Gimbal design for hard disk drive devices

Abstract

The head gimbal assembly includes a gimbal comprising a base portion and a tongue portion joined together by a neck portion; a circuit mounted on the gimbal; a slider mounted on the tongue portion and electrically connected to the circuit; a first PZT actuator having a proximal end mounted on a first coupling portion of the circuit and a distal end mounted on a second coupling portion of the circuit; and a second PZT actuator having a proximal end mounted on a third coupling portion of the circuit and a distal end mounted on a fourth coupling portion of the circuit. The first and third coupling portions do not overlap with the base portion and are not directly supported by the base portion. The second and fourth coupling portions overlap with the tongue portion and are directly supported by the tongue portion.

Description

Technical Field

[0001] The present disclosure relates to a hard disk drive, and more particularly, to a gimbal design as part of a suspension assembly for a hard disk drive.

Background Art

[0002] A hard disk drive (HDD) is a non-volatile storage device that stores digitally encoded data on one or more circular disks having a magnetic surface. During operation, each disk rotates at high speed. Data is read from and written to the disk using a read-write head positioned over a specific data track or location on the disk surface by a suspension assembly. The suspension assembly is mounted on an arm of a head stack assembly, which is rotated by a voice coil motor or actuator integrated into the head stack assembly. The primary function of the suspension assembly during hard disk drive operation is to stabilize the read-write head and keep it aligned with the target data track on the disk surface. Optimized suspension assembly design and manufacturing minimize the effects of mechanical, thermal, and other off-track disturbances that could degrade the performance of the hard disk drive. The suspension assembly includes a load beam. During operation, an actuator positions the distal end of the load beam over a desired portion of the disk (e.g., one of the circular tracks on the disk surface). A gimbal assembly (also called a flexure) is mounted on the distal end of the load beam. The gimbal assembly includes components such as a slider containing a read-write head, and a microactuator device (piezoelectric element, hereafter referred to as PZT) that rotates a portion of the gimbal assembly for fine positioning of the slider (as opposed to coarser slider positioning by actuators). The pressure caused by the viscosity of the air between the slider and the rotating disk causes the slider to float above (very close to) the surface of the disk. The load beam is relatively rigid, particularly in the transverse axis, while the gimbal assembly is more flexible, allowing the slider to oscillate vertically and laterally while floating above the disk surface in order to maintain its operating distance just above the disk surface.

[0003] Figure 1 shows a portion of a conventional head stack assembly 1, while Figures 2 and 3 show a conventional head gimbal assembly 10 of a head stack assembly 2. The head stack assembly 2 includes a suspension assembly 3 having a load beam 4, which terminates at a proximal end having a hinge 6 connected to a base plate 8. The head gimbal assembly 10 is mounted on the distal end of the load beam 4. The base plate 8 is connected to an actuator arm 12 of the head stack assembly 2, which is rotated by an integrated actuator (not shown).

[0004] As best illustrated in Figures 2 and 3, the head gimbal assembly 10 comprises a gimbal 14 of a thin component made of sheet metal (e.g., stainless steel), a circuit 16 including conductive traces (e.g., copper) and insulating material (e.g., polyimide), a slider 18 having a read / write head mounted on the gimbal 14 (e.g., by adhesive), and a PZT actuator 22 mounted on the same side of the gimbal 14 as the slider 18. The circuit 16 extends along the load beam 4 and the head gimbal assembly 10 for electrical signal communication to the read / write head of the slider 18 and the PZT actuator 22. The conductive traces of the circuit 16 are electrically isolated from the gimbal 14 by the insulating material of the circuit 16.

[0005] The gimbal 14 includes a base portion 14a and a tongue portion 14b, which are connected to each other by a neck portion 14c. The tongue portion 14b is configured to rotate about the neck portion 14c (for fine positional control of the slider 18). The slider 18 is mounted on the tongue portion 14b. The PZT actuator 22 is mounted between the tongue portion 14b and the base portion 14a so as the PZT actuator 22 expands and contracts in response to an electrical signal supplied by the circuit 16, it rotates the tongue portion 14b about the neck portion 14c, thereby providing fine movement control of the slider 18 relative to the moving disc track. In this example, the PZT actuator 22 is indirectly mounted on the gimbal 14, which means that the PZT actuator 22 is mounted on the circuit 16, and the circuit 16 is mounted on the gimbal 14. Conventional thinking dictates that for better stroke performance, the base portion 14a should be made more rigid and the tongue portion 14b more flexible. This is achieved by positioning the base portion 14a completely beneath the coupling portion 16a of the circuit 16 to which the PZT actuator 22 is mounted, thereby fully supporting the coupling portion 16a, while positioning the tongue portion 14b only partially beneath the coupling portion 16b of the circuit 16 to which the PZT actuator 22 is mounted, thereby only partially supporting the coupling portion 16b.

[0006] The PZT actuator 22 can be a multilayer device of piezoelectric material. A commonly used example of piezoelectric material may be lead zirconate titanate, but other piezoelectric materials that expand and contract in response to electronic signals are also used and are known. Figure 4 shows a cross-section of a conventional PZT actuator 22 having three layers 24, 26, and 28 of piezoelectric material, but more or fewer layers can also be used. The PZT actuator 22 may include a first electrode 30 positioned on at least a portion of the bottom surface of the first PZT layer 24. A second electrode 32 can be positioned between at least a portion of the first PZT layer 24 and the second PZT layer 26. A third electrode 24 can be positioned between at least a portion of the second PZT layer 26 and the third PZT layer 28. Finally, a fourth electrode 36 can be positioned on at least a portion of the top surface of the third PZT layer 28. The shared length (i.e., overlap) between the first electrode 30 and the second electrode 32 can define the effective electrode length 38, and therefore the active piezoelectric layer length of the PZT layer 24. Furthermore, the shared length (i.e., overlap) between the third electrode 34 and the fourth electrode 36 can define the effective electrode length 40, and therefore the active piezoelectric layer length of the PZT layer 28. Conventionally, in order to maximize the expansion / contraction performance of the PZT actuator 22 in response to a given electrical signal, it is necessary to maximize the effective electrode length and the active piezoelectric layer lengths 38 and 40. However, as shown in Figure 4, it is also known that the length L1 of the top electrode (i.e., the fourth electrode 36 in this example) can be made shorter than the lengths L2 of the other electrodes 30, 32, and 34 in order to increase stroke sensitivity, even though the effective electrode length 40 is shortened.

[0007] However, the inventors have found that using the PZT actuator 22 of Figure 4, which has a shortened top electrode 36, together with the head gimbal assembly of Figures 2 and 3 results in low-frequency modes with greater variation over various z heights. Specifically, Figure 5 is a graph of the resonant frequency (FRF) of the suspension assembly 3 with a multilayer PZT 22 mounted on the gimbal 14 as shown in Figures 2 and 3. This resonant frequency (FRF) has low-frequency modes around 9000 Hz and 14000 Hz with greater variation over various z heights.

[0008] A gimbal design is needed that is better suited to PZT actuators with shortened top electrodes and offers a better balance between stroke sensitivity and resonant frequency performance. [Overview of the Initiative]

[0009] The aforementioned problems and needs are addressed by a head gimbal assembly comprising a gimbal having a base portion and a tongue portion joined together by a neck portion; a circuit mounted on the gimbal; a slider mounted on the tongue portion and electrically connected to the circuit; a first PZT actuator having a proximal end mounted on a first coupling portion of the circuit and a distal end mounted on a second coupling portion of the circuit; and a second PZT actuator having a proximal end mounted on a third coupling portion of the circuit and a distal end mounted on a fourth coupling portion of the circuit. The first and third coupling portions do not overlap with the base portion and are not directly supported by the base portion. The second and fourth coupling portions overlap with the tongue portion and are directly supported by the tongue portion.

[0010] The suspension assembly includes a base plate, a load beam connected to the base plate by a hinge, a gimbal mounted on the load beam, the gimbal including a base portion and a tongue portion joined together by a neck portion, a circuit mounted on the gimbal, a slider mounted on the tongue portion and electrically connected to the circuit, a first PZT actuator having a proximal end mounted on a first coupling portion of the circuit and a distal end mounted on a second coupling portion of the circuit, and a second PZT actuator having a proximal end mounted on a third coupling portion of the circuit and a distal end mounted on a fourth coupling portion of the circuit. The first and third coupling portions do not overlap with the base portion and are not directly supported by the base portion. The second and fourth coupling portions overlap with the tongue portion and are directly supported by the tongue portion.

[0011] Other purposes and features of this disclosure will become apparent upon consideration of the text of the specification, the claims, and the accompanying drawings. [Brief explanation of the drawing]

[0012] [Figure 1] This is a partial perspective view of a conventional head suspension assembly. [Figure 2] This is a bottom view of a conventional head gimbal assembly. [Figure 3] This is a top view of a conventional head gimbal assembly. [Figure 4] This is a side view of a conventional PZT actuator. [Figure 5] Figures 1 to 4 show graphs of the resonant frequency (FRF) of the suspension assembly using the PZT actuator and gimbal. [Figure 6] This is a bottom view of an embodiment of the head gimbal assembly. [Figure 7] This is a top view of an embodiment of a head gimbal assembly. [Figure 8] This is an exploded perspective view of an example of a head gimbal assembly. [Figure 9] Figure 4 shows a graph of the resonant frequency (FRF) of the suspension assembly using the PZT actuator and Figures 6 and 7 show the head gimbal assembly. [Modes for carrying out the invention]

[0013] Contrary to conventional thinking, it was found that by lowering the rigidity of the gimbal's base and increasing the rigidity of the gimbal's tongue, the gimbal is better suited to PZTs with short electrodes. Such a gimbal can be used with the head stack assembly 2 shown in Figure 1.

[0014] Figures 6 and 7 show a top and bottom view, respectively, of a head gimbal assembly 50 according to one embodiment, the head gimbal assembly 50 being compatible with the head stack assembly 2 and suspension assembly 3 described above (i.e., the head gimbal assembly 50 can be mounted on the load beam 4 described above with respect to Figure 1). The head gimbal assembly 50 includes a gimbal 52 forming a thin component made of sheet metal. The gimbal 52 can be made of stainless steel. A circuit 54 is mounted on the gimbal 52 or otherwise attached and includes conductive traces and insulating material. The conductive traces can be copper and the insulating material can be polyimide. A slider 56 is mounted on the gimbal 52 and includes a read / write head. The slider can be mounted on the gimbal 52 by adhesive.

[0015] The gimbal 52 includes a base portion 52a and a tongue portion 52b, which are joined together by a neck portion 52c. The slider 56 is mounted on the tongue portion 52b (directly, indirectly if the slider 56 is mounted directly on the circuit 54 and the circuit 54 is mounted directly on the tongue portion 52b, or both). The tongue portion 52b is configured to rotate or otherwise displace around the neck portion 52c relative to the base portion 52a to allow for relatively small movements of the slider 56 for fine positional control of the slider 56 in operation. The PZT actuator 58 is mounted between the tongue portion 52b and the base portion 52a such that when the PZT actuator 58 expands and contracts in response to an electrical signal supplied by the circuit 54 (to provide fine positional control of the slider 56 relative to the operating disc track), it rotates the tongue portion 52b (and the slider 56 attached to the tongue portion 52b) relative to the base portion 52a about the neck portion 52c, or otherwise displaces it.

[0016] The circuit 54, slider 56, and PZT actuator 58 are all mounted on the same side (i.e., the first side) of the gimbal 52, which has the advantage of simplifying the manufacturing process because it does not need to be flipped over during manufacturing before welding the gimbal 52 onto the load beam 4. In this embodiment, the PZT actuator 58 is indirectly mounted on the gimbal 52, which means that the PZT actuator 58 is mounted on the circuit 54, and the circuit 54 is mounted on the gimbal 52. The circuit 54 extends along the gimbal 52 and is mounted on the gimbal 52 in order to transmit electrical signals from the read / write head of the slider 56 and to transmit electrical signals for fine positioning control of the slider 56 to the PZT actuator 58. Therefore, circuit 54 is electrically connected to the electrodes of the PZT actuator 58 (to supply signals to expand and contract the PZT actuator) and electrically connected to the slider 56 (to transmit signals to and from the slider 56 for performing operations such as reading and writing).

[0017] The inventors have found that lowering the rigidity of the base portion 52a and increasing the rigidity of the tongue portion 52b results in better resonant frequency performance. This is achieved by providing a notch 60 within the base portion 52a such that no part of the base portion 52 is positioned below the coupling portion 54a of the circuit 54 to which the proximal end of the PZT actuator 58 is attached. Specifically, the coupling portion 54a is the portion of the circuit 54 to which the proximal end of the PZT actuator 58 is attached. No part of the coupling portion 54a overlaps with the base portion 52a (due to the notch 60) (and is not directly supported by the base portion 52a). Instead, the notch 60 results in the coupling portion 54a being positioned adjacent to the base portion 52a laterally but with a gap between them, so that the coupling portion 54a does not overlap with the base portion 52a and is not directly supported by the base portion 52a. Since the base portion 52a overlaps with and directly supports other parts of the circuit 54 that are not the coupling portion 54a, the coupling portion 54a is supported only indirectly by the base portion 52a. Figure 8 is an exploded view of the head gimbal assembly 50, showing the gimbal 52, the insulator 62 of the circuit 54, the conductive trace 64 of the circuit 54, the PZT actuator 58, and the slider 56 separately.

[0018] In this configuration, where the coupling portion 54a is adjacent to the base portion 52a but spaced apart from it, the circuit 54 is more flexible than the gimbal base portion 52a. Therefore, the rigidity between the proximal end of the PZT actuator 58 and the gimbal base portion 52a is lower compared to the case where the gimbal base portion 52a extends directly below the coupling portion 54a and directly supports it. This flexibility is achieved by overlapping a portion of the circuit (the portion other than the coupling portion 54a) with the gimbal base portion and allowing it to be directly supported by the gimbal base portion. Furthermore, the tongue portion 52b is positioned below the coupling portion 54b of the circuit 54 to which the distal end of the PZT actuator 58 is attached, and directly supports the coupling portion 54b. Specifically, the coupling portion 54b is the portion of the circuit 54 to which the distal end of the PZT actuator 58 is attached. The connection portion 54b overlaps with the tongue portion 52b and is directly supported by the tongue portion 52b. In this configuration, the rigidity between the distal end of the PZT actuator 58 and the gimbal tongue portion 52b is higher compared to a case where the gimbal tongue portion 52b does not extend directly below the connection portion 54b and does not directly support the connection portion 54b.

[0019] The combination of lower stiffness between the PZT actuator 58 and the gimbal base portion 52a, and higher stiffness between the PZT actuator 58 and the gimbal tongue portion 52b, reduces or eliminates low-frequency modes around 9000Hz and 140000Hz. While the reduced stiffness between the PZT actuator 58 and the gimbal base portion 52a may reduce the stroke level and therefore stroke performance, improved stroke performance can be achieved to offset this reduction by using the PZT configuration of Figure 4, i.e., a PZT actuator configuration with a shortened upper electrode length. Figure 9 is a graphical representation of the resonant frequency (FRF) of a suspension assembly with a multilayer PZT 58 having the electrode configuration of Figure 4 mounted on a gimbal 52 as shown in Figures 6-8. This resonant frequency (FRF) has much cleaner low-frequency modes around 9000Hz and 14000Hz.

[0020] This disclosure is not limited to the embodiments described above and shown herein, but should be understood to encompass any modifications that fall within the scope of any claim. For example, references to the invention, embodiments, or examples herein are not intended to limit the scope of any claim or claim term, but rather to one or more features that can be covered by one or more of the claims. The materials, processes, and numerical examples described above are illustrative and should not be considered to limit the scope of the claims.

Claims

1. A gimbal having a base portion and a tongue portion joined together by a neck portion, The circuit mounted on the gimbal, A slider mounted on the tongue portion and electrically connected to the circuit, A first PZT actuator having a proximal end mounted on a first coupling portion of the circuit and a distal end mounted on a second coupling portion of the circuit, A second PZT actuator having a proximal end mounted on a third coupling portion of the circuit and a distal end mounted on a fourth coupling portion of the circuit, A head gimbal assembly comprising, The first and third connecting portions do not overlap with the base portion and are not directly supported by the base portion. The second and fourth connecting portions overlap with the tongue portion and are directly supported by the tongue portion. Head gimbal assembly.

2. A portion of the circuit, different from the first and third connection portions, overlaps with the base portion and is directly supported by the base portion. The head gimbal assembly according to claim 1.

3. The head gimbal assembly according to claim 1, wherein the circuit and the slider are mounted on the first side of the gimbal.

4. Each of the first PZT actuator and the second PZT actuator, A first layer of piezoelectric material, A second layer of piezoelectric material disposed on the first layer of piezoelectric material, A third layer of piezoelectric material disposed on the second layer of piezoelectric material, A first electrode disposed beneath the first layer of piezoelectric material, A second electrode is disposed between the first layer of piezoelectric material and the second layer of piezoelectric material, A third electrode is disposed between the second layer of piezoelectric material and the third layer of piezoelectric material, A fourth electrode disposed on the aforementioned fourth layer of piezoelectric material, Includes, The fourth electrode has a length shorter than the lengths of the first electrode, the second electrode, and the third electrode. The head gimbal assembly according to claim 1.

5. Each of the first PZT actuator and the second PZT actuator, A first layer of piezoelectric material, A second layer of piezoelectric material disposed on the first layer of piezoelectric material, A third layer of piezoelectric material disposed on the second layer of piezoelectric material, A first electrode disposed beneath the first layer of piezoelectric material, A second electrode is disposed between the first layer of piezoelectric material and the second layer of piezoelectric material, A third electrode is disposed between the second layer of piezoelectric material and the third layer of piezoelectric material, A fourth electrode disposed on the aforementioned fourth layer of piezoelectric material, Includes, The fourth electrode has a length shorter than the length of the third electrode. The head gimbal assembly according to claim 1.

6. base plate and A load beam connected to the base plate by a hinge, A gimbal attached to the aforementioned road beam, comprising a base portion and a tongue portion joined together by a neck portion, The circuit mounted on the gimbal, A slider mounted on the tongue portion and electrically connected to the circuit, A first PZT actuator having a proximal end mounted on a first coupling portion of the circuit and a distal end mounted on a second coupling portion of the circuit, A second PZT actuator having a proximal end mounted on a third coupling portion of the circuit and a distal end mounted on a fourth coupling portion of the circuit, A suspension assembly comprising, The first and third connecting portions do not overlap with the base portion and are not directly supported by the base portion. The second and fourth connecting portions overlap with the tongue portion and are directly supported by the tongue portion. Suspension assembly.

7. A portion of the circuit, different from the first and third connection portions, overlaps with the base portion and is directly supported by the base portion. The suspension assembly according to claim 6.

8. The suspension assembly according to claim 6, wherein the circuit and the slider are mounted on the first side of the gimbal.

9. Each of the first PZT actuator and the second PZT actuator, A first layer of piezoelectric material, A second layer of piezoelectric material disposed on the first layer of piezoelectric material, A third layer of piezoelectric material disposed on the second layer of piezoelectric material, A first electrode disposed beneath the first layer of piezoelectric material, A second electrode is disposed between the first layer of piezoelectric material and the second layer of piezoelectric material, A third electrode is disposed between the second layer of piezoelectric material and the third layer of piezoelectric material, A fourth electrode disposed on the aforementioned fourth layer of piezoelectric material, Includes, The fourth electrode has a length shorter than the lengths of the first electrode, the second electrode, and the third electrode. The suspension assembly according to claim 6.

10. Each of the first PZT actuator and the second PZT actuator, The first layer of the piezoelectric material and A second layer of piezoelectric material disposed on the first layer of piezoelectric material, A third layer of piezoelectric material disposed on the second layer of piezoelectric material, A first electrode disposed beneath the first layer of piezoelectric material, A second electrode is disposed between the first layer of piezoelectric material and the second layer of piezoelectric material, A third electrode is disposed between the second layer of piezoelectric material and the third layer of piezoelectric material, A fourth electrode disposed on the aforementioned fourth layer of piezoelectric material, Includes, The fourth electrode has a length shorter than the length of the third electrode. The suspension assembly according to claim 6.

11. A gimbal having a base portion and a tongue portion joined together by a neck portion, and configured to receive a circuit, The tongue portion is configured to receive a slider, and the slider is electrically connected to the circuit of the gimbal, A first PZT actuator having a proximal end mounted on a first coupling portion of the circuit and a distal end mounted on a second coupling portion of the circuit, A second PZT actuator having a proximal end mounted on a third coupling portion of the circuit and a distal end mounted on a fourth coupling portion of the circuit, A head gimbal assembly comprising, The first and third connecting portions do not overlap with the base portion and are not directly supported by the base portion. The second and fourth connecting portions overlap with the tongue portion and are directly supported by the tongue portion. Head gimbal assembly.

12. base plate and A load beam connected to the base plate by a hinge, A gimbal attached to the aforementioned road beam, comprising a base portion and a tongue portion joined together by a neck portion, and configured to receive a circuit, The tongue portion is configured to receive a slider, and the slider is electrically connected to the circuit of the gimbal, A first PZT actuator having a proximal end mounted on a first coupling portion of the circuit and a distal end mounted on a second coupling portion of the circuit, A second PZT actuator having a proximal end mounted on a third coupling portion of the circuit and a distal end mounted on a fourth coupling portion of the circuit, A suspension assembly comprising, The first and third connecting portions do not overlap with the base portion and are not directly supported by the base portion. The second and fourth connecting portions overlap with the tongue portion and are directly supported by the tongue portion. Suspension assembly.

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