Abstract: A magnetic recording head includes an active component and a piezoelectric actuator. The active component is disposed proximal to a media-facing surface of the magnetic recording head. The piezoelectric actuator includes a piezoelectric layer, a first electrode coupled to the piezoelectric layer, and a second electrode coupled to the piezoelectric layer. The piezoelectric actuator is configured to exert a mechanical force to displace the active component such that the displacement changes a protrusion of the active component from the media-facing surface.

Abstract: An HGA includes a slider and a suspension for supporting the slider, wherein the suspension includes a flexure having a plurality of electrical traces formed thereon and a gimbal connection area supported and connected to the slider, a first surface of the gimbal connection area is provided with a first adhesive and a second adhesive respectively formed thereon and between the first surface and an opposite surface of an air bearing surface of the slider, an opposite surface of the first surface of the gimbal connection area is contacted with a dimple, and the dimple is located at a position between first adhesive and the second adhesive. The HGA can eliminate torsion and sway gain in frequency response function testing, and maintain AC stroke sensitivity and linearity of elements, thereby finally improving the performance of the disk drive unit.

Abstract: A manufacturing method of a disc device suspension includes forming a load beam blank including the load beam and a first frame continuous to the load beam, forming a flexure blank including the flexure and a second frame continuous to the flexure, forming a convex portion in the first frame, forming an opening in the second frame in a position corresponding to the convex portion to receive the convex portion, overlapping the load beam blank with the flexure blank to insert the convex portion into the opening, fixing the flexure to the load beam, and separating the load beam from the first frame and the flexure from the second frame after the fixing.

Abstract: The present disclosure generally relates to a magnetic media drive employing a magnetic recording head. The magnetic recording head comprises a first write head and a second write head each coupled to a first pad and a second pad of a slider pad and an electrical circuit coupled to the first and second pads. The first write head comprises a first main pole and a first thermal fly height (TFH) element, and the second write head comprises a second main pole and a second TFH element. The electrical circuit comprises a capacitor and a connection to the first TFH element of the first write head, and an inductor and a connection to the second TFH element of the second write head. The electrical circuit is configured to independently power the first TFH element and the second TFH element.

Abstract: One embodiment of a robust process for the repair of a solder bridge defect in a Surface Mount Technology micro-electronic circuit assembly with fine pitch components. The defective solder joint is heated by various means and a cold gas jet blast is applied to the defective solder joint. An effect is created whereby the solder inducing the defect is conveyed away by the impact of the cold gas jet blast. The advantages of this embodiment include scalability for pin spacing and elimination of heat induced latent defects. The process is applicable to any pin spacing, but is of particular usefulness with pin spacing of 0.025 inch or finer. Other embodiments are described and shown.

Abstract: A head suspension assembly for a disk drive includes a load beam and a laminated flexure that comprises a stainless steel layer, a copper trace layer, and a dielectric layer between the stainless steel layer and the copper trace layer. The laminated flexure includes a flexure tail that extends away from the load beam to a flexure tail terminal region. The copper trace layer includes a plurality of flexure bond pads in the flexure tail terminal region. The stainless steel layer includes a plurality of backing islands in the flexure tail terminal region. Each of the plurality of backing islands is aligned with a corresponding one of the plurality of flexure bond pads. A noble metal layer is disposed on the plurality of backing islands.

Abstract: The present disclosure provides a method and a device for titling, which can achieve automatic correction when deviation occurs between a real titling position of a product to be titled and a preset titling position, so as to avoid an ID shift phenomenon, and thus ensure accuracy of titling positions and improve titling efficiency. The titling method provided in the present disclosure comprises: determining a real titling position of a product to be titled; comparing the real titling position with a preset titling position; and titling the product to be titled in accordance with the comparison result.

Abstract: A method for manufacturing a disk drive head suspension including a load beam, a flexure and a limiter for restricting the range of motion of the flexure with respect to the load beam. The load beam includes an aperture and an engaged portion adjacent to the aperture. The flexure, in an unformed state, includes a slider mounting region and a generally planar engagement structure extending from the slider mounting region. The engagement structure includes a tab portion extending from the slider mounting region and a hook portion extending from the tab portion. During a first forming operation the hook portion is bent around a tooling die to a ninety degree angle with respect to the tab portion. The flexure is then welded to the load beam with the hook portion extending into the aperture. During a second forming operation the tab portion is bent around a tooling die to a ninety degree angle with respect to the slider mounting region.

Abstract: A method for manufacturing a disk drive head suspension having a plated load point dimple. An aperture is etched into the spring metal member. A photoresist mask having an opening with load point-defining side walls and a load point diameter is formed over a portion of a spring metal member including the aperture. Metal is plated onto the spring metal member and into the aperture in the opening to form a load point having the load point diameter on the spring metal member.

Abstract: A method for bonding a first substrate to a second substrate is described. The first substrate includes a first plurality of solder pads, a first alignment mark set, and a first plurality of dots. The second substrate includes a second plurality of solder pads, a second alignment mark set, and a second plurality of dots configured to interlock with the first plurality of dots. The method includes aligning the first alignment mark set with the second alignment mark set. The first alignment mark sets being aligned corresponds to the dots and the solder pads being aligned. The method also includes locking the first plurality of dots with the second plurality of dots to form an interlocking key. The method also includes reflowing at least one of the first and second pluralities of solder pads. The dots remain substantially solid during the reflow.

Abstract: A method of reclaiming a head suspension includes detaching a slider 225 from a tongue 221 of the head suspension and removing an adhesive 227 remaining on the tongue 221. Removing the adhesive 227 remaining on the tongue 221 includes feeding a solvent 243, which promotes the removal of the adhesive 227, to a part of the tongue 221 where the adhesive 227 remains and promoting the removal of the remaining adhesive 227 from the tongue 221 by applying physical energy to the adhesive remaining part on the tongue 221. The physical energy is produced by heating, supersonic vibration, and the like. The method easily removes the adhesive 227 from the tongue 221 without directly applying mechanical force to the tongue 221, thereby improving yields.

Abstract: A disk drive includes a disk drive base comprising a first metal material. The disk drive base may include a first opening and a first attachment feature to which a head actuator assembly pivot may be attached. A motor support may be embedded in the first opening in the disk drive base. The motor support consists of a second metal material having a damping coefficient higher than that of the first metal material. A rotary spindle may be attached to the motor support, and a disk may be attached to the rotary spindle.

Abstract: A system is provided that increases the spindle stiffness of a disk drive while optimizing power consumption. A multipurpose bearing provides axial stiffness and enhanced stiffness against radial and pitch loads applied to the spindle. When used in combination with a journal bearing, conventional thrust bearings may be eliminated without sacrificing overall stiffness. As a result, the height of the disk drive may be reduced, thereby making the system desirable to be used in smaller electronic devices.

Abstract: A method of forming a hardened layer on a tape drive head assembly comprising building a tape drive head assembly, in which a number of layers of amorphous material are applied along read and write components of the tape drive head assembly as the tape drive head assembly is built and selectively heating portions of the amorphous material. A drive head assembly comprising a write component, a magnetic resistive element, and a number of layers of amorphous material, in which a portion of the amorphous material is hardened.

Abstract: A disk drive device includes a hub, a base plate, and a bearing unit. The bearing unit includes a shaft housing member, joined to the hub, having a through-hole in the center, a shaft having a smaller diameter section and a larger diameter section, a radial dynamic pressure grooves, and a lubricant agent. The opening shape of bearing hole of the base plate is so formed as to be larger than the outer shape of the larger diameter section. In the bearing unit, the larger diameter section of the bearing unit is fixed by a hardening resin present between the bearing unit and the bearing hole.

Abstract: A flexure 11 has a substrate 13 made of a thin conductive metal plate, a base insulating layer 31 made of flexible resin formed on the substrate, wiring patterns 15 formed on the base insulating layer and connected to a slider mount 17, and a cover insulating layer 33 formed over the wiring patterns. The flexure 11 is substantially coated with a conductive polymer layer 39 having a thickness in the range of 18 to 130 nm. The flexure 11 prevents electrostatic accumulation and ion migration that are trade-offs.

Abstract: A defect inspection is performed for each of glass substrates by a surface defect detector. The distance from the center of the glass substrate to a detected defect, as a radius of a nonmagnetic region to be formed circular, is recorded along with an ID assigned to the glass substrate. Such defect information is recorded in a defect list using a printer or recorded in an RFID tag using an RFID writer. The defect list or the RFID tag is attached to a glass-substrate case. Each glass substrate and its defect information are in one-to-one correspondence and are provided to a customer as a magnetic disk manufacturer. Based on the obtained defect information, the customer manufactures magnetic disks each being a discrete track recording medium having the nonmagnetic region formed at the position where the defect is present.

Abstract: A method of picking and placing a workpiece relative to a disk drive may include steps of providing a robotically controlled tool, a servo motor assembly for moving the tool, at least one controller for controlling the tool and the servo motor assembly, and a machine vision assembly coupled to the controller and located relative to the tool so that a selected feature is within a field of view of the machine vision assembly while the tool is picking up the workpiece. The workpiece may be coupled to the tool, and the workpiece may be aligned with the selected feature of the disk drive using the machine vision assembly and the controller to control the servo motor assembly, such that the workpiece is aligned with the selected feature. The aligned workpiece may then be placed onto the selected feature of the disk drive.

Abstract: According to one embodiment, a head stack assembly cartridge is provided. The head stack assembly cartridge includes a base plate having a pivot shaft for pivotally mounting a head stack assembly and a base voice coil motor magnet attached to an inner surface of the base plate. The base voice coil motor magnet is arranged on the inner surface of the base plate to be adjacent to a coil of the head stack assembly pivotally mounted on the pivot shaft. The head stack assembly cartridge further includes a cover removably attached to the base plate and a pivot clamp removably attached to the cover and configured to secure the head stack assembly pivotally mounted on the pivot shaft.

Abstract: A method of assembling a hard disk drive comprises steps of: sealing an interface of the base and the cover of an enclosed housing with an infrared-transmissive tape; filling the enclosed housing with a desired gaseous medium; optionally, testing the hard disk drive; and, optionally; re-working the hard disk drive. Preferably, the enclosed housing is free of rubber gasket materials between the base and the cover. A hermetically sealed hard disk drive of the invention comprises: a housing comprising a base and a cover; and disk drive components enclosed within the housing for facilitating reading and recording of data at any desired location on at least one disk contained within the housing, wherein the hard disk drive is free of rubber gasket materials between the base and the cover.

Abstract: A slider tester includes a disk, movable table, table drive mechanism, guide member, etc. A plurality of suspensions are mounted on the movable table. A slider is mounted on each suspension. A guide member can support respective lift tabs of the suspensions. The guide member includes a first guide surface, second guide surface, and opening arranged in a track width direction of the disk. When any of the lift tabs gets into the opening as the movable table moves in the track width direction of the disk, the slider is dropped toward a recording surface of the disk.

Abstract: In a method of manufacturing a disk drive device, a cleaning process and an assembly process are performed in succession in a clean room having a predetermined cleanness level. The cleaning process includes an alkali cleaning process, a first purified water cleaning process, a second purified water cleaning process, a spray cleaning process, a draining process and a drying process. In the first purified water cleaning process, purified water ultrasonic wave cleaning is sequentially performed on the base member of the disk drive device to be cleaned by using ultrasonic waves of frequencies of 40 kHz, 68 kHz and 132 kHz in purified water filled in a first purified water cleaning tank. The cleaned base member and other components having a predetermined cleanness level are assembled in the assembly process continuous from the cleaning process.

Abstract: A method of centering a disk of a hard disk drive includes arranging a disk on an upper end portion of a hub on which a plurality of disks are rotatably assembled, and assembling the disk on the hub by vibrating the hub. Accordingly, the disks and/or spacers may be easily assembled on the hub, a time of centering may be relatively much reduced, and a superior centering quality may be obtained.

Abstract: A method for manufacturing a perpendicular magnetic disk 100 that includes a step of forming, on a base 110, a granular magnetic layer 160 in which a grain boundary portion is formed by segregation of a non-magnetic substance containing an oxide as a main component around magnetic particles containing a CoCrPt alloy grown in a columnar shape as a main component. The method also includes a step of forming an auxiliary recording layer 180 that contains a CoCrPtRu alloy as a main component and has a film thickness of 1.5 to 4 nm above the granular magnetic layer, and a step of heating the base formed with the auxiliary recording layer in a temperature range of 210 to 250° C.

Abstract: An integrated lead head suspension flexure including a plurality of integrated leads each including at least one lead portion unbacked by the flexure spring metal layer and configured to be substantially inline with the general plane of the spring metal layer. The leads are disposed on a dielectric layer including an unbacked dielectric layer portion having a surface positioned between the major surfaces of the spring metal layer.

Abstract: A disk drive is assembled to have a cover that includes a hole therethrough, and an annular gasket continuously encircling the hole and being adhered to an undersurface of the disk drive cover. A breather filter is adjacent the disk drive base. The breather filter includes a breather filter housing having a top surface and an entrance port. The annular gasket is in compressive contact with, but not adhered to, the top surface of the breather filter housing. The annular gasket encircles the entrance port. In certain embodiments, this method of assembly may facilitate disk drive rework.

Abstract: A rotating device comprises a hub on which a magnetic recording disk is to be mounted and a base rotatably supporting the hub. At least one of the base and the hub is an item of manufacture. A method for manufacturing the rotating device comprises the steps of forming the item of manufacture, immersing the formed item of manufacture in an aqueous solution, the solute of which being a surfactant and the temperature of which being higher than the melting point of heptacosane, taking out the item of manufacture from the aqueous solution and immersing the item of manufacture in a liquid that can be regarded as pure water, taking out the item of manufacture from the liquid and drying the item of manufacture, and assembling the rotating device using the dried item of manufacture.

Abstract: A method for manufacturing an head gimbal assembly (HGA) according to the present invention is comprised of: a step for preparing a thin film piezoelectric actuator including a first piezoelectric laminate having a first piezoelectric layer, and a second piezoelectric laminate having a second piezoelectric layer; a step for preparing a suspension; a fixing step for fixing the thin film piezoelectric actuator to the suspension; a first repolarization treatment step for performing repolarization treatment to the first piezoelectric layer after the fixing step; and a second repolarization treatment step for performing repolarization treatment to the second piezoelectric layer after the fixing step.

Abstract: Multi-layer ground plane structures and methods of manufacture for integrated lead suspension flexures. A flexure in accordance with one embodiment of the invention includes an insulating layer, a plurality of traces on the insulating layer and a stainless steel base layer on the side of the insulating layer opposite the traces. The stainless steel base layer includes one or more void portions with voids in the base layer opposite the insulating layer from the traces and one or more backed portions with the base layer backing the traces. A plurality of patterned and transversely-spaced first conductive ground planes are located opposite the insulating layer from the traces at the void portions and backed portions of the stainless steel base layer. A continuous gold second conductive ground plane is located opposite the insulating layer and the first ground planes from the side of the insulating layer adjacent to the traces at the void portions and backed portions of the stainless steel base layer.

Abstract: A method of assembling a head stack assembly (HSA) includes securing a flex cable to an actuator including an actuator arm having a side slot with a slot end. A first head gimbal assembly (HGA) is attached to the actuator arm. The first HGA includes a first laminated flexure having a first flexure tail with a first raised region that includes an out-of-plane bend. The first raised region is squeezed while inserting the first flexure tail partially within the side slot with the first raised region adjacent the slot end. The first raised region is allowed to expand into contact with the side slot adjacent the slot end. The first flexure tail is electrically connected to the flex cable.

Abstract: A method of manufacturing a head suspension includes a punching process, a positioning process, and an affixing process. An objective part on the head suspension to which a damper 73 is affixed includes a discontinuous section 72. The punching process punches a damper material into the damper 73 whose shape corresponds to the shape of the objective part excluding the discontinuous section 72. The positioning process positions the damper 73 to the objective part so that the damper 73 avoids and surrounds the discontinuous section 72, and the affixing process affixes the damper 73 to the objective part. The method secures a uniform damping effect among manufactured head suspensions and improves the yield of dampers and head suspensions without deteriorating the functions and performances of the head suspensions.

Abstract: A slider tester includes a disk, movable table, table drive mechanism, guide member, etc. A plurality of suspensions are mounted on the movable table. A slider is mounted on each suspension. A guide member can support respective lift tabs of the suspensions. The guide member includes a first guide surface, second guide surface, and opening arranged in a track width direction of the disk. When any of the lift tabs gets into the opening as the movable table moves in the track width direction of the disk, the slider is dropped toward a recording surface of the disk.

Abstract: In a manufacturing method for a head gimbal assembly, before mounting a slider on a suspension, coating films each made of solder are formed on respective terminals of a plurality of leads to be connected to a plurality of electrode pads of the slider. After mounting the slider on the suspension, the coating films are heated with laser light to thereby melt the solder, with the respective terminals of the plurality of leads in contact with the corresponding electrode pads via the respective coating films, whereby the terminals are electrically and physically connected to the electrode pads.

Abstract: According to one embodiment, a head stack assembly incorporating device connects a head stack assembly to the base of a magnetic disk device by screwing a connector on the bottom surface of the rotational shaft of the head stack assembly and a connector on the base of the magnetic device together. The head stack assembly incorporating device includes a chuck and a driving-force transmitter. The chuck pinches the rotational shaft of the head stack assembly from the upper surface of the head stack assembly to be fixed to the rotational shaft. The chuck is rotatable around the central axis of the rotational shaft. The driving-force transmitter transmits a rotational force to the chuck.

Abstract: A suspension for supporting a magnetic head is provided with a load beam formed of a thin-plate spring. A recess for accommodating a damper is formed in the load beam. The damper is affixed to a bottom surface of the recess.

Abstract: An HSA transport comb includes an alignment pin extending from the comb body into a tooling hole of the actuator arm, and a separator finger in contact with a suspension assembly of an HGA with the transport comb in a second angular orientation with respect to the actuator arm, but not in a first angular orientation. The transport comb includes a restraining tower extending into a mass-reduction opening of the actuator arm. The restraining tower includes a first lobe that fits within the mass-reduction opening with the transport comb in the first angular orientation, but not with the transport comb in the second angular orientation. The restraining tower also includes a first neck that fits within the mass-reduction opening with the transport comb in either angular orientation, and has a neck height that is greater than the actuator arm thickness.

Abstract: A method for manufacturing a head suspension is capable of suppressing the dispersion in the vibration control effect of a head suspension and improve productivity, the manufacturing method includes a step of punching, by use of a hollow punch having a tooth portion at a distal end thereof, a vibration damper piece out from a base material having a vibration damper provided detachably on a liner through an attaching surface, to hold the vibration damper piece on a hollow internal surface of the punch, a step of positioning the punch holding the vibration damper piece on an objective portion of a semi-finished head suspension, and a step of attaching, by use of an extruding implement, the vibration damper piece on the objective portion with the attaching surface through extruding the vibration damper piece from the punch.

Abstract: A head suspension for supporting a head slider over a storage media in a dynamic storage device is provided with a head suspension component having a spring metal layer, an electrically conductive layer and a dielectric layer interposed between the metal layer and the electrically conductive layer. A plurality of electrically conductive traces with bond pads are formed in the electrically conductive layer. A feature datum is also formed in the electrically conductive layer on a detachable carrier strip. The feature datum defines a first edge in the electrically conductive layer parallel to an edge of the bond pads.

Abstract: A row bar holder to hold a plurality of row bars containing reader heads for scanning operations is disclosed. The row bar holder includes: a base fixture having a length defining a y-axis and a width defining an x-axis, a plurality of separator walls formed on a top surface of the base fixture spaced from one another to separate the plurality of row bars containing reader heads, a plurality of grooves defined between the adjacent separator walls to receive the row bars, respectively, and a draw bar mountable within the base fixture, the draw bar having a plurality of draw bar walls that approximately align with the plurality of separator walls of the base fixture along the y-axis.

Abstract: A magnetic head includes a reproducing element for reproducing information recorded on a magnetic recording medium, a recording element for recording information on the magnetic recording medium, and a heating resistor. The magnetic head has a magnetic medium-facing surface on which the reproducing element and the recording element are exposed.

Abstract: The application discloses an assembly tool for installing a disc clamp on a spindle hub. In the illustrated embodiments, the assembly tool includes a head including an inner portion, an intermediate portion and an outer portion configured to install a disc clamp on a spindle motor assembly. In the illustrated embodiments, the inner portion includes a raised portion and datum surface that interface with the spindle hub to align the spindle hub for installation of the disc clamp.

Abstract: A defect inspection is performed for each of glass substrates by a surface defect detector. The distance from the center of the glass substrate to a detected defect, as a radius of a nonmagnetic region to be formed circular, is recorded along with an ID assigned to the glass substrate. Such defect information is recorded in a defect list using a printer or recorded in an RFID tag using an RFID writer. The defect list or the RFID tag is attached to a glass-substrate case. Each glass substrate and its defect information are in one-to-one correspondence and are provided to a customer as a magnetic disk manufacturer. Based on the obtained defect information, the customer manufactures magnetic disks each being a discrete track recording medium having the nonmagnetic region formed at the position where the defect is present.

Abstract: A micro-actuator to which no head slider is adhesively bonded is mounted on a suspension. The head slider is adhesively bonded to the micro-actuator mounted on the suspension. Before the head slider adheres to the micro-actuator, an electrical connecting work of the slider is completed, and a characteristic test is carried out. If the head slider is judged as being normal as a result of the characteristic test, the head slider concerned is bonded to the micro-actuator by the adhesive.

Abstract: Approaches for helping to decrease the amount of inactive gas necessary for reflow to interconnect connection terminals of a head slider and a suspension. Inactive gas is blown from a nozzle of a reflow apparatus toward interconnection joints of a head slider and a suspension. The head slider is bonded onto a gimbal tongue. The nozzle comprises a duct through which the inactive gas passes and a porous member fitted in an ejection outlet of the tube. Placing the porous member close to the head slider achieves effective reduction of oxygen concentration around solder balls.

Abstract: A method of swaging a head gimbal assembly (HGA) to an actuator arm comprises positioning a tubular element on the HGA adjacent a hole in the actuator arm; restraining the subassembly; providing a rod formed from a shape memory alloy (SMA), the SMA having a martensitic phase at a low temperature and an austenitic phase above a phase transition temperature that is higher than the low temperature, the rod having an initial diameter that is smaller than diameters of the tubular element and the hole; extending the rod through the tubular element and hole; heating the rod above the phase transition temperature such that the rod expands to a second diameter that is greater than the initial diameter to plastically deform the HGA and swage together the HGA and actuator arm to form an assembly; cooling the rod and removing the rod from the assembly such that the rod returns to the initial diameter.

Abstract: A method to assemble a disk drive having a spindle that includes a hub. At least one disk is placed on the hub. A clamp is fastened to the hub by a plurality of threaded fasteners. Each of the plurality of threaded fasteners is initially tightened. After initial tightening, an initial couple imbalance of the spindle is determined. After the initial couple imbalance is determined, a first selected threaded fastener of the plurality of threaded fasteners is selected and rotated by a first amount of rotation that is significantly different from a second amount of rotation of a second selected threaded fastener of the plurality of threaded fasteners. The selection and rotation of the first selected threaded fastener of the plurality of fasteners is determined based on the initial couple imbalance of the spindle.

Abstract: A method of manufacturing a disk drive is disclosed. After installing at least one disk into a base, a media cover is coupled to the base, wherein the media cover covers at least a portion of the disk. After coupling the media cover to the base, a head coupled to an actuator arm and a voice coil motor for rotating the actuator arm about a pivot is installed into the base. After installing into the base the head coupled to the actuator arm and the voice coil motor, the media cover is removed from the base. After removing the media cover from the base, a HDA cover is coupled to the base to form a head disk assembly (HDA).

Abstract: Certain example embodiments relate to a manufacturing method for a disk drive unit. At least one head gimbal assembly having first terminal pads is provided. A controlling circuit for controlling the at least one head gimbal assembly is provided, with the controlling circuit having second terminal pads to connect with the first terminal pads. The at least one head gimbal assembly is disposed in a motor base. The controlling circuit is disposed in the motor base. The at least one head gimbal assembly and the controlling circuit are tightened to the motor base such that the first and second terminal pads are face-to-face and have an electrical touch contact therebetween.

Abstract: A system and method for the production level screening of low flying magnetic heads in the manufacture of disk drive head disk assemblies (HDAs) is disclosed. A test disk is provided and has a plurality of bumps extending from at least one surface thereof to a predetermined height between 2 and 12 nanometers. The test disk is rotated to fly a head of a head gimbal assembly selected from the group adjacent the surface of the test disk. An interaction of the head with one or more of the plurality of bumps may be sensed and the head gimbal assembly may be screened out from the group in response to the sensing of the interaction.

Abstract: A method for manufacturing a hard-disk drive (HDD). The method for manufacturing a HDD includes writing servo tracks, and writing servo tracks into the HDD using a calculated control target value of a calculated servo pattern overlap amount. Writing servo tracks includes a first, second, third and fourth operation. The first operation includes: producing a first control equation for obtaining a servo pattern overlap amount; and, converting a root-mean-square error (RMSE) into a probability distribution. The second operation includes calculating a second control target value that results in an increased product yield, from the RMSE probability distribution. The third operation includes producing a second control equation for obtaining a calculated servo pattern overlap amount, by assigning the second control target value into the first control equation.