PZT element, head gimbal assembly, and disk drive unit with same

A PZT element of the present invention includes a laminated structure which is laminated with electrode layer and PZT layer alternatively to define a thickness direction; wherein each PZT layer is sandwiched between two adjacent electrode layers; and at least one support element provided on a side portion of the laminated structure and substantially extending along a longitudinal direction thereof; wherein the PZT element is bent at least towards a latitudinal direction thereof when being applied an electrical voltage thereon through the electrode layers. The invention also discloses a method of manufacturing the PZT element, a HGA and disk drive unit with the same.

FIELD OF THE INVENTION

This invention generally relates to disk drive unit, and more particularly to PZT element used for disk drive unit and its manufacturing method.

BACKGROUND OF THE INVENTION

One known type of information storage device is a disk drive device that uses magnetic media to store data and a movable read/write head that is positioned over the magnetic media to selectively read from or write to the disk.

Consumers are constantly desiring greater storage capacity for such disk drive devices, as well as faster and more accurate reading and writing operations. Thus, disk drive manufacturers have continued to develop higher capacity disk drives by, for example, increasing the density of the information tracks on the disks by using a narrower track width and/or a narrower track pitch. However, each increase in track density requires that the disk drive device have a corresponding increase in the positional control of the read/write head in order to enable quick and accurate reading and writing operations using the higher density disks. As track density increases, it becomes more and more difficult using known technology to quickly and accurately position the read/write head over the desired information tracks on the storage media. Thus, disk drive manufacturers are constantly seeking ways to improve the positional control of the read/write head in order to take advantage of the continual increases in track density.

One approach that has been effectively used by disk drive manufacturers to improve the positional control of read/write heads for higher density disks is to employ a secondary actuator, known as a micro-actuator, which works in conjunction with a primary actuator to enable quick and accurate positional control for the read/write head. Disk drives that incorporate a micro-actuator are known as dual-stage actuator systems.

Various dual-stage actuator systems have been developed in the past for the purpose of increasing the speed and fine tuning the position of the read/write head over the desired tracks on high density storage media. Such dual-stage actuator systems typically include a primary voice-coil motor (VCM) actuator and a secondary micro-actuator, such as a PZT micro-actuator. The VCM actuator is controlled by a servo control system that rotates the actuator arm that supports the read/write head to position the read/write head over the desired information track on the storage media. The PZT micro-actuator is used in conjunction with the VCM actuator for the purpose of increasing the positioning speed and fine tuning the exact position of the read/write head over the desired track. Thus, the VCM actuator makes larger adjustments to the position of the read/write head, while the PZT micro-actuator makes smaller adjustments that fine tune the position of the read/write head relative to the storage media. In conjunction, the VCM actuator and the PZT micro-actuator enable information to be efficiently and accurately written to and read from high density storage media.

One known type of micro-actuator incorporates PZT elements for causing fine positional adjustments of the read/write head. Such PZT micro-actuators include associated electronics that are operable to excite the PZT elements on the micro-actuator to selectively cause expansion or contraction thereof. The PZT micro-actuator is configured such that expansion or contraction of the PZT elements causes movement of the micro-actuator which, in turn, causes movement of the read/write head. This movement is used to make faster and finer adjustments to the position of the read/write head, as compared to a disk drive unit that uses only a VCM actuator. Exemplary PZT micro-actuators are disclosed in, for example, JP 2002-133803, entitled “Micro-actuator and HGA” and JP 2002-074871, entitled “Head Gimbal Assembly Equipped with Actuator for Fine Position, Disk Drive Equipped with Head Gimbals Assembly, and Manufacture Method for Head Gimbal Assembly.”

FIG. 1aillustrates a portion of a conventional disk drive unit and shows a magnetic disk101mounted on a spindle motor102for spinning the disk101. A voice coil motor arm104carries a HGA100that includes a micro-actuator105and a read/write head103. A voice-coil motor (VCM) is provided for controlling the motion of the motor arm104and, in turn, controlling the slider103to move from track to track across the surface of the disk, thereby enabling the read/write head to read data from or write data to the disk. In operation, a lift force is generated by the aerodynamic interaction between the slider, incorporating the read/write head, and the spinning magnetic disk. The lift force is opposed by equal and opposite spring forces applied by a suspension of the HGA such that a predetermined flying height above the surface of the spinning disk is maintained over a full radial stroke of the motor arm104.

FIG. 1billustrates the head gimbal assembly100(HGA) of the conventional disk drive device ofFIG. 1aincorporating a dual-stage actuator. However, because of the inherent tolerances of the VCM and the head suspension assembly, the slider103cannot achieve quick and fine position control which adversely impacts the ability of the read/write head to accurately read data from and write data to the disk. As a result, a PZT micro-actuator105, as described above, is provided in order to improve the positional control of the slider and the read/write head. More particularly, the PZT micro-actuator105corrects the displacement of the slider103on a much smaller scale, as compared to the VCM, in order to compensate for the resonance tolerance of the VCM and head suspension assembly. The micro-actuator105enables, for example, the use of a smaller recording track pitch, and can increase the “tracks-per-inch” (TPI) value by 50% for the disk drive unit, as well as provide an advantageous reduction in the head seeking and settling time. Thus, the PZT micro-actuator105enables the disk drive device to have a significant increase in the surface recording density of the information storage disks used therein.

As shown inFIGS. 1aand1b, one known type of micro-actuator is a U-shaped micro-actuator105. This U-shaped micro-actuator105has two side arms107that hold the slider103therebetween and displace the slider by movement of the side arms.

Referring more particularly toFIG. 1c, a conventional PZT micro-actuator105includes a ceramic U-shaped frame which has two ceramic beams or side arms107each having a PZT element thereon. With reference toFIGS. 1band1c, the PZT micro-actuator105is physically coupled to a flexure114.FIG. 1dgenerally shows an exemplary process for assembling the slider103with the micro-actuator105. As shown inFIGS. 1dand2, the slider103is partially bonded with the two ceramic beams107at two predetermined positions106by epoxy112. This bonding makes the movement of the slider103dependent on the movement of the ceramic beams107of the micro-actuator105. A PZT element116is attached on each of the ceramic beams107of the micro-actuator to enable controlled movement of the slider103through excitation of the PZT elements. More particularly, when power is supplied through the suspension traces110, the PZT elements expand or contract to cause the two ceramic beams107of the U-shape micro-actuator frame to deform, thereby making the slider103move on the track of the disk in order to fine tune the position of the read/write head. In this manner, controlled displacement of slider103can be achieved for fine positional tuning.

FIG. 1eillustrates the micro-actuator and slider after being assembled as shown inFIG. 1d.FIGS. 1eand2also show the two possible translational movements, illustrated by arrows117aand117b, that the micro-actuator can produce upon excitation, as well as the resulting reaction forces (118aand118b, respectively) generated in the base-part plate of the micro-actuator as a result of the translational movement.

However, referring toFIG. 2, when being applied an electrical voltage thereon, the PZT element116only produces a bending displacement substantially along its thickness direction which is perpendicular to electrode layers171and PZT layer172of the PZT element116, but cannot produces a bending displacement along its width direction (or latitudinal direction) which is parallel to electrode layers171and PZT layer172of the PZT element116. This greatly limits the application scope of the PZT element116.

Hence, it is desired to provide a PZT element and manufacturing method thereof to solve the above-mentioned problem.

BRIEF DESCRIPTION OF THE INVENTION

A main feature of the present invention is to provide a PZT element which can produce a bending displacement along its latitudinal direction.

Another feature of the present invention is to provide a HGA and disk drive unit with a PZT element which can produce a bending displacement along its latitudinal direction.

A further feature of the present invention is to provide a manufacturing method of a PZT element which can produce a bending displacement along its latitudinal direction.

To attain the above features, a PZT element of the invention comprises a laminated structure which is laminated with electrode layer and piezoelectric layer alternatively to define a thickness direction; wherein each piezoelectric layer is sandwiched between two adjacent electrode layers; and at least one support element provided on a side portion of the laminated structure and substantially extending along a longitudinal direction thereof; wherein the piezoelectric element is bent at least towards a latitudinal direction thereof when being applied an electrical voltage thereon through the electrode layers.

In an embodiment of the invention, the support element is provided on a side surface of the laminated structure, which is parallel to the thickness direction of the piezoelectric element. In a further embodiment, the support element comprises an insulative layer and a support layer provided on the insulative layer; and the insulative layer is sandwiched between the support layer and the laminated structure. In a still embodiment, the laminated structure may further comprise at least one notch or slot therein for bending piezoelectric element easily.

A HGA of the invention comprises a slider; a PZT element; and a suspension to support the slider and the piezoelectric element; wherein the piezoelectric element comprises: a laminated structure which is laminated with electrode layer and PZT layer alternatively to form a thickness direction; wherein each PZT layer is sandwiched between two of the electrode layer; and at least one support element provided on one side portion of the laminated structure and substantially extending along a longitudinal direction thereof; wherein the PZT element is sandwiched between the slider and the suspension, and bent at least towards a latitudinal direction thereof when being applied an electrical voltage thereon through the electrode layers.

In the invention, a method of manufacturing a PZT element comprising the following steps: 1) forming a laminated structure by laminating electrode layer and PZT layer alternatively in a thickness direction so as to make each PZT layer being sandwiched between two adjacent electrode layers; 2) attaching at least one support element on a side portion of the laminated structure to make the at least one support element substantially extend along a longitudinal direction of the laminated structure.

A disk drive unit of the invention comprises a HGA; a drive arm to connect with the HGA; a disk; and a spindle motor to spin the disk; wherein the HGA comprising: a slider; a PZT element; and a suspension to support the slider and the PZT element; wherein the PZT element comprises: a laminated structure which is laminated with electrode layer and PZT layer alternatively to form a thickness direction; wherein each PZT layer is sandwiched between two of the electrode layer; and at least one support element provided on one side portion of the laminated structure and substantially extending along a longitudinal direction thereof; wherein the PZT element is sandwiched between the slider and the suspension, and bent at least towards a latitudinal direction thereof when being applied an electrical voltage thereon through the electrode layers.

For the purpose of making the invention easier to understand, several particular embodiments thereof will now be described with reference to the appended drawings in which:

DETAILED DESCRIPTION OF THE INVENTION

Various preferred embodiments of the instant invention will now be described with reference to theFIGS. 3-13, wherein like reference numerals designate similar parts throughout the various views. As indicated above, the instant invention is to provide a PZT element which comprises: a laminated structure which is laminated with electrode layer and piezoelectric layer alternatively to define a thickness direction; wherein each piezoelectric layer is sandwiched between two adjacent electrode layers; and at least one support element provided on a side portion of the laminated structure and substantially extending along a longitudinal direction thereof; wherein the piezoelectric element is bent at least towards a latitudinal direction thereof when being applied an electrical voltage thereon through the electrode layers. In the present invention, the PZT element gets a special bending direction which is parallel to the electrode layer and the piezoelectric layer by the at least one support element provided on the side portion of the laminated structure. That is to say, the PZT element can be used for displacing an object, such as a slider along the bending direction which is parallel to the electrode layer and the piezoelectric layer.

According to an exemplary embodiment of the invention, referring toFIGS. 3a-3c, a PZT element90aincludes a laminated structure91and a support element94. The laminated structure91is formed by alternatively laminating electrode layer and PZT layer, such as laminating four electrode layers202and three PZT layers201. Thus, each of the PZT layers201is sandwiched between two adjacent electrode layers202for being applied with an exciting voltage. In an exemplary embodiment of the invention, a thin film process, such as coating and/or photo masking process, which is rather simple and has a lower cost, may be used to forming the PZT layers201of the laminated structure91layer by layer. Also, a plurality of conductive terminals, such as two conductive terminals203,204can be provided on one end of the outer electrode layer202for applying a voltage on the PZT element90athereby.

Referring toFIG. 3a, the PZT element90adefines a length direction701, a thickness direction802, and a width direction901which are perpendicular to each other. In an exemplary embodiment of the invention, all the PZT layers201have a same thickness, which are substantially identical in structure. Referring toFIG. 10a, each PZT layer201also has a polarized direction801formed by a magnetizing process, and may be magnetized before or after forming the laminated structure91. In an embodiment of the invention, the adjacent PZT layers201have reverse polarized directions.

Referring toFIG. 3a, the electrode layers202are made of conductive material, such as copper, gold, or other suitable materials having good electrical conductivity. The electrode layers202are substantially same as the PZT layer201in size for covering the entire surface of the PZT layer201. In an embodiment of the invention, all the electrode layers202have an even thickness, which have a substantially identical structure.

Also referring toFIG. 3a, the two conductive terminals203,104are electrically isolated with each other, and are electrically connected with two adjacent electrode layers202respectively, which sandwich the PZT layer201therebetween. As such, when the two conductive terminals203,204are respectively connected with external power supplier (not shown), an electrical voltage is then applied on each of the PZT layers201to make it expand or shrink.

Referring toFIG. 3a, the support element94is provided on a side portion of the laminated structure91and substantially extending along a longitudinal direction thereof, which is parallel to the length direction701. In an embodiment of the invention, the support element94includes an insulative layer205and a support layer206provided on the insulative layer205. In an embodiment, the support layer206may be conductive, which may be made from stainless steel, silicon, copper alloy, or other suitable conductive materials. When the support element94is mounted on the laminated structure91, the insulative layer205is sandwiched between the support layer206and the laminated structure91so as to prevent the conductive support layer206from contacting with the laminated structure91electrically, thus eliminating short circuit issue caused thereby.

In another embodiment of the invention, the support layer206may be made of a suitable non-conductive material, in this case, the insulative layer205may be omitted from the support element94.

FIGS. 4-5illustrate two alternative PZT elements90b,90capplicable to the invention. Referring toFIG. 4, the PZT elements90bhas a substantially similar structure to the PZT element90ashown inFIG. 3a, however, which comprises a laminated structure911with one notch501formed therein for easily bending the piezoelectric element90b. In the embodiment, the notch501is substantially rectangular in shape, but not limited to the shape, any suitable shape may be applicable to the notch. Referring toFIG. 5, the PZT element90cmay comprise a laminated structure912with three notches501formed therein for bending the PZT element90ceasier. Understandably, any suitable number of the notches501may be formed in the laminated structure of the PZT element of the invention. Also, in the invention, the notch501may be replaced with slot or other suitable structure for bending the PZT element of the invention easily.

FIG. 6illustrates an alternative PZT element90daccording to a further embodiment of the invention. The PZT element90dhas a substantially similar structure to the PZT element90aas shown inFIG. 3a. Differently, instead of one support element94, two support elements944are provided on an upper surface and a lower surface of a side portion of the laminated structure91, which is parallel to the electrode layers202and the PZT layers201of the laminated structure91.

FIG. 7illustrates still an alternative PZT element90eaccording to another embodiment of the invention. The PZT element90ehas a substantially similar structure to the PZT element90das shown inFIG. 6. Differently, a fixing portion507is formed on an end of the laminated structure91thereof, which is configured to mount the PZT element90eonto a rigid support part, such as a suspension30(shown inFIG. 12).

FIG. 8illustrates still an alternative PZT element90faccording to an embodiment of the invention. The PZT element90fcomprises a laminated structure913which is formed by alternatively laminating two electrode layers202and one PZT layer201. The support element94, which comprises the insulative layer205and the support layer206, is attached on a side portion of the laminated structure913.

FIG. 9illustrates still an alternative PZT element90gaccording to an embodiment of the invention. The PZT element90gis substantially similar in structure with respect to the PZT element90fas shown inFIG. 8. Differently, a single support element945is positioned on an upper surface of a side portion of the laminated structure913, which is parallel to the electrode layers202and the PZT layer201of the laminated structure913.

FIG. 10aillustrates a schematic view of an electrical connection of the PZT element90ashown inFIG. 3a, and the polarized directions801of the adjacent PZT layers201are opposite. However, it is understandable that the electrical connection shown inFIG. 10amay also be applied to the PZT elements90b-90gshown inFIGS. 4-9.

Referring toFIG. 10a, one of the two electrode layers202is set to an electrical voltage via the conductive terminal203, and another is grounded (GND) via the conductive terminal204. As such, the polarity of voltage applied on each of the PZT layers201is opposite to the polarized direction801of the PZT layer201so as to make all the PZT layers201contract or expand simultaneously.

FIG. 10billustrates a schematic view of another electrical connection of the PZT element90ashown inFIG. 3a, the conductive terminal203is grounded and the conductive terminal204is set to a voltage V. As such, the polarity of voltage applied on each of the PZT layer201is consistent with the polarized direction801of the PZT layer201so as to make all the PZT layers201expand and contract simultaneously.

FIG. 10cillustrates a typical connection between the electrode layers202shown inFIG. 3a. In an exemplary embodiment, every adjacent electrode layers202are not electrically connected, but every two electrode layers202at intervals are electrically connected with each other by a conductive layer provided therebetween.

FIG. 11illustrates an operating state of the PZT element90aas shown inFIG. 3a. When the laminated structure91, i.e. the PZT layers201(seeFIG. 3a) are applied with a voltage, they will contract or expand simultaneously. However, because the support element94has a suitable rigidity to restrict the contract or expand of the PZT layers201, so the contract or expand of the PZT layers201will exert a counterforce to the support element94and make the support element94, together with the PZT element90abend towards a latitudinal direction thereof, i.e. a width direction901thereof, which is parallel to the PZT layers201. In the invention, the PZT element90ahas an end92fixed to a rigid support part, such as a suspension30as shown inFIG. 12, and a free end93to produce a displacement to precisely control position of an object, such as a slider, and a detail operation of the PZT element90ais believed to be within the purview of those in the art without further discussion.

In the invention, a method of manufacturing a PZT element comprises the following steps: 1) forming a laminated structure by laminating electrode layer and PZT layer alternatively in a thickness direction so as to make each PZT layer being sandwiched between two adjacent electrode layers; 2) attaching at least one support element on a side portion of the laminated structure to make the at least one support element substantially extend along a longitudinal direction of the laminated structure. In an embodiment of the invention, the support element is attached on a side surface of the laminated structure, which is parallel to the thickness direction of the piezoelectric element. In another embodiment of the invention, forming the support element comprises the steps of: forming an insulative layer and a support layer on the insulative layer; and bonding the insulative layer with the laminated structure together. In the invention, forming the laminated structure may further comprise a step of forming at least one notch or slot therein for bending the piezoelectric element easily.

Referring toFIG. 12, according to an embodiment of the invention, a HGA70comprises a slider71, the PZT element90a, and a suspension30to support the slider71and the PZT element90a. The suspension30comprises a base plate321, a hinge324, a flexure325and a load beam326, which are assembled together. The flexure325has a suspension tongue328for mounting the PZT element90athereon. Specifically, the end92of the PZT element90amay be fixed on the suspension30, and the free end93may be used to precisely adjust the position of the slider71. Understandably, other PZT elements of the embodiments of the invention can also be applicable to a suitable HGA.

According to an embodiment of the invention, referring toFIG. 13, a disk drive unit80can be attained by assembling a housing808, a disk803, a spindle motor802, a VCM807with the HGA70of the present invention. Because the structure and/or assembly process of disk drive unit of the present invention are well known to persons ordinarily skilled in the art, a detailed description of such structure and assembly is omitted herefrom.

However, it is contemplated that the present invention is applicable, not only to magnetic disk units, such as the magnetic disk unit shown inFIG. 13, but to other forms of devices as well, such as, but not limited to, optical disk drivers which utilizes actuators to adjust the position of optical heads. Therefore, the magnetic disk unit shown inFIG. 13is provided by way of illustration rather than limitation, and accordingly there is no intention to limit application of the present invention to any particular devices, such as the magnetic disk unit.