Magnetic head with a slider and a gimbal suspension having a flexure including spacer projections for bonding the slider

A magnetic head is provided that is formed by fixedly bonding a slider having a thin-film magnetic element on a flexure formed of metallic material which constitutes a gimbal suspension. The slider includes electrodes conducted to the thin-film magnetic head on an end surface thereof on a trailing side which is orthogonal to the recording-medium-opposed surface. The flexure has independent spacer projections. The slider and the flexure are bonded by an adhesive agent applied to bonding areas on end surfaces of a pair of spacer projections positioned in the vicinity of the end surface of the slider on the trailing side of the spacer projections.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic head and, more specifically, to a magnetic head having a bonding structure between a slider and a flexure of a head gimbal assembly for supporting the slider.

2. Description of the Related Art

An HGA (head gimbal assembly) which is widely used in HDD is formed by fixedly bonding a slider having a thin-film magnetic head element (MR element, GMR element) on one end portion of a flexure formed of metallic material which is fixed to a distal end of a load beam. In the related art, a spacer projection is fixed to a surface of the flexure, and the slider is bonded in an area surrounded by the spacer projection where adhesive agent is applied (Japanese Unexamined Patent Application Publication No. 9-282824 (U.S. Pat. No. 5,880,908), Japanese Unexamined Patent Application Publication No. 10-27447, and Japanese Unexamined Patent Application Publication No. 11-39627).

FIG. 9is a plan view of a distal end portion of the flexure in the related art, andFIG. 10is a side view showing a state in which the slider is bonded to the flexure. On a flexure121, there are provided a plurality of spacer projections122a,122b,122cthat support a slider111of a magnetic head, and electrodes133ato133dformed on an FPC substrate which is connected to electrodes114d(although there are a plurality of electrodes, only one of those is shown inFIG. 10) provided on an end surface B of the slider111on a trailing side by ball bonding. A back surface of the slider111on the opposite side from a recording-medium-opposed surface (ABS surface)112, which is a surface opposing to a magnetic recording medium, is bonded to surfaces of the spacer projections122ato122cby an adhesive agent124applied thereon. After this bonding operation, the electrodes114dprovided on the end surface B of the slider111on the trailing side is joined to the electrodes133ato133dformed on the flexure121via a ball bonding portion125formed by ball bonding using gold or the like.

However, in the related art, a length of the bonding portion between the ball bonding portion125of the end surface B of the slider111on the trailing side and the spacer projection122bin the vicinity of an end surface A on a leading side is long. Therefore, the ball bonding portion125which is a rigid joint becomes a point of support a′ of deformation, and the bonded portion with respect to the adhesive agent becomes a load center b′, so that flatness of the ABS of the slider111is susceptible to deformation disadvantageously due to expansion of the flexure121by heat applied during bonding and contraction of the flexure121by a subsequent cooling operation. There is also a problem such that the flatness of the recording-medium-opposed surface of the slider is significantly changed due to expansion or contraction of the flexure due to change in temperature of operating environment in a state of being assembled in a hard disk device. In this manner, when the flatness of the recording-medium-opposed surface is changed, the raising amount is increased and hence writing/reading performance is lowered. Therefore, it is desirable that the variation of the flatness of the recording-medium-opposed surface of the slider is small.

SUMMARY OF THE INVENTION

In view of the problems of the magnetic head in the related art as described above, it is an object of the invention to provide a magnetic head in which a variation in flatness of a recording-medium-opposed surface of a slider is small even when it is subjected to change in temperature.

In order to achieve the object described above, the invention provides a magnetic head including a slider having a thin-film magnetic element fixedly bonded to a flexure formed of metallic material constituting a gimbal suspension, wherein the slider includes a plurality of electrodes that are conducted to the thin-film magnetic element on an end surface thereof on a trailing side orthogonal to a recording-medium-opposed surface, and a portion of the slider closer to the end surface on the trailing side with respect to a center of the plane thereof is bonded to the flexure.

In an embodiment, a bonding position between the slider and the flexure is deviated to an area closer to the end surface on the trailing side having the electrodes with respect to the center of the plane of the slider.

In another embodiment, a plurality of independent spacer projections are provided on the flexure, and the slider is bonded to the spacer projections located near the end surface on the trailing side out of the spacer projections with an adhesive agent applied to surfaces thereof.

More practically, the spacer projections include pair of two spacer projections extending in parallel to each other in the direction orthogonal to the end surface on the trailing side, and a spacer projection provided non-continuously from the pair of two spacer projections at a position apart from the end surface on the trailing side and extending in the direction orthogonal to the direction of extensions of the pair of two spacer projections, and the adhesive agent is applied only on portions of the pair of two spacer projections closer to the end surfaces on the trailing side.

A contact surface area of the adhesive agent is reduced from the portion closer to the end surfaces of the spacer projections on the trailing side toward an end surfaces on a leading side. In this structure, deformation of the slider in association with change in temperature at the time of curing the adhesive agent can be reduced, and the bonding surface area can be secured to improve the bonding strength.

Preferably, fillets are formed between opposing side surfaces of the slider in the vicinity of the end surface on the trailing side and the surface opposing to the flexure, and the slider and the flexure are bonded by an adhesive agent filled between the respective fillets and the flexures. With these fillets, the bonding surface area is secured, and deformation of the slider can be reduced, and also the bonding strength can be secured.

Since the distance between the ball bonding portion on the end surface of the slider on the trailing side and the bonding portion is short, even when the flexure and the slider are expanded and contracted at different coefficients of thermal expansion due to change in temperature, the influence of the difference of expansion and contraction is small and hence the amount of deformation of the recording-medium-opposed surface of the slider is small.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a plan view of a distal end portion of a flexure21which constitutes a head gimbal assembly according to an embodiment to which the invention is applied;FIG. 2is an exploded perspective view of a flexure portion. The flexure21is formed of stainless steel welded by a laser beam to a distal end portion of a load beam which is rotatably supported on a revolving shaft, not shown.

A slider bonding tongue21bwhich is resiliently deformable by a U-shaped through groove21ais formed at a distal end portion of the flexure21. An FPC substrate31is provided on the flexure21so as to surround the U-shaped through groove21a. InFIG. 2, although the FPC substrate31is shown as a separate member from the flexure21for the sake of convenience, the FPC substrate31is actually formed by laminating a resin base and a lead on the flexure21. The slider bonding tongue21bis exposed from a hole31aon the FPC substrate31.

The FPC substrate31is formed with lead patterns32a,32band lead patterns32c,32dalong an edge of the hole31a, that is, along outer portions on both side edges of the slider bonding tongue21b, and bonding pads33ato33dare formed on distal end portions of the lead patterns32ato32d. Although the lead patterns32ato32dand the bonding pads33ato33dare shown as separate members from the flexure21inFIG. 2, they are actually formed by laminating a resin base and a lead on the flexure21.

Provided on the slider bonding tongue21bare a pair of spacer projections22a,22bextending in parallel to each other in a direction orthogonal to an end surface B on a trailing side, and a spacer projection22cprovided non-continuously from the pair of spacer projections22a,22bat a position apart from the end surface B on the trailing side and extending in a direction orthogonal to the direction of extensions of the pair of two spacer projections22a,22bfor fixedly adhering a slider11. The spacer projections22ato22care formed of, for example, polyimide resin so as to have flat surfaces and are bonded to the slider bonding tongue21b. Surfaces of the bonding pads33ato33dand surfaces of the spacer projections22ato22care formed so as to position at the same level (on the same surface). InFIG. 1, reference numeral15cdesignates the position of a plane center with which a plane center on a back surface of the slider11is overlapped when the slider11is fixedly bonded.

The slider11is formed of ceramic material such as alumina-titan carbide or Si (Silicon), and is formed with an air-group and an ABS surface, not shown, on a recording-medium-opposed surface12opposing to a recording medium. A surface of the slider11on the opposite side from the recording-medium-opposed surface12corresponds to a bonding surface15.

A thin-film magnetic element13and four electrodes14ato14dconnected to the thin-film magnetic element13are provided on the end surface B (end portion) of the slider11on the trailing side. The thin-film magnetic element13is formed by laminating permalloy as magnetic material (Ni—Fe alloy) and alumina as insulating material, and includes a magnetic detection unit for reproducing magnetic recording signal recorded on a magnetic disk, or a magnetic recording unit for recording the magnetic signal on the magnetic disk, or both of the magnetic detection unit and the magnetic recording unit. The magnetic detection unit is a GMR head composed, for example, of a giant magnetoresistive effect element (GMR element). The magnetic recording unit is composed of an inductive head in which a coil and a core are patterned. The magnetic recording unit and the magnetic detection unit are connected to corresponding electrodes14ato14d. The electrodes14ato14dare joined to the bonding pads33ato33dby ball bonding with gold balls or the like.

A bonding area23for bonding the slider11is shown inFIG. 1. In this example, ends of the pair of spacer projections22a,22bin the vicinity of the bonding pads33ato33dare set as the bonding areas23. An adhesive agent24is applied to the bonding areas23and the bonding surface15of the slider11is pressed against the spacer projections22ato22c, and then bonding pads33ato33dand the electrodes14ato14dof the slider11are joined by ball bonding portions25formed by ball bonding with golden balls. Subsequently, the bonding areas23and the portion therearound are heated to cure the adhesive agent24. The adhesive agent24is not applied to the spacer projection22c. By pressing the slider11toward the spacer projections22ato22c, the adhesive agent24may be spread in the periphery of the bonding area23or along the surfaces of the pair of spacer projections22a,22b, but it may not be spread over the portion of the spacer projection22c. In other words, according to this embodiment, the slider11is bonded to the bonding area23of the pair of spacer projections22a,22bwhich are located on the side of the slider11(bonding surface15) closer to the bonding pads33ato33dwith respect to the plane center15c.

FIG. 3is a side view of the slider11fixedly bonded to the flexure21as described above. In the embodiment shown in the drawing, a fixed position between the slider11and the flexure21, that is, the joint portion joined by rigid bonding with the ball bonding portion25becomes a point of support a, and a bonding portion bonded to the bonding area23of the pair of spacer projection22a(22b) with the adhesive agent24becomes a load center b. The distance between the point of support a and the load center b is relatively small. Therefore, even when the temperatures of the flexure21and the slider11are changed, and the flexure21is expanded or contracted, a force applied to the slider11is weak and hence deformation of the slider11is small.

The adhesive agent24is applied to the respective bonding areas23of the pair of spacer projections22a,22band the slider11is clamped between the pair of spacer projections22a,22bwith a pressure. Then, the adhesive agent24amay be protruded from the pair of spacer projections22a,22b, and spread in a gap between the bonding surface15of the slider11and the pair of spacer projections22a,22btoward an end surface A on a leading side. In this example, the bonding surface area and the thickness of the bonded portion between the bonding surface15of the slider11and the pair of spacers22a,22bis increased in the bonding areas23closer to the end surface B on the trailing side and the area therearound and decreased toward the end surface A on the leading side (seeFIG. 4). Therefore, deformation of the slider11in association with the change in temperature when curing the adhesive agent24can be reduced, and the bonding surface area can be secured to improve the bonding strength.

FIG. 5andFIG. 6show a front view and a perspective view of another embodiment of the invention, respectively. In this embodiment, fillets16are formed between both side surfaces in the vicinity of the end surface B of the slider11on the trailing side and the adhesive surface15. Then, the adhesive agent24bis filled between the respective fillets16and the flexure21(slider bonding tongue21b). By forming the fillets16in this manner, the bonding surface area between the portion in the vicinity of the end surface B of the slider11on the trailing side and the adhesive agent24bis increased, and hence deformation of the slider11can be reduced and the bonding strength can be secured. The fillets16may be any form that allows the adhesive agent24bto spread easily to increase the bonding surface area.

FIG. 7shows a state in which the slider11(111) is deformed. In this drawing, a case in which the coefficient of heat expansion of the flexure is larger than that of the slider11(111), and the slider11(111) is sagged in the direction in which the recording-medium-opposed surface12(112) is protruded, and the amount of deformation Δx.FIG. 8is a graph showing a relation between the amount of deformation Δx and the temperature. In this graph, a lateral axis represents the temperature (° C.), a vertical axis represents the amount of deformation Δx (nm). In the graph, a solid line indicates the case of the embodiment of the invention (slider11), and a broken line indicates the case of the related art (slider111). It will be understood from this graph that the embodiment of the invention is smaller in the amount of deformation Δx due to the change in temperature.

Although the pair of spacer projections22a,22bextending in parallel and the spacer projection22cextending orthogonally thereto are arranged in the embodiment shown in the drawing, the number of spacer projections and the arrangement thereof are not limited thereto. The spacer projections to be bonded may be of any number and arrangement as long as they are arranged so as to deviate on the side of the end surface B of the slider11on the trailing side with respect to the plane center position11cand do not extend to the area of the end surface A on the leading side with respect to the plane center position11c, or are separated from the spacer projection in the area of the end surface A on the leading side.