivot;

a coarse actuator attached to the disk drive base, the coarse actuator comprising an actuator arm; and

a suspension assembly attached to the actuator arm, the suspension assembly comprising:

a mounting plate having a through-hole extending from a top of the mounting plate to a bottom of the mounting plate;

a micro-actuator mounting structure formed in the mounting plate;

a micro-actuator mounted in the micro-actuator mounting structure, the micro-actuator for positioning a read head; and

a flexure attached to a bottom of the mounting plate, the flexure comprising a metal layer, an insulator layer, a trace layer including a ground trace, and an opening, wherein the opening extends through the metal layer and the insulator layer to a gold plated ground trace; and

a conductive epoxy bonded to the micro-actuator extending through the through-hole to bond to the flexure, wherein the epoxy extends through the opening of the flexure to the gold-plated ground trace of the flexure such that the micro-actuator is grounded to the flexure.

2. The disk drive of claim 1 further comprising a plurality of micro-actuators, each micro-actuator mounted in a respective micro-actuator mounting structure of the mounting plate, the epoxy being bonded to each micro-actuator and extending through the through-hole to bond to the flexure.

3. The disk drive of claim 1 wherein the microactuator is a piezoelectric microactuator.

4. The disk drive of claim 3 wherein the piezoelectric microactuator is gold (Au) plated.

5. The disk drive of claim 1 wherein the epoxy comprises silver (Ag).

6. The disk drive of claim 1 wherein the metal layer of the flexure is stainless steel and the insulator layer is polyimide.

7. The disk drive set forth in claim 1 wherein said flexure further comprises a copper layer including said ground trace and a plurality of conductive traces, wherein said ground trace is grounded to said metal layer.

8. The disk drive of claim 7 wherein the copper layer is gold (Au) plated such that the epoxy extends from the gold plating layer of the microactuator to the gold-plated copper layer.

9. The disk drive of claim 7 wherein the read head is electrically connected to one or more of the plurality of conductive traces.

10. The disk drive of claim 7 further comprising air holes formed through the copper layer to allow air flow.

11. The disk drive of claim 1 wherein the metal layer of the flexure includes gaps that allow air flow.

12. The disk drive of claim 1 wherein the load beam of the mounting plate includes a gap to allow air flow.

13. A suspension assembly comprising:

a mounting plate having a through-hole extending from a top of the mounting plate to a bottom of the mounting plate;

a micro-actuator mounting structure formed in the mounting plate;

a micro-actuator mounted in the micro-actuator mounting structure, the micro-actuator for positioning a read head; and

a flexure attached to a bottom of the mounting plate, the flexure comprising a metal layer, an insulator layer, a trace layer including a ground trace, and an opening, wherein the opening extends through the metal layer and the insulator layer to a gold plated ground trace; and

a conductive epoxy bonded to the micro-actuator extending through the through-hole to bond to the flexure, wherein the epoxy extends through the opening of the flexure to the gold-plated ground trace of the flexure such that the micro-actuator is grounded to the flexure.

14. The suspension assembly of claim 13, further comprising a plurality of micro-actuators, each micro-actuator mounted in a respective micro-actuator mounting structure of the mounting plate, the epoxy being bonded to each micro-actuator and extending through the through-hole to bond to the flexure.

15. The suspension assembly of claim 13, wherein the micro-actuator is a piezoelectric micro-actuator.

16. The suspension assembly of claim 15, wherein the piezoelectric microactuator is gold (Au) plated.

17. The suspension assembly of claim 13, wherein the epoxy is silver (Ag).

18. The suspension assembly of claim 13, wherein the metal layer of the flexure is stainless steel and the insulator layer is polyimide.

19. The suspension assembly of claim 13, wherein the flexure further comprises a copper layer including the ground trace and a plurality of conductive traces, wherein the ground trace is grounded to the metal layer.

20. The suspension assembly of claim 19, wherein the copper layer is gold (Au) plated such that the epoxy extends from the gold plating layer of the micro-actuator to the gold plated copper layer.

21. The suspension assembly of claim 19, wherein the read head is electrically connected to one or more of the plurality of conductive traces.

22. The suspension assembly of claim 19, further comprising air holes formed through the copper layer to allow air flow.

23. The suspension assembly of claim 13, wherein the metal layer of the flexure includes a gap that allows air flow.

24. The suspension assembly of claim 13, wherein the load beam of the mounting plate includes a gap that allows air flow.