CN1967662A - Magnetostrictive micro-actuator used for head servo - Google Patents
Magnetostrictive micro-actuator used for head servo Download PDFInfo
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Abstract
The invention discloses a super-magnetostrictive actuator for the magnetic head servo, including the magnetic circuit, the super-magnetostrictive actuator block, the flexible linking board, the linking pad, the pad wire, the coil pad, the fixed pad, the access point, the flexible wire, the inner and outer magnetic shielding layer, the embedded snail loop and the single crystal silicon spring. The invention uses the giant magnetostrictive effect of special materials, machining and molding in the magnetic head slider with conjunction manufacturing techniques, and producing a two-way servo movement by the use of permanent magnets or repeating addition of DC bias current in driven current. This super-magnetostrictive actuator can work in a lower voltage; can output greater driving force, and response speed over piezoelectric ceramic materials, and no failure of the Curie point.
Description
Technical Field
The invention belongs to the technical field of data storage, and particularly relates to a giant magnetostrictive micro actuator for magnetic head servo.
Background
In data storage devices such as computer hard disks, thin film magnetic heads are commonly used to write and read magnetic information to and from the disk surface. An overall structure of a hard disk is shown in fig. 1, and 10 is an internal main structure seen by disassembling a hard disk casing in a clean room environment. The various components within the disk are first fixedly mounted to the chassis 14 and then screwed into the computer housing through mounting holes 12. The read/write head 13 is mounted on the slider at the foremost end of the head arm 16, and the head actuator 11 drives the head arm 16 to rotate around the fixed shaft, so as to drive the read/write head 13 to perform seeking and tracking actions on the disk body 15. The magnetic head actuator 11 in the current hard disk generally employs a voice coil motor as a servo driving device. The read/write head 13 is integrally formed directly on the slider, which can fly at a nanometer level of height over the surface of the rotating disk body 15 under the action of an air gap. The slider is mounted directly to the Gimbal and suspension of the head arm 16 by the HGA (head Gimbal Assembly) process.
With the rapid development of material preparation science and microelectronic technology, computer hard disk magnetic track positioning mechanisms are continuously developing towards miniaturization and light weight. The flying height of the magnetic head on the computer hard disk is developed from about 140 μm from the hard disk to below 20nm, and the track width and track pitch are also developed from about 100 μm at first to about 1 μm at present, so that the disk capacity is dramatically increased. Meanwhile, the rotating speed of the magnetic head on the hard disk is increased from 360r/min at the beginning to 7200r/min at present, and the rotating speed is further increased to 12000 r/min. However, as the flying height of the magnetic head is continuously reduced and the rotating speed is rapidly increased, the magnetic head deviates from the track due to the eccentricity of the hard disk, and it is difficult to capture the signal on the track quickly, so that the improvement of the positioning accuracy and the track following speed of the magnetic head of the computer hard disk becomes an urgent requirement for the increasing capacity of the computer hard disk.
The currently and generally used positioning mode of a computer hard disk magnetic head is a voice coil motor closed loop servo mode, which can better meet the requirement of servo tracking when the magnetic storage density is lower, but the rapid high-precision positioning of a submicron-order magnetic track is very difficult. The problem can be better solved by adopting a secondary servo mechanism, namely, a voice coil motor is used as a primary servo mechanism to perform coarse positioning, and a micro actuator closer to the sliding block is additionally added to directly perform high-precision secondary servo positioning on the magnetic head on the sliding block. There are three kinds of mounting positions for the second stage servo positioning micro actuator, including mounting between the gimbal and the slider, mounting in the middle of the suspension of the magnetic head, and manufacturing and molding with the slider. Fig. 2 shows a micro-actuator block 3a designed separately between the gimbal 5 and the slider 2a and connected to the gimbal 5 via a pad 4. The conjuncted micro actuator is integrally manufactured on the slider through an MEMS process, and the read-write head is driven to move left and right by the action of the conjuncted micro actuator to perform servo positioning. The two mounting positions are suitable for adopting the electrostatic flat-plate type micro-actuator, and the electrostatic flat-plate type micro-actuator has the advantages that a very complex micro-structure can be manufactured through an MEMS process, but the output force of the electrostatic flat-plate type micro-actuator is smaller. Fig. 3 shows a structure in which a micro actuator 3c is formed between a cantilever 6c and a slider 2c, which is suitable for a micro actuator using a piezoelectric ceramic (PZ) material, and has advantages of simpler control and easier processing, and the micro actuator on a magnetic head is mainly manufactured by PZT piezoelectric Technology (piezo-electric Technology) at present. However, the micro-actuator using piezoelectric material has the following disadvantages: firstly, the method comprises the following steps: piezoelectric materials can be deformed by expansion and contraction in an electric field, but because the deformation ratio of the materials is not high, in order to meet the requirement of deformation length, a higher driving voltage is often required to be applied to form a stronger electric field, and the requirement is quite difficult for a hard disk with the working voltage generally lower than 5 volts. Secondly, the method comprises the following steps: the curie point failed. When the working temperature of the piezoelectric ceramic exceeds the Curie point temperature, the piezoelectric ceramic can cause failure problems due to depolarization, and the piezoelectric effect can be permanently failed. Whereas the curie temperature of piezoceramic materials is only about 180 ℃ ± 100. Thirdly, the method comprises the following steps: the response speed is not fast enough, and the application in a device requiring fast execution is difficult.
The "Modeling and Simulation of an area Crystal Silicon micro-actuator for Hard Disk Drive" published by Mou Jiangjiang DSI institute, Chen Shixin et al, Modeling and Simulation of Microsystems 2001, shows a single micro-actuator block structure as shown in FIG. 2; the document "A MEMS Piggyback Actuator for Hard-Disk Drives" published by Hiroshi Toshiyoshi and Makoto Mita et al in JOURNAL OFMICROELECTROMECHANICAL SYSTEMS, VOL.11, NO.6, DECEMBER 2002 discloses the structure of the conjunct microactuator as shown in FIG. 3; the document "development of Shear-Mode Piezoelectric actuator for precision Head Positioning", published by Shinji Koganezawa and Takeyori Hara in FUJITSU Sci.Tech.J., 37, 2, p.212-219, December 2001, shows a Microactuator structure designed with piezoceramic material as shown in FIG. 4.
A.E. Clark et al in the early 70 s of the United states discovered that an intermetallic compound Tb1-xDyxFe2-y with a laves phase structure has good magnetostriction performance, low magnetocrystalline anisotropy and Curie temperature exceeding room temperature, and that the magnetostriction coefficient of the directionally solidified crystal of the material under a low magnetic field can be obviously improved by applying a pre-compressive stress, so that the material becomes a material capable of being practically applied, and the wide attention of the scientific field and the industrial field is attracted. The material has a saturation magnetostriction coefficient of 1500-2000 ppm and is called a giant magnetostrictive material. The giant magnetostrictive material has the characteristics of large strain, high reliability, large energy density, high response speed (< ═ 1 mus), wide response frequency band (1 Hz-10 kHz) and the like.
Terbium-dysprosium-iron Giant Magnetostrictive Material (Tb-Dy-Fe Giant Magnetostrictive Material, abbreviated as REGMSM or GMM), i.e. Super Magnetostrictive Material (Super Magnetostrictive Material), Giant Magnetostrictive Material or Terfenol-D. It is also known as a "super magnetic" material in china. Compared with piezoelectric materials (PZT) and traditional magnetostrictive materials Ni, Co and the like, GMM has unique properties: (1) the magnetostrictive strain at room temperature is large, 40-50 times that of Ni and 5-8 times that of PZT; (2) the energy density is high and is 400-500 times of Ni and 10-25 times of PZT; (3) the response speed is high, generally below dozens of milliseconds, even reaching microsecond level; (4) the output force is large, the loading capacity is strong, and the output force can reach 220-800N; (5) the coupling coefficient of the magnetic machine is large, and the conversion efficiency of electromagnetic energy and mechanical energy is high and generally reaches 72 percent; (6) the temperature of Curie point is high, the working performance is stable, in case of high power, the permanent polarization of PZT is easy to disappear completely because of the overheating of the device, the magnetostriction characteristic of GMM is only temporarily disappeared even if the GMM works above the temperature of Curie point, and the magnetostriction characteristic is completely recovered when the GMM is cooled below the temperature of Curie point. In addition, the speed of sound is low, about 1/3 for Ni and 1/2 for PZT.
In addition, the giant magnetostrictive material can be deposited on the substrate in a thin film form to form an intelligent device. In recent years, many researchers have prepared amorphous rare earth-transition metal thin films on non-magnetic substrates (such as silicon and polyimide) by sputtering, and have studied the structure and magnetostrictive characteristics of the thin films, and found that magnetostrictive thin films have good soft magnetic properties, have low magnetocrystalline anisotropy, and can generate large magnetostrictive strain at room temperature and low magnetic field. These manufacturing methods also make it possible to manufacture micro-actuators of giant magnetostrictive material using micro-electromechanical manufacturing processes.
Embedded solenoids have been used in the fields of communications and the like, and there are many reports on the processing method. Reference may be made to Chong H.Ahn, and Mark G.Allen articles "Micromachined Planar Inductors ON Silicon Wafers for MEMAPLICATIONS", IEEE TRANSACTIONS INDUSTRIAL ELECTRICS, VOL.45, NO.6, DECEMBER 1998, and Yong-Kyu Yoon, Emery Chen, Mark G.Allen, and Joy Lackar articles "Embedded formed solid Inductors for RF CMOS Power amplifiers".
Disclosure of Invention
The invention aims to provide a giant magnetostrictive micro actuator for magnetic head servo, which can work under lower voltage, can output larger driving force, has response speed exceeding that of piezoelectric ceramic materials and does not have the problem of Curie point failure.
The invention provides a giant magnetostrictive micro actuator for magnetic head servo, which is characterized in that: the micro-actuator comprises a magnetic circuit, a giant magnetostrictive actuating block, a flexible connecting plate, a connecting pad, a lead pad, a coil pad, a fixed pad, a connecting point, a flexible lead, an inner magnetic shielding layer, an outer magnetic shielding layer, an embedded solenoid and a monocrystalline silicon spring; wherein,
the connecting pad is positioned on one side of the top surface of the sliding block close to the read-write head; the magnetic circuit is positioned in the sliding block and is in a shape of a flat E, the side surface of one end, close to the connecting pad, of the magnetic circuit is connected with the side surface of the top end of the giant magnetostrictive actuating block, and the top surface of the middle protruding part is in contact with the bottom surface of the other end of the giant magnetostrictive actuating block to form a closed magnetic circuit; one end of the giant magnetostrictive actuating block, which is positioned at the middle protruding part, is fixed with the flexible connecting plate through a middle fixing bonding pad on the side surface; one end of the giant magnetostrictive actuating block is fixed with the magnetic circuit, and the giant magnetostrictive actuating block is wrapped in the magnetic circuit;
the giant magnetostrictive actuator block comprises a positive magnetostrictive material layer, a middle layer and a negative magnetostrictive material layer, wherein the middle layer is made of silicon substrates or polyimide and the like, the positive magnetostrictive material layer and the negative magnetostrictive material layer are respectively positioned on two sides of the middle layer, and the middle layer plays a role in supporting and fixing the micro actuator;
the monocrystalline silicon spring is composed of a pair of springs, one end of each spring is respectively contacted with the positive magnetic material layer and the negative magnetic material layer of the giant magnetostrictive actuating block and is close to one end of the magnetic circuit, and the other end of each spring is connected with the silicon substrate into a whole;
the embedded solenoid coil surrounds the giant magnetostrictive actuating block, and a lead terminal of the embedded solenoid coil is connected to the flexible lead through a coil bonding pad;
one end of the flexible connecting plate is inserted between one end of the magnetic circuit and the giant magnetostrictive actuating block and is fixed with the giant magnetostrictive actuating block, and the other end of the flexible connecting plate is fixed with the cantilever beam; the flexible connecting plate is provided with a coil pad and a side surface middle fixed pad, the coil pad is connected with a flexible lead of the cantilever beam, and the connecting point is used for fixing the flexible connecting plate and the cantilever beam; the middle fixing pad on the side surface is used for fixing the flexible connecting plate and the giant magnetostrictive actuating block, and the coil pad is used for connecting a lead of the embedded solenoid;
the inner magnetic shielding layer covers the magnetic circuit, and the outer magnetic shielding layer is located between the magnetic circuit and the silicon substrate.
The present invention mainly uses the giant magnetostrictive effect of special material, and it adopts a new type giant magnetostrictive material to substitute piezoelectric ceramic material, and adopts conjoined manufacturing process to make the microactuator of magnetic head slider. The phenomenon of dimensional and volumetric changes under the action of an applied magnetic field is known as the magnetostrictive effect. The magnetostriction coefficients of conventional magnetostrictive materials such as iron, nickel, etc. are small, 21ppm (parts per million) and-46 ppm, respectively. Because the giant magnetostrictive material has excellent performance, the novel material is adopted to replace a piezoceramic material, a novel micro-actuating structure, an embedded driving coil, a closed magnetic circuit and the like are designed, and the design adopts the scheme that a combined micro-actuator is made on a sliding block. The novel magnetic head micro-actuator provided by the invention can achieve the following technical effects: firstly, the response speed can reach microsecond level, the requirement of quickly tracking and positioning magnetic tracks under the condition of high storage density can be met, and the response speed is one order of magnitude faster than that of a PZT micro-actuator; secondly, the working voltage is low, and the hard disk magnetic head can work normally under the voltage below 5 volts, so that the working environment limitation of the hard disk magnetic head is met; thirdly, the problem of permanent Curie point failure of a PZT micro-actuator is solved, the magnetostrictive characteristic of the micro-actuator can only disappear temporarily when the micro-actuator works above the Curie point temperature, and the magnetostrictive characteristic can be completely recovered when the micro-actuator is cooled below the Curie point temperature; fourthly, the positioning precision is high, the swing amplitude is large, the positioning precision can be as small as a nanometer level, the motion amplitude can be more than a micron level, and the precision and the amplitude of the micro actuator are analyzed later; fifthly, the coupling coefficient of the magnetic machine is large, the energy conversion efficiency is high, and the conversion efficiency of electromagnetic energy and mechanical energy can reach 72 percent generally. In addition, compared with the electrostatic flat-plate micro-actuator, the micro-actuator has the characteristics of large output force, strong loading capacity and high energy density.
Drawings
FIG. 1 is a schematic view of the overall structure of a magnetic disk;
FIG. 2 is a prior art microactuator structure interposed between a slider and a gimbal;
FIG. 3 is a prior art piezo ceramic micro-actuator structure between a slider and a cantilever;
FIG. 4A is a partial cross-sectional view of a super-magnetostrictive micro-actuator structure for head servo according to the present invention;
FIG. 4B is a cross-sectional view A-A of FIG. 4A;
FIG. 4C is a schematic structural view of a flexible connecting plate, wherein FIG. 4C (a) is a side view, and FIG. 4C (b) is a left side view;
FIG. 4D is a schematic structural diagram of the slider shown in FIG. 4A;
FIG. 5 is a layered structure diagram of a head suspension;
FIG. 6 is a schematic diagram of the layered structure of the super-magnetostrictive micro-actuator block of FIG. 4A.
Detailed Description
As shown in fig. 4A, 4B, 4C and 4D, the giant magnetostrictive microactuator for head servo according to the present invention is manufactured and molded integrally with the slider 25. The micro-actuator is composed of the following parts: the magnetic circuit 28, the giant magnetostrictive actuator block 29, the flexible connecting plate 30, the connecting pad 24, the lead pad 32, the coil pad 33b, the fixing pad 34, the connecting point 31, the flexible lead 35, the inner and outer magnetic shielding layers 50, 51, the embedded solenoid 53 and the single crystal silicon spring 55. The components of the micro-actuator may be in two parts, one part being located on the flexible connecting plate and the other part being located inside the slider 25, the slider 25 being machined on the silicon substrate 27.
The connection pads 24 are located on the top surface of the slider on the side near the read/write head 26. The magnetic circuit 28 is made of soft magnetic material such as permalloy material, and the like, and plays a role of enhancing the magnetic field, so that the magnetic field in the magnetic circuit 28 can be enhanced when the excitation field is applied, and the requirement on the driving current is reduced. The magnetic circuit 28 is located within the slider 25 and is shaped as a lying "E". The side surface of one end 28a of the magnetic circuit 28 near the connection pad 24 is connected to the side surface of the tip end of the super magnetostrictive actuator block 29, and the top surface of the intermediate protrusion 28b is in contact with the bottom surface of the other end of the super magnetostrictive actuator block 29, but is not fixed, to form a closed magnetic circuit. The giant magnetostrictive actuator mass 29 is fixed to the flexible connecting plate 30 at one end of the middle protruding portion 28b by a side middle fixing pad 34. The other end surface 28c of the magnetic circuit 28 is not in contact with the super magnetostrictive actuator block 29. One end of the giant magnetostrictive actuator block 29 is fixed to the magnetic circuit 28, the other end is not fixed to the magnetic circuit 28, and the giant magnetostrictive actuator block 29 is wrapped in the magnetic circuit 28, so that the swinging motion of the micro-actuator is not hindered, and the leakage of magnetic flux can be reduced.
The giant magnetostrictive actuator block 29 is made of 3 layers of materials, the middle layer 29c is made of silicon substrate or polyimide or other materials, and the positive magnetostrictive material layer 29a and the negative magnetostrictive material layer 29b are respectively positioned on two sides of the middle layer 29 c. The intermediate layer 29c, which serves to support and hold the microactuator, may be formed integrally with the slider silicon substrate 27 or may be formed of polyimide or the like. The positive and negative magnetic material layers 29a and 29b have low tensile strength, high brittleness and easy fracture, and cannot bear tensile stress or shear stress during working.
The giant magnetostrictive actuator block 29 is an output source of the actuator force, and the embedded solenoid coil 53 generates a changing magnetic field under the driving of the exciting current to influence the deformation of the giant magnetostrictive film materials 29a and 29b and drive the read-write head 26 on the front end face of the slider 25 to swing left and right to realize the servo action.
The single crystal silicon spring 55 is formed by a pair of springs, one end of each spring is respectively contacted with the positive magnetic material layer 29a and the negative magnetic material layer 29b of the giant magnetostrictive actuator block 29, is close to one end 28a of the magnetic circuit 28, and the other end of each spring is connected with the silicon substrate 27 into a whole to play a role in reducing impact. Such a shaped spring can be grown using silicon deposition and High Aspect Ratio (High Aspect Ratio) processing techniques.
For ease of manufacture, the single crystal silicon spring 55 may be made "A "shaped configuration.
The embedded solenoid 53 is wound around the super magnetostrictive actuator block 29 to provide excitation, and its lead terminal 33a is connected to the flexible lead 35 through the coil pad 33 b.
One end of the flexible connecting plate 30 is inserted between the one end 28c of the magnetic circuit 28 and the giant magnetostrictive actuator block 29, and is fixed to the giant magnetostrictive actuator block 29, and the other end is fixed to the cantilever beam 21. The flexible connecting board 30 is provided with a lead pad 32 and a connecting point 31 at one end connected to the cantilever beam 21, and a coil pad 33b and a side surface intermediate fixing pad 34 at the other end. The lead pad 32 is connected to the flexible lead 35 of the cantilever beam 21, and the connection point 31 is used for fixing the flexible connection board 30 and the cantilever beam 21. The side middle fixing pad 34 is used for fixing the flexible connecting plate 30 and the giant magnetostrictive actuator block 29, and the coil pad 33b is used for connecting the lead of the embedded solenoid 53. The flexible link plate 30 has a thin and wide profile and thus has a certain elasticity in the vertical direction, while it can be used as a fixing shaft of the super magnetostrictive actuator block 29 because it is wide in the horizontal direction. This makes one end of the super magnetostrictive actuator block 29 fixed and the other end driven by the super magnetostrictive actuator block 29 capable of swinging left and right to achieve precise positioning of the pickup head 26.
An inner magnetic shield layer 50 overlies the magnetic circuit 28 and an outer magnetic shield layer 51 is located between the magnetic circuit 28 and the silicon substrate 27. The inner and outer magnetic shielding layers 50, 51 are made of a material with high magnetic permeability by sputtering or deposition, and the magnetic circuit 28 is wrapped in the inner magnetic shielding layers, so that the interference of the driving magnetic field of the micro-actuator on the magnetic head or the storage medium is prevented.
In general, the slider 25 includes a conventional side read/write head 26 and a bottom ABS air bearing and top center attachment point, and the micro-actuator of the present invention, integrated with the slider 25, extends the conventional top center attachment point to the forward attachment point 24 and the attachment point 31 to balance the weight of the slider.
The embedded solenoid 53 mainly generates an excitation magnetic field. The single crystal silicon spring 55 is mainly used to reduce the impact of the motion. The giant magnetostrictive actuator block 29 deflects (bends) under the action of the excitation magnetic field, thereby driving the slider 25 to move integrally. In order for the super magnetostrictive actuator block 29 to normally oscillate, the space between the embedded solenoid 53 and the super magnetostrictive actuator block 29 must be unobstructed. This can be achieved by filling the sacrificial layer 56 during processing.
In order for the super magnetostrictive actuator block 29 to normally oscillate, the space between the embedded solenoid 53 and the super magnetostrictive actuator block 29 must be unobstructed. This can be achieved by filling the sacrificial layer 56 during processing. That is, when the embedded solenoid 53, the microactuator 29 and the single crystal silicon spring 55 are grown on the silicon substrate 29c, a sacrificial material, such as a silicon dioxide material, is filled in the gap, and then the sacrificial layer 56 is washed away by cleaning with salicylic acid after the embedded solenoid 53, the single crystal silicon spring 55 and the giant magnetostrictive actuator block 29 are grown. The bending section of the flexible connecting plate 30 is inserted into a gap between the right end face of the giant magnetostrictive actuator block 29 and the right end of the magnetic circuit 28, and is bonded or welded and fixed with the right end face of the giant magnetostrictive actuator block 29, so that firm bonding between the giant magnetostrictive actuator block and the giant magnetostrictive actuator block can be ensured. In consideration of the difficulty of manufacturing, the bending section of the flexible connecting plate 30 can be bonded or welded with the upper part of the right end of the giant magnetostrictive actuator block 29 instead.
Figure 5 shows the layered structure of the cantilever beam portions with the connection pads 24, flexible leads 35 and flexible connection cables 36 connected to the slider. The magnetic head arm 16 in fig. 1 is drawn again as a cantilever beam 21 in fig. 5, a flexible plate 22 is fixed below the cantilever beam 21, a gimbal 23 is designed at the front end of the flexible plate 22, a slider bonding disk 20 is designed in the middle of the gimbal 23, and the slider bonding disk 20 can be a bonding pad or a bonding point which is welded or bonded with a connecting pad 24 on a slider 25, thereby providing support and fixation for the slider 25. The flexible plate 22 and the gimbal 23 are elastic elements, and can provide several degrees of freedom in horizontal, vertical, roll, pitch, and other directions. The flexible connection cable 36 is directly connected to the head 26 to input a write signal or output a read signal. The flexible lead 35 is directly connected to the lead pad 32 of the flexible connection board 30 and connected to the lead terminal 33a of the embedded solenoid 53 to supply the driving current of the embedded solenoid 53. The connection point 31 of the flexible web 30 is also fixed to the cantilever beam 21.
FIG. 6 illustrates a layered structure of a giant magnetostrictive actuator mass. It is made of material with positive giant magnetostrictive effect (such as TbFe)2Film), intermediate layer (such as silicon substrate or polyimide substrate), and material with negative giant magnetostrictive effect (such as SmFe)2Film) groupThe negative giant magnetostrictive layer. The substrate may be a polyimide material as shown or other material such as silicon. The research on the rare earth-iron giant magnetostrictive material shows that SmFe is generated at room temperature2Has a magnetostriction value close to TbFe2Polycrystalline SmFe2The room temperature saturated magnetostriction lambda is-1560 x 10-6，TbFe2Is 1753X 10-6In particular, the magnetostriction coefficients of the two are equal in a low magnetic field. The bimetallic cantilever beam formed by combining the positive and negative magnetic effects can enhance the overall magnetic striction effect and reduce the initial curve of the cantilever beam. The micro-actuator of the present invention employs such a thin film type giant magnetostrictive layered structure.
The structure of the universal joint and the flexible plate can be basically the same as that of the universal joint and the flexible plate of the current commercial hard disk, but the difference lies in the connecting part of the universal joint and the sliding block, in order to accumulate a certain amount of deformation energy of the giant magnetostrictive film, the length of the film cannot be too short, therefore, the bonding pad of the universal joint and the sliding block must be moved to one side of the sliding block, and the other side can have the length of hundreds of micrometers to manufacture the giant magnetostrictive film. The universal joint that slider and cantilever beam flexible sheet are connected has three kinds of structures commonly used: (i) is in a cross structure; (ii) is of a convex structure; (iii) is of a snake-shaped structure. The first and third types can make the sliding block have better suspension characteristic, but the structure is complex, the second type has simple structure, and various response characteristics can meet the requirement of the magnetic head, thus being a common choice of the current commercial magnetic disk. The invention also adopts the structure, but the connection point with the sliding block is adjusted to one side close to the read-write head, and a flexible connecting plate is added on the other side for fixing, the design can deteriorate the dynamic response characteristic of the sliding block, and the flexible connecting plate which is as soft as possible is needed for the design.
From the above structure, it can be seen that the main operation principle of the micro-actuator is: the embedded solenoid coil generates an electromagnetic field after being electrified, a giant magnetostrictive film material with positive giant magnetostrictive effect in the embedded solenoid coil can extend in the magnetic field direction, a thin film material with negative giant magnetostrictive effect can shorten in the magnetic field direction, and one end of the thin film type micro actuator is connected to the cantilever beam through the flexible connecting plate for fixing, so that the whole sliding block can be driven to swing due to the reaction force, the movement track is arc-shaped, but the movement direction is along the vertical direction of the magnetic disk track, and the embedded solenoid coil can be used as a secondary servo mechanism to realize the precise positioning of the magnetic disk track.
It is known from the structure and working principle of the micro-actuator that the micro-actuator can deflect to the side of the negative magnetic material but can not deflect to the side of the positive magnetic material, i.e. the movement of the micro-actuator is always unidirectional. It is certainly possible to achieve movement in both directions if pairs of such micro-actuators are used, but this is costly and even impossible. If only a single microactuator is used, it is required that the motion of the first stage be designed with a certain overshoot (/ or undershoot) and the motion of the second stage be used for compensation when designing the two-stage servo system. This effectively shifts the complexity of the architecture into the complexity of the system control. The solution to achieve bidirectional motion can also be accomplished by two sets of solenoids. The group of spiral coils generates an excitation magnetic field in the length direction of the film, so that the film cantilever beam is bent towards one side of the negative giant magnetostrictive material; the other set of solenoid coils generates a magnetic field in the direction of the transverse axis of the film, so that the film cantilever beam bends towards the side of the giant magnetostrictive material. However, the difficulty of processing two sets of solenoids in a very small space is great, and the cost is likely to exceed the benefits brought by the solenoids.
The solution adopted by the invention is to add a bias magnetic field to ensure that the giant magnetostrictive material is positioned at the center of the deflection motion when in a static state, thus realizing the motion in two directions. The bias magnetic field can be generated by adding a permanent magnet or by superimposing a suitable dc bias current on the driving current, or by arranging permanent magnets on both sides of the super magnetostrictive actuator block 29.
Claims (3)
1. A super-magnetostrictive micro-actuator for head servoing, characterized by: the micro-actuator comprises a magnetic circuit (28), a giant magnetostrictive actuating block (29), a flexible connecting plate (30), a connecting pad (24), a lead pad (32), a coil pad (33b), a fixed pad (34), a connecting point (31), a flexible lead (35), inner and outer magnetic shielding layers (50, 51), an embedded solenoid (53) and a monocrystalline silicon spring (55); wherein,
the connecting pad (24) is positioned on one side of the top surface of the sliding block (25) close to the read-write head (26); the magnetic circuit (28) is positioned in the sliding block (25) and is in a shape of a flat lying 'E', the side surface of one end (28a) of the magnetic circuit (28) close to the connecting pad (24) is connected with the side surface of the top end of the giant magnetostrictive actuator block (29), and the top surface of the middle protruding part (28b) is contacted with the bottom surface of the other end of the giant magnetostrictive actuator block (29) to form a closed magnetic circuit; one end of the giant magnetostrictive actuating block (29) positioned at the middle protruding part (28b) is fixed with the flexible connecting plate (30) through a side middle fixing pad (34); one end of the giant magnetostrictive actuator block (29) is fixed with the magnetic circuit (28), and the giant magnetostrictive actuator block (29) is wrapped in the magnetic circuit (28);
the giant magnetostrictive actuator block (29) comprises a positive magnetostrictive material layer (29a), an intermediate layer (29c) and a negative magnetostrictive material layer (29b), wherein the intermediate layer (29c) is made of silicon substrates or polyimide and the like, the positive magnetostrictive material layer (29a) and the negative magnetostrictive material layer (29b) are respectively positioned on two sides of the intermediate layer (29c), and the intermediate layer (29c) plays a role in supporting and fixing the micro actuator;
the monocrystalline silicon spring (55) is composed of a pair of springs, one end of each spring is respectively contacted with the positive magnetic material layer (29a) and the negative magnetic material layer (29b) of the giant magnetostrictive actuating block (29), is close to one end (28a) of the magnetic circuit (28), and the other end of each spring is connected with the silicon substrate (27) into a whole;
an embedded solenoid coil (53) wound around the giant magnetostrictive actuator block (29) with its lead terminal (33a) connected to the flexible lead (35) through a coil pad (33 b);
one end of the flexible connecting plate (30) is inserted between one end (28c) of the magnetic circuit (28) and the giant magnetostrictive actuating block (29) and is fixed with the giant magnetostrictive actuating block (29), and the other end of the flexible connecting plate is fixed with the cantilever beam (21); one end of the flexible connecting plate (30) connected with the cantilever beam (21) is provided with a lead bonding pad (32) and a connecting point (31), the other end of the flexible connecting plate is provided with a coil bonding pad (33b) and a side surface middle fixing bonding pad (34), the lead bonding pad (32) is connected with a flexible lead (35) of the cantilever beam (21), and the connecting point (31) is used for fixing the flexible connecting plate (30) and the cantilever beam (21); the side surface middle fixing pad (34) is used for fixing the flexible connecting plate (30) and the giant magnetostrictive actuating block (29), and the coil pad (33b) is used for connecting a lead of the embedded solenoid coil (53);
the inner magnetic shielding layer (50) covers the magnetic circuit (28), and the outer magnetic shielding layer (51) is located between the magnetic circuit (28) and the silicon substrate (27).
2. A giant magnetostrictive microactuator as in claim 1, wherein: a pair of monocrystalline silicon springs (55)A spring in a shape structure.
3. A giant magnetostrictive microactuator as claimed in claim 1 or 2, characterized in that: permanent magnets are respectively arranged on two sides of the giant magnetostrictive actuating block (29).
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| CNB2006101247558A CN100424756C (en) | 2006-10-13 | 2006-10-13 | Magnetostrictive micro-actuator used for head servo |
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| CNB2006101247558A CN100424756C (en) | 2006-10-13 | 2006-10-13 | Magnetostrictive micro-actuator used for head servo |
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| CN100424756C CN100424756C (en) | 2008-10-08 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109581082A (en) * | 2018-12-25 | 2019-04-05 | 中国科学院电子学研究所 | Trigone structure mini three-dimensional electric field sensor and technology of preparing based on micro-group dress |
| CN110634667A (en) * | 2019-09-29 | 2019-12-31 | 苏州蓝沛无线通信科技有限公司 | Assembling method of wireless charging receiving coil module |
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| KR100580242B1 (en) * | 1999-10-21 | 2006-05-16 | 삼성전자주식회사 | Micro-actuator |
| US6744173B2 (en) * | 2000-03-24 | 2004-06-01 | Analog Devices, Inc. | Multi-layer, self-aligned vertical combdrive electrostatic actuators and fabrication methods |
| JP2003208769A (en) * | 2002-01-11 | 2003-07-25 | Data Storage Inst | Microactuator for disk drive suspension |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109581082A (en) * | 2018-12-25 | 2019-04-05 | 中国科学院电子学研究所 | Trigone structure mini three-dimensional electric field sensor and technology of preparing based on micro-group dress |
| CN109581082B (en) * | 2018-12-25 | 2020-09-25 | 中国科学院电子学研究所 | Triangular structure micro three-dimensional electric field sensor based on micro assembly and preparation technology |
| CN110634667A (en) * | 2019-09-29 | 2019-12-31 | 苏州蓝沛无线通信科技有限公司 | Assembling method of wireless charging receiving coil module |
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