Head gimbal assembly for hard disk drive device

A gimbal having a base portion and a tongue joined together by a neck portion. The base portion includes a first proximal edge facing away from the tongue. A circuit is mounted on the gimbal and includes a portion mounted to the base portion having a circuit extension region that extends beyond the first proximal edge. The circuit extension region includes a second proximal edge facing away from the tongue. A slider may be mounted on the tongue and electrically connected to the circuit. First and second PZT actuators are mounted to the head gimbal assembly and electrically connected to the circuit. The circuit extension region has a circuit extension region width W of at least 0.1 mm as measured in a direction extending away from the tongue relative to a furthest extending portion of the first proximal edge and a furthest extending portion of the second proximal edge.

FIELD OF THE INVENTION

The present disclosure relates to hard disk drives, and more particularly to a head gimbal assembly and a suspension assembly for hard disk drives.

BACKGROUND OF THE INVENTION

A hard disk drive (HDD) is a non-volatile storage device that stores digitally encoded data on one or more circular disks having magnetic surfaces. In operation, each disk spins rapidly. Data is read from and written to the disk using a read-write head that is positioned over a specific data track or location on the disk surface by a suspension assembly, which in turn is attached to the arm of the head stack assembly, which is rotated by a voice coil motor or actuator integral to the head stack assembly. Keeping the read-write head stable, and aligned with a targeted data track upon the disk surface defines the primary function of the suspension assembly during hard disk drive operation. Optimized suspension assembly design and manufacture can minimize the effects of mechanical, thermal, and other off-track disturbances which can degrade the performance of the hard disk drive. The suspension assembly includes a load beam. In operation, the actuator positions the distal end of the load beam over the desired portion of the disk (e.g., one of the circular tracks on the disk surface). A gimbal assembly (also sometimes referred to as a flexure) is mounted on the distal end of the load beam. The assembly may further include components such as a slider containing the read-write head and microactuator devices (piezoelectric devices, also referred to as PZT herein) that rotate a portion of the gimbal assembly for fine positioning of the slider (as opposed to more coarse positioning of the slider by the actuator). The pressure caused by air viscosity between the slider and the spinning disk causes the slider to hover over (in close proximity to) the surface of the disk. While the load beam is relatively stiff, particularly in the lateral axis, the gimbal assembly is more flexible so that the slider can pitch and roll as it floats over the disk surface in order to maintain its operational distance immediately over the disk surface.

FIG.1illustrates a portion of a conventional head stack assembly2, whileFIGS.2-3illustrate a conventional head gimbal assembly10of the head stack assembly2. The head stack assembly2includes a suspension assembly3with a load beam4terminating at a proximal end with a hinge6that is connected to a baseplate8. A head gimbal assembly10is mounted on the distal end of the load beam4. The baseplate8is connected to an actuator arm12of the head stack assembly2, which is rotated by an integral actuator (not shown).

As best shown inFIGS.2and3, head gimbal assembly10comprises a gimbal14of thin components of sheet metal (e.g., stainless steel), a circuit16that includes conductive traces (e.g., copper) and insulation material (e.g., polyimide), a slider18with the read/write head mounted on the gimbal14(e.g., by adhesive), and PZT actuators20mounted on the same side of the gimbal14as the slider18. Circuit16extends along the load beam4and head gimbal assembly10for electrical signal communication to the read/write head of the slider18and to PZT actuators20. The conductive traces of the circuit16are electrically insulated from the gimbal14by the insulation material of the circuit16.

The gimbal14includes a base portion14aand a tongue14b, which are connected to each other by a neck portion14c. The tongue14bis configured to rotate about the neck portion14c(for fine position control of the slider18). The slider18is mounted on the tongue14b. The PZT actuators20are mounted between the tongue14band the base portion14a, for rotating the tongue14babout the neck portion14cwhen the PZT actuators20expand and contract in response to electrical signals provided by the circuit16, which provides fine movement control of the slider18relative to the disk tracks during operation. In this example, the PZT actuators20are indirectly mounted on the gimbal14, meaning that the PZT actuators20are mounted on the circuit16, which is in turn mounted on the gimbal14.

PZT actuators20can be multi-layer devices of piezoelectric material. A commonly used example of piezoelectric material can be lead zirconate titanate, although other piezoelectric materials are also used and known, which expand and contract in response to electronic signals. PZT materials can be brittle. When the suspension assembly3is not in use, it can be parked on a ramp to help protect the suspension assembly3from potentially damaging movement caused by non-operational shock events (e.g., caused when the HDD is roughly handled or dropped). However, during a non-operational shock event, the head gimbal assembly10can be damaged (e.g., the PZT material can suffer from cracking, and/or the circuit16can suffer from permanent deformation). Damage can result from large movement of the base portion14ain the pitch direction, where the proximal edge of the base portion14amay contact the load beam4, causing undue stress on the PZT actuators20.

There is a need for a head gimbal assembly design that is less susceptible to damage from non-operational shock events.

BRIEF SUMMARY OF THE INVENTION

The aforementioned problems and needs are addressed by a head gimbal assembly that includes a gimbal having a base portion and a tongue that are joined together by a neck portion, wherein the base portion includes a first proximal edge facing away from the tongue, a circuit mounted on the gimbal, wherein the circuit includes a portion mounted to the base portion that includes a circuit extension region that extends beyond the first proximal edge of the base portion, wherein the circuit extension region includes a second proximal edge facing away from the tongue, and a first PZT actuator and a second PZT actuator mounted to the head gimbal assembly and electrically connected to the circuit, for displacing the tongue relative to the base portion. The head gimbal assembly may also include a slider mounted on the tongue, and electrically connected to the circuit. The circuit extension region has a circuit extension region width W of at least 0.1 mm as measured in a direction extending away from the tongue relative to a furthest extending portion of the first proximal edge in the direction extending away from the tongue and a furthest extending portion of the second proximal edge in the direction extending away from the tongue.

In other embodiments, a suspension assembly is provided comprising generally a baseplate; a load beam connected to the baseplate by a hinge; a gimbal mounted to the load beam, wherein the gimbal comprises a base portion and a tongue that are joined together by a neck portion, wherein the base portion includes a first proximal edge facing away from the tongue. A circuit is mounted on the gimbal, wherein the circuit includes a portion mounted to the base portion that includes a circuit extension region that extends beyond the first proximal edge of the base portion, wherein the circuit extension region includes a second proximal edge facing away from the tongue; and a first PZT actuator and a second PZT actuator mounted to the suspension assembly and electrically connected to the circuit, for displacing the tongue relative to the base portion. The circuit extension region has a circuit extension region width W of at least 0.1 mm as measured in a direction extending away from the tongue relative to a furthest extending portion of the first proximal edge in the direction extending away from the tongue and a furthest extending portion of the second proximal edge in the direction extending away from the tongue.

Other objects and features of the present disclosure will become apparent by a review of the specification, claims and appended figures.

DETAILED DESCRIPTION OF THE INVENTION

It has been discovered by the present inventors that by providing a circuit extension region that extends the circuit beyond the proximal edge of the base portion of the gimbal by at least a certain width dimension provides a significant reduction of stress on the PZT actuators during non-operational shock events. Such a gimbal can be used with the head stack assembly2shown inFIG.1.

FIGS.4and5illustrate top and bottom views, respectively, of a head gimbal assembly30according to one example, which is compatible with the head stack assembly2and suspension assembly3discussed above (i.e., the head gimbal assembly30can be mounted on the load beam4discussed above with respect toFIG.1). Head gimbal assembly30includes a gimbal32, forming thin components of sheet metal. The gimbal32may be formed of stainless steel. A circuit34is mounted or otherwise attached to the gimbal32, and includes conductive traces and insulation material. The conductive traces can be copper, and the insulation material can be polyimide. A slider36is mounted on the gimbal32, and includes a read/write head. The slider36can be mounted on the gimbal32by an adhesive.

The gimbal32includes a base portion32aand a tongue32b, which are joined together by a neck portion32c. The slider36is mounted on the tongue32b(either directly to the tongue, or indirectly to the tongue with the slider36directly mounted on the circuit34and the circuit34is directly mounted on the tongue32bsuch that the circuit34is disposed between the slider36and the tongue32b). The tongue32bis configured to rotate or otherwise be displaced relative to the base portion32aabout the neck portion32c, in order to provide relatively small movements of the slider36for fine position control of the slider36during operation. PZT actuators38are mounted between the tongue32band the base portion32a, for rotating or otherwise displacing the tongue32b(and the slider36mounted thereto) relative to the base portion32aabout the neck portion32cwhen the PZT actuators38expand and contract in response to electrical signals provided by the circuit34(for providing fine positioning control of the slider36relative to the disk tracks during operation).

The circuit34, slider36and PZT actuators38can all be mounted on the same side (i.e., a first side or bottom side) of the gimbal52. Alternatively, as shown inFIGS.4-5, the PZT actuators38can be mounted on an opposite side (i.e., a second side or top side) of the gimbal32while the circuit34and slider36are mounted on the first side of the gimbal32. In this example, the PZT actuators38are indirectly mounted on the gimbal32, meaning that the PZT actuators38are mounted to bonding sites34a/34bof the circuit34, and the circuit34is mounted on the gimbal32. Specifically, bonding sites34aare those portions of circuit34to which the proximal ends of the PZT actuators38are mounted (adjacent the base portion32a), and bonding sites34bare those portions of circuit34to which the distal ends of PZT actuators38are mounted (adjacent the tongue32b). Therefore, the forces of expansion and contraction of the PZT actuators38used to displace the tongue32bare translated to the base portion32aand tongue32bvia the circuit34.

Circuit34extends along and is mounted on the gimbal32, for conveying electrical signals to and from the read/write head of the slider36, and conveying electrical signals to the PZT actuators38for fine positioning control of the slider36. Therefore, the circuit34is electrically connected to the electrodes of the PZT actuators38(for providing signals that cause the PZT actuators to expand and contract) and to the slider36(for conveying signals to and from the slider36to conduct operations such a reading and writing).

The present inventors have discovered that having the portion of the circuit34mounted to the base portion32ainclude a circuit extension region34c, which is that portion of the circuit34that extends beyond a first proximal edge40of the base portion32a, where the circuit extension region34chas a circuit extension region width W of at least 0.1 mm, a significant reduction in the maximum stress on the PZT actuators38and the rest of the head gimbal assembly30in the event of a non-operation shock event can be achieved. Circuit extension region width W is the width of the circuit extension region34c(as measured in the direction extending away from tongue32b) relative to the furthest extending portion of the first proximal edge40of base portion32a(in the direction extending away from tongue32b), and the furthest extending portion of the second proximal edge42of the circuit extension region34c(in the direction extending away from tongue32b). Both first proximal edge40and second proximal edge42face away from tongue32b. The circuit extension region34cincludes the insulation material of the circuit34, but not electrical traces of the circuit34. Having the circuit extension region34cinclude only the more flexible insulation material and not the more rigid electrical traces provides better performance.

FIG.6shows the relationship between maximum stress on the PZT actuators from non-operational shock as a function of circuit extension region width W, where the present inventors have discovered there is a significant and unexpected drop of maximum stress as circuit extension region width W reaches at least 0.1 mm. This drop in the maximum stress can be attributed to the fact the insulation material of circuit34is more flexible than gimbal32, so if the circuit extension region width W is sufficiently large, then there is sufficient insulation material of the circuit34to contact with the load beam during a non-operational shock event and to absorb the energy of collisions between the gimbal assembly30and the load beam4to significantly reduce any resulting stresses on the PZT actuators38. The benefits of significant shock reduction are achieved when the circuit extension region width W meets or exceeds 0.1 mm. Therefore, by having the portion of the circuit34mounted to the base portion32include a circuit extension region34chaving a circuit extension region width W of at least 0.1 mm, the maximum stress from non-operational shock events can be significantly reduced, and damage to the PZT actuators and/or the head gimbal assembly30can be avoided.

In the example ofFIG.6, proximal edge40of base portion32ais not linear, while proximal edge42of the circuit extension region34cis substantially linear. However, proximal edge42of the circuit extension region34cneed not be substantially linear.FIG.7is a second example of a head gimbal assembly30, where the proximal edge42of the circuit extension region34cis not linear but instead includes a cut-out44, which may be desirable to avoid blocking an alignment feature on load beam4.FIG.8is a third example of a head gimbal assembly, where the furthest extending portion of the first proximal edge40of base portion32a(in the direction extending away from tongue32b) is offset from the furthest extending portions of the second proximal edge42of the circuit extension region34c(in the direction extending away from tongue32b).

It is to be understood that the present disclosure is not limited to the example(s) described above and illustrated herein, but encompasses any and all variations falling within the scope of any claims. For example, references to the present invention, embodiments or examples herein are not intended to limit the scope of any claim or claim term, but instead merely make reference to one or more features that may be covered by one or more of the claims. Materials, processes and numerical examples described above are exemplary only, and should not be deemed to limit the claims.