Patent Publication Number: US-8537499-B2

Title: Disk drive suspension having flexure and load beam with insulating space between load beam and conductor of flexure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a Divisional of U.S. application Ser. No. 12/711,370, filed Feb. 24, 2010 now U.S. Pat. No. 8,243,394, which is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2009-053563, filed Mar. 6, 2009, the entire contents of both of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a disk drive flexure used in a hard disk drive (HDD) for an information processing apparatus, such as a personal computer. 
     2. Description of the Related Art 
     A hard disk drive is used in an information processing apparatus, such as a personal computer. The hard disk drive comprises a magnetic disk that rotates around a spindle, a carriage that turns around a pivot, etc. A disk drive suspension is disposed on an arm of the carriage. 
     The disk drive suspension comprises a load beam, a flexure lapped on the load beam, etc. A slider is mounted on a gimbal portion formed near the distal end of the flexure. The slider is provided with elements (transducers) for access, such as reading or writing. The suspension, flexure, etc., constitute a head gimbal assembly. 
     The flexure may be of any of various practical types corresponding to required specifications, and a flexure with conductors is disclosed as one example thereof in Jpn. Pat. Appln. KOKAI Publication No. 2004-133988 (Patent Document 1). The flexure with conductors comprises a metal base, insulating layer formed on the metal base, and conductors formed on the insulating layer. The metal base consists of a thin stainless-steel plate. The insulating layer consists of an electrically insulating material, such as polyimide. The conductors consist of copper. Respective one ends of the conductors are connected to elements (e.g., magnetoresistive [MR] elements) of the slider. The other ends of the conductors are connected to an electronic circuit, such as an amplifier. 
     The impedance of a conductive circuit portion of the flexure is expected to be reduced in order to match the amplifier and slider elements and reduce energy consumption. In laying out the flexure in a narrow space within the disk drive, the thickness and width of the conductive circuit portion should be minimized. 
     The flexure disclosed in Patent Document 1 comprises a conductive circuit portion of a multi-layer type.  FIG. 17  shows an example of the multi-layer conductive circuit portion. In the conductive circuit portion shown in  FIG. 17 , an insulating layer  2  is formed thicknesswise relative to a metal base  1 . A first conductor  3  is formed on the insulating layer  2 . The first conductor  3  is covered by a first cover layer  4  made of an insulating material. A second conductor  5  is formed on the first cover layer  4 . The second conductor  5  is covered by a second cover layer  6  made of an insulating material. 
     In the multi-layer conductive circuit portion shown in  FIG. 17 , the conductors  3  and  5  are located thicknesswise, so that their width W 1  can be made relatively large despite the narrowness of the conductive circuit portion. Thus, the conductive circuit portion has an advantage that its impedance can be reduced. Since the metal base  1 , insulating layer  2 , conductors  3  and  5 , and cover layers  4  and  6  are lapped thicknesswise relative to the conductive circuit portion, however, a thickness H 1  of the circuit portion is inevitably large. 
       FIG. 18  shows a conventional flat-type conductive circuit portion. In this flat circuit portion, first and second conductors  3  and  5  are arranged transversely relative thereto in parallel relation along an insulating layer  2  formed on a metal base  1 . The conductors  3  and  5  are covered by a cover layer  4 . The flat conductive circuit portion has an advantage over the multi-layer version in having a smaller thickness H 2 . Since the pair of conductors  3  and  5  are arranged transversely within the width W 2  of the conductive circuit portion, however, the conductors  3  and  5  cannot be widened. Thus, there is a problem that the inductance and impedance of the conductive circuit portion are high. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a disk drive flexure with excellent electrical properties of which a multi-layer conductive circuit portion can be thinned. 
     A flexure according to the present invention is disposed on a load beam of a disk drive suspension. The flexure comprises a plate-like metal base made of an electrically conductive material, a slit formed between two opposite side portions of the metal base, an insulating layer made of an electrically insulating material, a first conductor formed within the slit, and a second conductor. 
     The slit penetrates the metal base thicknesswise, and extending longitudinally relative to the metal base. The insulating layer is formed on the metal base. The first conductor is laminated to a first surface of the insulating layer on the same side as the metal base, and extending longitudinally relative to the metal base along the slit. The second conductor is laminated to a second surface of the insulating layer on the side opposite from the metal base. The second conductor is facing the first conductor across the insulating layer, and extending longitudinally relative to the metal base along the first conductor. According to the present invention, the first conductor is located within the slit in the metal base, so that the conductive circuit portion can be thinned despite its multi-layer structure. Since the relatively wide first and second conductors are lapped thicknesswise, they can be located within a restricted width of the circuit portion. Thus, the inductance and impedance of the circuit portion can be reduced. Since the slit is formed in the metal base so as to extend along the conductors, moreover, an eddy-current loss of the circuit portion can be reduced to ensure excellent electrical properties. 
     In an aspect of the invention, the first conductor and the metal base consist of a common base material (e.g., stainless-steel plate), and contours of the metal base, the first conductor and the slits are shaped by etching the base material. In another aspect of the invention, the first conductor consists of a conductor material (e.g., copper) different from that of the metal base, the electrical conductivity of the conductor material being higher than that of the metal base. 
     In the present invention, the metal base may be lapped on the load beam so that an insulating space is defined between the first conductor and the load beam. A highly electrically conductive layer of a metal more conductive than the metal base may be formed between the first conductor and the insulating layer. An electrically conductive cover layer of a metal more conductive than the metal base may be formed on at least a part of the outer peripheral surface of the first conductor. An insulating coating of an electrically insulating material may be formed on at least a part of the outer peripheral surface of the first conductor. 
     Additional objects and advantages of the invention will be set forth in 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 may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a perspective view showing an example of a disk drive with suspensions; 
         FIG. 2  is a partial sectional view of the disk drive shown in  FIG. 1 ; 
         FIG. 3  is a plan view of a disk drive suspension with a flexure according to a first embodiment of the invention; 
         FIG. 4  is a partial cross-sectional view of the flexure taken along line F 4 -F 4  of  FIG. 3 ; 
         FIG. 5  is a partial cross-sectional view of the flexure taken along line F 5 -F 5  of  FIG. 3 ; 
         FIG. 6  is a partial sectional view of a flexure according to a second embodiment of the invention; 
         FIG. 7  is a partial sectional view of a flexure according to a third embodiment of the invention; 
         FIG. 8  is a partial sectional view of a flexure according to a fourth embodiment of the invention; 
         FIG. 9  is a partial sectional view of a flexure according to a fifth embodiment of the invention; 
         FIG. 10  is a partial sectional view of a flexure according to a sixth embodiment of the invention; 
         FIG. 11  is a partial sectional view of a flexure according to a seventh embodiment of the invention; 
         FIG. 12  is a partial sectional view of a flexure according to an eighth embodiment of the invention; 
         FIG. 13  is a partial sectional view of a flexure according to a ninth embodiment of the invention; 
         FIG. 14  is a partial sectional view of a flexure according to a tenth embodiment of the invention; 
         FIG. 15  is a partial sectional view of a flexure according to an eleventh embodiment of the invention; 
         FIG. 16  is a partial sectional view of a flexure according to a twelfth embodiment of the invention; 
         FIG. 17  is a partial sectional view of a conventional flexure; and 
         FIG. 18  is a partial sectional view of another conventional flexure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A disk drive flexure according to a first embodiment of the present invention will now be described with reference to  FIGS. 1 to 5 . 
     A hard disk drive (HDD)  10  shown in  FIG. 1  comprises a case  11 , disk  13 , carriage  15 , positioning motor  16 , etc. The disk  13  rotates around a spindle  12 . The carriage  15  is turnable around a pivot  14 . The positioning motor  16  serves to drive the carriage  15 . The case  11  is covered by a lid (not shown). 
       FIG. 2  is a sectional view typically showing a part of the disk drive  10 . As shown in  FIG. 2 , arms  17  are disposed on the carriage  15 . A suspension  20  is mounted on a distal end portion of each arm  17 . A slider  21  constituting a magnetic head is disposed on the distal end of the suspension  20 . If the disk  13  rotates at high speed, an air bearing is formed between the disk  13  and slider  21 . 
     If the carriage  15  is turned by the positioning motor  16 , the suspension  20  moves radially relative to the disk  13 . Thereupon, the slider  21  moves to a desired track of the disk  13 . A head portion of the slider  21  is provided with elements, such as MR elements, which can convert electrical and magnetic signals. The disk  13  can be accessed for writing or reading by these elements. 
       FIG. 3  shows the suspension  20  according to the first embodiment of the invention. The suspension  20  comprises a baseplate  30 , load beam  31 , hinge member  32  made of a thin spring plate, flexure  40  with conductors, etc. The flexure  40  with conductors will hereinafter be referred to simply as the flexure. A boss portion  30   a  of the baseplate  30  is fixed to the arms  17  (shown in  FIGS. 1 and 2 ) of the carriage  15 . 
     As shown in  FIG. 3 , the flexure  40  is located along the load beam  31 . A portion  40   a  of the flexure  40  that overlaps the load beam  31  is fixed to the load beam  31  by fixing means, such as laser welding. A tongue  41  that functions as a gimbal portion is formed near the distal end of the flexure  40 . The slider  21  is mounted on the tongue  41 . A rear portion (tail portion)  40   b  of the flexure  40  extends behind the baseplate  30 . 
       FIG. 4  is a partial sectional view of the flexure  40  taken along line F 4 -F 4  of  FIG. 3 . The flexure  40  includes a metal base  50  and conductive circuit portion  51  formed along the metal base  50 . In  FIG. 4 , arrow A indicates the thickness direction of the metal base  50 . In  FIG. 3 , arrows B and C indicate the longitudinal and transverse directions, respectively, of the metal base  50 . 
     A slit  52  is formed between opposite side portions  50   a  and  50   b  ( FIG. 3 ) of the metal base  50 . The slit  52  extends longitudinally relative to the metal base  50 . As shown in  FIG. 4 , the slit  52  penetrates the metal base  50  thicknesswise. 
     The conductive circuit portion  51  includes an insulating layer  54  formed on the metal base  50 , first and second conductors  55  and  56 , and cover layer  57  that covers the second conductor  56 . The insulating layer  54  and cover layer  57  consist of an electrically insulating material, such as polyimide. The first conductor  55  may be covered by an insulating cover layer. The pair of conductors  55  and  56  shown in  FIG. 4  are used for writing. The flexure  40  may be provided with a pair of conductors  58  for reading (typically shown in  FIG. 3 ). 
     The metal base  50  consists of an electrically conductive base material  60 . The base material  60  is a springy stainless-steel plate, such as SUS304. The chemical composition (weight %) of SUS304, as defined by JIS (Japanese Industrial Standard) G4303, is as follows: 0.08 w % or less of C, 1.00 w % or less of Si, 2.00 w % or less of Mn, 0.045 w % or less of P, 0.030 w % or less of S, 8.00 to 10.50 w % of Ni, 18.00 to 20.00 w % of Cr, and the balance of Fe. The metal base  50  or base material  60  is thinner than the load beam  31 . The thickness of the metal base  50  ranges, for example, from 15 to 20 μm. The thickness of the load beam  31  ranges, for example, from 30 to 62 μm. An example of the thickness of the conductors  55  and  56  is 10 μm. An example of the thickness of the insulating layer  54  is also 10 μm. 
     The first and second conductors  55  and  56  extend along the opposite side portions  50   a  and  50   b , respectively, of the metal base  50 . These conductors  55  and  56  are individually continuous longitudinally relative to the metal base  50 . Respective one ends of the conductors  55  and  56  are connected to the elements (not shown) of the slider  21 . The other ends of the conductors  55  and  56  are connected to an amplifier (not shown) of the disk drive  10 . 
     The first conductor  55  is located within the slit  52 . The first conductor  55  is laminated to a first surface  54   a  of the insulating layer  54 . The first surface  54   a  is that one of the opposite surfaces of the insulating layer  54  on which the metal base  50  is located. The first conductor  55  extends longitudinally relative to the metal base  50  along the slit  52 . 
     The second conductor  56  is laminated to a second surface  54   b  of the insulating layer  54 . The second surface  54   b  is the other surface of the insulating layer  54  opposite from the metal base  50 . The first and second conductors  55  and  56  face each other with the insulating layer  54  between them. The second conductor  56  extends longitudinally relative to the metal base  50  along the first conductor  55 . The second conductor  56  consists of a highly conductive metal, such as deposited copper. The second conductor  56  is formed into a predetermined pattern along the insulating layer  54  by etching. 
     In the present embodiment, the metal base  50  and first conductor  55  consist of the common metallic base material  60 . An example of the base material  60  is a stainless-steel plate, such as SUS304. The respective contours of the metal base  50 , slit  52 , and first conductor  55  are shaped as specified by etching the base material  60 . Since the metal base  50  and first conductor  55  are equal in thickness, the first conductor  55  can be prevented from projecting outside the slit  52 . 
       FIG. 5  shows a portion  40   a  at which the flexure  40  and load beam  31  overlap each other. The portion  40   a  is fixedly superposed on the load beam  31 . The first conductor  55  is made thinner than the metal base  50  by half-etching or some other processing. Since the first conductor  55  is thinner than the metal base  50 , an insulating space G for electrical insulation is defined between the first conductor  55  and load beam  31 . 
     According to the conductive circuit portion  51  of the flexure  40  of the present embodiment, the first conductor  55  is confined within the slit  52  formed in the metal base  50 . The second conductor  56  is located thicknesswise relative to the first conductor  55 . Specifically, the first and second conductors  55  and  56  are lapped thicknesswise to form the multi-layer conductive circuit portion  51 . Although the circuit portion  51  of the present embodiment has a multi-layer structure, its thickness H ( FIG. 4 ) can be made smaller than that of the conventional multi-layer conductive circuit portion. 
     Since the first and second conductors  55  and  56  are lapped thicknesswise, moreover, their width W ( FIG. 4 ) can be made relatively large despite the narrowness of the conductive circuit portion  51 . Thus, the inductance and impedance of the circuit portion  51  can be reduced. Since the slit  52  is formed in the metal base  50  so as to extend along the conductors  55  and  56 , furthermore, an eddy-current loss of the circuit portion  51  can be reduced. The higher the frequencies of transmitted signals, the higher the eddy-current loss is. Since the eddy-current loss of the circuit portion  51  can be reduced, therefore, a high-frequency band can be obtained, so that the signals can be transmitted at higher speed. 
       FIG. 6  is a partial sectional view of a flexure  40  according to a second embodiment of the invention. A recess  70  is formed opposite a first conductor  55  of a load beam  31 . The recess  70  is formed by reducing the thickness of a part of the load beam  31  by half-etching or some other processing. The recess  70  defines an insulating space G for electrical insulation between the first conductor  55  and load beam  31 . Since other configurations, functions, and effects of this second embodiment are the same as those of the flexure  40  of the first embodiment, common numbers are used to designate portions common to these two embodiments, and a description of those portions is omitted. 
       FIG. 7  is a partial sectional view of a flexure  40  according to a third embodiment of the invention. An opening  71  is formed opposite a first conductor  55  of a load beam  31 . The opening  71  penetrates the load beam  31  thicknesswise. The opening  71  defines an insulating space for electrical insulation between the first conductor  55  and load beam  31 . Since other configurations, functions, and effects of this third embodiment are the same as those of the flexure  40  of the first embodiment, common numbers are used to designate portions common to these two embodiments, and a description of those portions is omitted. 
       FIG. 8  is a partial sectional view of a flexure  40  according to a fourth embodiment of the invention. A first conductor  55  and metal base  50  consist of a common base material  60 . An example of the base material  60  is a stainless-steel plate. A highly conductive layer  80  is formed between a first conductor  55  and insulating layer  54 . The conductive layer  80  consists of a material (e.g., deposited copper) that is more conductive than the base material  60 . The conductivity of the first conductor  55  is increased by the conductive layer  80 . Since other configurations, functions, and effects of this fourth embodiment are the same as those of the flexure  40  of the first embodiment, common numbers are used to designate portions common to these two embodiments, and a description of those portions is omitted. 
       FIG. 9  is a partial sectional view of a flexure  40  according to a fifth embodiment of the invention. A first conductor  55  and metal base  50  consist of a common base material  60 . An example of the base material  60  is a stainless-steel plate. A conductive cover layer  90  is formed on the outer peripheral surface of the first conductor  55  by, for example, plating. The conductive cover layer  90  consists of a metal (e.g., copper) that is more conductive than the base material  60 . The conductivity of the first conductor  55  is increased by the conductive cover layer  90 . Since other configurations, functions, and effects of this fifth embodiment are the same as those of the flexure  40  of the first embodiment, common numbers are used to designate portions common to these two embodiments, and a description of those portions is omitted. 
       FIG. 10  is a partial sectional view of a flexure  40  according to a sixth embodiment of the invention. A first conductor  55  and metal base  50  consist of a common base material  60 . An example of the base material  60  is a stainless-steel plate. A conductive cover layer  90  is formed on a part of the outer peripheral surface of the first conductor  55  by, for example, plating. The conductive cover layer  90  consists of a metal (e.g., copper) that is more conductive than the base material  60 . The conductivity of the first conductor  55  is increased by the conductive cover layer  90 . Since other configurations, functions, and effects of this sixth embodiment are the same as those of the flexure  40  of the first embodiment, common numbers are used to designate portions common to these two embodiments, and a description of those portions is omitted. 
       FIG. 11  is a partial sectional view of a flexure  40  according to a seventh embodiment of the invention. A first conductor  55  and metal base  50  consist of a common base material  60 . An example of the base material  60  is a stainless-steel plate. Conductive cover layers  90  are formed individually on two opposite side surfaces of the first conductor  55  by, for example, partial plating. The conductive cover layers  90  consist of a metal (e.g., copper) that is more conductive than the base material  60 . The conductivity of the first conductor  55  is increased by the cover layers  90 . Since other configurations, functions, and effects of this seventh embodiment are the same as those of the flexure  40  of the first embodiment, common numbers are used to designate portions common to these two embodiments, and a description of those portions is omitted. 
       FIG. 12  is a partial sectional view of a flexure  40  according to an eighth embodiment of the invention. This flexure  40 , like those of the foregoing embodiments, comprises first and second conductors  55  and  56 . The first conductor  55  is located on a first surface  54   a  of an insulating layer  54 . The second conductor  56  is located on a second surface  54   b  of the insulating layer  54 . In this embodiment, the metal base  50  is removed by etching or the like. Thus, the first and second conductors  55  and  56  are substantially symmetrical with respect to the insulating layer  54  between them. In some cases, therefore, the flexure  40  can be used inside out. 
       FIG. 13  is a partial sectional view of a flexure  40  according to a ninth embodiment of the invention. A first conductor  55  consists of a conductor material  100 . The conductor material  100  is, for example, copper or nickel. The conductor material  100  is more conductive than a base material  60  that forms a metal base  50 . A highly conductive layer  80  is formed between an insulating layer  54  and first conductor  55 . The conductive layer  80  consists of a metal more conductive than the base material  60 . The first conductor  55  is formed on a surface of the highly conductive layer  80  by, for example, plating. Since other configurations, functions, and effects of this ninth embodiment are the same as those of the flexure  40  of the first embodiment, common numbers are used to designate portions common to these two embodiments, and a description of those portions is omitted. 
       FIG. 14  is a partial sectional view of a flexure  40  according to a tenth embodiment of the invention. A first conductor  55  consists of a conductor material  100 . The conductor material  100  is more conductive than a base material  60  that forms a metal base  50 . The conductor material  100  is, for example, copper or nickel. A highly conductive layer  80  of a metal more conductive than the base material  60  is formed between an insulating layer  54  and first conductor  55 . A conductive cover layer  90  is formed on the outer peripheral surface of the first conductor  55  by, for example, plating. The conductive cover layer  90  consists of a metal (e.g., copper) that is more conductive than the metal base  50 . Since other configurations, functions, and effects of this tenth embodiment are the same as those of the flexure  40  of the first embodiment, common numbers are used to designate portions common to these two embodiments, and a description of those portions is omitted. 
       FIG. 15  is a partial sectional view of a flexure  40  according to an eleventh embodiment of the invention. A first conductor  55  consists of a conductor material  100 . The conductor material  100  is more conductive than a base material  60  that forms a metal base  50 . The conductor material  100  is, for example, copper or nickel. A highly conductive layer  80  of a metal more conductive than the base material  60  is formed between a first conductor  55  and insulating layer  54 . An insulating coating  110  of an electrically insulating material is formed on the outer peripheral surface of the first conductor  55 . Since other configurations, functions, and effects of this eleventh embodiment are the same as those of the flexure  40  of the first embodiment, common numbers are used to designate portions common to these two embodiments, and a description of those portions is omitted. 
       FIG. 16  is a partial sectional view of a flexure  40  according to a twelfth embodiment of the invention. In this embodiment, a first conductor  55  for writing and another first conductor  120  for reading are located within a slit  52  in a metal base  50 . These conductors  55  and  120  are laminated to a first surface  54   a  of an insulating layer  54 . A second conductor  56  for writing and another second conductor  121  for reading are laminated to a second surface  54   b  of the insulating layer  54 . Since other configurations, functions, and effects of this twelfth embodiment are the same as those of the flexure  40  of the first embodiment, common numbers are used to designate portions common to these two embodiments, and a description of those portions is omitted. 
     It is to be understood, in carrying out the present invention, that the constituent elements of the invention, including the slit, insulating layer, first and second conductors, etc., as well as the metal base that constitutes the flexure, may be embodied in various forms without departing from the spirit or scope of the invention. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various 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.