HK1163923B - Suspension assembly having a microactuator bonded to a flexure - Google Patents

Description

Suspension assembly for bonding flexure to micro-actuator

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 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., writing, fly height control, touchdown 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.

HGAs also typically include a suspension assembly that includes a mounting plate, a load beam, and a laminated flexure to carry electrical signals to and from the read head. The read head is typically bonded to the tongue of the laminated flexure. In turn, 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 soldering).

Modern laminated flexures typically include conductive copper traces separated from a stainless steel support layer by a polyimide dielectric layer. Enabling signals from/to the head 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 head 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, terminating at electrical connection points at the flexure tail.

A rotary actuator, typically driven by a Voice Coil Motor (VCM), actively controls the position of the HSA relative to the rotating disk in the disk drive, and thus the position of the read head relative to the data tracks/tracks on the disk. Specifically, the current conducted through the coil of the VCM applies a torque to the rotary actuator, enabling the read head to seek and follow a desired data track on the rotating disk.

However, industry trends to increase areal data density have necessitated a substantial reduction in the spacing between data tracks on the disk. In addition, disk drive performance requirements, particularly with respect to the time required to access desired data, have not allowed for reduced disk rotational speeds. In fact, for many disk drive applications, the rotational speed has been increased significantly. The result of these trends is a demand for increased bandwidth for servo control of read head position relative to data tracks on the rotating disk.

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

The micro-actuator may be electrically connected to the flexure through the bond connector in a manner that after extended storage, shipping times, exposure to high temperatures and humidity, the bond connector creates a high resistance to current flow and reduced mechanical strength that may lead to bond connector breakage. Therefore, there is a need in the information handling device art for a bonded connector between a flexure and a microactuator that maintains good current flow and maintains good mechanical strength.

Disclosure of Invention

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 bottom view illustrating a flexure connected to a micro-actuator with a single through-hole according to one embodiment of the present invention;

FIG. 4 is a bottom view illustrating a flexure connected to a micro-actuator with a plurality of through-holes according to one embodiment of the present invention;

FIG. 5 is a cross-sectional view of an epoxy extending through a through-hole of a flexure to bond the flexure to a bottom surface of a micro-actuator, according to one embodiment of the present invention;

fig. 6 is a close-up view of an epoxy extending through a through-hole 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 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 HGA118 may be positioned in a desired manner relative to one or more tracks of information on the magnetic disk 104. Preferably, each disk surface of disk drive 100 will include one HGA118, 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. Electrical signals to/from HGA118 are carried to other driver electronics, in part via a flex cable (not shown) and flex cable mount 116.

FIG. 2 is a bottom perspective view of HGA 200. Referring again to FIG. 2, the HGA200 includes a load beam (loadbeam)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 shown in the view of FIG. 2, but disposed on the trailing face 212). In some embodiments, the read/write transducer is preferably an inductive magnetic write transducer mixed 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 "force loading".

In the embodiment of FIG. 2, the HGA200 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 angle (pitch and roll) 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 aid in signal transmission to/from the read head 210. For the second use, the laminate flexure 204 includes a plurality of conductive traces 218 defined in an electrical conductor (e.g., copper) sub-layer of the laminate 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 and the microactuator mounting structure 250 via the hinge plates 222 and 224. 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 physical continuity.

The load beam 202 with the hinge plates 222, 224 (if present), the microactuator mounting structure 250, 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 (swageboss)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".

It can be seen that the microactuator mounting structure 250 extends from the suspension assembly mounting plate 220. In this embodiment, it can be seen that the microactuator mounting structure 250 is a separate sub-component that is attached (e.g., by a plurality of spot welds) to the suspension assembly mounting plate 220. Alternatively, however, the microactuator mounting structure 250 and the suspension assembly mounting plate 220 may be a single component with material continuity rather than an assembly of subcomponents. The micro-actuator 255 may be mounted in a window of the mounting structure 250. The micro-actuator 255 has a top surface (not shown) and a bottom surface 257.

Turning to fig. 3, fig. 3 is a bottom view illustrating the flexure 204 coupled to the micro-actuator 255 according to one embodiment of the present invention. The flexure 204 includes a pad layer 310 and a through-hole 260, wherein the through-hole 260 extends through the pad layer 310. The epoxy 311 seats in the through-holes 260 of the flexure 204 and bonds the flexure 204 to the micro-actuator 255, as described below.

Specifically, the flexure 204 is attached to the bottom surface of the micro-actuator 255 and is electrically coupled to the micro-actuator 255 through an epoxy bond (epoxy bond) 311. The epoxy adhesive 311 may also be referred to as a joint connector (joincon). To electrically couple the flexure 204 to the micro-actuator 255, a conductive epoxy 311, such as silver (Ag), may be used.

In one embodiment, the flexure 204 may include a pad layer 310 and a through-hole 260, wherein the through-hole 260 extends through the pad layer 310. An epoxy adhesive 311 may be placed in the through-holes 260 of the flexure 204 and bond the flexure 204 to the bottom surface of the micro-actuator 255. For example, the epoxy adhesive 311 may be placed directly on the pad layer 310 below the through-hole 260 of the flexure 204 and press the micro-actuator 255 in the direction of the epoxy adhesive 311, such that the epoxy adhesive 311 extensively bonds to the bottom surface of the micro-actuator 255 and extends through the through-hole 360, as described below.

In one embodiment, referring to fig. 4, a plurality of through-holes 350 may be used. As in fig. 3, each through-hole 350 extends through the pad layer 310. An epoxy adhesive 311 may be respectively placed in each of the through-holes 350 to be respectively bonded to the bottom surface of the micro-actuator 255.

According to one embodiment, micro-actuator 255 may be a Piezoelectric (PZT) micro-actuator. The piezoelectric microactuator may include a gold (Au) layer overcoat bonded to an epoxy.

Further, as shown in fig. 3 and 4, in one embodiment, the pad layer 310 may include a copper (Cu) layer 316 including a gold (Au) coating 312 and a metal layer 357. Additionally, in one embodiment, vias 360 may connect Cu layer 316 of flexure 204 to metal layer 357 of the flexure. In one embodiment, metal layer 357 is stainless steel.

Referring to fig. 5, a cross-sectional view of epoxy 311 (e.g., silver) extending through the through-hole 260 of the flexure 204 while bonding the flexure 204 to the bottom surface 257 of the microactuator 255 is shown. As described above, the epoxy adhesive 311 may be placed directly on the pad layer below the through-hole 260 of the flexure 204 and the micro-actuator 255 is pressed in the direction of the epoxy adhesive 311, such that the epoxy adhesive 311 extensively bonds to the bottom surface 257 of the micro-actuator 255 and extends through the through-hole 360. As shown in fig. 5, the silver epoxy 311 extends through the through-hole 260 of the flexure 204 and through and around the gold coating 312 of the copper layer 316, through the insulator layer 317, and through the stainless steel metal layer 357 of the flexure 204, and extensively adheres to the bottom surface 257 of the microactuator 255. In one embodiment, the insulator layer 317 is polyimide. Additionally, the piezoelectric microactuator 255 may include a gold covering bonded by silver epoxy 311.

In addition, vias 360 may connect Cu layer 316 to metal layer 357 of flexure 204. In one embodiment, metal layer 357 is stainless steel. Thus, in one embodiment, the pad layer may include a copper layer 316 with a gold coating 312, an insulator layer 317, and a stainless steel metal layer 357.

Referring briefly to fig. 6, which is a close-up view of the silver epoxy 311 extending through the copper layer 316 of the flexure 204 having the gold coating 312, it can be seen that the silver epoxy 311 has overflowed through the through-hole 260.

In this manner, it has been found that the silver epoxy 311 makes extensive contact with the micro-actuator 255 and creates a large amount of contact area between the silver epoxy 311 and the micro-actuator 255. This provides a large electrical conductivity of the silver epoxy adhesive 311 between the flexure 204 and the microactuator 255 even under extreme environmental conditions.

Furthermore, the shear strength of the epoxy adhesive 311 (otherwise referred to as a joint connector) is increased due to the rivet-like member formed by the epoxy 311. In addition, electrical conductivity and shear strength are further improved when utilizing a plurality of through-holes 260, such as those previously described with reference to fig. 4, wherein three through-holes 350 are used for bonding of epoxy adhesive 311 to form a plurality of bonded connectors. It should be understood that although fig. 3 and 4 illustrate one and three through-hole embodiments, any suitable number of through-holes may be utilized.

In addition, by connecting the copper layer 316 of the flexure 204 to the stainless steel metal layer 357 of the flexure 204 with vias 360, a better electrical connection is provided between the flexure 204 and the microactuator 255.

In the previously described embodiment, the flexure 204 is energized by the micro-actuator 255 to drive the micro-actuator 255, and the epoxy adhesive 311 or bonding connector between the flexure 204 and the micro-actuator 255 is improved while further providing better bonding mechanical strength. It has been found that with this type of epoxy adhesive 311 or splice connector, current flow and mechanical strength is advantageously maintained even when exposed to high temperatures and humidity and extended storage times.

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. "comprising," "including," and "having" are intended to be open-ended terms.

Claims (18)

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 including an actuator arm; and

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

a mounting plate having a top surface and a bottom surface;

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

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

a flexure attached to the bottom surface of the mounting plate, the flexure comprising:

a pad layer including a copper (Cu) layer and a metal layer; and

a through-hole extending through the copper layer and the metal layer of the pad layer, wherein the epoxy on the pad layer is bonded to the micro-actuator and extends through the through-hole; and

a via connecting a copper (Cu) layer of the pad layer to a metal layer of the pad layer.

2. The disk drive of claim 1 further comprising a plurality of through-holes, each through-hole extending through the pad layer.

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 comprises a layer of gold bonded by an epoxy.

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

6. The disk drive of claim 1 wherein the pad layer of the flexure comprises an insulator layer.

7. The disk drive of claim 1 wherein the copper (Cu) layer has a gold (Au) coating.

8. The disk drive of claim 7 wherein the copper layer further comprises a ground trace and a plurality of other traces.

9. The disk drive of claim 1 wherein the metal layer is stainless steel.

10. A suspension assembly comprising:

a mounting plate having a top surface and a bottom surface;

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

a micro-actuator mounted in the micro-actuator mounting structure to position a read head;

a flexure attached to the bottom surface of the mounting plate, the flexure comprising:

a pad layer including a copper (Cu) layer and a metal layer;

and a through-hole extending through the copper layer and the metal layer of the pad layer, wherein the epoxy on the pad layer is bonded to the micro-actuator and extends through the through-hole; and

a via connecting a copper (Cu) layer of the pad layer to a metal layer of the pad layer.

11. The suspension assembly of claim 10, further comprising a plurality of through-holes, each through-hole extending through the pad layer.

12. The suspension assembly of claim 10, wherein the micro-actuator is a piezoelectric micro-actuator.

13. The suspension assembly of claim 12, wherein the piezoelectric microactuator comprises a layer of gold bonded with an epoxy.

14. The suspension assembly of claim 10, wherein the epoxy includes silver (Ag).

15. The suspension assembly of claim 10, wherein the pad layer of the flexure includes an insulator layer.

16. The suspension assembly of claim 10, wherein the copper (Cu) layer has a gold (Au) coating.

17. The suspension assembly of claim 16, wherein the copper layer further comprises a ground trace and a plurality of other traces.

18. The suspension assembly of claim 10, wherein the metal layer is stainless steel.