CN1273961C - Suspension rack for disk drive - Google Patents

Abstract

The present invention relates to a suspension rack (10A) for a disk drive, which comprises a load beam (11), an actuator base seat (25), a hinge element (14) and a pair of piezoelectric ceramic elements (40), wherein a flexible element (15) is arranged on the load beam (11); the actuator base seat (25) comprises a bottom plate (13); the hinge element (14) is thinner than the bottom plate (13); each of the piezoelectric ceramic elements (40) is positioned in the opening part (23) of the actuator base seat (25) and is fixed on the actuator base seat (25) by a binding agent layer (80). The binding agent layer (80) comprises an electric insulating binding agent (81) and multiple fillings (82) mixed with the electric insulation binding agent (81) and formed by electric insulating materials. The fillings (82) are positioned between the piezoelectric ceramic elements (40) and the actuator base seat (25) so as to obtain an interval for electric insulation.

Description

disk drive suspension

technical field

The present invention relates to a suspension for a disk drive mounted in an information processing device such as a personal computer.

Background technique

In a disk drive having a rotating magnetic disk or a magneto-optical disk, a magnetic head is used to record or read data from the recording surface of the disk. The magnetic head includes a slider facing the recording surface of the magnetic disk, a sensor hidden in the slider, and the like. When the disk rotates at high speed, the slider rises slightly on the disk, thereby forming an air cushion between the disk and the slider. A suspension to which a magnetic head is fixed includes a beam member called a load beam, a flexure formed of a very thin leaf spring fixed to the load beam, a bottom plate provided at a proximal end portion of the load beam, and the like. A slider constituting a magnetic head is mounted on an end portion of the flexure.

In a hard disk drive (HDD), the track centerline of the magnetic disk must be subject to control within ±10% of the track width. With the recent development of high-density magnetic disks, the track width has been reduced to 1 µm or less, making it difficult to keep the slider on the track centerline. Therefore, it is necessary to achieve precise position control of the slider and increase the rigidity of the magnetic disk, thereby reducing the wobble of the magnetic disk.

Typically, conventional disk drives are of the single-actuation type, with a suspension moved by voice coil motors only. Single-actuation suspensions have many resonant peaks on the low frequency band. Thus, in the high frequency band, it is difficult to control the slider (head) on the end of the suspension only by the voice coil motor, and the bandwidth of the servo system cannot be increased.

Therefore, a dual-actuation suspension has been developed which includes a micro-actuation section and a voice coil motor. The micro-actuating part causes the second actuator to slightly move the end part of the load beam or the slider in the transverse direction of the suspension (the so-called swing direction).

Since the movable part driven by the second actuator is much lighter in weight than that of a single-actuation suspension, the slider can be controlled over a high frequency band. In this way, the dual-actuation suspension allows several times higher bandwidth of the servo system for position control of the slide compared to a single-actuation suspension, and correspondingly reduces seek errors.

It is well known that piezoelectric ceramic elements such as lead zirconate titanate (a solid solution of _PbZrO3 and _PbTiO3 ) called PZT can be used as the material of the second actuator. Since PZT has a rather high resonance frequency, it is suitable as the second actuator of a dual-actuation suspension. The piezoelectric ceramic element is fixed on an actuator base with adhesive.

Piezoelectric ceramic elements such as PZT used as micro-actuating parts are as thin as 10-100 micrometers and fragile. Electrodes for supplying current to the piezoelectric ceramic element are formed on the front or back side of the element. On the other hand, a metal base plate or the like constituting the base of the actuator is used as an electrical ground. Therefore, in order to prevent a short circuit between the electrodes of the piezoceramic element and the actuator base, an electrically insulating distance between the electrodes and the actuator base must be ensured. Usually, the gap is believed to be secured by positioning and clamping the piezoceramic element and the actuator base with a jig to cure the adhesive.

However, if the piezoceramic element is held by a jig, in some cases, it may break due to stress because the adhesive shrinks slightly while curing. If the piezoceramic element is not broken during the bonding process, it may break due to residual stress when it is subjected to an external force during the subsequent bonding process.

Contents of the invention

It is therefore an object of the present invention to provide a suspension for a magnetic disk drive in which a piezoelectric ceramic element can be safely insulated from an actuator base without breaking.

In order to achieve the above object, the suspension of the present invention includes a load beam on which a flexure is mounted, the load beam has a proximal portion and an end portion opposite to the proximal portion; an actuator base, which mounts on the proximal portion of the load beam; a piezoceramic element mounted on the actuator base that deforms to move the load beam in the swing direction when a voltage is applied to it; and an adhesive layer that Fix the piezoelectric ceramic element on the actuator base; the adhesive layer includes an electrically insulating adhesive and mixed with the adhesive, a number of fillers formed of electrically insulating materials, the fillers have Dimensions to obtain electrically insulating spacing between the element and the actuator base. The filling may be formed of a material having electrically insulating properties that does not readily deform under compressive loads, such as silica particles.

According to the present invention, an appropriate spacing for electrical insulation can be easily obtained between a conductive portion of the piezoelectric ceramic element, such as an electrode, and the actuator base. In this way, the adhesive can be solidified without clamping the piezoelectric ceramic element with a jig, thereby avoiding stress generation and preventing the piezoelectric ceramic element from breaking.

In the suspension of the present invention, the actuator base may be formed with an opening portion capable of installing the piezoelectric ceramic element, and the piezoelectric ceramic element is installed in the opening portion. According to the present invention, since the piezoelectric ceramic element is installed in the opening portion of the actuator base, it can be protected, and the micro-actuating portion can be thinned. In addition, since the thickness direction center of the piezoelectric ceramic element is less deviated from the thickness direction center of the bottom plate, the movement of the piezoelectric ceramic element can be effectively transmitted in the swing direction.

Furthermore, in the suspension of the present invention, electrodes (first and second electrodes) of different polarities are formed on the front and back surfaces of the piezoelectric ceramic element, respectively. In the micro-actuating part designed like this, the first electrode of the piezoelectric ceramic element is grounded through the actuator base, and a lead is connected with the second electrode. According to the present invention, the first electrode and the actuator base can be Obtain proper spacing for electrical isolation.

In the suspension of the present invention, the recommended particle size of the filler is 10 μm or above, preferably 30 μm or above. According to the present invention, good electrical insulating properties can be obtained at high voltages, not to mention voltages applied to conventional piezoelectric ceramic elements.

Preferably, the Young's modulus of the adhesive in a cured state is 60 MPa or above. Since the Young's modulus of the adhesive is 60 MPa or more, according to the present invention, the stroke of the piezoelectric ceramic element can be maintained at a practical and reasonable level. Thus, if a filler having a higher Young's modulus than that of the adhesive layer is mixed in the adhesive, the Young's modulus of the adhesive layer can be further improved.

In the suspension of the present invention, the actuator base may include a bottom plate and an elastic hinge fixed to the bottom plate, and the elastic hinge is also fixed to the load beam such that the bottom plate is connected to the load beam through the elastic hinge. According to the present invention, the performance of the suspension can be improved by using materials matching the required properties of the load beam, actuator base and hinge.

Additional objects and advantages of the invention will appear from the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention can be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the presently preferred embodiment of the invention and, together with the foregoing general description and the following detailed description of the preferred embodiment, serve to describe the principles of the invention .

1 is a plan view of a suspension according to a first embodiment of the present invention;

Figure 2 is a plan view of the base plate in the suspension shown in Figure 1;

Figure 3 is a plan view of a hinge in the suspension shown in Figure 1;

Figure 4 is a cross-sectional view of the micro-actuating part of the suspension along the line F4-F4 in Figure 1;

FIG. 5 is an enlarged cross-sectional view showing a portion of the microactuating portion shown in FIG. 4;

Fig. 6 is a graph showing the relationship between the spacing between each piezoelectric ceramic element and the hinge and the number of suspensions ensuring electrical insulation;

7 is a graph showing the relationship between the spacing between each piezoelectric ceramic element and the base plate and the number of suspensions ensuring electrical insulation;

8 is a graph showing the relationship between the Young's modulus of the binder and the stroke of each piezoelectric ceramic element; and

Fig. 9 is a sectional view showing a part of a suspension according to a second embodiment of the present invention.

Detailed ways

A suspension 10A for a magnetic disk drive according to a first embodiment of the present invention will now be described with reference to FIGS. 1 to 5. FIG.

A suspension 10A of a dual-actuation type shown in FIG. 1 includes a load beam 11, micro-actuation portions 12, a base plate 13, hinges 14, and the like.

The load beam 11 is formed of an elastic metal plate having a thickness of, for example, about 100 μm. The flexure 15 is mounted on the load beam 11 . The flexure 15 is formed of a high-precision metal leaf spring thinner than the load beam 11 . A slider 16 constituting a magnetic head is mounted on an end portion of the flexure 15 .

As shown in FIG. 2 , a circular hub hole 21 is formed at the proximal portion 20 of the base plate 13 . A pair of hole portions 23 are formed between the proximal end portion 20 and the front end portion 22 of the bottom plate 13 . Each hole portion 23 is large enough to accommodate a piezoelectric ceramic element 40 . The strip-shaped connection portion 24 extends between the pair of hole portions 23 along the longitudinal direction of the bottom plate 13 (the axial direction of the suspension 10A). The connecting portion 24 can be bent to some extent along the lateral direction of the bottom plate 13 (the swinging direction indicated by the arrow S in FIG. 1 ).

The proximal portion 20 of the base plate 13 is secured to the end portion of an actuator arm driven by and rotated by a voice coil motor (not shown). The bottom plate 13 is formed of a metal plate having a thickness of, for example, about 200 μm. In the case of this embodiment, the base plate 13 and the hinge 14 form the actuator base 25 according to the invention.

As shown in Figure 3, the hinge 14 includes a proximal portion 30 overlapping and fixed on the proximal portion 20 of the base plate 13, and a bar-shaped bridging portion 31 formed at a position corresponding to the connecting portion 24 of the base plate 13, formed at the same position as the connecting portion 24 of the base plate 13 The front end portion 22 of the bottom plate 13 corresponds to the middle portion 32 , a pair of flexible hinge portions 33 elastically deformable in the thickness direction, and an end portion 34 fixed on the load beam 11 . The hinge 14 is formed of an elastic metal plate having a thickness of about 50 μm.

The micro-actuating portion 12 includes a pair of piezoelectric ceramic elements 40, plate-shaped piezoelectric elements such as PZT. Each rectangular piezoelectric ceramic element 40 has a front face 50 and a back face 51 (shown in FIG. 4 ) in the thickness direction, end faces 52 and 53 at opposite longitudinal ends, and opposite side faces 54 and 55 .

The piezoelectric ceramic elements 40 are accommodated in the opening portions 23 of the actuator base 25, respectively, so as to extend substantially parallel to each other. When each element 40 is installed in the corresponding opening portion 23, the opposite ends 52 and 53 of each element 40 are respectively on the longitudinal opposite ends of each opening portion 23, and cross the gap between the end surface and the inner surface 60 and 61. Gap, facing inner surfaces 60 and 61 . The side 54 of each element 40 adjacent to the connecting portion 24 faces the side 24 a of the connecting portion 24 across the gap between this side 54 and the side 24 a of the connecting portion 24 .

As shown in FIG. 4, electrodes 70 and 71 of conductive material such as metal are formed on the front side 50 and the back side 51 of each piezoelectric ceramic element 40, respectively, by spraying or plating. One electrode 70 is grounded to the bottom plate 13 through silver conductive glue 72 . One wire 73 is connected to the other electrode 71 . The wire 73 is connected to the terminal 74 of the wiring member on the flexure 15 .

One end portion 40 a of each piezoceramic element 40 is fixed to the proximal end portion 30 of the hinge member 14 with an adhesive layer 80 . The other end 40 b of the element 40 is secured to the middle portion 32 of the hinge 14 by means of an adhesive layer 80 . In doing so, the adhesive layer 80 must also be applied in the space between the element 40 and the inner surfaces 60 and 61 of the respective opening portions 23 of the actuator base 25 . In this way, the deformation (movement) of the piezoceramic element 40 can be more effectively transmitted to the load beam 11 and the end faces 52 and 53 and the side faces 54 and 55 of the element 40 can be safely electrically isolated from the actuator base 25 .

When a voltage is applied, one of the pair of piezoelectric ceramic elements 40 extends in the longitudinal direction, and the other element 40 contracts in the longitudinal direction. In this way, the load beam 11 moves a required distance in the lateral direction (swing direction) according to the deformation direction and stroke of the piezoelectric ceramic element 40 .

As schematically shown in FIG. 5 , the binder layer 80 includes a binder 81 serving as an electrically insulating matrix resin, and a large amount of particle filler 82 . These particle fillers 82 are formed of an electrically insulating material and contained in a binder 81 . While epoxy is one example of adhesive 81, other plastic adhesives including acrylic resins may also be used for this purpose.

The filler 82 has such a size that it can be inserted between each piezoceramic element and the actuator base 25 and can ensure an electrically insulating space therebetween. The particle size of the filler 82 should be 10 μm or larger, preferably 30 μm or larger. Although the filler 82 is formed of, for example, silica (silicon dioxide), it may also be formed of other materials that have electrical insulating properties and cannot be easily deformed under a compressive load, such as ceramics, glass, synthetic resin, or the like.

Since the filler 82 is used in the adhesive layer 80, a predetermined spacing can be obtained between each piezoelectric ceramic element 40 and the actuator base 25 without using any jig. As shown schematically in FIG. 5, the distance C1 between the electrode 71 of each ceramic element 40 and the hinge 14, and the distance C2 between the end surfaces 52 and 53 of the element 40 and the inner surfaces 60 and 61 of the base plate 13 are 10 μm in length or greater length.

In order to check the electrical insulation performance of the piezoelectric ceramic element 40 of the suspension 10A, tests were performed at voltages of 100V, 200V, 300V and 400V, respectively. It is determined through these tests that when using the adhesive layer 80 of this embodiment, electrical insulation can be obtained at any of the above-mentioned voltage levels.

On the other hand, the same electrical insulation test was performed with the above-mentioned voltages without using any jig and fixing each piezoelectric ceramic element 40 to the actuator base 25 using an adhesive that did not include the filler 82 . At this time, some samples lack the spacing for insulation, and insulation failure will occur at or below 100V.

The present inventors have trial-produced a large number of suspensions in which piezoelectric ceramic elements are fixed to an actuator base using an adhesive with a filler. The present inventors examined the relationship between the number of suspensions ensuring a given degree of electrical insulation and the spacing C1 (the spacing between each piezoelectric ceramic element 40 and the hinge 14 ). Figure 6 shows the inspection results.

7 shows the number of suspensions and the spacing C2 (the spacing between each piezoceramic element 40 and the base plate 13) under the condition that each ceramic element 40 is fixed on the actuator base using an adhesive with a filler. ) of the relationship between the inspection results. These insulation tests have shown that a given degree of electrical insulation can be ensured if the distances C1 and C2 are greater than 10 μm. In other words, if a filler of 10 µm or more is mixed in the binder 81, a given degree of insulation can be obtained.

In the above-described embodiment, the piezoelectric ceramic element 40 is fixed on the actuator base 25 through the adhesive layer 80 applied with a filler of 10 [mu]m or more. Due to the use of such an adhesive layer 80, an appropriate pitch (about 10 [mu]m to 50 [mu]m) can be obtained without using any jig. According to this embodiment, it is possible to avoid the occurrence of stress after curing of the adhesive, which would occur when the piezoelectric ceramic element is held by the jig.

The present inventors produced five samples according to the above-described examples, and examined the load that would break the piezoelectric ceramic element 40 after the adhesive was cured. On the other hand, the present inventors prepared five samples for comparison, in which piezoelectric ceramic elements were held by jigs while the adhesive (without filler) was being cured, and examined the load that fractured the ceramic elements.

These destructive tests showed that samples 1 to 5 based on the above examples broke when subjected to loads of 140 g, 160 g, 130 g, 180 g and 130 g, respectively, such that their average load was 148 g. On the other hand, Comparative Samples 1 to 5 broke when subjected to loads of 90 g, 70 g, 80 g, 40 g, and 80 g, respectively, so that their average load decreased to 72 g.

FIG. 8 shows the relationship between the Young's modulus of the adhesive and the stroke of the piezoelectric ceramic element 40 . In FIG. 8, L1 and L2 denote analyzed values and measured values, respectively. From Figure 8 it can be seen that the higher the Young's modulus of the binder, the more favorable the travel of the ceramic component can be obtained. In particular, a stroke suitable for practical use can be obtained by using a binder having a Young's modulus of 60 MPa or more.

FIG. 9 shows a suspension 10B according to a second embodiment of the present invention. In this suspension 10B, a pair of electrodes 91 and 92 are formed on the reverse side 51 of each piezoelectric ceramic element 40, and the first electrode 92 is grounded to the hinge 14 through the silver conductive paste 72. A wire 73 connected to the second electrode 92 is connected to the terminal 74 on the flexure 15 . The second embodiment has other structures and functions of the suspension 10A in the first embodiment. Therefore, the same reference numerals are used to designate the same parts in the two embodiments, and the descriptions of these parts are omitted here. In the suspension 10B of this embodiment, the spacing for insulation is also obtained by providing the adhesive layer 80 with a filler between the electrode 92 of the piezoelectric ceramic element 40 and the hinge member 14 .

In the above-described embodiments, the piezoelectric ceramic elements 40 are installed in the opening portions 23 of the actuator base 25, respectively. However, instead of installing the element 40 in the opening portion 23, the element 40 can also be superimposed on the bottom plate 13 and fixed on the bottom plate 13 with an adhesive layer 80, as shown by the two-dot chain line F in FIG. 9 .

It should be understood that in practicing the present invention including the above-described embodiments, without departing from the scope or spirit of the present invention, the components constituting the present invention, including the load beam, the actuator base, the base plate, the adhesive, the filler, the pressing Parts such as electroceramic elements can be variously changed or improved. To reduce weight, the base plate and load beam may be formed from light metal alloys such as aluminum alloys, or thin sheets (eg, cladding) of light metal alloys and stainless steel.

Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broadest sense is not limited to the specific details and exemplary embodiments shown and described herein. Many modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

Claims (13)

1. A suspension of a disk drive, characterized in that it comprises: a load beam (11) on which is mounted a flexure (15), the load beam having a proximal portion and an end portion opposite the proximal portion; an actuator base (25), which is mounted on the proximal portion of the load beam (11); a piezoceramic element (40) mounted on the actuator base (25) which deforms to move the load beam (11) when a voltage is applied thereto; and an adhesive layer (80), which fixes the piezoceramic element (40) on the actuator base (25), The adhesive layer (80) includes an electrically insulating adhesive (81) and mixed with the adhesive (81), a plurality of fillers (82) formed of an electrically insulating material, the fillers (82) having The dimensions of the electrically insulating spacing are obtained between the electroceramic element (40) and the actuator base (25). 2. the suspension of disk drive as claimed in claim 1 is characterized in that, described actuator base (25) is formed with the opening part (23) that piezoelectric ceramic element (40) can be installed, and opening part (23 ) to install a piezoelectric ceramic element (40). 3. The disk drive suspension according to claim 2, characterized in that electrodes (70, 71) with different polarities are respectively formed on the front and back sides of the piezoelectric ceramic element (40). 4. The disk drive suspension according to claim 2, characterized in that the particle size of the filler (82) is 10 μm or above. 5. The disk drive suspension according to claim 1, characterized in that the Young's modulus of the adhesive (81) in a cured state is 60 MPa or above. 6. The disk drive suspension according to claim 2, characterized in that the Young's modulus of the adhesive (81) in a cured state is 60 MPa or above. 7. The disk drive suspension according to claim 3, wherein the Young's modulus of the adhesive (81) in a cured state is 60 MPa or above. 8. The disk drive suspension according to claim 4, characterized in that the Young's modulus of the adhesive (81) in a cured state is 60 MPa or above. 9. The suspension of disk drive as claimed in claim 1, it is characterized in that, described actuator base (25) comprises a base plate (13) and an elastic hinge (14) that is fixed on this base plate, the The elastic hinge (14) is also fixed to the load beam (11) so that the bottom plate (13) is connected to the load beam (11) through the elastic hinge (14). 10. The suspension of disk drive as claimed in claim 2, is characterized in that, described actuator base (25) comprises a bottom plate (13) and an elastic hinge (14) that is fixed on this bottom plate, and this The elastic hinge (14) is also fixed to the load beam (11) so that the bottom plate (13) is connected to the load beam (11) through the elastic hinge (14). 11. The suspension of disk drive as claimed in claim 3, it is characterized in that, described actuator base (25) comprises a base plate (13) and an elastic hinge (14) that is fixed on this base plate, the The elastic hinge (14) is also fixed to the load beam (11) so that the bottom plate (13) is connected to the load beam (11) through the elastic hinge (14). 12. The suspension of disk drive as claimed in claim 4, it is characterized in that, described actuator base (25) comprises a bottom plate (13) and an elastic hinge (14) that is fixed on this bottom plate, and this The elastic hinge (14) is also fixed to the load beam (11) so that the bottom plate (13) is connected to the load beam (11) through the elastic hinge (14). 13. The suspension of the disk drive as claimed in claim 5, wherein the actuator base (25) comprises a base plate (13) and an elastic hinge (14) fixed on the base plate, the The elastic hinge (14) is also fixed to the load beam (11) so that the bottom plate (13) is connected to the load beam (11) through the elastic hinge (14).

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