JP2006277908A - Head stack assembly and its manufacturing method and magnetic disk device having the head stack assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a head stack assembly (an HSA) in which deformation of an arm is efficiently prevented and its manufacturing method and to provide a magnetic disk device having the HSA. <P>SOLUTION: The manufacturing method is provided with a step in which a pair of base plates 150A and 150B each having a boss having an opening is inserted into both sides of a through-hole of an arm 144 and the pair of the base plates are fastened by caulking to the arm by passing a processing member, whose size is larger than the opening, through the base plate in one direction within the through-hole. The thickness of the arm is made into one half at the cross section which includes the center axis of the through-hole. Let the surface, which is normal to the cross section, be a neutral surface, the position, where the base plates have a minimum internal diameter, be a first position and the position, which is the closest position to the neutral surface among the positions where the base plates contact with the arm, be a second position. Then, the distance between the neutral surface and the second position prior to the caulking and fastening step is set equal to or less than the distance between the neutral surface and the first position. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention generally relates to a head stack assembly (HSA) that supports and drives a head and a magnetic disk device having the head stack assembly (HSA), and more particularly to a connection between a suspension and an arm in the head stack assembly. The present invention is suitable for manufacturing an HSA used in, for example, a hard disk drive (HDD).

  With the recent spread of the Internet and the like, the demand for recording a large amount of information including images and videos has increased. For this reason, the demand for increasing the capacity of magnetic disk devices such as HDDs is increasing. The HDD typically includes a disk with a magnetic material attached thereto and a head stack assembly that supports the head and moves to a desired position on the disk. The HSA is a carriage that swings around an axis by a motor (“actuator”, also called “E block” or “actuator (AC) block” because the cross section is substantially E-shaped), and a support portion of the carriage (Hereinafter referred to as “arm”), a magnetic head portion supported by the suspension, and a base plate for attaching the suspension to the arm. The magnetic head unit is composed of a micro head core (hereinafter simply referred to as “head”) for recording and reproducing signals and a slider for supporting the head core.

  The suspension also has a leaf spring function that presses the slider against the disk with a predetermined pressing force. When the disk rotates, an air flow (air bearing) accompanying the rotation is formed between the slider and the disk, and the slider floats from the disk surface. The flying slider is separated from the disk by a certain distance due to the balance between the flying force and the pressing force. In this state, the arm turns to move (seek) the head to a desired position on the disk to read and write information.

  Recent high recording density disks require high precision head positioning accuracy, and it is necessary to manufacture HSA with high precision. For example, if the suspension is warped or twisted due to a manufacturing error, the pressing force acting on the slider, the flying height, the posture, the vibration characteristics and the like are changed from the design values, and the positioning accuracy is lowered.

  In HSA, the suspension and the base plate are laser welded, but the base plate and the arm are crimped. Caulking is a method in which a part of a base plate is crushed against an arm and plastically deformed to join the two. The base plate and the arm that have been crimped can be separated by inserting a sharp member such as a knife between them, and such crimping improves the economics of the magnetic disk drive. This is because if there is a defect in the suspension or the magnetic head, it is sufficient to replace only the base plate side, and there is no need to replace the entire HSA.

However, the force applied to plastically deform the base plate brings about deformation such as warping of the base plate, and lowers the head positioning accuracy. Therefore, a method has been proposed in which a thin portion is formed between a portion where the base plate receives the deformation force and a joint portion of the suspension, thereby reducing the deformation of the base plate from affecting the suspension (for example, Patent Document 1). See
JP-A-7-192420

  The inventors of the present invention have found that the deformation of the base plate is a superposition of the deformation of the base plate itself subjected to the plastic deformation force and the deformation of the arm. For this reason, in the method of patent document 1 which tries to prevent only the former, it cannot fully reduce that the deformation | transformation by an arm reaches a baseplate.

  Accordingly, an object of the present invention is to provide an HSA that effectively suppresses deformation of the arm, a method for manufacturing the same, and a magnetic disk device having the HSA.

  An HSA manufacturing method according to an aspect of the present invention includes a head stack including a pair of suspensions each supporting a head, an arm that drives the head, and a pair of base plates that attach the pair of suspensions to both sides of the arm. A method of manufacturing an assembly, wherein a pair of base plates each having a boss having an opening is inserted on both sides of a through hole of the arm, and a processing member larger than the opening is inserted into the base plate in the through hole. A pair of base plates that are caulked and fastened to the arm by passing through the arm in one direction, and in a cross section including the central axis of the through hole, the thickness of the arm is halved and the surface is perpendicular to the cross section Is the neutral plane, and the position having the minimum inner diameter of the base plate is the first position. Assuming that the position closest to the neutral plane among the positions where the base plate and the arm are in contact is the second position, the distance between the neutral plane and the second position is the neutral position before the caulking fastening step. The distance is set to be equal to or less than the distance between the surface and the first position. According to this method, when penetrating a processed member (for example, a ball) in one direction, the force point of the base plate that receives a force by the processed member is closer to the neutral plane than the fulcrum as a contact point between the base plate and the arm. For this reason, the pair of base plates are both easily deformed toward the neutral surface, and the force acting on the arm is equal to the neutral surface as compared with the conventional case. As a result, the deformation of the arm is reduced. In the caulking and fastening step, it is preferable that the base plate downstream of the pair of base plates along the one direction is deformed in a direction approaching the neutral surface. When the position having the minimum inner diameter of the base plate forms a surface, the first position is the position farthest from the neutral surface and the closest from the neutral surface among the positions having the minimum inner diameter. It is an intermediate position.

  Assuming that θ is an angle from the straight line passing through the second position and parallel to the neutral plane to the straight line connecting the first position and the second position in the cross section, −17 ° ≦ θ ≦ Satisfies 0 °. This is because when the position having the minimum inner diameter of the base plate in the cross section is a point, the amount of warping with respect to the arm angle is substantially constant in this range. However, it preferably satisfies −12 ° ≦ θ ≦ 0 °. This is because, in this range, the warpage amount with respect to the angle of both base plates is substantially constant.

  Before the insertion step, the pair of base plates may have the same shape. Thereby, since it is not necessary to prepare two types of base plates, workability is improved.

The HSA as another aspect of the present invention is a head stack assembly including a pair of suspensions each supporting a head, an arm that drives the head, and a pair of base plates that attach the pair of suspensions to both sides of the arm. There,
The base plate is crimped to the through hole of the arm,
Of the positions where the base plate and the arm contact each other, the larger of the distances between the position closest to the neutral plane that halves the thickness of the arm and the pair of base plates closest to the neutral plane is the smaller distance. 130% or less, preferably 115% or less. The moment acting on the arm can be reduced by making the distance between the two base plates and the neutral plane substantially equal.

  A magnetic disk device having such an HSA or an HSA manufactured from any one of the methods described above constitutes one aspect of the present invention because it can maintain high positioning accuracy.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  According to the present invention, it is possible to provide an HSA that effectively suppresses deformation of the arm, a manufacturing method thereof, and a magnetic disk device having the HSA.

  Hereinafter, an HDD 100 as an embodiment of the present invention will be described with reference to the accompanying drawings. As shown in FIG. 1, the HDD 100 houses a plurality of magnetic disks 104 serving as record carriers, a spindle motor 106, and an HSA 110 in a housing 102. Here, FIG. 1 is a schematic plan view of the internal structure of the HDD 100.

The casing 102 is made of, for example, an aluminum die-cast base or stainless steel, has a rectangular parallelepiped shape, and is coupled with a cover (not shown) that seals the internal space. The magnetic disk 104 of this embodiment has a high surface recording density, for example, 100 Gb / in ² or more. The magnetic disk 104 is mounted on the spindle of the spindle motor 106 through a hole provided in the center thereof.

  The spindle motor 106 rotates the magnetic disk 104 at a high speed such as 15000 rpm, and has, for example, a brushless DC motor (not shown) and a spindle that is a rotor part thereof. For example, when two magnetic disks 104 are used, a disk, a spacer, a disk, and a clamp are stacked in this order on the spindle and fixed by bolts fastened to the spindle. Unlike the present embodiment, the magnetic disk 104 may be a disk having a hub without having a central hole. In this case, the spindle rotates the disk through the hub.

  The HSA 100 includes a magnetic head unit 120, a suspension 130, a carriage 140, and a base plate 150.

As shown in FIG. 2, the magnetic head unit 120 is joined to an Al ₂ O ₃ —TiC (Altic) slider 121 formed in a substantially rectangular parallelepiped and an air outflow end of the slider 121 for reading and writing. And a head element built-in film 123 made of Al ₂ O ₃ (alumina) in which the head 122 is built. Here, FIG. 2 is an enlarged perspective view of the magnetic head unit 120. The slider 121 and the head element built-in film 123 define a medium facing surface that faces the magnetic disk 104, that is, an air bearing surface 124. The airflow 125 generated based on the rotation of the magnetic disk 104 is received by the air bearing surface 124.

  On the air bearing surface 124, two rails 126 extending from the air inflow end toward the air outflow end are formed. A so-called ABS (air bearing surface) 127 is defined on the top surface of each rail 126. In the ABS 127, buoyancy is generated according to the action of the airflow 125. The head 122 embedded in the head element built-in film 123 is exposed by the ABS 127. The flying method of the magnetic head unit 120 is not limited to this form, and a known dynamic pressure lubrication method, static pressure lubrication method, piezo control method, and other flying methods can be applied. The starting method may be a contact start / stop method in which the magnetic head unit 120 contacts the disk 104 at the time of stopping, or the magnetic head unit 120 is lifted from the disk 104 at the time of stopping and is magnetically displayed by a ramp outside the disk 104. A dynamic loading method or a ramp loading method in which the head unit 120 is held in non-contact with the disk 104 and dropped from the holding unit onto the disk 104 at the time of activation may be employed.

  The head 122 operates from an induction writing head element (hereinafter referred to as “inductive head element”) that writes binary information on the magnetic disk 104 using a magnetic field generated by a conductive coil pattern (not shown), and the magnetic disk 104. An MR inductive composite head having a magnetoresistive effect (hereinafter referred to as “MR”) head element that reads binary information based on a resistance that changes in accordance with a magnetic field. MR head elements include GMR (current magnetoplane) using CIP (Current in Plane) structure, GMR using Current Perpendicular to Plane (CPP) structure, Giant Magnetoresistive (TMR), and TMR (Tunneling Magnetive MR). (Anisotropic Magnetosensitive) etc. are not ask | required.

  The suspension 130 has a function of supporting the magnetic head unit 120 and applying an elastic force to the magnetic head unit 120 against the magnetic disk 104, and is, for example, a stainless steel Watras suspension. Such a suspension includes a flexure (sometimes referred to as a gimbal spring or other name) for cantilevering the magnetic head portion 120 and a load beam (sometimes referred to as a load arm or other name) connected to a base plate. The load beam has a spring portion at the center so as to apply a sufficient pressing force in the Z direction. Therefore, the load beam has a rigid portion at the base end, a spring portion at the center, and a rigid portion at the distal end. Further, the load beam and the flexure are in contact with each other through a projection called a dimple (sometimes referred to as a pivot or other name) so that the ABS 124 always follows the warp and waviness of the disk and is always parallel to the disk surface. The magnetic head unit 120 is designed so that it can be pitched and rolled softly around the dimples. The suspension 130 also supports a wiring part 138 connected to the magnetic head part 120 via a lead wire or the like. The wiring part 138 is shown in FIG. Sense current, write information, and read information are supplied and output between the head 122 and the wiring unit 138 through such lead wires. The wiring part 138 is connected to a relay flexible circuit board (relay FPC) 143 that passes under the arm 144 shown in FIG.

  In the present embodiment, as will be described later, since the amount of warping of the base plate 150 is reduced, the flatness of the suspension 130 and the magnetic head unit 120 is improved. For this reason, it is possible to prevent a crash and a decrease in positioning accuracy due to excessive elastic force or twisting force.

  The carriage 140 has a function of rotating the magnetic head unit 120 in the direction of the arrow shown in FIG. 1, and as shown in FIGS. 1 and 3A to 3B, the carriage 140 and the support are supported. It has a shaft 142, an FPC 143, and an arm 144. 3A is a left side view of the HSA 110, FIG. 3B is a plan view of the HSA 110, and FIG. 3C is a right side view of the HSA 110. Here, the carriage 140 that drives the six magnetic head units 120 that record and reproduce both surfaces of the three disks 104 is shown, but it goes without saying that the number of disks is not limited to three.

  The voice coil motor 141 has a flat coil 141b sandwiched between two yokes 141a. The flat coil 141b is provided to face a magnetic circuit provided on the housing 102 side of the HDD 100 (not shown), and the carriage 140 swings around the support shaft 142 in accordance with the value of the current flowing through the flat coil 141b. . The magnetic circuit has, for example, a permanent magnet fixed to an iron plate fixed in the housing 102 and a movable magnet fixed to the carriage 140. The support shaft 142 is fitted into a cylindrical hollow hole provided in the carriage 140 and is disposed in the housing 102 so as to extend perpendicular to the paper surface of FIG. The FPC 143 supplies a control signal, a signal to be recorded on the disk 104, and power to the wiring unit 138 and receives a signal reproduced from the disk 104.

  The arm 144 is a rigid body made of aluminum provided to be rotatable or swingable around the support shaft 142, and a through-hole 145 described later is provided at the tip thereof. The suspension 130 is attached to the arm 144 through the through hole 145 of the arm 144 and the base plate 150. As shown in FIGS. 3A and 3C, the arm 144 is formed in a comb shape when viewed from the side.

  The base plate 150 has a function of attaching the suspension 130 to the arm 144. As shown in FIGS. 4A to 5B, the base plate 150 includes a flat plate portion 151, a welded portion 152, and a dent (dowel) 154. Have. The welded portion 152 is the tip of a flat plate portion 151 that is laser-welded to the suspension 130. The recess 154 is a portion that is fastened to the arm 144 by caulking. 4A is a schematic plan view of the suspension 130 to which the base plate 150 is joined, and FIG. 4B is a schematic cross-sectional view thereof. FIG. 5A is a schematic plan view of the base plate 150, and FIG. 5B is a schematic cross-sectional view of the base plate 150.

  Hereinafter, the connection between the second arm 144 from the top shown in FIG. 3A and the base plate 150 will be described with reference to FIG. The second arm 144 from the top shown in FIG. 3A has a double head structure to which the base plate 150 is attached on both sides thereof. Here, FIG. 6 is a flowchart for explaining the connection between the arm 144 and the base plate 150.

  First, as shown in FIGS. 5A and 5B, a base plate 150 is created (step 1002). In step 1002, the depression 154 is formed in the flat plate portion 151 of the base plate 150 by press working. As shown in FIG. 7, the recess 154 has a protruding portion 156 and an opening 157 at its tip. The overhanging portion 156 and the vicinity thereof constitute an L-shaped boss 155 that is plastically deformed. Here, FIG. 7 is a schematic enlarged plan view and a sectional view of the base plate 150.

  Next, as shown in FIGS. 4A and 4B, the welded portion 152 of the base plate 150 and the suspension 130 are laser-welded (step 1004). The magnetic head unit 120 is attached to the suspension 130 before or after step 1004.

  Next, as shown in FIG. 8, the base plate is disposed on both sides of the arm so that the recess 152 of the base plate 150 is inserted into the through hole of the arm 144 (step 1006). Here, FIG. 8 is a view showing a state in which the pair of base plates 150 are arranged on both sides of the arm 144. Next, crimping is performed (step 1008). In the caulking, as shown in FIG. 8, a ball 50 having a diameter slightly larger than the diameter of the opening 157 is passed through the through hole 145 along one direction indicated by an arrow. As a result, the boss 155 of the base plate 150 is crushed and plastically deformed as indicated by the horizontal arrow shown in FIG. 8, thereby joining the base plate 150 and the arm 144 together. In addition, as shown by a one-dot chain line in FIG. 8, a surface that halves the thickness of the arm 144 and is perpendicular to the central axis of the through hole 145 is called a neutral surface IS.

  If the conventional upper and lower base plates are warped upward if the conventional upper and lower base plates are in FIG. 8, the deformation of the base plate is only the deformation by the base plate itself subjected to the plastic deformation force by the balls 50. In addition, it was discovered that the deformation of the arm 144 also has an effect.

First, if the shape of the conventional base plate is exaggerated and written, it becomes as shown in FIG. Here, FIG. 9A is a partially enlarged sectional view showing the arrangement of the conventional base plates 30A and 30B and the arm 144 before the caulking. Position the ball 50 is in contact with the first and the upper base plate 30A (power point) _{P 2} is a position where the base plate 30A contacts the arm 144 (the fulcrum) above the _{P 1} (i.e., the fulcrum _{P 1} than the power point _{P 2} Neutral Surface IS side). This is easily deformed in the direction of the arrow in the counterclockwise than the power point P ₂ is the ball 50 if the neutral plane IS side than the fulcrum P ₁ passes above the projecting portion 32A is deformed in the arm 144 direction . If the deformation force applied by the ball 50 is spent much in the downward deformation of the overhanging portion 32A and the horizontal deformation is reduced, the fastening force or contact force exerted on the arm 144 by the boss 31A becomes weak, and the base plate 30A This is not preferable because the arm 144 is easily separated. For the same reason, the position where the ball 50 is in contact with the first and the lower base plate 30B (power point) _{P 4} is a position where the base plate 30A contacts the arm 144 (the fulcrum) lower than _{P 3} (i.e., the fulcrum _{P 3} in the neutral plane IS side) than the power point _{P 4.}

  Next, the upper base plate 30A has a boss 31A having an L-shaped cross section, whereas the lower base plate 30B has a boss 31B having an inverted L-shaped cross section. 9B, when both the L-shaped boss 31A and the inverted L-shaped boss 31B receive a vertical downward force by the ball 50, the bosses 31A and 31B only deform in the horizontal direction. They both deform downward. Here, FIG. 9B is a partially enlarged cross-sectional view showing the magnitude of the force acting on the conventional base plate and the contact force from the base plate to the arm by caulking.

In this case, the force F ₁ to open the L-shape is smaller than the force F ₂ to be close the L-shaped. Therefore, the ball 50 when moving downwardly, but suffice the boss 31A small force _{F 1,} which requires a large force _{F 2} in the boss 31B. This relationship also applies to the contact force, which is a horizontal force. That is, the contact force _{F 3} acting from the boss 31A to the arm 144 is smaller than the contact force _{F 4} acting from the boss 31B to the arm 144.

Since the arm 144 receives a counterclockwise moment in FIG. 9B from the relationship between the contact force F ₃ around the neutral plane IS and the contact force F ₄ , the arm 144 is deformed upward as shown in FIG. 9C. . Here, FIG. 9C is a partially enlarged cross-sectional view showing the deformation of the base plate and the arm after the caulking. Then, following the arm 144, the base plates 30A and 30B are deformed upward. At this time, the deformation of the base plate 30B is restricted by the arm 144 on the upper side. However, since the base plate 30A has no member for restricting the upper deformation, the base plate 30A is deformed to the upper side. Further, after the caulking, the base plate 30A is closer to the neutral plane IS than the base plate 30B. This is a modification of the base plate 30A and 30B are brought about by deformation of the arm 144, a base plate 30A and 30B, due to the deformation of the overhanging portions 32A and 32B by the force _{F 1} and _{F 2} itself is also deformed. As a result, the deformation of the base plates 30 </ b> A and 30 </ b> B is a superposition of their own deformation and the deformation by the arm 144.

In order to reduce the deformation of the base plates 30A and 30B due to the deformation of the arm 144, the present inventors studied to reduce the difference between the contact forces F ₃ and F ₄ in FIG. 9B. This is because if the difference between the contact forces F ₃ and F ₄ is reduced, the moment acting on the arm 144 is reduced and deformation is reduced. The difference between the contact forces F ₃ and F ₄ in FIG. 9B is that the protrusion 32A of the upper base plate 30A is deformed outward (that is, in the direction of opening the L shape), whereas the protrusion of the lower base plate 30B is The portion 32B is deformed inward (that is, in the direction of closing the L shape), that is, the deformation directions of the upper and lower projecting portions 32A and 32B are different.

For this reason, in this embodiment, in principle, the relationship between the positions P ₁ and P ₂ and the positions P ₃ and P ₄ in FIG. 9A is reversed as shown in FIG. I am letting. Here, FIG. 10A shows the base plates 150A and 150B of the present embodiment shown in FIG. 8 in which the force points P ₂ ′ and P ₄ ′ are arranged closer to the neutral plane IS than the fulcrums P ₁ ′ and P ₃ ′. It is a schematic diagram. In the present invention, before the caulking fastening step, the distance between the neutral plane IS and the force point P ₂ ′ (or P ₄ ′) is the distance between the neutral plane IS and the fulcrum P ₁ ′ (or P ₃ ′). The following settings are sufficient. In order to create the structure shown in FIG. 10A, for example, the lower mold forming the bottom surface of the protruding portion of the base plate 150 among the molds of the press apparatus used in Step 1002 is an inclined surface.

With this arrangement, when the force points P ₂ ′ and P ₄ ′ are subjected to a horizontal force by the ball 50, the overhanging portion 156A of the upper base plate 150A and the overhanging portion 156B of the lower base plate 150B are both in the same direction. That is, it will be deformed (in the direction of opening the L shape), and the resistance force to the ball 50 will be substantially the same. As a result, the difference between the contact force _{F 22} of the boss 155B of the contact force _{F 11} and a lower base plate 150B of the boss 155A of the upper base plate 150A shown in FIG. 8 on the arm 144 on the arm 144 is reduced. As a result, the deformation of the arm 144 is reduced, and the warpage of the base plates 150A and 150B and the suspension 130 connected thereto is reduced.

As described above, when the force points P ₂ ′ and P ₄ ′ are arranged closer to the neutral plane IS than the fulcrums P ₁ ′ and P ₃ ′, the contact force exerted on the arm 144 by the bosses 155A and 155B is reduced, but somewhat contact Even if the force is sacrificed, it is preferable to maintain the flatness of the suspension 130 in order to maintain the positioning accuracy of the head 122. However, if the contact force is too low, the suspension 130 is easily separated from the arm 144 and the vibration characteristics are deteriorated. Therefore, in this embodiment, a predetermined lower limit is provided as described later.

Further, as shown in FIG. 10B, in addition to the structure of FIG. 10A, the minimum thickness in the through hole 145 than the original thickness T ₁ outside the through hole 145 of the base plates 150C and 150D. by reducing the T _2, the influence of the deformation of the base plate itself due to the ball 50 can be prevented from being spread to the suspension 130. Here, FIG.10 (b) is a schematic expanded sectional view of the modification of Fig.10 (a).

  In the present embodiment, the pair of base plates 150A and 150B (or 150C and 150D) have the same shape. Thereby, since it is not necessary to prepare two types of base plates, workability is improved.

The base plate 150A and 150B as shown in FIG. 11 (a) is fastened with a shape before being fastened, and the shape as shown in FIG. 11 (b) is obtained by simulation using the finite element method (FEM).
(Comparative example)
The conventional base plates 30A and 30B as shown in FIG. 12 (a) are fastened by caulking and the shape as shown in FIG. 12 (b) is obtained by simulation using FEM.

  When the contact force was obtained for FIGS. 11B and 12B, as shown in FIG. 11C, in this example, the upper contact force was 210 N and the lower contact force was 240 N. On the other hand, in the comparative example, the upper contact force is 220 N and the lower contact force is 266 N. In this example, the upper and lower contact forces are balanced, and the effect of reducing the warpage amount by about 40% is obtained.

  In Example 1, after the caulking shown in FIGS. 11B and 11C, the vertical distance between the base plates 150A and 150B and the neutral plane IS (the vertical direction in FIG. 11C) is substantially the same. Equally, of the distances between the contact positions of the base plates 150A and 150B and the arm 144 and the point closest to the neutral plane of the base plates 150A and 150B, the larger distance is 130% or less of the smaller distance (Example 3 described later). -17 ° ≦ θ ≦ 0), more preferably 115% or less (corresponding to −12 ° ≦ θ ≦ 0 of Example 3 described later). The moment acting on the arm 144 can be reduced by making the distance between the two base plates 150 and the neutral plane substantially equal. On the other hand, in the comparative example shown in FIGS. 12B and 12C, the large distance among the distances from the base plates 30 to the neutral plane IS is three times or more the small distance.

In the structure of Example 1, as shown in FIG. 10 (b), it was examined base plate warpage and arm displacement in the half of the _second thickness T ₂ of the thickness T _1. The results of Example 1, Comparative Example, and Example 2 are shown in Table 1. In Table 1, the upward displacement is positive, UP of “position” means the upper base plate 150A (or 150C), and DN means the lower base plate 150B (or 150D).

As shown in FIG. 13, the upper base plate 150A, _'draw a straight line parallel to the neutral plane IS from, such a straight line and the fulcrum P _1' fulcrum P ₁ and the angle of the straight line θ connecting the and the power point P _{2 '} . Here, FIG. 13 is a cross-sectional view showing a state before crimping including the central axis of the through hole 145. The force points P ₂ ′ and P ₄ ′ are positions farthest from the neutral plane IS among the positions having the minimum inner diameters of the base plates 150A and 150B. Further, the fulcrum P ₁ ′ and the fulcrum P ₃ ′ are positions closest to the neutral plane IS among positions where the base plates 150A and 150B and the arm 144 are in contact with each other.

Similarly, the lower base plate 150B, _'draw a straight line parallel to the neutral plane IS from, such a straight line and the fulcrum P _3' fulcrum P ₃ and and angle of the power point P ₄ connecting the _'linear theta. In FIG. 13, the force points P ₂ ′ and P ₄ ′ protrude from the ball 50 and can be regarded as points. For the upper base plate 150A, θ is positive in the clockwise direction, and for the lower base plate 150B, θ is positive in the counterclockwise direction. 14A and 14B show the amount of warpage of the base plates 150A and 150B and the arm 144, the vertical contact force, and the difference between them while changing the angle θ.

  From FIG. 14A, it is understood that the amount of warping of the arm 144 is approximately constant in the range of −17 ° ≦ θ ≦ 5 °, but it is preferable that θ is 0 or less, so −17 ° ≦ θ ≦ 0 is preferable. However, in the range of θ ≦ −12 °, the difference between the warpage amount of the upper and lower base plates and the upper and lower contact force changes rapidly, and therefore −12 ° ≦ θ ≦ 0 ° is preferable.

  Further, if the stable contact force between the base plate 150 and the arm 144 is set to 200 N, the upper contact force is 200 N or less in the range of θ ≦ −12 °, so −12 ° ≦ θ is preferable.

This example is the same as Example 3, but differs from FIG. 13 in that the innermost diameter is a surface and the area is large as shown in FIG. In this embodiment, there are a plurality of positions (positions where the force points P ₂ ′ and P ₄ ′ exist) having the minimum inner diameter of the base plates 150A and 150B. Also in the present embodiment, when the amount of warpage of the base plates 150A and 150B and the arm 144, the vertical contact force, and the difference thereof are examined while changing θ ′, the results are as shown in FIGS. 16 (a) and 16 (b). The sign of θ ′ is the same as that of θ.

  From FIG. 16A, it is understood that the amount of warping of the arm 144 is approximately constant in the range of −10 ° ≦ θ ≦ 10 °, but it is preferable that θ is 0 or less, so −10 ° ≦ θ ≦ 0 is preferable. However, in the range of θ ≦ −5 °, the difference between the warping amount of the upper and lower base plates and the upper and lower contact force changes rapidly, so −5 ° ≦ θ ≦ 5 ° is preferable, but θ is 0 or less. Since it is preferable, −5 ° ≦ θ ≦ 0 is preferable.

  Further, when the stable contact force between the base plate 150 and the arm 144 is set to 200 N, the upper contact force is 200 N or less in the range of θ ≦ −5 °, so −5 ° ≦ θ is preferable.

When the thickness T ₂ or the ratio of the thickness T ₁ and the thickness T ₂ is changed in the configuration shown in FIG. 10B and the warping amounts of the base plates 150C and 150D and the arm 144 are examined, FIG. It came to show in FIG.17 (b). The warpage amount of the upper base plate 150C and the warpage amount of the lower base plate 150D are the sum of the warpage amount of the base plate itself and the warpage amount of the arm. Warpage to warpage of the base plate 150 itself larger the the _second thickness T ₂ is lowered is reduced. However, with increasing thickness T _2, because the warp amount of the arm 144 increases, resulting in having extreme values at a point in the warp amount of the total of the base plate 150. Referring to FIG. 17 (a), the warp amount of the total in the _second thickness _{T 2} is 0.1 mm (50% thickness with respect to thickness _{T 1)} is the smallest. From FIG. 17A and FIG. 17B, 0.12 mm ≦ T ₂ ≦ 0.07 mm is preferable, and 0.08 mm ≦ T ₂ ≦ 0.12 mm is more preferable in consideration of manufacturing variation. Further, 35% ≦ T ₂ / T ₁ ≦ 60% is preferable, and 40% ≦ T ₂ / T ₁ ≦ 60% is more preferable in consideration of manufacturing variation.

In the present embodiment, unlike Patent Document 1, the thin portion is disposed not in the arm 144 but in the through hole 145. If the thin portion is arranged on the arm 144 as in Patent Document 1, the rigidity of the thin portion is reduced, and particularly when the caulking is fastened, the lower base plate 150B is excessively deformed downward. Therefore, in this embodiment, deformation of the base plate at the time of caulking is spread to the suspension 130 direction while maintaining the flatness of the lower base plate 150B disposed a thin portion inside the through-hole 145 having a the _second thickness T ₂ To prevent that.

Note that the thickness T _{2 of the} boss in the through hole 145 does not change much before and after the crimping is fastened, so if T ₂ and T ₂ / T ₁ after the crimping are fast as described above, this is the manufacturing of this embodiment. There is an effect of the method.

FIG. 18 shows a control block diagram of the control system 160 of the HDD 100. The control system 160 is an example of control when the head 122 includes an inductive head and an MR head. The control system 160 of the HDD 100 includes a control unit 161, an interface 162, a hard disk controller (hereinafter referred to as “HDC”) 163, a write modulation unit 164, a read demodulation unit 165, a sense current control unit 166, and a head IC 167. It is embodied in the HDD 100 as a control board or the like. Of course, only the head IC 167 need not be integrally formed, for example, mounted on the carriage 140.

  The control unit 161 includes any processing unit such as CPU or MPU regardless of the name, and controls each unit of the control system 160. The interface 162 connects the HDD 100 to an external device such as a personal computer (hereinafter referred to as “PC”), which is a host device. The HDC 163 transmits the data demodulated by the read demodulation unit 165 to the control unit 161, transmits the data to the write modulation unit 164, and transmits the current value set by the control unit 161 to the sense current control unit 166. Or In FIG. 17, the control unit 161 servo-controls the spindle motor 106 and the carriage 140 (motor thereof), but the HDC 163 may have a servo control function.

  The write modulation unit 164 is supplied from the host device via the interface 162, for example, modulates data written to the disk 104 by the inductive head, and supplies the data to the head IC 162. The read demodulator 165 samples the data read by the MR head from the disk 104 and demodulates it into the original signal. The write modulation unit 164 and the read demodulation unit 165 may be grasped as an integral signal processing unit. The head IC 167 functions as a preamplifier. In addition, since any configuration known in the art can be applied to each part, the detailed structure is omitted here.

  In the operation of the HDD 100, the control unit 161 drives the spindle motor 106 to rotate the disk 104. An air flow accompanying the rotation of the disk 104 is wound between the slider 121 and the disk 104 to form a minute air film, and a buoyancy that floats from the disk surface acts on the slider 121. On the other hand, the suspension 130 applies an elastic pressing force to the slider 121 in a direction opposite to the buoyancy of the slider 121. Due to the balance between the buoyancy and the elastic force, the magnetic head unit 120 and the disk 104 are spaced apart from each other by a constant distance. As described above, since the amount of warping of the base frame 150 is suppressed, the elastic pressing force applied by the suspension 130, the posture, the flying height, the posture, the vibration characteristics, etc. of the slider 121 are close to the design values. The head 122 can be positioned with high accuracy by preventing the occurrence.

  Next, the control unit 161 controls the carriage 140 to rotate the carriage 140 around the support shaft 142 to cause the head 122 to seek on the target track of the disk 104. The present embodiment is a swing arm type in which the path of the slider 121 draws an arc around the support shaft 142 in this way, but the present invention does not prevent the application of a linear type in which the path of the slider 121 is linear. Absent.

  At the time of writing, the control unit 161 receives data obtained from a host device such as a PC (not shown) via the interface 162, selects an inductive head, and transmits it to the write modulation unit 164 via the HDC 163. In response to this, the write modulation unit 164 modulates the data and then transmits the modulated data to the head IC 167. The head IC 167 amplifies the modulated data and supplies it to the inductive head as a write current. As a result, the inductive head writes data to the target track.

  At the time of reading, the control unit 161 selects the MR head, and transmits a predetermined sense current to the sense current control unit 166 via the HDC 163. In response to this, the sense current control unit 166 supplies the sense current to the MR head via the head IC 167. As a result, the MR head reads desired information from a desired track on the disk 104.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary. Further, although the present embodiment has been described for the HDD, the present invention is also applicable to other types of magnetic disk devices (such as magneto-optical disk devices).

It is a top view which shows the internal structure of the hard disk drive as one Example of this invention. It is an expansion perspective view of the magnetic head part of the hard disk drive shown in FIG. 3A to 3C are a left side view and a plan view showing a detailed structure of the head stack assembly shown in FIG. 4 (a) and 4 (b) are a schematic plan view and a schematic cross-sectional view of a suspension to which a base plate is fixed. 5 (a) and 5 (b) are a schematic plan view and a schematic cross-sectional view of the base plate shown in FIGS. 4 (a) and 4 (b). It is a flowchart for demonstrating the manufacturing method of the baseplate shown to Fig.5 (a) and FIG.5 (b). It is the schematic plan view and schematic sectional drawing of the hollow of the baseplate shown to Fig.5 (a) and FIG.5 (b). It is a schematic sectional drawing for demonstrating the caulking fastening of the base plate and arm which are shown to Fig.5 (a) and FIG.5 (b). FIG. 9A to FIG. 9C are schematic cross-sectional views showing the structure of a conventional base plate. 10A and 10B are schematic cross-sectional views of the shape of the base plate shown in FIG. FIG. 11A to FIG. 11C are schematic cross-sectional views of the base plate according to the first embodiment of the present invention. 12 (a) to 12 (c) are schematic cross-sectional views of a base plate of a comparative example. It is a schematic sectional drawing of the baseplate of Example 3 of this invention. 14A and 14B are graphs showing the results of Example 3. FIG. It is a schematic sectional drawing of the baseplate of Example 4 of this invention. FIG. 16A and FIG. 16B are graphs showing the results of Example 4. FIG. It is a graph showing the result of Example 5 of this invention. FIG. 2 is a block diagram of a control system of the hard disk drive shown in FIG. 1.

Explanation of symbols

100 Magnetic disk unit (hard disk drive)
110 Head stack assembly 120 Magnetic head unit 130 Suspension 140 Carriage 144 Arm 150 Base plate

Claims (10)

A method of manufacturing a head stack assembly having a pair of suspensions each supporting a head, an arm for driving the head, and a pair of base plates for attaching the pair of suspensions to both sides of the arm,
With the pair of base plates each having a boss having an opening inserted into both sides of the through hole of the arm, a processing member larger than the opening is passed through the base plate in one direction in the through hole. A step of caulking and fastening a pair of base plates to the arm;
In a cross section including the central axis of the through hole, the thickness of the arm is halved, a plane perpendicular to the cross section is a neutral plane, a position having a minimum inner diameter of the base plate is a first position, and the base plate Assuming that the position closest to the neutral plane among the positions in contact with the arm is the second position, before the caulking fastening step, the distance between the neutral plane and the second position is The method is set to be equal to or less than a distance from the first position.   When the position having the minimum inner diameter of the base plate constitutes a surface, the first position is a position farthest from the neutral surface and a position closest to the neutral surface among the positions having the minimum inner diameter. 2. The method of claim 1, wherein the method is an intermediate position. Assuming that the angle from the straight line passing through the second position and parallel to the neutral plane to the straight line connecting the first position and the second position in the cross section is θ, θ represents the following equation: The method according to claim 1 or 2, wherein the method is satisfied.
−17 ° ≦ θ ≦ 0 ° Assuming that the angle from the straight line passing through the second position and parallel to the neutral plane to the straight line connecting the first position and the second position in the cross section is θ, θ represents the following equation: The method according to claim 1 or 2, wherein the method is satisfied.
-12 ° ≦ θ ≦ 0 °   2. The method according to claim 1, wherein, in the caulking and fastening step, a base plate downstream of the pair of base plates along the one direction is deformed in a direction approaching the neutral surface.   The method of claim 1, wherein the pair of base plates have the same shape before the inserting step. A head stack assembly having a pair of suspensions each supporting a head, an arm for driving the head, and a pair of base plates for attaching the pair of suspensions to both sides of the arm;
The base plate is crimped to the through hole of the arm,
Of the positions where the base plate and the arm contact each other, the larger of the distances between the position closest to the neutral plane that halves the thickness of the arm and the pair of base plates closest to the neutral plane is the smaller distance. 130% or less of the head stack assembly.   The larger distance of the distance between the position closest to the neutral plane that halves the thickness of the arm and the pair of base plates closest to the neutral plane among the positions where the base plate and the arm contact each other is the smaller distance. The head stack assembly according to claim 7, wherein the head stack assembly is 115% or less.   A magnetic disk drive comprising a head stack assembly manufactured from the method according to claim 1.   A magnetic disk apparatus comprising the head stack assembly according to claim 8.