Actuator assembly and magnetic disk device

Abstract

To provide actuator assemblies and magnetic disk devices that prevent interference and contact, and offer improved reliability. [Solution] According to the embodiment, the actuator assembly comprises a first head suspension assembly having a suspension having a first surface and a second surface, and a piezoelectric element mounted on the suspension and joined to the suspension by a first conductive adhesive applied to the second surface, and a second head suspension assembly having a suspension having a first surface and a second surface, and a piezoelectric element mounted on the suspension and joined to the suspension by a second conductive adhesive applied to the second surface. The second surfaces of the suspensions of the first head suspension assembly and the second head suspension assembly are facing each other, and the piezoelectric elements are facing each other. The top of the first conductive adhesive is positioned offset in the direction of the suspension relative to the top of the second conductive adhesive.

Description

Technical Field

[0001] Embodiments of this invention relate to an actuator assembly and a magnetic disk device.

Background Art

[0002] As a magnetic disk device, for example, a hard disk drive (HDD) includes a plurality of magnetic disks rotatably disposed in a housing, a plurality of magnetic heads for reading and writing information to and from the magnetic disks, and a head actuator (actuator assembly) that supports the magnetic heads so as to be movable relative to the magnetic disks. The head actuator has an actuator block supported rotatably, and a plurality of head suspension assemblies (sometimes referred to as head gimbal assemblies) each extending from the actuator block and supporting a magnetic head at its tip. The head suspension assembly has a base plate with one end fixed to an arm, a load beam extending from the base plate, a tab extending from the tip of the load beam, and a flexure (wiring member) provided on the load beam and the base plate. The flexure has a displaceable gimbal portion, and a magnetic head is supported on this gimbal portion.

[0003] In recent years, a configuration has been proposed in which a plurality of, for example, two piezoelectric elements are mounted on a suspension assembly and used as a micro actuator. Each piezoelectric element is electrically connected to the base plate or the load beam by a conductive adhesive or the like.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[0005] When multiple suspension assemblies with the above configuration are attached to an actuator arm and stacked, the conductive adhesive portions of adjacent suspension assemblies are positioned facing each other. Therefore, when stacking multiple suspension assemblies on an arm, the base plate or load beam undergoes elastic deformation, which can cause the conductive adhesives of adjacent suspension assemblies to interfere with, or even come into contact with, each other. In particular, in disk drives equipped with many magnetic disks, the thickness of the arm is thin, and the suspension assemblies themselves are also thinly formed. Therefore, the conductive adhesives are even more likely to come into contact with each other. The problem that this embodiment of the invention aims to solve is to provide an actuator assembly and magnetic disk device that prevent interference and contact and have improved reliability. [Means for solving the problem]

[0006] According to the embodiment, the actuator assembly comprises: a first head suspension assembly having a suspension having a first surface, an opposite second surface, and a central axis; a wiring member and a magnetic head mounted on the first surface of the suspension; and a piezoelectric element mounted on the suspension and joined to the suspension by a first conductive adhesive applied to the second surface; and a second head suspension assembly having a suspension having a first surface, an opposite second surface, and a central axis; a wiring member and a magnetic head mounted on the first surface of the suspension; and a piezoelectric element mounted on the suspension and joined to the suspension by a second conductive adhesive applied to the second surface. The first suspension assembly and the second suspension assembly are arranged with the second surfaces of the suspensions facing each other and the piezoelectric elements facing each other. The top of the first conductive adhesive is positioned offset in the plane direction of the suspension relative to the top of the second conductive adhesive. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is an exploded perspective view showing the base and top cover of a hard disk drive (HDD) according to the first embodiment. [Figure 2] Figure 2 is a perspective view showing the head actuator and FPC unit of the HDD. [Figure 3] Figure 3 is a schematic side view showing the head actuator. [Figure 4] Figure 4 is a perspective view showing the up-head suspension assembly of the head actuator. [Figure 5] Figure 5 is a plan view showing the magnetic head side of the uphead suspension assembly. [Figure 6] Figure 6 is a plan view showing the side of the up-head suspension assembly opposite the magnetic head (the back side). [Figure 7] Figure 7 is a cross-sectional view of the piezoelectric element portion along line AA in Figure 5. [Figure 8] Figure 6 is a plan view showing the side surface of the magnetic head of the downhead suspension assembly. [Figure 9] Figure 9 is a schematic plan view showing the up-head suspension assembly and the down-head suspension assembly in a stacked configuration. [Figure 10] Figure 10 is a plan view showing the side of the up-head suspension assembly opposite the magnetic head (back side) in a hard disk drive (HDD) according to the second embodiment. [Figure 11] Figure 11 is a plan view showing the side of the downhead suspension assembly opposite the magnetic head (back side) in a hard disk drive (HDD) according to the second embodiment. [Figure 12] Figure 12 is a schematic side view showing a part of the actuator assembly in an HDD according to the third embodiment. [Modes for carrying out the invention]

[0008] A magnetic disk device according to an embodiment will be described below with reference to the drawings. Furthermore, the disclosure is merely an example, and any modifications that can be easily conceived by a person skilled in the art while maintaining the spirit of the invention are naturally included within the scope of the present invention. In addition, the drawings may schematically represent the size, shape, etc. of each part in order to clarify the explanation, but these are merely examples and do not limit the interpretation of the present invention. In addition, in this specification and each drawing, elements similar to those described above in previously shown drawings are denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0009] (First Embodiment) A hard disk drive (HDD) according to the first embodiment will be described in detail as a magnetic disk device. Figure 1 is a disassembled perspective view of an HDD according to an embodiment shown with the cover removed. As shown in Figure 1, the HDD comprises a rectangular enclosure 10. The enclosure 10 has a rectangular box-shaped base 12 with an open top and a cover (top cover) 14. The base 12 has a rectangular bottom wall 12a and side walls 12b erected along the periphery of the bottom wall 12a, and is integrally molded from, for example, aluminum. The cover 14 is formed from, for example, stainless steel in a rectangular plate shape. The cover 14 is screwed onto the side walls 12b of the base 12 with a plurality of screws 13, and the top opening of the base 12 is airtightly closed.

[0010] The housing 10 contains multiple magnetic disks 18 as disk-shaped recording media, for example, 10 disks, and a spindle motor 19 for supporting and rotating the magnetic disks 18. The spindle motor 19 is mounted on the bottom wall 12a. Each magnetic disk 18 is formed in the shape of a disc, for example, with a diameter of 95 mm (3.5 inches), and has a substrate made of a non-magnetic material, such as glass, and magnetic recording layers formed on the upper and lower surfaces of the substrate. Each magnetic disk 18 is coaxially fitted to the hub of the spindle motor 19 and further clamped by a clamp spring 20. As a result, the magnetic disks 18 are supported at predetermined intervals, parallel to each other, and approximately parallel to the bottom wall 12a. The multiple magnetic disks 18 are rotated in the direction of arrow B at a predetermined rotational speed by the spindle motor 19. Note that the number of magnetic disks 18 mounted is not limited to 10, but may be 9 or less, or 10 or more.

[0011] Inside the housing 10, there are provided a plurality of magnetic heads 17 for recording and playing information with respect to the magnetic disk 18, and an actuator assembly 22 that supports these magnetic heads 17 movably with respect to the magnetic disk 18. Further, inside the housing 10, there are provided a voice coil motor (VCM) 24 for rotating and positioning the actuator assembly 22, a ramp load mechanism 25 for holding the magnetic head 17 at an unload position spaced apart from the magnetic disk 18 when the magnetic head 17 moves to the outermost periphery of the magnetic disk 18, a substrate unit (FPC unit) 21 on which electronic components such as a conversion connector are mounted, and a spoiler 15. The VCM 24 includes a pair of yokes 35 provided on the bottom wall 12a and a magnet (not shown) fixed to the yokes 35. The ramp load mechanism 25 includes a ramp 16 erected on the bottom wall 12a. A printed circuit board 27 is screwed to the outer surface of the bottom wall 12a of the base 12. The printed circuit board 27 controls the operation of the spindle motor 19 and constitutes a control unit that controls the operations of the VCM 24 and the magnetic head 17 via the substrate unit 21.

[0012] FIG. 2 is a perspective view showing the actuator assembly. As shown in the figure, the actuator assembly 22 includes an actuator block 29 having a through hole 26, a bearing unit (unit bearing) 28 provided in the through hole 26, a plurality of, for example, 11 arms 32 extending from the actuator block 29, a head suspension assembly (sometimes referred to as a head gimbal assembly: HGA) 30 attached to each arm 32, and a magnetic head 17 supported by the head suspension assembly 30. A support shaft (spindle) 31 is erected on the bottom wall 12a of the base 12. The actuator block 29 is rotatably supported by the bearing unit 28 around the support shaft 31.

[0013] In this embodiment, the actuator block 29 and the eleven arms 32 are integrally formed of aluminum or the like, constituting a so-called E-block. The arms 32 are formed, for example, in an elongated flat plate shape and extend from the actuator block 29 in a direction orthogonal to the support shaft 31. The eleven arms 32 are provided in parallel with a gap therebetween. The actuator assembly 22 has a support frame 33 that extends from the actuator block 29 in a direction opposite to the arms 32, and the voice coil 39 that forms a part of the VCM 24 is supported by this support frame 33. As shown in FIG. 1, the voice coil 39 is located between a pair of yokes 35, one of which is fixed on the base 12, and together with these yokes 37 and the magnet fixed to any one of the yokes, constitutes the VCM 24.

[0014] As shown in FIG. 2, the actuator assembly 22 includes twenty head suspension assemblies 30 that respectively support the magnetic heads 17. The head suspension assemblies 30 are respectively attached to the tip portions 32a of the respective arms 32. The plurality of head suspension assemblies 30 include an up-head suspension assembly (30u) (sometimes referred to as the first head suspension assembly) that supports the magnetic head 17 upward, and a down-head suspension assembly (30d) (sometimes referred to as the second head suspension assembly) that supports the magnetic head 17 downward. These up-head suspension assemblies (30u) and down-head suspension assemblies (30d) are configured by arranging the head suspension assemblies 30 having the same structure with their up and down directions reversed. However, the extending direction of the flexure 42 described later is opposite between the up-head suspension assembly (30u) and the down-head suspension assembly (30d), and by stacking and arranging one of the up-head suspension assembly and the down-head suspension assembly in an inverted state, the extending directions of the flexures coincide.

[0015] Figure 3 is a schematic side view showing multiple head suspension assemblies 30. In this embodiment, as shown in Figures 2 and 3, each arm 32 has a first seating surface 33a formed on its tip 32a and a second seating surface 33b opposite the first seating surface. A down head suspension assembly 30d is attached to the second seating surface 33b of the uppermost arm 32, and an up head suspension assembly 30u is attached to the first seating surface 33a of the lowermost arm 32. An up head suspension assembly 30u and a down head suspension assembly 30d are attached to the first seating surface 33a and second seating surface 33b of each of the nine intermediate arms 32.

[0016] The head suspension assembly 30 includes a substantially rectangular base plate 38, a load beam 40 made of an elongated leaf spring, and an elongated strip-shaped flexure (wiring member) 42. The flexure 42 has a gimbal section, which will be described later, and the magnetic head 17 is mounted on this gimbal section. The base end of the base plate 38 is fixed to the tip 32a of the arm 32, for example, by crimping. The base end of the load beam 40 is fixed to the end of the base plate 38 by overlapping it. The load beam 40 extends from the base plate 38 and is tapered towards the extended end. The base plate 38 and the load beam 40 constitute a support plate, i.e., a suspension 34. A tab 46 protrudes from the tip of the load beam 40. The tab 46 is engageable with the aforementioned ramp 16 and together with the ramp 16 constitutes a ramp road mechanism 25.

[0017] As shown in Figure 2, the FPC unit 21 integrally comprises a substantially rectangular base portion 21a bent into an L-shape, an elongated strip-shaped relay portion 21b extending from one side edge of the base portion 21a, and a joint portion 21c continuously provided at the tip of the relay portion 21b. The base portion 21a, the relay portion 21b, and the joint portion 21c are formed from a flexible printed circuit board (FPC). The flexible printed circuit board has an insulating layer such as polyimide, a conductive layer formed on this insulating layer with multiple wirings, connection pads, etc., formed on it, and a protective layer covering the conductive layer.

[0018] Electronic components such as a conversion connector (not shown) and multiple capacitors are mounted on the base portion 21a and electrically connected to wiring (not shown). The base portion 21a is installed on the bottom wall 12a of the base 12. The relay portion 21b extends from the side edge of the base portion 21a toward the actuator block 29 of the actuator assembly 22. The joint portion 21c provided at the extended end of the relay portion 21b is formed in a rectangular shape with height and width approximately equal to the side surface (mounting surface) of the actuator block 29. The joint portion 21c is attached to the mounting surface of the actuator block 29 via a backing plate made of aluminum or the like, and is further fixed to the mounting surface with fixing screws 72. Numerous connection pads are provided on the joint portion 21c. For example, one head IC (head amplifier) ​​67 is mounted on the joint portion 21c, and this head IC 67 is connected to the connection pads and the base portion 21a via wiring. Furthermore, the joint portion 21c is provided with a connection terminal 68 to which a voice coil 39 is connected.

[0019] Each head suspension assembly 30's flexiser 42 has one end electrically connected to the magnetic head 17, the other end extending to the actuator block 29 through a groove formed on the side edge of the arm 32, and a connecting end (tail connection terminal section) 42c provided at the other end. The connecting end 42c is formed in an elongated rectangular shape. Multiple, for example, 13, connecting terminals (connecting pads) 51 are provided at the connecting end 42c. These connecting terminals 51 are each connected to the wiring of the flexiser 42. That is, the multiple wires of the flexiser 42 extend over almost the entire length of the flexiser 42, with one end electrically connected to the magnetic head 17 and the other end connected to the connecting terminals (connecting pads) 51.

[0020] The connection terminals 51 provided on the connection ends 42c of the 20 flexures 42 are joined to the connection pads of the joint 21c, and are electrically connected to the wiring of the joint 21c via the connection pads. As a result, the 20 magnetic heads 17 of the actuator assembly 22 are electrically connected to the base 21a through the wiring of the flexures 42, the connection ends 42c, the joint 21c of the FPC unit 21, and the relay section 21b.

[0021] With the actuator assembly 22 configured as described above mounted on the base 12, the support shaft 31 is erected approximately parallel to the spindle of the spindle motor 19. Each magnetic disk 18 is located between two head suspension assemblies 30. During HDD operation, the magnetic heads 17 supported by the two head suspension assemblies 30 face the upper and lower surfaces of the magnetic disks 18, respectively.

[0022] Next, the configuration of the head suspension assembly 30 will be described in detail. Figure 4 is a perspective view showing the magnetic head side of the uphead suspension assembly, and Figure 5 is a plan view showing the magnetic head side of the uphead suspension assembly. As shown in Figures 4 and 5, the head suspension assembly 30 has a suspension 34 that functions as a support plate. The suspension 34 has a rectangular base plate 38 made of a metal plate several hundred microns thick and an elongated leaf spring-shaped load beam 40 made of a metal plate several tens of microns thick. In one example, the thickness of the base plate 38 is about 150 to 200 μm, and the thickness of the load beam 40 is about 25 to 30 μm. The base plate 38 and the load beam 40 are made of stainless steel, for example. The upper surface of the suspension 34 is the first surface S1, and the back surface of the suspension 34 is the second surface S2.

[0023] The load beam 40 is positioned with its base end overlapping the tip of the base plate 38 and is fixed to the base plate 38 by welding at multiple points. The width of the base end of the load beam 40 is formed to be approximately equal to the width of the base plate 38. The load beam 40 extends from the base plate 38. The load beam 40 is tapered, that is, its width gradually narrows from the base end to the tip. A long, slender, rod-shaped tab 46 is provided protruding from the tip of the load beam 40.

[0024] The base plate 38 has a circular through-hole (crimping hole) 38a and an annular flange 38b located around the through-hole 38a. The flange 38b extends into the through-hole 38a. On the other hand, as shown in Figure 4, the arm 32 has a flat first seating surface 33a and a second seating surface 33b formed on its tip portion 32a, and a circular crimping hole 33c formed through the seating surfaces 33a and 33b. The first seating surface 33a and the second seating surface 33b are parallel to each other and face each other. The second surface S2 of the base plate 38 is placed on the first seating surface 33a, and the flange 38b is fitted into the crimping hole 33c. By crimping this flange 38b, the base plate 38 is fastened to the tip portion 32a of the arm 32. The base plate 38 may be fixed to the tip portion 32a of the arm 32 by laser welding, spot welding, or adhesive bonding.

[0025] As shown in Figures 4 and 5, the head suspension assembly 30 has a central axis C1 passing through the center of the through-hole 38a and the tab 46. The load beam 40 extends from the base plate 38 along the central axis C1. The direction of extension of the central axis C1 is defined as the first direction (longitudinal direction) X of the suspension assembly, and the direction perpendicular to the first direction X is defined as the second direction (width direction) Y. The direction perpendicular to the first direction X and the second direction Y is defined as the third direction (height direction) Z. In addition, the direction parallel to the XY plane is sometimes referred to as the plane direction.

[0026] In the region where the base plate 38 and the load beam 40 overlap, a pair of rectangular openings (notches) 41a, each functioning as a mounting portion, are formed at the tip of the base plate 38. Furthermore, a pair of rectangular openings (notches) 41b, each functioning as a mounting portion, are formed at the base end of the load beam 40. Each opening 41a, 41b opens to both sides of the base plate 38 and the load beam 40. Each opening 41a, 41b extends in the second direction Y and opens to the side edge of the base plate 38 and the side edge of the load beam 40. The pair of openings 41a are located on both sides of the central axis C1 of the base plate 38, spaced apart from each other in the second direction Y. Similarly, the pair of openings 41b are located on both sides of the central axis C1 of the load beam 40, spaced apart from each other in the second direction Y. As a result, the pair of openings 41a and the pair of openings 41b overlap each other. Two overlapping apertures 41a and 41b are each oriented with a first piezoelectric element (PZT element) 50A, which will be described later.

[0027] The head suspension assembly 30 has an elongated, strip-shaped flexi-shape (wiring member) 42 for transmitting recording, playback signals, and drive signals. The leading edge portion 42a of the flexi-shape 42 is mounted on the first surface S1 of the suspension 34. The rear half portion (extension portion) 42b of the flexi-shape 42 extends outward from the side edge of the base plate 38 and extends along the side edge of the arm 32 (see Figure 2). The connecting end 42c located at the tip of the extension portion 42b is connected to the joint portion 21c of the FPC unit 21 described above. The tip of the flexure 42 is located on the tip of the load beam 40 and constitutes a gimbal section 45 that functions as an elastic support. The magnetic head 17 is mounted and fixed on the gimbal section 36 and is supported by the load beam 40 via this gimbal section 45. A pair of second piezoelectric elements 50B are attached to the gimbal section 45 and are located on the base end side of the load beam 40 relative to the magnetic head 17.

[0028] The flexiser 42 has a base metal sheet (metal plate) 44a made of stainless steel or the like, and a strip-shaped laminated member 44b attached or fixed on the metal sheet 44a, forming an elongated laminated plate. The laminated member 44b has a base insulating layer that is mostly fixed to the metal sheet 44a, a conductive layer (wiring pattern) formed on the base insulating layer that constitutes multiple signal wirings and drive wirings, and a cover insulating layer laminated on the base insulating layer, covering the conductive layer. At the tip end portion 42a of the flexiser 42, the metal sheet 44a side is attached to the surface of the load beam 40 and the base plate 38, or spot-welded at multiple welding points.

[0029] In the gimbal section 45, the thin metal plate 44a has a rectangular tongue section (support section) 45a located at the tip end, and a pair of elongated outriggers (link sections) 45b extending from the tongue section 45a to the base end. The tongue section 45a is formed to a size and shape that can accommodate the magnetic head 17, and is, for example, formed in a substantially rectangular shape. The laminated member 44b also has a tip section 44c attached to the tongue section 45a. The tongue portion 45a has its approximate center in contact with a dimple (protrusion) (not shown) protruding from the tip of the load beam 40. The tongue portion 45a can be displaced in various directions around the dimple as a pivot point by the elastic deformation of a pair of outriggers 45b. As a result, the tongue portion 45a, the tip portion 44c mounted on the tongue portion 45a, and the magnetic head 17 can flexibly follow surface fluctuations of the magnetic disk 18 in the roll and pitch directions, and maintain a minute gap between the surface of the magnetic disk 18 and the magnetic head 17.

[0030] The magnetic head 17 has a substantially rectangular slider 17a, which is fixed to the tip portion 44c and tongue portion 45a by adhesive. The magnetic head 17 is positioned so that its longitudinal central axis coincides with the central axis C1 of the suspension 34, and the approximate center of the magnetic head 17 is located on a dimple. The recording and playback elements of the magnetic head 17 are electrically connected to multiple electrode pads PT on the tip portion 44c by solder or a conductive adhesive such as silver paste. As a result, the magnetic head 17 is connected to the signal wiring W of the flexi 42 via the electrode pads PT.

[0031] The pair of second piezoelectric elements 50B are, for example, rectangular plate-shaped thin-film piezoelectric elements (PZT elements). Each second piezoelectric element 50B is attached to the tip portion 44c of the flexure 42 with an adhesive or the like. Each second piezoelectric element 50B is electrically connected to the drive wiring of the flexure 42. The second piezoelectric elements 50B are arranged so that their longitudinal direction (extension direction) is parallel to the longitudinal direction of the load beam 40. The two second piezoelectric elements 50B are arranged parallel to each other and are positioned on both sides of the magnetic head 17, offset from the magnetic head 17 towards the base end of the load beam 40. Note that the second piezoelectric elements 50B are not limited to the above arrangement; for example, they may be arranged at an angle with respect to the central axis C1.

[0032] Each second piezoelectric element 50B expands and contracts along the first direction X of the suspension 34 when a voltage is applied. By driving these two second piezoelectric elements 50B in opposite directions of expansion and contraction relative to each other, the tongue portion 45a can be oscillated and the magnetic head 17 can be displaced. In this way, the second piezoelectric elements 50B constitute a second microactuator for fine-tuning the magnetic head 17.

[0033] Next, the arrangement configuration of the first piezoelectric element 50A will be described in detail. Figure 6 is a plan view showing the back side (second surface) of the uphead suspension assembly opposite the magnetic head, and Figure 7 is a cross-sectional view of the piezoelectric element section along line AA in Figure 5. As shown in Figures 6 and 7, the pair of first piezoelectric elements 50A are, for example, rectangular plate-shaped thin-film piezoelectric elements (PZT elements). In one example, the first piezoelectric element 50A has a piezoelectric body 50a formed in a flattened rectangular parallelepiped shape from a piezoelectric material, and a first electrode 51a and a second electrode 51b provided on the outer surface of the piezoelectric body 50a. As the piezoelectric material, for example, zinc zirconate titanate, ceramics, etc. are used.

[0034] The first electrode 51a is provided extending from one end of the upper surface of the piezoelectric body 50a to the side and most of the upper surface on the shorter side. The second electrode 51b is provided extending from one end of the lower surface of the piezoelectric body 50a to the other side and most of the lower surface on the shorter side. In one example, the first electrode 51a is the voltage application (Vin) side electrode, and the second electrode 51b is the ground (GND) side electrode.

[0035] A pair of first piezoelectric elements 50A are each positioned within the openings 41a and 41b of the suspension 34. Each first piezoelectric element 50A is positioned such that its longitudinal element central axis C2 is approximately parallel to the central axis C1 of the suspension 34. The pair of first piezoelectric elements 50A are spaced apart in the second direction Y, parallel to each other, and positioned on both sides of the central axis C1. The distance between the element central axis C2 and the central axis C1 of each first piezoelectric element 50A is set to be equal.

[0036] As shown in Figure 7, within the openings 41a and 41b, one and the other end of the first piezoelectric element 50A in the axial direction are fixed to the base plate 38 and the load beam 40 by a non-conductive adhesive Ad1. The first electrode 51a of the first piezoelectric element 50A is exposed upward through the openings 41a and 41b. The second electrode 51b is exposed downward through the openings 41a and 41b and is positioned almost flush with the second surface S2 of the suspension 34.

[0037] As shown in Figures 5 and 7, an electrode pad 54 is attached to the first electrode 51a using a conductive adhesive Ad2. The electrode pad 54 is connected to the drive signal line W of the flexi 42. Thus, the first piezoelectric element 50A is electrically connected to the drive signal line W of the flexi 42.

[0038] As shown in Figures 6 and 7, a plating layer 56 is formed on the tip of the base plate 38, on the second surface S2. As an example, gold plating is used for the plating layer 56. The plating layer 56 is installed between the tip of the base plate 38 and a pair of openings 41a, and extends over the entire width in the second direction Y. The second electrode 51b of the first piezoelectric element 50A and the plating layer 56 are electrically joined by a conductive adhesive Ad(u). The conductive adhesive Ad(u) is applied in dots to the boundary between the second electrode 51b and the plating layer 56 on the second surface S2 of the suspension 34, and is coated over both the second electrode 51b and the plating layer 56. The conductive adhesive Ad(u) has an arc shape with a peak height (top T) approximately in the middle of the first direction X and the second direction Y. As a result, the second electrode 51b is electrically joined to the plating layer 56 and the base plate 38 by the conductive adhesive Ad(u), and is connected to ground (G) via the base plate 38.

[0039] By applying a voltage between the first electrode 51a and the second electrode 51b, the piezoelectric body 50a sandwiched between the first electrode 51a and the second electrode 51b expands or contracts in the longitudinal direction (first direction X). By driving the two first piezoelectric elements 50A in opposite directions of expansion and contraction relative to each other, the load beam 40 can be oscillated and the magnetic head 17 can be displaced. In this way, the pair of first piezoelectric elements 50A constitute a first microactuator that causes minute displacements of the magnetic head 17.

[0040] As shown in Figure 6, in a plan view, the conductive adhesive Ad(u) has a substantially elliptical outer shape. At least one of the pair of conductive adhesives Ad(u) is provided at a position offset in the planar direction, for example, in the second direction Y, with respect to the element central axis C2 of the first piezoelectric element 50A. More specifically, the conductive adhesive Ad(u) is positioned such that its top T is offset in the second direction Y with respect to the element central axis C2.

[0041] In this embodiment, both of the pair of conductive adhesives Ad(u) are positioned offset in the second direction Y with respect to the element's central axis C2. The pair of conductive adhesives Ad(u) are offset in the same direction, and in this case, offset in the second direction Y away from the rear half portion (extension portion) 42b of the flexure 42. The amount of offset can be set arbitrarily. In the illustrated example, the peripheral edge of the conductive adhesive Ad(u) is positioned to be in contact with the element's central axis C2. The direction of offset may be the opposite direction to that shown in the illustrated example, i.e., the direction approaching the rear half portion (extension portion) 42b. Furthermore, the direction of offset is not limited to the second direction Y, but may be any direction intersecting the central axis C1 in the planar direction.

[0042] Figure 8 is a plan view showing the back side (second surface S2) of the downhead suspension assembly opposite the magnetic head. As shown in Figure 8, the down-head suspension assembly 30d is configured identically to the up-head suspension assembly 30u described above, except for the following: In the down-head suspension assembly 30d, the rear half portion (extension portion) 42b of the flexure 42 extends in the opposite direction to that of the up-head suspension assembly 30u. In addition, at least one of the conductive adhesives Ad(d) of the pair of first piezoelectric elements 50A is provided at a position offset in the planar direction, for example, in the second direction Y, with respect to the element central axis C2 of the first piezoelectric element 50A. More specifically, the conductive adhesive Ad(d) is arranged such that its top portion T is offset in the second direction Y with respect to the element central axis C2.

[0043] In this embodiment, both of the pair of conductive adhesives Ad(d) are positioned offset in the second direction Y with respect to the element central axis C2. The pair of conductive adhesives Ad(d) are offset in the same direction, and in this case, in the second direction Y, they are positioned in the opposite direction to the conductive adhesive Ad(u) of the aforementioned uphead suspension assembly 30u, that is, in the direction approaching the rear half portion (extension portion) 42b of the flexure 42. The amount of displacement can be set arbitrarily. In the illustrated example, the peripheral edge of the conductive adhesive Ad(d) is positioned so that it is in contact with the element's central axis C2. Preferably, the direction of displacement is opposite to the direction of displacement of the conductive adhesive Ad(u) of the up-head suspension assembly 30u. Note that if the opposing conductive adhesive Ad(u) of the up-head suspension assembly 30u is positioned offset from the element's central axis C2, the opposing conductive adhesive Ad(d) of the down-head suspension assembly 30d may be positioned on the element's central axis C2.

[0044] As shown in Figure 3, the up-head suspension assembly 30u, configured as described above, is attached to the arm 32 with the second surface S2 of the base plate 38 crimped and fixed to the first seating surface 33a of the arm 32. The down-head suspension assembly 30d is attached to the arm 32 with the second surface S2 of the base plate 38 crimped and fixed to the second seating surface 33b of the arm 32. As a result, the second surface S2 of the up-head suspension assembly 30u (the surface opposite to the magnetic head 17) and the second surface S2 of the down-head suspension assembly 30d face each other with a gap in the third direction Z. In addition, the conductive adhesive Ad(u) of the up-head suspension assembly 30u faces the conductive adhesive Ad(d) of the down-head suspension assembly 30d in the third direction.

[0045] Figure 9 is a schematic plan view showing the up-head suspension assembly and the down-head suspension assembly in a stacked configuration. As mentioned above, the pair of conductive adhesives Ad(u) of the up-head suspension assembly 30u are offset in one direction of the second direction Y with respect to the element central axis C2 of the first piezoelectric element 50A. Similarly, the pair of conductive adhesives Ad(d) of the down-head suspension assembly 30d are offset in the opposite direction of the second direction Y with respect to the element central axis C2 of the first piezoelectric element 50A. Therefore, as shown in Figure 9, when the up-head suspension assembly 30u and the down-head suspension assembly 30d are facing each other, the conductive adhesives Ad(d) and Ad(u) are not completely opposite to each other, but are offset from each other in the planar direction, in this case, in the second direction Y.

[0046] Therefore, when the head suspension assembly 30 is attached to the arm 32, or when the head suspension assembly 30 undergoes elastic deformation, the possibility of contact or interference between the conductive adhesives Ad(d) and Ad(u) is significantly reduced. Consequently, damage to the conductive adhesive and connection failures of the piezoelectric element are suppressed, improving the reliability of the suspension assembly and the HDD.

[0047] According to the first embodiment configured as described above, interference and contact of conductive adhesives can be prevented, and a suspension assembly and magnetic disk device with improved reliability can be provided. In the first embodiment described above, the conductive adhesives Ad(d) and Ad(u) are arranged and offset so that they do not overlap in the third direction Z. However, this is not limited to this arrangement, and a portion may overlap in the third direction Z. It is sufficient that the vertices T do not face each other. In other words, if the vertices T are offset in the second direction Y, the same effects and advantages as in the first embodiment described above can be obtained.

[0048] Next, a head suspension assembly of an HDD according to another embodiment will be described. In the other embodiments described below, the same reference numerals are used for parts that are the same as those in the first embodiment described above, and their detailed descriptions are omitted or simplified. The focus will be on the parts that differ from the first embodiment.

[0049] (Second Embodiment) Figure 10 is a plan view showing the side opposite the magnetic head (back side) of the up-head suspension assembly in the HDD according to the second embodiment, and Figure 11 is a plan view showing the side opposite the magnetic head (back side) of the down-head suspension assembly in the HDD according to the second embodiment. In the second embodiment, the placement position of the conductive adhesive Ad connecting the first piezoelectric element 50A to ground differs from that in the first embodiment. In the second embodiment, the other components of the head suspension assembly 30 are the same as those of the head suspension assembly 30 in the first embodiment.

[0050] As shown in Figure 10, according to the second embodiment, the pair of conductive adhesives Ad(u) of the uphead suspension assembly 30u are offset in opposite directions in the second direction Y with respect to the element central axis C2 of the first piezoelectric element 50A. More specifically, the pair of conductive adhesives Ad(u) are positioned such that their tops T are offset with respect to the element central axis C2 in a direction away from the central axis C1 of the suspension 34. The amount of offset can be set arbitrarily. In the illustrated example, the peripheral edge of the conductive adhesive Ad(u) is offset to a position where it is in contact with the element central axis C2.

[0051] As shown in Figure 11, in the downhead suspension assembly 30d, the pair of conductive adhesives Ad(d) are positioned offset from the element central axis C2 of the first piezoelectric element 50A in opposite directions in the second direction Y, and in the opposite direction to the offset direction of the conductive adhesive Ad(u) of the uphead suspension assembly 30u. In detail, the pair of conductive adhesives Ad(d) are positioned such that their tops T are offset from the element central axis C2 in a direction approaching the central axis C1 of the suspension 34. The amount of offset can be set arbitrarily. In the illustrated example, the peripheral edge of the conductive adhesive Ad(d) is positioned so that it is in contact with the element central axis C2.

[0052] According to the second embodiment described above, when the up-head suspension assembly 30u and the down-head suspension assembly 30d are facing each other, the conductive adhesive Ad(d) and the conductive adhesive Ad(u) are not completely opposite to each other, but are offset from each other in the planar direction, in this case in the second direction Y. Therefore, when the head suspension assembly 30 is attached to the arm 32, or when the head suspension assembly 30 undergoes elastic deformation, the possibility of contact or interference between the conductive adhesives Ad(d) and Ad(u) is greatly reduced. Consequently, damage to the conductive adhesive Ad and connection failures of the piezoelectric element are suppressed, and the reliability of the suspension assembly and the HDD can be improved.

[0053] (Third embodiment) Figure 12 is a side view showing a part of the head actuator assembly in an HDD according to the third embodiment. As shown in the figure, according to the third embodiment, the conductive adhesive Ad(u) of the up-head suspension assembly 30u and the conductive adhesive Ad(d) of the down-head suspension assembly 30d are each provided on the element central axis C2 of the first piezoelectric element 50A.

[0054] When the central axis C3 is defined as the line passing through the center of conductive adhesive Ad(u) and the center of conductive adhesive Ad(d), conductive adhesive Ad(u) is formed and positioned such that its top T is offset in the first direction X with respect to the central axis C3. In one example, the top T is offset in the plane direction approaching the tip 32a of the arm. The conductive adhesive Ad(d) is formed and positioned such that its top T is offset in a first direction X with respect to the central axis C3. In one example, the top T is offset away from the tip 32a of the arm, i.e., in the opposite direction to the offset of the top T of the conductive adhesive Ad(u).

[0055] As described above, the top T of conductive adhesive Ad(u) and the top T of conductive adhesive Ad(d) are offset from each other in the planar direction, in this case in the first direction X, without overlapping in the third direction Z. Therefore, when the head suspension assembly 30 is attached to the arm 32, or when the head suspension assembly 30 undergoes elastic deformation, the possibility of contact or interference between conductive adhesives Ad(d) and Ad(u) is greatly reduced. Consequently, damage to the conductive adhesive Ad and connection failures of the piezoelectric element are suppressed, and the reliability of the suspension assembly and the HDD can be improved.

[0056] In the third embodiment, the amount of displacement of the top T of the conductive adhesive Ad can be set arbitrarily. Furthermore, it is not limited to both conductive adhesives Ad(u) and Ad(d), but it is sufficient that the top T of at least one of the conductive adhesives is displaced in the planar direction with respect to the central axis C3.

[0057] The present invention is not limited to the embodiments described above, and in the implementation stage, the components can be modified and implemented without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments. Moreover, components from different embodiments may be appropriately combined. For example, the head suspension assembly may omit the second piezoelectric element (second microactuator). The direction of displacement of the conductive adhesives Ad(u) and Ad(d) is not limited to the first direction X and the second direction Y, but can be any other direction. The number of magnetic disks installed is not limited to 10, but can be increased to 11 or 12. [Explanation of Symbols]

[0058] 10...Housing, 12...Base, 12a...Bottom wall, 12b...Side wall, 17...Magnetic head 18...Magnetic disk, 19...Spindle motor, 22...Actuator assembly, 30... Head suspension assembly, 30d... Downhead suspension assembly, 30u... Up-head suspension assembly, 32... Arm, 38...Base plate, 40...Load beam, 41a, 41b...Opening, 42...Flexible cable (wiring component), 50A...First piezoelectric element, 50B...Second piezoelectric element, Ad(d), Ad(u)... Conductive adhesives

Claims

1. A first head suspension assembly comprising: a suspension having a first surface, an opposite second surface, and a central axis; a wiring member and a magnetic head mounted on the first surface of the suspension; and a piezoelectric element mounted on the suspension and joined to the suspension by a first conductive adhesive applied to the second surface side; A second head suspension assembly comprising: a suspension having a first surface, an opposite second surface, and a central axis; a wiring member and a magnetic head mounted on the first surface of the suspension; and a piezoelectric element mounted on the suspension and joined to the suspension by a second conductive adhesive applied to the side of the second surface, The first head suspension assembly and the second head suspension assembly are arranged so that the second surfaces of the suspensions face each other and the piezoelectric elements face each other, and the top of the first conductive adhesive is positioned offset in the direction of the suspension relative to the top of the second conductive adhesive. Actuator assembly.

2. The arm comprises a first seat surface and a second seat surface facing the first seat surface, The actuator assembly according to claim 1, wherein a portion of the second surface of the suspension of the first head suspension assembly is fixed to the first seat surface, and a portion of the second surface of the suspension of the second head suspension assembly is fixed to the second seat surface.

3. Each of the piezoelectric elements has an element central axis that extends parallel to the central axis of the suspension, The top of the first conductive adhesive is positioned offset from the central axis of the suspension with respect to the central axis of the element, The actuator assembly according to claim 1, wherein the top of the second conductive adhesive is positioned offset from the central axis of the element in a direction approaching the central axis of the suspension.

4. Each of the piezoelectric elements has an element central axis that extends parallel to the central axis of the suspension, The first conductive adhesive is positioned offset from the central axis of the element in a direction approaching the central axis of the suspension, The actuator assembly according to claim 1, wherein the second conductive adhesive is positioned offset from the central axis of the suspension with respect to the central axis of the element.

5. Each of the piezoelectric elements has an element central axis that extends parallel to the central axis of the suspension, The top of the first conductive adhesive is located on the central axis of the element, The actuator assembly according to claim 1, wherein the top of the second conductive adhesive is located on the central axis of the element and is offset from the top of the first conductive adhesive in a direction along the central axis of the element.

6. Each of the suspensions includes a base plate fixed to the seating surface of the arm, and a road beam extending from the base plate. Each of the first head suspension assemblies has a pair of piezoelectric elements provided between the base plate and the load beam, and each piezoelectric element is joined to the suspension by a first conductive adhesive applied to the second surface side. Each of the second head suspension assemblies has a pair of piezoelectric elements provided between the base plate and the road beam, and each piezoelectric element is joined to the suspension by a second conductive adhesive applied to the second surface. The pair of piezoelectric elements are arranged facing each other, and the top of the first conductive adhesive is positioned offset from the top of the second conductive adhesive in the plane direction of the suspension. The actuator assembly according to claim 2.

7. The actuator assembly according to claim 6, wherein each of the pair of piezoelectric elements has an element central axis extending parallel to the central axis of the suspension, and is arranged at equal intervals and spaced apart on both sides of the central axis with the central axis in between.

8. Each of the pair of first conductive adhesives is positioned offset from the central axis of the element in one direction that intersects with the central axis of the suspension, The actuator assembly according to claim 7, wherein the pair of second conductive adhesives are each positioned offset from the central axis of the element in the direction opposite to the one direction.

9. The pair of first conductive adhesives are each positioned offset from the central axis of the suspension with respect to the central axis of the element, The actuator assembly according to claim 7, wherein each pair of the second conductive adhesives is positioned offset from the central axis of the element in a direction approaching the central axis of the suspension.

10. Multiple rotatable disk-shaped magnetic recording media, The actuator assembly according to claim 1, A magnetic disk drive equipped with the following features.

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