Flexure having arms with reduced centroid offset for supporting a head in a disk drive

A flexure for supporting a head in a disk drive includes a tongue including a head mounting surface for attaching the head. The flexure further includes a first arm on a first side of the tongue. The first arm includes a structural material and has a first cross-sectional area in a plane perpendicular to the head mounting surface. The first cross-sectional area has a first centroid. The flexure further includes a second arm on the first side of the tongue. The second arm includes a conductive material layer. The second arm has a second cross-sectional area in the plane perpendicular to the head mounting surface. The second cross-sectional area has a second centroid. The second centroid is not offset from the first centroid by more than 10 microns in a direction perpendicular to the head mounting surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to disk drives, and more particularly, to flexures for supporting a head in a disk drive.

2. Description of the Related Art

Disk drives (e.g., magnetic disk drives) utilize a rotating media surface and a head that is suspended above the rotating media surface. The head typically includes a slider (e.g., comprising a ceramic material), one or more transducers (e.g., read transducer, write transducer), and heater elements. The slider comprises a surface facing the rotating media surface and serving as an air bearing to suspend the head above the rotating media surface. The head is attached to a flexure that helps position and move the head from track to track across the rotating media surface. The flexure provides flexibility for pitch and roll motion of the head relative to the rotating media surface.

Flexures typically have a composite or laminate structure with a thin structural layer (e.g., stainless steel), an electrically insulating layer, and patterned electrical leads formed thereon. The flexure is designed to have high lateral stiffness but sufficiently low pitch and roll stiffnesses so that the head can pitch and roll in response to undulations of the rotating media surface without excessive torques acting upon the air bearing. Lower and lower pitch and roll stiffnesses of the flexure are desirable as slider dimensions and fly heights are reduced.

Previous attempts to lower the pitch and roll stiffnesses of the flexure have included: (1) using outboard traces and making the copper traces more flexible to reduce the copper trace stiffness contribution to the total stiffness of the flexure; (2) forming curved traces to reduce the copper trace stiffness contribution; and (3) reducing the thickness of the flexure by using thinner layers (e.g., stainless steel thinner than 15 microns). However these techniques have significant disadvantages. For example, outboard traces may be more easily damaged during head gimbal assembly (HGA) or head stack assembly (HSA) processes. Curved traces can reduce maximum data bandwidth. Thinner flexures may be more prone to damage through ultrasonic cleaning processes, introducing yield problems at both the suspension component level and at the HGA level. Therefore, there is a need in the art for an improved way to reduce the pitch and/or roll stiffnesses of a flexure supporting a head in a disk drive.

SUMMARY OF THE INVENTION

A flexure for supporting a head in a disk drive comprises a tongue including a head mounting surface for attaching the head. The flexure further comprises a first arm on a first side of the tongue. The first arm comprises a structural material and has a first cross-sectional area in a plane perpendicular to the head mounting surface. The first cross-sectional area has a first centroid. The flexure further comprises a second arm on the first side of the tongue. The second arm comprises a conductive material layer. The second arm has a second cross-sectional area in the plane perpendicular to the head mounting surface. The second cross-sectional area has a second centroid. The second centroid is not offset from the first centroid by more than 10 microns in a direction perpendicular to the head mounting surface.

A method of forming a flexure for supporting a head in a disk drive comprises providing a flexure. The flexure comprises a tongue including a head mounting surface for attaching the head. The flexure further comprises a first arm on a first side of the tongue. The first arm comprises a structural material and having a first cross-sectional area in a plane perpendicular to the head mounting surface. The first cross-sectional area has a first centroid. The flexure further comprises a second arm on the first side of the tongue. The second arm comprises a conductive material layer. The second arm has a second cross-sectional area in the plane perpendicular to the head mounting surface. The second cross-sectional area has a second centroid. The second centroid is offset from the first centroid by more than 10 microns in a direction perpendicular to the head mounting surface. The method further comprises plastically deforming at least one of the first arm and the second arm. The second centroid is not offset from the first centroid by more than 10 microns in a direction perpendicular to the head mounting surface.

A method of forming a flexure for supporting a head in a disk drive comprises providing a substrate. The method further comprises forming a first layer over a first portion of the substrate. The first layer comprises a structural material. The method further comprises forming a second layer over a second portion of the substrate laterally spaced from the first portion of the substrate. The second layer comprises an electrically conductive material. The method further comprises removing the substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1Aschematically illustrates an example flexure10for supporting a head in a disk drive in accordance with certain embodiments described herein. The flexure10comprises a tongue20including a head mounting surface22for attaching the head (not shown). The flexure10further comprises a first arm30on a first side of the tongue20. The first arm30comprises a structural material and has a first cross-sectional area with a first centroid34. The flexure10further comprises a second arm40on the first side of the tongue20. The second arm40comprises a conductive material layer44. The second arm40has a second cross-sectional area with a second centroid46. The second centroid46is not offset from the first centroid34by more than 10 microns in a direction perpendicular to the head mounting surface22of the tongue20.FIG. 1Bschematically illustrates a cross-sectional view of a portion of the first arm30and a portion of the second arm40of the example flexure10ofFIG. 1A, andFIG. 1Cschematically illustrates a cross-sectional view of a portion of a third arm50and a fourth arm60of the example flexure10ofFIG. 1A.FIGS. 2A-2C,3A-3C, and4A-4C schematically illustrate other example flexures10compatible with certain embodiments described herein.

In certain embodiments, the tongue20comprises a structural material (e.g., stainless steel) and is an integral portion of the flexure10. In certain embodiments, the tongue20has a generally elongate shape and extends along a longitudinal axis24of the flexure10, as schematically illustrated byFIG. 1A. For example, in certain embodiments, the tongue20has a lateral width generally perpendicular to the longitudinal axis24that is in a range between about 0.5 millimeters and about 1.5 millimeters and has a lateral length generally along the longitudinal axis24that is up to about 2.5 millimeters. The head mounting surface22is generally planar, and defines a direction generally perpendicular or normal to the head mounting surface22. In certain embodiments, the head mounting surface22is substantially flat, while in certain other embodiments, the head mounting surface22has one or more recesses, protrusions, holes, extensions, or other structural elements configured to facilitate mounting of the head to the head mounting surface22. In certain embodiments, the tongue20has a thickness between about 10 microns and about 25 microns.

In certain embodiments, the structural material of the first arm30comprises steel (e.g., stainless steel), while in certain other embodiments, other structural materials (e.g., metals, various ceramics, etc.) may be used. The first arm30of certain embodiments has a generally elongate shape and extends along a first side of the tongue20, as schematically illustrated byFIG. 1A. In certain embodiments, the first arm30is substantially straight while in other embodiments, the first arm30is curved or has one or more angles along its length. For example, as schematically illustrated inFIG. 1A, the first arm30has a curve or non-zero angle at a region32along the length of the first arm30. In certain embodiments, the first arm30is substantially planar, while in other embodiments, the first arm30has two or more portions which are non-planar with one another. As schematically illustrated byFIG. 3A, the first arm30of certain embodiments comprises one or more extensions33(e.g., tabs) that are mechanically coupled to corresponding portions of the second arm40.

In certain embodiments, the first arm30has a generally rectangular first cross-sectional area, as schematically illustrated byFIG. 1B, while other cross-sectional area shapes are also compatible with various embodiments described herein. In certain embodiments, the first cross-sectional area of the first arm30is substantially constant along the length of the first arm30, while in other embodiments, the first cross-sectional area of the first arm30varies along the length of the first arm30. For example, the width of the first arm30can vary along the length of the first arm30, as schematically illustrated byFIG. 1A, or the thickness of the first arm30can vary along the length of the first arm30. The first arm30of certain embodiments has a thickness no less than 10 microns.

The first cross-sectional area of the first arm30in a plane perpendicular to the head mounting surface22has a first centroid34, as schematically illustrated byFIG. 1B. As used herein, the term “first centroid” is used in its broadest sense, including but not limited to, the geometric center of the first cross-sectional area. In certain embodiments, the first centroid is the geometric center of the smallest quadrangle that bounds the first cross-sectional area. In certain embodiments in which the first arm30has a uniform density, the first centroid34of the first cross-sectional area coincides with the center of mass of the first cross-sectional area.

As schematically illustrated byFIGS. 1A-1C,2A-2C,3A-3C, and4A-4C, the second arm40comprises the conductive material layer44and a dielectric material layer42(e.g., a support layer for the conductive material layer44). In certain embodiments, the dielectric material layer42of the second arm40comprises polyimide or Kapton®, while in certain other embodiments, other dielectric materials capable of being etched may be used. In certain embodiments, the dielectric material layer42has a thickness in a range between about 5 microns and about 20 microns.

In certain embodiments, the conductive material layer44of the second arm40comprises copper or aluminum. In certain embodiments, the conductive material layer44further comprises a gold plating layer or a nickel layer that provides improved protection against corrosion of the conductive material layer44. In certain other embodiments, other conductive materials may be used. In certain embodiments, the conductive material layer44has a thickness in a range between about 5 microns and about 20 microns.

In certain embodiments, the conductive material layer44comprises a plurality of electrically conductive conduits47that are substantially isolated from one another and that extend along the length of the second arm40, as schematically illustrated byFIG. 1A. These electrically conductive conduits47each have one or more electrical contacts48on or in proximity to the tongue20and which are configured to be electrically coupled to corresponding electrical contacts of the head when mounted to the head mounting surface22. In certain embodiments, the conductive material layer44comprises three electrically conductive conduits47, as schematically illustrated byFIG. 1A. In certain other embodiments, the conductive material layer44comprises one, two, four, five, six, or other number of electrically conductive conduits47.

In certain other embodiments, the second arm40comprises only the conductive material layer44, as schematically illustrated byFIG. 5A.FIG. 5Bschematically illustrates a second arm40comprising the conductive material layer44and a dielectric material layer42. In certain other embodiments, the second arm40comprises the conductive material layer44, a first dielectric material layer42(e.g., serving as a support layer) on a first side of the conductive material layer44, and a second dielectric material layer70(e.g., serving as a cover layer) on a second side of the conductive material layer44, as schematically illustrated byFIG. 5C. The second dielectric material layer70of certain such embodiments comprises a polymer (e.g., polyimide) and has a thickness in a range between about 3 microns and about 20 microns. In still other certain embodiments, the second arm40comprises the conductive material layer44, first and second dielectric material layers42,70(e.g., serving as a support layer and as a cover layer), a second conductive layer72electrically isolated from the conductive material layer44(e.g., serving as a ground plane), and a third dielectric material layer74(e.g., serving as a cover layer for the second conductive layer72). The second conductive layer72of certain such embodiments comprises copper and has a thickness in a range between about 0.5 micron and about 5 microns. The third dielectric material layer74of certain such embodiments comprises a polymer (e.g., polyimide) and has a thickness in a range between about 1 micron and about 10 microns.

The second arm40of certain embodiments has a generally elongate shape and extends along the first side of the tongue20, as schematically illustrated byFIG. 1A. In certain embodiments, the second arm40is substantially straight while in other embodiments, the second arm40is curved or has one or more angles along its length. In certain embodiments, the second arm40is substantially planar, while in other embodiments, the second arm40has two or more portions which are non-planar with one another. In certain embodiments, the second arm40is substantially parallel to the first arm30.

In certain embodiments, the second arm40has a generally rectangular second cross-sectional area, as schematically illustrated byFIG. 1B, while other cross-sectional area shapes are also compatible with various embodiments described herein. In certain embodiments, the second cross-sectional area of the second arm40is substantially constant along the length of the second arm40, while in other embodiments, the second cross-sectional area of the second arm40varies along the length of the second arm40. For example, the width of the second arm40can vary along the length of the second arm40, or the thickness of the second arm40can vary along the length of the second arm40. In certain embodiments in which the second arm40comprises only the conductive material layer44, the second arm40has a thickness of no less than 5 microns. In certain embodiments in which the second arm40comprises the conductive material layer44and the dielectric material layer42, the second arm40has a thickness of no less than 10 microns.

The second cross-sectional area of the second arm40in a plane perpendicular to the head mounting surface22has a second centroid46, as schematically illustrated byFIG. 1B. As used herein, the term “second centroid” is used in its broadest sense, including but not limited to, the geometric center of the second cross-sectional area. In certain embodiments, the second centroid is the geometric center of the smallest quadrangle that bounds the second cross-sectional area. For example, as schematically illustrated byFIG. 1B, the second centroid46is the geometric center of a rectangle which bounds the second cross-sectional area. In certain embodiments in which the second arm40has a uniform density, the second centroid46of the second cross-sectional area coincides with the center of mass of the second cross-sectional area.

In certain embodiments, as schematically illustrated byFIG. 1A, the first arm30is closer to the tongue20than is the second arm40, and the first arm30and the second arm40do not cross or overlap one another. In certain embodiments, the first arm30is closer to the tongue20than is the second arm40, and the first arm30and the second arm40cross at one or more regions49, as schematically illustrated byFIG. 2A. In certain embodiments, as schematically illustrated byFIG. 4A, the first arm30is farther from the tongue20than is the second arm40and the first arm30and the second arm40do not cross or overlap one another. In certain embodiments, the first arm30is farther from the tongue20than is the second arm40, and the first arm30and the second arm40cross at one or more regions49, as schematically illustrated byFIG. 3A.

As schematically illustrated byFIG. 1B, in certain embodiments, the first centroid34of the first cross-sectional area of the first arm30is substantially aligned with the second centroid46of the second cross-sectional area of the second arm40. In certain embodiments, the second centroid46is not offset by more than 10 microns from the first centroid34in a direction perpendicular to the head mounting surface22. In certain other embodiments, the second centroid46is not offset by more than 6 microns from the first centroid34in a direction perpendicular to the head mounting surface22. In still other embodiments, the second centroid46is not offset by more than 3 microns from the first centroid34in a direction perpendicular to the head mounting surface22.

In certain embodiments, the flexure10further comprises a third arm50on a second side of the tongue20and a fourth arm60on the second side of the tongue20, as schematically illustrated byFIG. 1A. In certain embodiments, the third arm50has a third cross-sectional area in a plane perpendicular to the head mounting surface22and the fourth arm60has a fourth cross-sectional area in a plane perpendicular to the head mounting surface22.

In certain embodiments, the structural material of the third arm50comprises steel (e.g., stainless steel), while in certain other embodiments, other structural materials (e.g., metals, various ceramics, etc.) may be used. The third arm50of certain embodiments has a generally elongate shape and extends along a second side of the tongue20, as schematically illustrated byFIG. 1A. In certain embodiments, the third arm50is substantially straight while in other embodiments, the third arm50is curved or has one or more angles along its length. For example, as schematically illustrated inFIG. 1A, the third arm50has a curve or non-zero angle at a point52along the length of the third arm50. In certain embodiments, the third arm50is substantially planar, while in other embodiments, the third arm50has two or more portions which are non-planar with one another. As schematically illustrated byFIG. 3A, the third arm50of certain embodiments comprises one or more extensions53(e.g., tabs) that are mechanically coupled to corresponding portions of the fourth arm60.

In certain embodiments, the third arm50has a generally rectangular third cross-sectional area, as schematically illustrated byFIG. 1C, while other cross-sectional area shapes are also compatible with various embodiments described herein. In certain embodiments, the third cross-sectional area of the third arm50is substantially constant along the length of the third arm50, while in other embodiments, the third cross-sectional area of the third arm50varies along the length of the third arm50. For example, the width of the third arm50can vary along the length of the third arm50, as schematically illustrated byFIG. 1A, or the thickness of the third arm50can vary along the length of the third arm50. The third arm50of certain embodiments has a thickness no less than 10 microns.

The third cross-sectional area of the third arm50in a plane perpendicular to the head mounting surface22has a third centroid54, as schematically illustrated byFIG. 1C. As used herein, the term “third centroid” is used in its broadest sense, including but not limited to, the geometric center of the third cross-sectional area. In certain embodiments, the third centroid is the geometric center of the smallest quadrangle that bounds the third cross-sectional area. In certain embodiments in which the third arm50has a uniform density, the third centroid54of the third cross-sectional area coincides with the center of mass of the third cross-sectional area.

In certain embodiments, the fourth arm60comprises a dielectric material layer62and a conductive material layer64. In certain embodiments, the dielectric material layer62of the fourth arm60comprises polyimide or Kapton®, while in certain other embodiments, other dielectric materials capable of being etched may be used. In certain embodiments, the dielectric material layer62has a thickness in a range between about microns and about 20 microns.

In certain embodiments, the conductive material layer64of the fourth arm60comprises copper or aluminum. In certain embodiments, the conductive material layer64further comprises a gold plating layer or a nickel layer that provides improved protection against corrosion of the conductive material layer64. In certain other embodiments, other conductive materials may be used. In certain embodiments, the conductive material layer64has a thickness in a range between about 5 microns and about 20 microns.

In certain embodiments, the conductive material layer64comprises a plurality of electrically conductive conduits67that are substantially isolated from one another and that extend along the length of the fourth arm60, as schematically illustrated byFIG. 1A. These electrically conductive conduits67each have one or more electrical contacts68on or in proximity to the tongue20and which are configured to be electrically coupled to corresponding electrical contacts of the head when mounted to the head mounting surface22. In certain embodiments, the conductive material layer64comprises three electrically conductive conduits67, as schematically illustrated byFIG. 1A. In certain other embodiments, the conductive material layer64comprises one, two, four, five, six, or other number of electrically conductive conduits67.

In certain other embodiments, the fourth arm60comprises (i) only the conductive material layer64, (ii) the conductive material layer64and a dielectric material layer62, (iii) the conductive material layer64, a first dielectric material layer62(e.g., serving as a support layer) on a first side of the conductive material layer64, and a second dielectric material layer (e.g., serving as a cover layer) on a second side of the conductive material layer44, or (iv) the conductive material layer64, first and second dielectric material layers (e.g., serving as a support layer and as a cover layer), a second conductive layer electrically isolated from the conductive material layer64(e.g., serving as a ground plane), and a third dielectric material layer (e.g., serving as a cover layer for the second conductive layer). The second dielectric material layer of certain embodiments comprises a polymer (e.g., polyimide) and has a thickness in a range between about 3 microns and about 20 microns. The second conductive layer of certain embodiments comprises copper and has a thickness in a range between about 0.5 micron and about 5 microns. The third dielectric material layer of certain embodiments comprises a polymer (e.g., polyimide) and has a thickness in a range between about 1 micron and about 10 microns.

The fourth arm60of certain embodiments has a generally elongate shape and extends along the second side of the tongue20, as schematically illustrated byFIG. 1A. In certain embodiments, the fourth arm60is substantially straight while in other embodiments, the fourth arm60is curved or has one or more angles along its length. In certain embodiments, the fourth arm60is substantially planar, while in other embodiments, the fourth arm60has two or more portions which are non-planar with one another. In certain embodiments, the fourth arm60is substantially parallel to the third arm50.

In certain embodiments, the fourth arm60has a generally rectangular fourth cross-sectional area, as schematically illustrated byFIG. 1C, while other cross-sectional area shapes are also compatible with various embodiments described herein. In certain embodiments, the fourth cross-sectional area of the fourth arm60is substantially constant along the length of the fourth arm60, while in other embodiments, the fourth cross-sectional area of the fourth arm60varies along the length of the fourth arm60. For example, the width of the fourth arm60can vary along the length of the fourth arm60, or the thickness of the fourth arm60can vary along the length of the fourth arm60. In certain embodiments in which the fourth arm60comprises only the conductive material layer64, the fourth arm60has a thickness of no less than 5 microns. In certain embodiments in which the fourth arm60comprises the conductive material layer64and the dielectric material layer62, the fourth arm60has a thickness no less than 10 microns.

The fourth cross-sectional area of the fourth arm60in a plane perpendicular to the head mounting surface22has a fourth centroid66, as schematically illustrated byFIG. 1C. As used herein, the term “fourth centroid” is used in its broadest sense, including but not limited to, the geometric center of the fourth cross-sectional area. In certain embodiments, the fourth centroid is the geometric center of the smallest quadrangle that bounds the fourth cross-sectional area. For example, as schematically illustrated byFIG. 1C, the fourth centroid66is the geometric center of a rectangle which bounds the fourth cross-sectional area. In certain embodiments in which the fourth arm60has a uniform density, the fourth centroid66of the fourth cross-sectional area coincides with the center of mass of the fourth cross-sectional area.

In certain embodiments, as schematically illustrated byFIG. 1A, the third arm50is closer to the tongue20than is the fourth arm60, and the third arm50and the fourth arm60do not cross or overlap one another. In certain embodiments, the third arm50is closer to the tongue20than is the fourth arm60, and the third arm50and the fourth arm60cross at one or more regions69, as schematically illustrated byFIG. 2A. In certain embodiments, as schematically illustrated byFIG. 4A, the third arm50is farther from the tongue20than is the fourth arm60and the third arm50and the fourth arm60do not cross or overlap one another. In certain embodiments, the third arm50is farther from the tongue20than is the fourth arm60, and the third arm50and the fourth arm60cross at one or more regions69, as schematically illustrated byFIG. 3A.

As schematically illustrated byFIG. 1C, in certain embodiments, the third centroid54of the third cross-sectional area of the third arm50is substantially aligned with the fourth centroid66of the fourth cross-sectional area of the fourth arm60. In certain embodiments, the fourth centroid66is not offset by more than 10 microns from the third centroid54in a direction perpendicular to the head mounting surface22. In certain other embodiments, the fourth centroid66is not offset by more than 6 microns from the third centroid54in a direction perpendicular to the head mounting surface22. In still other embodiments, the fourth centroid66is not offset by more than 3 microns from the third centroid54in a direction perpendicular to the head mounting surface22.

In certain embodiments, the first centroid34, the second centroid46, the third centroid54, and the fourth centroid66are substantially aligned with one another. For example, in certain embodiments, the first centroid34, the second centroid46, the third centroid54, and the fourth centroid66are not offset by more than 10 microns from one another in a direction perpendicular to the head mounting surface22. In certain other embodiments, the first centroid34, the second centroid46, the third centroid54, and the fourth centroid66are not offset by more than 6 microns from one another in a direction perpendicular to the head mounting surface22. In still other embodiments, the first centroid34, the second centroid46, the third centroid54, and the fourth centroid66are not offset by more than 3 microns from one another in a direction perpendicular to the head mounting surface.

FIGS. 6A-6Eschematically illustrate cross-sectional views of a sequence of structures produced during the fabrication of a conventional flexure. As schematically illustrated byFIG. 6A, a first layer80comprising a structural material (e.g., stainless steel) is provided. As schematically illustrated byFIG. 6B, a second layer90comprising an electrically insulating material (e.g., polyimide) is formed on the first layer80. As schematically illustrated byFIG. 6C, a third layer100comprising an electrically conductive material (e.g., copper) is formed on the second layer90and is patterned to form electrical conduits47. As schematically illustrated byFIG. 6D, a portion of the first layer80is removed (e.g., etched) from below the second layer90, thereby forming the first arm30and the second arm40. As schematically illustrated byFIG. 6E, the first centroid34of the first arm30and the second centroid46of the second arm40are substantially offset (e.g., by more than 10 microns) from one another along a direction substantially perpendicular to the head mounting surface22.

FIGS. 7A-7Fschematically illustrate cross-sectional views of a sequence of structures produced during the fabrication of a flexure10in accordance with certain embodiments described herein. As schematically illustrated byFIG. 7A, a substrate110is provided, and a first layer120comprising a structural material (e.g., stainless steel) is formed over a first portion of the substrate110and a second layer130comprising an electrically insulating material (e.g., polyimide) is formed over a second portion of the substrate110laterally spaced from the first portion of the substrate110.

As schematically illustrated byFIGS. 7A and 7B, in certain embodiments, the first layer120is formed over the first and second portions of the substrate110and the structural material is removed (e.g., by etching) from the second portion of the substrate110. As schematically illustrated byFIG. 7C, the second layer130is formed over the second portion of the substrate110. In certain other embodiments, the second layer130is formed over the first and second portions of the substrate110, the electrically insulating material is removed (e.g., by etching) from the first portion of the substrate110, and the first layer120is formed on the first portion of the substrate110.

As schematically illustrated byFIG. 7D, a third layer140comprising an electrically conductive material (e.g., copper) is formed over the second layer130and is patterned to form electrical conduits47. In certain embodiments in which the second arm40comprises an electrically conductive material and an electrically insulating material, forming the third layer140comprises depositing the electrically conductive material over the first portion of the substrate110and the second portion of the substrate110, and removing the electrically conductive material from the first portion of the substrate110. In certain such embodiments, removing the electrically conductive material from the first portion of the substrate110comprises etching the electrically conductive material. In certain embodiments in which the second arm40comprises only the electrically conductive material, the electrically conductive material of the third layer140is deposited over the substrate110without an intervening layer of electrically insulating material.

As schematically illustrated byFIG. 7E, the substrate110is removed (e.g., by etching or by peeling away), thereby forming the first arm30and the second arm40. In certain embodiments in which the substrate110is etched from the first arm30and the second arm40, the substrate110comprises an etchable material (e.g., ceramic, silicon). In certain other embodiments in which the substrate110is peeled away from the first arm30and the second arm40, the substrate110comprises a suitable material (e.g., stainless steel). Other process steps and sequences of process steps are also compatible with various embodiments described herein. As schematically illustrated byFIG. 7F, the first centroid34of the first arm30and the second centroid46of the second arm40are not offset from one another by more than a predetermined distance (e.g., 10 microns) along a direction substantially perpendicular to the head mounting surface22.

In certain embodiments, the flexure10is formed by deforming one or more portions of a flexure fabricated using a conventional process. Using a conventional process (e.g., the process schematically illustrated byFIGS. 6A-6E), a flexure10to be deformed is provided. The flexure10is placed on a first portion of a forming tool (not shown), and is plastically deformed by pressing a second portion of the forming tool against the first portion of the forming tool such that the flexure10is sandwiched between the first and second portions of the forming tool. In certain embodiments, the flexure10is held in place at two positions along an arm to be plastically deformed, and the portion of the arm between the two positions is pressed so as to plastically deform the arm.

In certain embodiments, at least one of the first arm30and the second arm40is deformed such that the second centroid46is not offset from the first centroid34by more than 10 microns in a direction perpendicular to the head mounting surface. In certain embodiments, at least one of the third arm50and the fourth arm60is deformed such that the fourth centroid66is not offset from the third centroid54by more than 10 microns in a direction perpendicular to the head mounting surface, by more than 6 microns in a direction perpendicular to the head mounting surface, or by more than 3 microns in a direction perpendicular to the head mounting surface.FIGS. 8A-8Cschematically illustrate an example flexure10fabricated by plastically deforming the second arm40and the fourth arm60such that a portion of the second arm40and a portion of the fourth arm60between the lines200are displaced by a predetermined amount (e.g., by about 0.02 millimeters) in a direction substantially perpendicular to the head mounting surface22.FIG. 8Aschematically illustrates the flexure10from a direction substantially perpendicular to the head mounting surface22.FIG. 8Bschematically illustrates a cross-sectional view of a portion of the flexure10that is not displaced by the deformation process andFIG. 8Cschematically illustrates a cross-sectional view of a portion of the flexure10that is displaced by the deformation process.

In the portion of the flexure10that is not displaced, the centroids of the first arm30and the second arm40in a plane substantially perpendicular to the head mounting surface22are substantially offset from one another in a direction substantially perpendicular to the head mounting surface22, and the centroids of the third arm50and the fourth arm60in a plane substantially perpendicular to the head mounting surface22are substantially offset from one another in a direction substantially perpendicular to the head mounting surface22. In the displaced portion of the flexure10, the centroids of the first arm30and the second arm40in a plane substantially perpendicular to the head mounting surface22are not offset from one another by more than 10 microns in a direction substantially perpendicular to the head mounting surface22, by more than 6 microns in a direction perpendicular to the head mounting surface, or by more than 3 microns in a direction perpendicular to the head mounting surface, and the centroids of the third arm50and the fourth arm60in a plane substantially perpendicular to the head mounting surface22are not offset from one another by more than 10 microns in a direction substantially perpendicular to the head mounting surface22, by more than 6 microns in a direction perpendicular to the head mounting surface, or by more than 3 microns in a direction perpendicular to the head mounting surface. In an exemplary embodiment, the deformation process reduces the pitch stiffness of the flexure10by about 35% (e.g., from 0.539 micronewton-meter per degree to 0.350 micronewton-meter per degree) and does not appreciably reduce the roll stiffness of the flexure10(e.g., from 0.564 micronewton-meter per degree to 0.562 micronewton-meter per degree).

FIGS. 9A-9Cschematically illustrate an example flexure10in which the first arm30comprises one or more (e.g., two) extensions33extending generally toward the second arm40and mechanically coupled to corresponding portions of the second arm40and in which the third arm50comprises one or more (e.g., two) extensions53extending generally toward the fourth arm60and mechanically coupled to corresponding portions of the fourth arm60. In certain embodiments, the extensions33,53have a length between about 0.1 millimeter and about 0.3 millimeter, a width between about 0.05 millimeter and about 0.2 millimeter, and a thickness between about 12 microns and about 25 microns.

While the extensions33,53ofFIG. 9Ahave a substantially rectangular shape, other shapes are also compatible with various embodiments described herein. In addition, in certain embodiments, the first arm30comprises a single extension33or more than two extensions33, and the third arm50comprises a single extension53or more than two extensions53.

The flexure10ofFIGS. 9A-9Cis fabricated by plastically deforming the extensions33,53, the second arm40, and the fourth arm60such that a portion of the second arm40and a portion of the fourth arm60between the lines200are displaced by a predetermined amount in a direction substantially perpendicular to the head mounting surface22.FIG. 9Aschematically illustrates the flexure10from a direction substantially perpendicular to the head mounting surface22.FIG. 9Bschematically illustrates a cross-sectional view of a portion of the flexure10that includes the deformed extension33andFIG. 9Cschematically illustrates a cross-sectional view of a portion of the flexure10between the lines200.

In certain embodiments, the deformations are sufficient such that the first centroid34and the second centroid46of the portions of the first arm30and the second arm40between the lines200are not substantially offset from one another in a direction substantially perpendicular to the head mounting surface22. In certain embodiments, the deformations are sufficient such that the third centroid54and the fourth centroid66of the portions of the third arm50and the fourth arm60between the lines200are not substantially offset from one another in a direction substantially perpendicular to the head mounting surface22.

In the example flexures10ofFIGS. 8A-8Cand9A-9C, the first arm30comprises a substantially planar first portion between the lines200and the second arm40comprises a substantially planar second portion between the lines200that is substantially co-planar with the first portion. In certain embodiments, the first portion and the second portion are configured to flex in a flexing direction substantially perpendicular to the first and second arms30,40, and the second portion is substantially co-planar with the first portion in a plane substantially perpendicular to the flexing direction.

In certain embodiments, the second arm40comprises one or more extensions extending generally toward the first arm30and mechanically coupled to the first arm30. In certain embodiments, the first arm30comprises one or more extensions extending generally toward the second arm40, and the second arm40comprises one or more extensions extending generally toward the first arm30. The one or more extensions of the first arm30in certain such embodiments are mechanically coupled to the one or more extensions of the second arm40. In certain embodiments, the fourth arm60comprises one or more extensions extending generally toward the third arm50and mechanically coupled to the third arm50. In certain embodiments, the third arm50comprises one or more extensions extending generally toward the fourth arm60, and the fourth arm60comprises one or more extensions extending generally toward the third arm50. The one or more extensions of the third arm50in certain such embodiments are mechanically coupled to the one or more extensions of the fourth arm60.

Certain embodiments described herein advantageously provide sufficient lateral stiffness with lower flexure stiffness values in selected directions (e.g., pitch stiffness and/or roll stiffness) that are useful for disk drives with increased tracks per inch and storage density. In certain embodiments, the flexure10has a pitch stiffness less than 0.4 micronewton-meter per degree. In certain embodiments, the flexure has a roll stiffness less than 0.4 micronewton-meter per degree.

Pitch movement of the head creates stresses and strains in the first arm30, the second arm40, the third arm50, and the fourth arm60. The reduced pitch stiffness of the flexure10of certain embodiments described herein can be attributed to a shifting of one or both of the neutral axes of the first arm30and the second arm40toward one another and to a shifting of one or both of the neutral axes of the third arm50and the fourth arm60toward one another. The neutral axis of an arm is a line along which the arm experiences neither tension nor compressive stresses upon flexing of the arm in a direction substantially perpendicular to the neutral axis.

The second moment of area of a shape about an axis is a property of the shape that is predictive of its resistance to bending and deflection. The second moment of area of a rectangular structure about the x-axis can be expressed as: Ix=∫y2dA=bh3/12, where Ixis the second moment of area about the x-axis, dA is the elemental area, y is the perpendicular distance to the element dA from the x-axis, b is the width or x-dimension of the rectangle, and h is the height or y-dimension of the rectangle. Thus, the stiffness of an arm having a rectangular cross-sectional area varies as the cube of the height of the arm along the direction of deflection.

The decrease of the pitch stiffness of certain embodiments of the flexure10described herein can be expressed using the parallel axis theorem: Ix=ICG+Ad2, where Ixis the second moment of area with respect to the x-axis, ICGis the second moment of area with respect to an axis parallel to the x-axis and passing through the centroid of the cross-sectional area (which, for shapes having uniform density, corresponds to the center-of-gravity), A is the cross-sectional area, and d is the offset distance between the x-axis and the centroidal axis.

FIG. 10Adepicts a cross-section of a prior art flexure having a first arm30and a second arm40with a substantial offset between the first centroid34and the second centroid46. The total second moment of area of the cross-section of the prior art flexure, about an axis that is parallel to the x-axis and passing through the first centroid34, is: Itotal=I30CG+I40CG+A40d2, where I30CGis the second moment of the cross-sectional area of the first arm30about its own centroid, I40CGis the second moment of the cross-sectional area of the second arm40about its own centroid, A40is the cross-sectional area of the second arm40, and d is the offset distance between the first centroid34and the second centroid46.

In contrast,FIG. 10Bdepicts a cross-section of a flexure according to an embodiment of the present invention, in which there the offset between the first centroid34and the second centroid46is reduced, for example to zero. The total second moment of area of this example cross-section, about an axis that is parallel to the x-axis and passing through the first centroid34is: Itotal=I30CG+I40CG. Thus, eliminating the offset reduces the flexure stiffness by an amount proportional to the square of the offset distance d.