Head gimbal assembly for hard disk drive device

Abstract

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.

Description

HEAD GIMBAL ASSEMBLY FOR HARD DISK DRIVE DEVICESPECIFICATIONCross-Reference To Related ApplicationsThis application claims priority from U.S. Patent Application No. 18 / 212,586 filedon June 21, 2023, the entirety of which is hereby incorporated by reference in its entirety.Field of the InventionThe present disclosure relates to hard disk drives, and more particularly to a headgimbal assembly and a suspension assembly for hard disk drives.Background of the InventionA hard disk drive (HDD) is a non-volatile storage device that stores digitallyencoded data on one or more circular disks having magnetic surfaces. In operation, eachdisk spins rapidly. Data is read from and written to the disk using a read-write head thatis positioned over a specific data track or location on the disk surface by a suspensionassembly, which in turn is attached to the arm of the head stack assembly, which is rotatedby 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 theprimary function of the suspension assembly during hard disk drive operation. Optimizedsuspension assembly design and manufacture can minimize the effects of mechanical,thermal, and other off-track disturbances which can degrade the performance of the harddisk drive. The suspension assembly includes a load beam. In operation, the actuatorpositions the distal end of the load beam over the desired portion of the disk (e.g., one ofthe circular tracks on the disk surface). A gimbal assembly (also sometimes referred toas a flexure) is mounted on the distal end of the load beam. The assembly may furtherinclude components such as a slider containing the read-write head and microactuatordevices (piezoelectric devices, also referred to as PZT herein) that rotate a portion of thegimbal assembly for fine positioning of the slider (as opposed to more coarse positioningof the slider by the actuator). The pressure caused by air viscosity between the slider andthe spinning disk causes the slider to hover over (in close proximity to) the surface of thedisk. While the load beam is relatively stiff, particularly in the lateral axis, the gimbalassembly is more flexible so that the slider can pitch and roll as it floats over the disksurface in order to maintain its operational distance immediately over the disk surface.Fig. 1 illustrates a portion of a conventional head stack assembly 2, while Figs. 2-3 illustrate a conventional head gimbal assembly 10 of the head stack assembly 2. Thehead stack assembly 2 includes a suspension assembly 3 with a load beam 4 terminatingat a proximal end with a hinge 6 that is connected to a baseplate 8. A head gimbalassembly 10 is mounted on the distal end of the load beam 4. The baseplate 8 isconnected to an actuator arm 12 of the head stack assembly 2, which is rotated by anintegral actuator (not shown).As best shown in Figs. 2 and 3, head gimbal assembly 10 comprises a gimbal 14of thin components of sheet metal (e.g., stainless steel), a circuit 16 that includesconductive traces (e.g., copper) and insulation material (e.g., polyimide), a slider 18 withthe read / write head mounted on the gimbal 14 (e.g., by adhesive), and PZT actuators 20mounted on the same side of the gimbal 14 as the slider 18. Circuit 16 extends along theload beam 4 and head gimbal assembly 10 for electrical signal communication to theread / write head of the slider 18 and to PZT actuators 20. The conductive traces of thecircuit 16 are electrically insulated from the gimbal 14 by the insulation material of thecircuit 16.The gimbal 14 includes a base portion 14a and a tongue 14b, which are connectedto each other by a neck portion 14c. The tongue 14b is configured to rotate about theneck portion 14c (for fine position control of the slider 18). The slider 18 is mounted onthe tongue 14b. The PZT actuators 20 are mounted between the tongue 14b and thebase portion 14a, for rotating the tongue 14b about the neck portion 14c when the PZTactuators 20 expand and contract in response to electrical signals provided by the circuit16, which provides fine movement control of the slider 18 relative to the disk tracks duringoperation. In this example, the PZT actuators 20 are indirectly mounted on the gimbal 14,meaning that the PZT actuators 20 are mounted on the circuit 16, which is in turn mountedon the gimbal 14.PZT actuators 20 can be multi-layer devices of piezoelectric material. A commonlyused example of piezoelectric material can be lead zirconate titanate, although otherpiezoelectric materials are also used and known, which expand and contract in responseto electronic signals. PZT materials can be brittle. When the suspension assembly 3 isnot in use, it can be parked on a ramp to help protect the suspension assembly 3 frompotentially damaging movement caused by non-operational shock events (e.g., causedwhen the HDD is roughly handled or dropped). However, during a non-operational shockevent, the head gimbal assembly 10 can be damaged (e.g., the PZT material can sufferfrom cracking, and / or the circuit 16 can suffer from permanent deformation). Damage canresult from large movement of the base portion 14a in the pitch direction, where theproximal edge of the base portion 14a may contact the load beam 4, causing undue stresson the PZT actuators 20.There is a need for a head gimbal assembly design that is less susceptible todamage from non-operational shock events.Brief Summary of the InventionThe aforementioned problems and needs are addressed by a head gimbalassembly that includes a gimbal having a base portion and a tongue that are joinedtogether by a neck portion, wherein the base portion includes a first proximal edge facingaway from the tongue, a circuit mounted on the gimbal, wherein the circuit includes aportion mounted to the base portion that includes a circuit extension region that extendsbeyond the first proximal edge of the base portion, wherein the circuit extension regionincludes a second proximal edge facing away from the tongue, and a first PZT actuatorand a second PZT actuator mounted to the head gimbal assembly and electricallyconnected to the circuit, for displacing the tongue relative to the base portion. The headgimbal assembly may also include a slider mounted on the tongue, and electricallyconnected to the circuit. The circuit extension region has a circuit extension region widthW of at least 0.1 mm as measured in a direction extending away from the tongue relativeto a furthest extending portion of the first proximal edge in the direction extending awayfrom the tongue and a furthest extending portion of the second proximal edge in thedirection extending away from the tongue.In other embodiments, a suspension assembly is provided comprising generally abaseplate; a load beam connected to the baseplate by a hinge; a gimbal mounted to theload beam, wherein the gimbal comprises a base portion and a tongue that are joinedtogether by a neck portion, wherein the base portion includes a first proximal edge facingaway from the tongue. A circuit is mounted on the gimbal, wherein the circuit includes aportion mounted to the base portion that includes a circuit extension region that extendsbeyond the first proximal edge of the base portion, wherein the circuit extension regionincludes a second proximal edge facing away from the tongue; and a first PZT actuatorand a second PZT actuator mounted to the suspension assembly and electricallyconnected to the circuit, for displacing the tongue relative to the base portion. The circuitextension region has a circuit extension region width W of at least 0.1 mm as measuredin a direction extending away from the tongue relative to a furthest extending portion ofthe first proximal edge in the direction extending away from the tongue and a furthestextending portion of the second proximal edge in the direction extending away from thetongue.Other objects and features of the present disclosure will become apparent by areview of the specification, claims and appended figures.Brief Description of the DrawingsFig. 1 is a partial perspective view of a conventional head suspension assembly.Fig. 2 is a bottom view of a conventional head gimbal assembly.Fig. 3 is a top view of a conventional head gimbal assembly.Fig. 4 is a top view of an example of a head gimbal assembly according to someembodiments of the present disclosure.Fig. 5 is a bottom view of the example of a head gimbal assembly according tosome embodiments of the present disclosure.Fig. 6 is a graphical representation of PZT maximum stress as a function of circuitextension region width W, for the head gimbal assembly of Figs. 4-5.Fig. 7 is a top view of a second example of a head gimbal assembly according tosome embodiments of the present disclosure.Fig. 8 is a top view of a third example of a head gimbal assembly according tosome embodiments of the present disclosure.Detailed Description of the InventionIt has been discovered by the present inventors that by providing a circuitextension region that extends the circuit beyond the proximal edge of the base portion ofthe gimbal by at least a certain width dimension provides a significant reduction of stresson the PZT actuators during non-operational shock events. Such a gimbal can be usedwith the head stack assembly 2 shown in Fig. 1.Figs. 4 and 5 illustrate top and bottom views, respectively, of a head gimbalassembly 30 according to one example, which is compatible with the head stack assembly2 and suspension assembly 3 discussed above (i.e., the head gimbal assembly 30 can bemounted on the load beam 4 discussed above with respect to Fig 1). Head gimbalassembly 30 includes a gimbal 32, forming thin components of sheet metal. The gimbal32 may be formed of stainless steel. A circuit 34 is mounted or otherwise attached to thegimbal 32, and includes conductive traces and insulation material. The conductive tracescan be copper, and the insulation material can be polyimide. A slider 36 is mounted onthe gimbal 32, and includes a read / write head. The slider 36 can be mounted on thegimbal 32 by an adhesive.The gimbal 32 includes a base portion 32a and a tongue 32b, which are joinedtogether by a neck portion 32c. The slider 36 is mounted on the tongue 32b (either directlyto the tongue, or indirectly to the tongue with the slider 36 directly mounted on the circuit34 and the circuit 34 is directly mounted on the tongue 32b such that the circuit 34 isdisposed between the slider 36 and the tongue 32b). The tongue 32b is configured torotate or otherwise be displaced relative to the base portion 32a about the neck portion32c, in order to provide relatively small movements of the slider 36 for fine position controlof the slider 36 during operation. PZT actuators 38 are mounted between the tongue 32band the base portion 32a, for rotating or otherwise displacing the tongue 32b (and theslider 36 mounted thereto) relative to the base portion 32a about the neck portion 32cwhen the PZT actuators 38 expand and contract in response to electrical signals providedby the circuit 34 (for providing fine positioning control of the slider 36 relative to the disktracks during operation).The circuit 34, slider 36 and PZT actuators 38 can all be mounted on the sameside (i.e., a first side or bottom side) of the gimbal 52. Alternatively, as shown in Figs. 4-5, the PZT actuators 38 can be mounted on an opposite side (i.e., a second side or topside) of the gimbal 32 while the circuit 34 and slider 36 are mounted on the first side of thegimbal 32. In this example, the PZT actuators 38 are indirectly mounted on the gimbal32, meaning that the PZT actuators 38 are mounted to bonding sites 34a / 34b of the circuit34, and the circuit 34 is mounted on the gimbal 32. Specifically, bonding sites 34a arethose portions of circuit 34 to which the proximal ends of the PZT actuators 38 aremounted (adjacent the base portion 32a), and bonding sites 34b are those portions ofcircuit 34 to which the distal ends of PZT actuators 38 are mounted (adjacent the tongue32b). Therefore, the forces of expansion and contraction of the PZT actuators 38 used todisplace the tongue 32b are translated to the base portion 32a and tongue 32b via thecircuit 34.Circuit 34 extends along and is mounted on the gimbal 32, for conveying electricalsignals to and from the read / write head of the slider 36, and conveying electrical signalsto the PZT actuators 38 for fine positioning control of the slider 36. Therefore, the circuit34 is electrically connected to the electrodes of the PZT actuators 38 (for providing signalsthat cause the PZT actuators to expand and contract) and to the slider 36 (for conveyingsignals to and from the slider 36 to conduct operations such a reading and writing).The present inventors have discovered that having the portion of the circuit 34mounted to the base portion 32a include a circuit extension region 34c, which is thatportion of the circuit 34 that extends beyond a first proximal edge 40 of the base portion32a, where the circuit extension region 34c has a circuit extension region width W of atleast 0.1 mm, a significant reduction in the maximum stress on the PZT actuators 38 andthe rest of the head gimbal assembly 30 in the event of a non-operation shock event canbe achieved. Circuit extension region width W is the width of the circuit extension region34c (as measured in the direction extending away from tongue 32b) relative to the furthestextending portion of the first proximal edge 40 of base portion 32a (in the directionextending away from tongue 32b), and the furthest extending portion of the secondproximal edge 42 of the circuit extension region 34c (in the direction extending away fromtongue 32b). Both first proximal edge 40 and second proximal edge 42 face away fromtongue 32b. The circuit extension region 34c includes the insulation material of the circuit34, but not electrical traces of the circuit 34. Having the circuit extension region 34cinclude only the more flexible insulation material and not the more rigid electrical tracesprovides better performance.Fig. 6 shows the relationship between maximum stress on the PZT actuators fromnon-operational shock as a function of circuit extension region width W, where the presentinventors have discovered there is a significant and unexpected drop of maximum stressas circuit extension region width W reaches at least 0.1 mm. This drop in the maximumstress can be attributed to the fact the insulation material of circuit 34 is more flexible thangimbal 32, so if the circuit extension region width W is sufficiently large, then there issufficient insulation material of the circuit 34 to contact with the load beam during a non-operational shock event and to absorb the energy of collisions between the gimbalassembly 30 and the load beam 4 to significantly reduce any resulting stresses on thePZT actuators 38. The benefits of significant shock reduction are achieved when thecircuit extension region width W meets or exceeds 0.1 mm. Therefore, by having theportion of the circuit 34 mounted to the base portion 32 include a circuit extension region34c having a circuit extension region width W of at least 0.4mm, the maximum stress fromnon-operational shock events can be significantly reduced, and damage to the PZTactuators and / or the head gimbal assembly 30 can be avoided.In the example of Fig. 6, proximal edge 40 of base portion 32a is not linear, whileproximal edge 42 of the circuit extension region 34c is substantially linear. However,proximal edge 42 of the circuit extension region 34c need not be substantially linear. Fig.7 is a second example of a head gimbal assembly 30, where the proximal edge 42 of thecircuit extension region 34c is not linear but instead includes a cut-out 44, which may bedesirable to avoid blocking an alignment feature on load beam 4. Fig. 8 is a third exampleof a head gimbal assembly, where the furthest extending portion of the first proximal edge40 of base portion 32a (in the direction extending away from tongue 32b) is offset fromthe furthest extending portions of the second proximal edge 42 of the circuit extensionregion 34c (in the direction extending away from tongue 32b).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 fallingwithin 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 claimterm, but instead merely make reference to one or more features that may be covered byone or more of the claims. Materials, processes and numerical examples described aboveare exemplary only, and should not be deemed to limit the claims.

Claims

ClaimsWhat is claimed is:

1. A head gimbal assembly comprising:a gimbal having a base portion and a tongue that are joined together by a neckportion, wherein the base portion includes a first proximal edge facing away from thetongue;a circuit mounted on the gimbal, wherein the circuit includes a portion mounted tothe base portion that includes a circuit extension region that extends beyond the firstproximal edge of the base portion, wherein the circuit extension region includes asecond proximal edge facing away from the tongue; anda first PZT actuator and a second PZT actuator mounted to the head gimbalassembly and electrically connected to the circuit, for displacing the tongue relative tothe base portion;wherein the circuit extension region has a circuit extension region width W of atleast 0.1 mm as measured in a direction extending away from the tongue relative to afurthest extending portion of the first proximal edge in the direction extending away fromthe tongue and a furthest extending portion of the second proximal edge in the directionextending away from the tongue.

2. The head gimbal assembly of claim 1, wherein the circuit comprises electricaltraces and insulation material, and wherein the circuit extension region of the circuitcomprises the insulation material without electrical traces.

3. The head gimbal assembly of claim 1, wherein:the first PZT actuator has a proximal end mounted on a first bonding site of thecircuit and a distal end mounted on a second bonding site of the circuit; andthe second PZT actuator has a proximal end mounted on a third bonding site ofthe circuit and a distal end mounted on a fourth bonding site of the circuit.

4. The head gimbal assembly of claim 3, wherein:the first bonding site and the third bonding site are adjacent the base portion; andthe second bonding site and the fourth bonding site are adjacent the tongue.

5. The head gimbal assemble of claim 1, further comprising:a slider mounted on the tongue, and electrically connected to the circuit.

6. The head gimbal assembly of claim 5, wherein:the circuit is disposed between the slider and the tongue.

7. A suspension assembly comprising:a baseplate;a load beam connected to the baseplate by a hinge;a gimbal mounted to the load beam, wherein the gimbal comprises a baseportion and a tongue that are joined together by a neck portion, wherein the base portionincludes a first proximal edge facing away from the tongue;a circuit mounted on the gimbal, wherein the circuit includes a portion mounted tothe base portion that includes a circuit extension region that extends beyond the firstproximal edge of the base portion, wherein the circuit extension region includes asecond proximal edge facing away from the tongue; anda first PZT actuator and a second PZT actuator mounted to the suspensionassembly and electrically connected to the circuit, for displacing the tongue relative tothe base portion;wherein the circuit extension region has a circuit extension region width W of atleast 0.1 mm as measured in a direction extending away from the tongue relative to afurthest extending portion of the first proximal edge in the direction extending away fromthe tongue and a furthest extending portion of the second proximal edge in the directionextending away from the tongue.8.The suspension assembly of claim 7, wherein the circuit comprises electricaltraces and insulation material, and wherein the circuit extension region of the circuitcomprises the insulation material without electrical traces.9.The suspension assembly of claim 7, wherein:the first PZT actuator has a proximal end mounted on a first bonding site of thecircuit and a distal end mounted on a second bonding site of the circuit; andthe second PZT actuator has a proximal end mounted on a third bonding site ofthe circuit and a distal end mounted on a fourth bonding site of the circuit.10.11.12.The suspension assembly of claim 9, wherein:the first bonding site and the third bonding site are adjacent the base portion; andthe second bonding site and the fourth bonding site are adjacent the tongue.The suspension assembly of claim 7, further comprising:a slider mounted on the tongue, and electrically connected to the circuit.The suspension assembly of claim 11, wherein:the circuit is disposed between the slider and the tongue.