Head suspension

A head suspension for a hard disk drive is thin from an arm to a head and involves a minimum step between the arm and a load beam. The head suspension includes a load beam that includes a rigid part and a resilient part. The load beam applies load onto a head that is arranged at a front end of the load beam to write and read data to and from a disk arranged in the hard disk drive. The head is connected to read/write wiring patterns of a flexure. The flexure supports the head and is attached to a disk-facing surface of the rigid part. An arm is attached to a carriage of the hard disk drive and is turned around a spindle. The arm supports the resilient part that is attached to a base end of the rigid part. A disk-facing surface of the arm is arranged within the total of thicknesses of the rigid part and head.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a head suspension for a hard disk drive installed in an information processing apparatus such as a computer.

2. Description of Related Art

FIG. 26is a perspective view showing a head suspension for a hard disk drive according to a related art. The head suspension201has a one-piece structure including a base plate203and a load beam205that are integrated into one piece to support a flexure207. The load beam205includes a rigid part (or stiff part)209and a resilient part (or hinge)211.

FIG. 27is a sectional view partly showing an example of the hard disk drive in which the head suspension201ofFIG. 26is arranged. The base plate203of the head suspension201is attached to a disk-side surface of an arm215by, for example, swaging. The arm215is attached to a carriage213.

The carriage213is turned around a spindle219by a positioning motor217such as a voice coil motor. By turning the carriage213around the spindle219, a head221of the head suspension201is moved to a target track on a disk223.

When the disk223is rotated at high speed, the head221slightly lifts from the surface of the disk223against a gram load that is a load applied to the head221by the head suspension201.

In recent years, portable music players and the like employ one-inch hard disk drives. For the use with such instruments and cellular phones, miniaturized hard disk drives such as 0.85-inch and 1-inch hard disk drives are intensely developed.

The miniaturized hard disk drives for the cellular phones and the like must have not only improved environmental resistance, antishock ability, and low power consumption but also thinness thinner than the appliances themselves.

According to the structure of the related art shown inFIGS. 26 and 27, the thicknesses of the arm215, load beam205, flexure207, and head221are added to the thickness of the disk223. The total thickness from the arm215to the head221is difficult to reduce, and therefore, it is not easy to thin the hard disk drive.

The arm215and load beam205involves a step with respect to the disk223. Namely, there is a difference between the center of gravity of the arm215and that of the load beam205with respect to the disk223. Due to this difference, the arm215is vulnerable to torsional motion and is limited in a shock property.

The step between the arm215and the load beam205must be reduced.

Reducing the step between the arm215and the load beam205, however, results in bringing the flexure207closer to the disk223, particularly on the arm215side.

The related art mentioned above is disclosed in Japanese Unexamined Patent Application Publication No. 09-282624.

SUMMARY OF THE INVENTION

An object of the present invention is to solve the problem of a miniaturized hard disk drive that a step between an arm and a load beam cannot be cancelled without bringing a flexure closer to a disk.

In order to accomplish the object, an aspect of the present invention provides a head suspension having a load beam including a resilient part and flexure. The resilient part and flexure are fixed to the opposite-to-disk surface of the arm, so that a step between the arm and the load beam is minimized without bringing the flexure on the arm side closer to the disk. This configuration can prevent wiring patterns on the flexure from being damaged during postprocesses.

DETAILED DESCRIPTION OF EMBODIMENTS

Head suspensions according to embodiments of the present invention will be explained in detail. Each of the embodiments has a novelty in the arrangement of a resilient part and flexure, to minimize a step between an arm and a load beam without bringing the flexure on the arm side closer to a disk.

First Embodiment

A head suspension according to the first embodiment of the present invention will be explained with reference toFIGS. 1 to 5in whichFIG. 1is a perspective view showing the head suspension with wiring patterns seen through a load beam,FIG. 2is a simple perspective view showing the head suspension,FIG. 3is a side view showing the head suspension,FIG. 4is a perspective view showing an arm of the head suspension, andFIG. 5is a sectional view showing a flexure of the head suspension.

InFIGS. 1 to 3, the head suspension1includes the load beam (LB)3, arm5, and flexure7. The head suspension1is used for, for example, a 0.85-inch or 1-inch hard disk drive.

The load beam3is made of, for example, nonmagnetic SUS304 (Japanese Industrial Standard) stainless steel and has a thickness (tL) of about 30 μm. The load beam3applies load (gram load) to a head9that writes and reads data to and from a disk. In this specification, the “disk” is a storage medium which is arranged in a hard disk drive and to and from which data is written and read through the head suspension. The load beam3includes a rigid part (stiff part)11and a resilient part (hinge)13.

The rigid part11extended from a front end to a base end thereof is generally narrow. The front end of the rigid part11has a load/unload tab15. In the vicinity of the front end, the rigid part11has a dimple17having a height (hDH) of about 50 μm. Each side edge in an across-the-width direction of the rigid part11has a reinforcing rail19that is formed by box-bending the side edge in a thickness direction of the rigid part11. Each rail19is oriented toward the disk. The height (hR) of the rail19from an opposite-to-disk surface21of the rigid part11is about 200 μm. The opposite-to-disk surface21is a surface of the rigid part11that is oriented opposite to the disk. In other words, the opposite-to-disk surface21is opposite to a disk-side surface69of rigid part11facing to the disk.

The resilient part13is integral with the rigid part11. The resilient part13includes two branches23and25that extend from both sides of a base end of the rigid part11in the across-the-width direction. The thickness (ts) of the resilient part13is the same as that of the rigid part11, i.e., about 30 μm.

The branches23and25have side edges24and26, respectively. The side edges24and26are cut along them when a sheet material is cut into a plurality of load beams3. With this configuration, the rails19are extendable to just before the resilient part13, thereby producing no blanks between the rails19and the resilient part13. This improves the first bending mode frequency (B1frequency) and shock property of the load beam3.

InFIGS. 1 to 4, the arm5includes an integral base plate27serving as a base. Namely, the base plate27is a component of the arm5side. The base plate27may be independent of the arm5and may be attached to the arm5by, for example, swaging. If the base plate27is independent of the arm5, the base plate27may be integral with the load beam3. The arm5has a thickness (tA) of about 200 μm. The arm5has a hole29to be fitted to a carriage of a hard disk drive so that the arm5is turned around a spindle.

InFIG. 4, an opposite-to-disk surface31of the base plate27has a groove33to receive wiring patterns47(to be explained later). The opposite-to-disk surface31is a surface of the base plate27that faces opposite to the disk. In other words, the opposite-to-disk surface31is opposite to a disk-side surface77of the arm5facing to the disk. The groove33is formed by pressing, machining, etching, or the like and has a depth (hD) of about 30 μm. The groove33is extended between a longitudinal edge and a side edge of the base plate27in a direction along the opposite-to-disk surface31and has ends35and37that are respectively open to the longitudinal and side edges. In the vicinity of the end35, the groove33has a flexure fixing projection39. The projection39has a surface41that is flush with the opposite-to-disk surface31.

InFIGS. 1 to 3, the branches23and25of the resilient part13are fixed to the opposite-to-disk surface31of the base plate27of the arm5at weld spots43. Two weld spots43are formed on each of the branches23and25by, for example, laser welding. Namely, the load beam3is supported with the base plate27such that the resilient part13at the base end of the rigid part11is fixed to the base plate27.

InFIGS. 1 to 3and5, the flexure7extends along the load beam3to the arm5, includes a base layer45and the wiring patterns47, and supports the head9. The wiring patterns47are connected to the head9to write and read data to and from the disk.

The base layer45is a conductive thin plate made of, for example, resilient stainless steel (SUS). At the head9, the base layer45has a tongue49that supports a slider whose thickness (tSH) is about 230 μm. On the arm5, the base layer45has a fixing circle53and a fixing tongue55. An end of the base layer45extends out of the arm5and forms a terminal support57.

Ends of the wiring patterns47are electrically connected to write and read terminals arranged on the slider51at the head9. The other ends of the wiring patterns47are connected to terminals arranged on the terminal support57.

InFIGS. 1 and 5, the wiring patterns47are made of conductors59. The conductors59are arranged on an insulating layer61made of, for example, polyimide resin on the base layer45. The conductors59are covered with an insulating cover63made of, for example, polyimide resin.

The base layer45, insulating layer61, conductors59, and insulating cover63have thicknesses of tBL=20 μm, tI=10 μm, tc=10 μm, and tIC=5 μm, respectively. The depth (hD) of the groove33formed in the base plate27is deeper than the total of the thicknesses of the insulating layer61, conductors59, and insulating cover63. The depth (hD) of the groove33may be equal to the total of the thicknesses of the insulating layer61, conductors59, and insulating cover63.

InFIGS. 1 to 3, the flexure7is arranged so that the wiring patterns47are oriented toward the disk. The flexure7is fixed to the disk-side surface69of the rigid part11at a weld spot71by, for example, laser welding.

The flexure7is arranged on the opposite-to-disk surface31of the arm5, and the circle53of the flexure7is fixed to the projection39at a weld spot72by, for example, laser welding. The tongue55of the flexure7is laser-welded to the opposite-to-disk surface31at weld spots73that are on each side of the end37of the groove33.

According to the first embodiment, the wiring patterns47are received in the groove33and are arranged between the base layer45of the flexure7and the base plate27of the arm5.

InFIG. 3, the disk-side surface77of the arm5is within the total thickness of the rigid part11and head9.

According to the first embodiment, a distance (HA) between the opposite-to-disk surface31of the arm5and a disk-side surface75of the slider51is 310 μm. The disk-side surface75is a surface of the slider51that faces the disk.

A distance between the opposite-to-disk surface21of the rigid part11and the disk-side surface75of the slider51is equal to the total of the thickness tSH=230 μm of the slider49, the thickness tBL=20 μm of the base layer45of the flexure7, the height hDH=50 μm of the dimple17, and the thickness tL=30 μm of the load beam3, i.e., Hs=330 μm in total.

According to the first embodiment, the distance HA=310 μm on the arm5side is smaller than the total distance Hs=330 μm of the rigid part11and head9side on the load beam3. It is possible to set as HA=Hs, or HA>Hs.

In this way, the head suspension1according to the first embodiment has the resilient part13and flexure7that are fixed to the opposite-to-disk surface31of the arm5. With this configuration, the first embodiment can reduce a step between the arm5and the load beam3while keeping the flexure7on the arm5side away from a disk. As a result, the wiring patterns47of the flexure7are not damaged during postprocesses.

The rigid part11has the reinforcing rails19formed by box-bending the side edges of the rigid part11in a direction toward the disk. The rails19can improve the shock property of the head suspension1and secure the rigidity of the load beam3. The height (hR=200 μm) of the rails19is lower than the total height (Hs=330 μm) of the rigid part11and head9, and therefore, the rails19constitute no obstacles when applied for a thin hard disk drive.

The flexure7includes the base layer45and wiring patterns47. The wiring patterns47are formed on the base layer45and are arranged between the base layer45and the arm5. While minimizing a step between the arm5and the load beam3, the resilient part13and flexure7can easily be attached to the arm5. The flexure7on the arm5side is apart from the disk so that the wiring patterns47are not damaged during postprocesses.

The arm5has the groove33to receive the wiring patterns47of the flexure7, so that the flexure7on the arm5is separated away from the disk. This configuration prevents the wiring patterns47from being damaged in postprocesses. In addition, the configuration suppresses a protrusion of the flexure7from the opposite-to-disk surface31of the arm5, thereby contributing to thinning a hard disk drive.

The resilient part13is integral with the rigid part11, to minimize a step between the arm5and the load beam3and easily fix the resilient part13to the opposite-to-disk surface31of the arm5. In addition, this configuration reduces the number of parts, simplifies the structure of the head suspension1, and lessens the managing and assembling labor of parts.

FIG. 6is a perspective view showing an arm according to a modification of the first embodiment of the present invention. The arm5has a groove33for receiving the wiring patterns47of the flexure7and grooves34for receiving the branches23and25of the resilient part13. Like the groove33, the grooves34are formed by pressing, machining, etching, or the like. The depth of the grooves34is equal to or greater than the thickness of the branches23and25.

The grooves33and34are made simultaneously, and therefore, labor for forming them is substantially the same as that for forming the groove33alone.

The branches23and25of the resilient part13are arranged in the grooves34and are fixed thereto. This prevents the resilient part13from protruding out of an opposite-to-disk surface31of the arm5, thereby contributing to thinning a hard disk drive.

Second Embodiment

A head suspension according to the second embodiment of the present invention will be explained with reference toFIGS. 7 and 8in whichFIG. 7is a simple perspective view showing the head suspension andFIG. 8is a partly sectioned side view showing part of the head suspension. The structure of the second embodiment is basically the same as that of the first embodiment, and therefore, the same or corresponding parts are represented with the same reference numerals or the same reference numerals plus “A.”

InFIGS. 7 and 8, the head suspension1A according to the second embodiment includes a resilient part13A whose thickness t1is greater than a thickness t2of a rigid part11A. This configuration is effective to thin a load beam3A and improve the resiliency of the resilient part13A. According to the second embodiment, the thicknesses are t1=25 μm and t2=20 μm.

The thicknesses t1and t2may be optionally set based on a hard disk drive in which the head suspension1A is installed, provided that the thickness t1of the resilient part13A is greater than the thickness t2of the rigid part11A to thin the load beam3and improve the resiliency of the resilient part13A.

FIG. 9is a list showing a relationship among the beam (rigid part) thickness, hinge (resilient part) thickness, and shock property of a head suspension.FIG. 10is a graph based on the list ofFIG. 9. The shock property of a load beam is expressed with the magnitude of a shock at which a slider of the load beam is lifted from the surface of a disk. The phenomenon that a slider of a load beam lifts off from the surface of a disk in response to the application of a shock is referred to as “G-lift-off.” The “G-lift-off” is also indicative of the magnitude of the shock that causes a lift-off of the slider.

InFIGS. 9 and 10, the thickness t1of the resilient part13A is fixed at 25 μm, and the thickness t2of the rigid part11A is changed as 35, 30, 25, and 20 μm. In response to these reductions in the thickness, the head suspension1increases its G-lift-off as 357.2 G/gf, 386.0 G/gf, 419.1 G/gf, and 462.3 G/gf.

When the thickness t2of the rigid part11A is 20 μm that is smaller than the thickness t1of the resilient part13A of 25 μm, the head suspension1greatly improves its G-lift-off as shown in grayed cells in the table ofFIG. 9.

FIGS. 11 to 13are graphs showing test results that verify that thinning a rigid part thinner than a resilient part improves the shock property of a head suspension.

FIG. 11shows a relationship between the width of a resilient part and a gram load measured on load beams having different thicknesses. An abscissa indicates the width of a resilient part (hinge), and an ordinate indicates gram load. The load beams shown inFIG. 11each include a rigid part and a resilient part that are integral with each other. The load beams have thicknesses of 20 μm, 25 μm, and 30 μm, respectively, a length (lL) of 6.25 mm, and a stress limit of 70 kgf/cm2because each is made of SUS304.

If a width allowed for a resilient part (hinge) is 2.0 mm, the resilient part may be drilled to have a hole to realize an effective width of, for example, 1.2 mm. If a resilient part has an effective width of 1.5 mm and a thickness of 20 μm which is equal to the thickness of a load beam, a limit gram load applied by the resilient part is 1.5 gf as shown inFIG. 11. A resilient part having an increased thickness of 30 μm and an effective width of 1.2 mm can achieve a gram load of 2.0 gf.

FIG. 12is a graph showing a relationship between the width of a resilient part and a gram load measured on load beams having different lengths. An abscissa indicates the width of a resilient part (hinge), and an ordinate indicates gram load. The load beams shown inFIG. 12have lengths of 5.50 mm, 6.25 mm, and 7.00 mm, respectively, a thickness (t) of 20 μm, and a stress limit of 70 kgf/cm2because each is made of SUS304.

As is apparent inFIG. 12, changes in the length of a load beam only slightly influence the gram load of the load beam.

It is understood fromFIGS. 11 and 12that the thickness, not length, of a load beam greatly influences a gram load applied by the load beam. Namely, a narrow load beam for a miniaturized hard disk drive must have a thick resilient part.

FIG. 13is a graph showing a relationship between the thickness of a load beam and a lift-off level (G-lift-off). An abscissa indicates the thickness of a load beam and an ordinate indicates G-lift-off.

It is clear inFIG. 13that the thicker the load beam, the poorer the G-lift-off or shock property of the load beam.

FromFIGS. 11 to 13, it is apparent that the resilient part must be thick and the rigid part must be thin to secure a high G-lift-off level and a high gram load.

For this, the second embodiment makes the thickness t1of the resilient part13A thicker than the thickness t2of the rigid part11A, to thereby thin the load beam3A and increase the resilience of the resilient part13A. As a result, the head suspension1A of the second embodiment can secure a high G-lift-off level and a high gram load.

The second embodiment provides effects similar to those of the first embodiment.

In addition, the second embodiment improves the shock property of the head suspension1A.

Third Embodiment

FIG. 14is a simple perspective view showing a head suspension according to the third embodiment of the present invention. The third embodiment substantially has the same structure as the first embodiment, and therefore, the same or corresponding parts are represented with the same reference numerals or the same reference numerals plus “B.”

InFIG. 14, the head suspension1B of the third embodiment includes a resilient part13B that is independent of a load beam3B and an arm5. The resilient part13B is fixed to the arm5at weld spots43and to the load beam3B at weld spots44.

The third embodiment provides effects similar to those of the first embodiment.

Fourth Embodiment

FIG. 15is a simple perspective view showing a head suspension according to the fourth embodiment of the present invention. The fourth embodiment substantially has the same structure as the first embodiment, and therefore, the same or corresponding parts are represented with the same reference numerals or the same reference numerals plus “C.”

InFIG. 15, the head suspension1C of the fourth embodiment includes a base plate27serving as a part of an arm5. Namely, the base plate27is a component of the arm5side. The base plate27has an opposite-to-disk surface31to which a flexure7C is fixed.

The flexure7C includes a base layer45C and wiring patterns47arranged on the base layer45C. The base layer45C of the flexure7C has a resilient part13C integrally. The resilient part13C is formed from each side of the base layer45C defined by an opening79.

The base layer45C includes a fix part81and a tongue55and is fixed to the opposite-to-disk surface31of the base plate27at weld spots43,72, and73. Between the base layer45C of the flexure7C and the base plate27, the wiring patterns47are arranged. Like the base plate27ofFIG. 4, the base plate27ofFIG. 15has a groove33in the opposite-to-disk surface31, to correspond to and receive the wiring patterns47.

A rigid part11C has a body82. A base end of the body82is a joint part83. The resilient part13C of the flexure7C is extended over the joint part83to the body82and fixed to the joint part83and the body82. Namely, the flexure7C is fixed to the rigid part11C at two weld spots85on each side at the resilient part13C. This is a 2-point laser weld technique.

Each side edge87of the joint part83of the rigid part11C is cut along the same when a plurality of rigid parts11C are formed from a plate material. Due to this, a rail19C formed along each side edge of the rigid part11C cannot be extended along the side edge87, thereby forming a blank89between the rail19C and the joint part83. If the flexure7C is fixed to the joint part83of the rigid part11C at a single weld spot (1-point laser weld technique) on each side, the presence of the blank89will decrease the B1frequency (first bending mode frequency) of the load beam1C.

To avoid this, the fourth embodiment welds the flexure7C to the joint part83and the body82of the rigid part11C at two weld spots85on each side, to reinforce each blank89between the rail19C and the joint part83without increasing the number of parts.

FIG. 16is a graph showing a distribution of vertical rigidity (stiffness) of the load beam1C of the fourth embodiment and that of a related art. An abscissa indicates a distance from a dimple17and an ordinate indicates rigidity (stiffness). The distance from the dimple17is zero at the dimple17, is −6 at an end of the arm5, and is approximately −5 at the blanks89.

InFIG. 16, a 2-point-laser-weld curve91represents the fourth embodiment and a 1-point-laser-weld curve93represents a related art employing the 1-point laser weld technique.

As is apparent inFIG. 16, the fourth embodiment that reinforces the blanks89can secure a proper vertical rigidity despite the presence of the blanks89.

FIG. 17is a list showing the first bending mode frequencies (B1 frequencies) and static shock properties (G-lift-off) of load beams having four different thicknesses ranging from 20 μm to 35 μm. The thickness of a resilient part (13C) is fixed at t=25 μm.

In the columns of B1frequencies, i.e., first bending frequencies, values in a left column are of the related art employing the 1-point laser weld technique and values in a right column are of the fourth embodiment employing the 2-point laser weld technique. Similarly, in the columns of G-lift-off, values in a left column are of the related art and values in a right column are of the fourth embodiment. Values in the column of ABI represent differences between the B1frequencies of the related art and those of the fourth embodiment.

FIGS. 18 and 19are graphs plotted from the values shown inFIG. 17. The graph ofFIG. 18shows the static shock properties of the load beams. An abscissa indicates the thickness of a load beam and an ordinate indicates the G-lift-off of the load beam. The graph ofFIG. 19shows the B1frequencies of the load beams. An abscissa indicates the thickness of a load beam and an ordinate indicates the B1frequency of the load beam.

InFIG. 18, a curve95represents the load beams according to the related art employing the 1-point laser weld technique and a curve97represents the load beams according to the fourth embodiment employing the 2-point laser weld technique. It is understood fromFIG. 18that the related art and fourth embodiment increase the G-lift-off as the thickness of the load beam becomes thinner. The head suspensions of the fourth embodiment show no deterioration in the shock properties thereof.

InFIG. 19, a curve99represents the load beams according to the fourth embodiment and a curve101represents the load beams according to the related art employing the 1-point laser weld technique. For each load beam thickness, the fourth embodiment demonstrates a higher B1frequency than the related art.

As is apparent inFIGS. 18 and 19, the fourth embodiment employing the 2-point laser weld technique can increase the B1frequency higher than the related art employing the 1-point laser weld technique, without deteriorating the static shock property. For a given B1frequency, the fourth embodiment can increase G-lift-off by 100 G/gf higher than the related art.

An analysis of characteristics or properties that are required for a load beam to follow the motion of an arm will be explained.

FIG. 20Ais an analytic model showing a head suspension andFIG. 20Bis a vibration model based on the model ofFIG. 20A. InFIGS. 20A and 20B, M is a mass assumed to be concentrated on the gravity center of a load beam3C, Ksp is a spring constant of the load beam3C from the gravity center to a resilient part13C, Klb is a spring constant due to the rigidity of a rigid part11C from the gravity center to a dimple, G's is a shock input, X0is an arm action, and X is a displacement of the load beam3C at the gravity center.

The displacement X is expressed as follows:
X=A/{(Klb/Ksp)−(ω/ω0)2+ω02}  (1)
ω02=Ksp/M

Reducing the displacement X results in suppressing a lift of a slider from a disk. For this, the expression (1) indicates that (Klb/Ksp) and ω02must be increased.FIG. 21is a graph showing a relationship between an increase in (Klb/Ksp) and a gain. When (Klb/Ksp) is increased as 0.5, 1, 2, 4, and 8 as shown inFIG. 21, the frequency increases and the gain decreases.

To increase (Klb/Ksp), Klb must be increased because Ksp is restricted by the resilient part13C. Namely, the vertical stiffness (rigidity) of the load beam must be improved. To increase ω02, M must be reduced.

In consequence, to reduce the displacement X, the vertical stiffness of the load beam must be improved and the mass M must be reduced.

FIG. 22is a graph showing a relationship among the B1frequency of an arm, the B1frequency of a load beam, and the lift-off of a slider. An abscissa represents the B1frequency of a load beam and an ordinate represents the acceleration of a shock at which a slider of the load beam lifts. A curve103is for an arm having a B1frequency of 1.20 kHz and a curve105is for an arm having a B1frequency of 1.52 kHz.

As is apparent inFIG. 22, a load beam having a low B1frequency is unable to follow the arm having the high B1frequency, demonstrates an inferior shock property, and causes the slider thereof to lift at a low acceleration. A load beam having a B1frequency of 4 kHz can sufficiently follow the arm having the high B1frequency of 1.52 kHz, demonstrates a superior shock property, and realizes a high acceleration level at which the slider thereof lifts.

Data shown inFIG. 22relates to assemblies each consisting of only a carriage arm and a head suspension. In practice, the behavior of a head suspension base, the operation mode of a disk, and other conditions are involved to complicate situations around the head suspension.FIG. 23shows data sampled from head suspensions in more practical situations.

FIG. 23is a list showing a relationship among the lift-off of a slider, the magnitude of a shock applied, and the B1frequency of a head suspension that supports the slider. The data shown inFIG. 23relates to a 2.5-inch hard disk drive. When the B1frequency of a load beam is increased from 3.11 kHz to 4.02 kHz as shown inFIG. 23, the level of a shock of 0.4 msec duration at which the slider of the load beam lifts increases from 296 G to 325 G. In this way, increasing the B1frequency of a load beam is effective to suppress a lift-off of the slider of the load beam.

FIG. 24is a graph showing the off-track property of a head suspension, including an arm, which has a total B1frequency of 3.6 kHz. An abscissa represents frequencies and an ordinate represents off-track amount. The data shown inFIG. 24relates to a 2.5-inch hard disk rotating at 7200 rpm.

FIG. 25is a graph showing the off-track property of a head suspension whose B1frequency is 3.1 kHz. An abscissa indicates the frequency and an ordinate indicates off-track displacement. In the graph ofFIG. 25, a curve depicted with a continuous line represents the off-track property of a head suspension measured on a 2.5-inch disk rotated at 5400 rpm and a curve depicted with a dotted line represents the off-track property of the head suspension measured on a 2.5-inch disk rotated at 7200 rpm.

InFIG. 25, the head suspension has a low B1frequency of 3.1 kHz, and therefore, the bending mode of the head suspension overlaps the bending mode of the arm. As a result, an off-track phenomenon is observed at 3.0 kHz and at 3.3 kHz.

To avoid the off-track phenomenon, the B1frequency of the load beam of the head suspension must be increased so that the bending mode of the head suspension will not overlap the bending mode of the arm.

The fourth embodiment improves the vertical stiffness (rigidity) of the load beam3C, to increase the B1frequency of the load beam3C. This results in eliminating the overlapping of the bending modes of the head suspension1C and arm5and reducing a bending amplitude. It is apparent from comparison between the fourth embodiment ofFIG. 24and the related art ofFIG. 25that the fourth embodiment causes no off-track error according to the bending mode of the head suspension1C.

The fourth embodiment can provide effects similar to those of the first embodiment.

According to the fourth embodiment, the flexure7C is fixed to the opposite-to-disk surface31of the arm5. The flexure7C includes the base layer45C and the wiring patterns47arranged on the base layer45C. The base layer45C of the flexure7C includes the resilient part13C. This configuration reduces a step between the arm5and the load beam3C, decreases the number of parts, simplifies the structure of the head suspension1C, and makes the management and assembling of parts easier.

The flexure7C can be easily attached to the arm5and can be apart from a disk because the wiring patterns47are arranged between the base layer45C of the flexure7C and the arm5. This configuration prevents the wiring patterns47of the flexure7C from being damaged in postprocesses.

The arm5is provided with the groove33to receive the wiring patterns47so that the flexure7C on the arm5is separated away from a disk. This configuration prevents the wiring patterns47of the flexure7C from being damaged during postprocesses as well as preventing the flexure7C from protruding from the opposite-to-disk surface31of the arm5, thereby contributing to thinning a hard disk drive.

The base layer45C of the flexure7C includes the resilient part13C. The resilient part13C extends over the joint part83to the body82of the rigid part11C and is fixed to the rigid part11C at least at two weld spots85along each side edge of the rigid part11C. Without regard to the presence of the blanks89in the load beam3C, this configuration can improve the vertical rigidity of the load beam3C, increase the B1frequency of the head suspension1C, and satisfy a shock property required for the head suspension1C.

According to the present invention, the disk-side surface of the arm is arranged within the total of the thicknesses of the rigid part and head. Whether or not the opposite-to-disk surface of the arm is arranged within the total of the thicknesses of the rigid part and head is optional.

According to the present invention, the rails formed along the side edges of the rigid part may be omitted, if not required.