Abstract:
A slider includes a slider body having a first side and edges defined adjacent to the first side, at least two separate insulators each adjacent to the first side of the slider body and supported by the slider body, and a conductive trace adjacent to each of the at least two separate insulators and opposite the first side of the slider body. The at least two separate insulators each are in physical contact with the slider body along the first side of the slider body such that the at least two separate insulators are physically attached to the slider body to electrically insulate each conductive trace from the slider body.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 11/439,047, filed May 23, 2006. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to electrical interconnection structures, and more particularly to interconnect trace and bond pad structures for use in conjunction with slider assemblies carrying transducing heads. 
         [0003]    Hard disc drives (HDDs) typically comprise one or more discs, each disc having concentric data tracks for storing data. Where multiple discs are used, a stack is formed of co-axial discs having generally the same diameter. A transducing head carried by a slider is used to read from and write to a data track on a disc. The slider is carried by a head arm assembly (HAA) that includes an actuator arm and a suspension assembly, which can include a separate gimbal structure or can integrally form a gimbal. As the disc is spun, the slider glides above the surface of the disc on a small cushion of air. The actuator arm movably positions the slider with respect to the disc. Electrical connections extend along the suspension to electrically connect the transducing head to components located at or near the actuator arm. Those electrical connections can be formed on the suspension itself, or can be located on a separate interconnect structure supported relative to the suspension, such as a flex-on suspension (FOS). 
         [0004]    The slider includes a slider body (called the “substrate”) and an overcoat that includes the transducing head. The slider body is electrically conductive, while the overcoat is electrically insulative. A plurality of bond pads, usually a minimum of four, are formed at a side or edge of the slider—typically at its trailing edge. These bond pads are directly connected through the overcoat to various components, such as to the transducing head or to a heater. During fabrication of a HDD, the bond pads are electrically connected to the electrical connections (i.e., traces) along the suspension. Typically, a conventional gold ball soldering operation is used to make the electrical connections from the bond pads of the slider to the electrical connections of the suspension. Separately, the slider is mechanically secured to a load button or load point of the gimbal at a back side of the slider (synonymously called the “top” of the slider), for example, with an adhesive. 
         [0005]    As areal recording density for HDDs increases, the sizes of sliders and transducing heads continue to decrease. Numerous other factors have also influenced smaller slider sizes. Accordingly, sliders can have dimensions of about 1 mm in width, 1.3 mm in length and 200-300 μm in thickness. Trends are for sliders to continue to be smaller, with lengths of 1 mm or less and widths of 700-800 μm or less. The sizes of bond pads decrease accordingly with smaller slider sizes. 
         [0006]    Decreasing slider and bond pad sizes present numerous difficulties. For example, conventional methods and equipment used for gold ball bonding are no longer reliable for smaller sliders with small conventional bond pads at a side or edge of the slider. Moreover, less space is available along the sides or edges of the slider for large numbers of electrically isolated bond pads. 
         [0007]    Thus, the present invention provides a slider assembly having an alternative slider interconnect trace and bond pad assembly. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    A slider according to the present invention includes a slider body having a first side and edges defined adjacent to the first side, at least two separate insulators each adjacent to the first side of the slider body and supported by the slider body, and a conductive trace adjacent to each of the at least two separate insulators and opposite the first side of the slider body. The at least two separate insulators each are in physical contact with the slider body along the first side of the slider body such that the at least two separate insulators are physically attached to the slider body to electrically insulate each conductive trace from the slider body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view showing the back side and trailing edge of a slider assembly according to the present invention. 
           [0010]      FIG. 2  is a top view of the slider assembly of  FIG. 1 , showing the back side of the slider assembly. 
           [0011]      FIG. 3  is a schematic top view of a portion of the slider assembly of  FIGS. 1 and 2 . 
           [0012]      FIG. 4  is a schematic side view of a portion of the slider assembly of  FIGS. 1-3 . 
           [0013]      FIG. 5  is a schematic side view of a portion of an alternative embodiment of a slider assembly according to the present invention. 
           [0014]      FIG. 6A  is a schematic cross-sectional view of a multi-layer bond pad stack according to the present invention. 
           [0015]      FIG. 6B  is a schematic cross-sectional view of the multi-layer bond pad stack of  FIG. 6A  soldered to an adjacent component. 
           [0016]      FIG. 6C  is a schematic cross-sectional view of an alternative embodiment of a multi-layer bond pad stack according to the present invention. 
           [0017]      FIG. 7  is a schematic cross-sectional view of a multi-layer interconnect trace stack according to the present invention. 
           [0018]      FIG. 8  is a simplified schematic side view of a slider assembly according to the present invention supported by a suspension assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIG. 1  is a perspective view of a slider assembly  20 , showing a back side  22  (synonymously called the “top”) and a trailing edge  24  of the slider assembly  20 . The slider assembly  20  includes a slider body  26  portion and an overcoat portion  28  that is located at the trailing edge  24 . The overcoat portion  28  can include a number of individual layers that are not shown for simplicity. As shown in  FIG. 1 , a plurality of conventional trailing edge bond pads  30  and conventional lapping pads  32  are located at the trailing edge  24  of the slider assembly  20 . A plurality of interconnect structures  34  are provided that extend along the back side  22  of the slider assembly  20 . In the illustrated example, eight interconnect structures  34  are provided, and each interconnect structure  34  is electrically connected with a corresponding bond pad  30 . 
         [0020]      FIG. 2  is a top view of the slider assembly  20 . As shown in  FIG. 2 , eight interconnect structures  34 A- 34 H extend along the back side  22  of the slider assembly  20 . Each interconnect structure  34 A- 34 H includes a respective interconnect trace  36 A- 36 H and a respective top bond pad  38 A- 38 H. The shape of each interconnect trace  36 A- 36 H can vary as desired. However, the interconnect traces  36 A- 36 H are generally elongate in shape and arranged so as to provide unobstructed electrical connection paths between the top bond pads  38 A- 38 H and desired connection points on the slider assembly  20 . The top bond pads  38 A- 38 H are generally positioned at a terminal region of the respective interconnect traces  36 A- 36 H. Each top bond pad  38 A- 38 H is generally larger than an adjacent portion of the respective interconnect trace  36 A- 36 H. As shown in  FIGS. 1 and 2 , the top bond pads  38 A- 38 H are circular in shape, although the top bond pads  38 A- 38 H can have other shapes as desired. 
         [0021]      FIG. 3  is a schematic top view of a portion of the slider assembly  20 . As shown in  FIG. 3 , each interconnect structure  34  (only interconnect structures  34 A- 34 C are shown in  FIG. 3 ) includes a respective electrically insulative portion  40 A- 40 C and a respective electrically conductive portion  42 A- 42 C. The insulative portions  40 A- 40 C are located adjacent to the back side  22  of the slider assembly  20 , and are located between the conductive portions  42 A- 42 C and the slider body  26 . The slider body  26  is formed of a conductive material (e.g., AlTiC), and the insulative portions  40 A- 40 C prevent shorting of the interconnect structures  34  through the slider body  26 . The insulative portions  40 A- 40 C are formed as discrete insulators that are localized relative to the conductive portions  42 A- 42 C, rather than as a unitary sheet across the entire back side  22  of the slider assembly  20 . The discrete, localized insulator patterns provide a number of benefits, such helping promoting simple and easy fabrication. The discrete, localized insulator patterns also can help improve stress conditions when the slider assembly  20  is attached to another component. 
         [0022]    It should be noted that additional layers can be included in the structures shown in  FIGS. 1-3 . For instance, as explained more fully below, the conductive portions  42 A- 42 C can include multiple layers, and their exposed surfaces can comprise a wick-stop (or anti-wetting) material. Suitable wick-stop materials include dielectric materials. 
         [0023]    Connection or wrap-around traces  44 A- 44 C are provided adjacent to the overcoat  28 . Each connection trace  44 A- 44 C is electrically connected between the conductive portion  42 A- 42 C of its respective interconnect structure  34 A- 34 C and a desired electrical connection point. The connection traces  44 A- 44 C enable the interconnect structures  34  to be electrically connected to components, for example, electrical connection studs, that are located at the overcoat  28 . The overcoat  28  is formed of an electrically insulative material (e.g., Al 2 O 3 ), and therefore the connection traces  44 A- 44 C can be deposited directly on the overcoat  28  without shorting. The connection traces  44 A- 44 C can be unitary with the conductive portions  42 A- 42 C of the interconnect structure, or can be separate and distinct as shown in  FIG. 3 . 
         [0024]      FIG. 4  is a schematic side view of a portion of the slider assembly  20 . As shown in  FIG. 4 , a conductive seed layer trace  46  is located at the trailing edge  24  of the slider assembly  20 . The seed layer trace  46  is electrically connected between the connection trace  44  and a stud  48  (i.e., an electrical lead embedded in the overcoat  28 ), which is in turn connected to a transducing head  50  or other component. The seed layer trace  46  is formed using a photolithography process similar to those conventionally used to form trailing edge seed layers (i.e., anode layers used for plating procedures) in conjunction with the fabrication of trailing edge bond pads. Seed layers, such as seed layer trace  46 , are typically formed of conductive materials that provide good adhesion (e.g., Cr, Ti, Ta, etc.). 
         [0025]    A trailing edge bond pad  30  is shown in phantom in  FIG. 4  disposed adjacent to the seed layer trace  46 . It should be recognized that conventional trailing edge bond pads  30  are optional according to the present invention, because slider assemblies having top bond pads do not require additional trailing edge bond pads. However, it may be desirable to provide redundant bond pad structures in some situations, for instance, where available testing equipment is configured for slider assemblies having trailing edge bond pads. 
         [0026]    Although the particular dimensions will vary according to the desired application, the seed layer trace  46  can have a thickness of about 2,000 Å and the optional bond pad  30  can have a thickness of about 4-5 μm. 
         [0027]    It is possible to configure a slider assembly according to the present invention in different ways, as desired. For instance,  FIG. 5  is a schematic side view of a portion of an alternative slider assembly  60 . The slider assembly  60  is similar to the slider assembly  20  described above. However, a stud  62  that is electrically connected to a component, for example, the transducing head  50 , extends to a location on the overcoat  28  at the back side  22  of the slider assembly  60 . A connection trace  64  electrically connects the stud  62  and the conductive portion  42  of the interconnect structure  34 . 
         [0028]      FIG. 6A  is a schematic cross-sectional view of a multi-layer stack  100  located adjacent to a slider body  26  (i.e., a conductive substrate). Stack  100  can form a bond pad portion of a slider assembly. Stack  100  includes an insulator layer  102 , a lower diffusion barrier layer  104 , a conductor layer  106 , a solder-wettable upper diffusion barrier layer  108 , a consumable oxidation barrier layer  110 , and a wick-stop layer  112  (i.e., an anti-wetting coating). Additional layers may be included in further embodiments, as desired. The insulator layer  102  is located adjacent to the back side  22  of the slider body  26 , and provides electrical insulation between the slider body  26  and other layers of the stack  100 . The insulator layer  102  can be formed of any suitable insulator material, for example, Al 2 O 3 . 
         [0029]    The lower diffusion barrier layer  104  is located adjacent to the insulator layer  102  and opposite the slider body  26 , that is, the lower diffusion barrier layer  104  is located on top of the insulator layer  102 . The lower diffusion barrier layer  104  is generally slightly smaller in width or diameter than the insulator layer  102 . The function of the lower diffusion barrier layer  104  is to minimize diffusion of materials (e.g., conductive materials) into the insulator layer  102 , and thereby help maintain the integrity of the insulator layer  102 . The lower diffusion barrier layer  104  can be formed of Cr, or another suitable material as desired (e.g., Ti Nitride and Ta Nitride). 
         [0030]    The conductor layer  106  is located adjacent to the lower diffusion barrier layer  104 , that is, the conductor layer  106  is located on top of the lower diffusion barrier layer  104  and, in turn, on top of the insulator layer  102 . The conductor layer  106  functions as the principle carrier of electrical current through the stack  100  and to other connected components (see  FIGS. 6B and 8 ). The conductor layer  106  can be formed of Cu, or another suitable material as desired. Cu is a desirable material due to its low electrical resistance and suitable mechanical properties. 
         [0031]    The upper diffusion barrier layer  108  is located adjacent to the conductor layer  106  and opposite the slider body  26 , that is, the upper diffusion barrier layer  108  is located on top of the conductor layer  106 . The function of the upper diffusion barrier layer  108  is to minimize diffusion of materials at or near the top of the conductor layer  106 . The upper diffusion barrier layer  108  can be formed of Ni, or another suitable material as desired. 
         [0032]    The oxidation barrier layer  110  is located adjacent to the upper diffusion barrier layer  108 , that is the oxidation barrier layer  110  is located on top of the upper diffusion barrier layer  108  and, in turn, on top of the conductor layer  106 . The oxidation barrier layer  110  forms a bonding layer that is consumed when forming a connection to the stack  100 , such as during an Ag—Sn soldering procedure similar to that described below with respect to  FIG. 6B . The oxidation barrier layer  110  can be formed of Au, which is a material with good wetting properties that also helps prevent oxidation or corrosion of the upper diffusion barrier layer  108 . 
         [0033]    The wick-stop layer  112  is disposed to cover otherwise exposed surfaces of the diffusion barrier layers  104  and  108  and the conductor layer  106 . The wick-stop layer  112  can optionally cover selected portions of the oxidation barrier layer  110  (not shown). The wick-stop layer  112  is a thin coating of material that minimizes wetting in particular regions when the stack  100  is connected to another component, such as during a soldering operation. This helps to avoid migration of reflowed solder material away from a desired location, which assists in the creation of reliable electromechanical connections to the stack  100 . The wick-stop layer  112  can be, for example, a dielectric material like SiO 2  or Al 2 O x . Alternatively, the wick-stop layer can include multiple materials. For example, wick-stop layer  112  can alternatively include an inner layer of a first material (e.g., Al 2 O 3 ) that is about 1,000-5,000 Å or more thick and an outer layer of a second material (e.g., diamond-like carbon) that is about 200-500 Å thick. 
         [0034]    The insulator layer  102  can have a thickness of, for example, about 3,000 Å and a width or diameter W I  of, for example, about 88-92 μm. The lower diffusion barrier layer  104  can have a thickness of, for example, about 500 Å and a width or diameter comparable to that of the conductor layer  106  (e.g., about 84-86 μm). The conductor layer  106  can have a thickness of, for example, about 3,000 Å and a width of diameter W C , for example, of about 84-86 μm. The upper diffusion barrier layer  108  can have a thickness of, for example, about 3,000 Å and a width or diameter comparable to that of the conductor layer  106  (e.g., about 84-86 μm). The oxidation barrier layer  110  can have a thickness of, for example, about 500 Å and can have a width or diameter W B  of, for example, about 80 μm. The wick-stop layer  112  can be applied to a thickness of about 200 Å. It should be recognized that the exemplary dimensions given above can vary according to the particular application, as desired. 
         [0035]    Electromechanical connections to the stack  100  can be formed according to the following example. First, a solder connection to the stack  100  is formed by placing a solder material (e.g., an Ag—Sn solder paste) between the stack  100  and an adjacent component, such as an electromechanical connection pad on a suspension assembly (see  FIG. 8 ). The solder is then reflowed and the oxidation barrier layer  110  of the stack  100  is consumed to form a soldered connection. In other words, the material of the oxidation barrier layer  110  and the solder material are heated (i.e., wet) and combined to form a metallurgical bond as they cool and harden. The wick-stop layer  112  constrains undesired migration of materials during the reflow process. 
         [0036]      FIG. 6B  is a schematic cross-sectional view of the multi-layer stack  100 ′ soldered to an adjacent component  114 , where stack  100 ′ represents stack  100  in a soldered state. As shown in  FIG. 6B , the oxidation barrier layer ( 110 ) is combined with solder material to form a soldered electromechanical connection  110 ′ between the stack  110 ′ and the component  114 . Electrical current can pass between the component  114  and the conductor layer  106  of the stack  100 ′ through the electromechanical connection  110 ′. It should be noted that the upper diffusion barrier layer  108  helps reduce the diffusion of material from the electromechanical connection  110 ′ to the conductor layer  106 , although it is possible that some diffusion may still occur. 
         [0037]      FIG. 6C  is a schematic cross-sectional view of an alternative multi-layer stack  120 . Stack  120  is similar to stack  100  shown and described with respect to  FIG. 6A . However, the stack  120  further includes an optional seed layer  122  located between the insulator layer  102  and the slider body  26 . The seed layer  122  facilitates plating of the insulator layer  102  onto the slider body  26 . The seed layer  122  can have a thickness of, for example, about 100 Å and a width commensurate with the desired width of the insulator layer  102 . The seed layer can comprise Ta, or another suitable material as desired. 
         [0038]      FIG. 7  is a schematic cross-sectional view of a multi-layer stack  200 , which can form part of an interconnect trace portion of a slider assembly. The stack  200  includes an insulator layer  102 , a lower diffusion barrier layer  104 , a conductor layer  106 , an upper diffusion barrier layer  108 , and a wick-stop layer  112 . Typically, the stack  200  forms an elongate path for transmitting electrical current, although the particular shape and arrangement of the stack  200  will vary according to the particular application. The conductor layer  106  is the primary carrier of electrical current through the stack  200 . 
         [0039]    The arrangement and composition of the layers of the stack  200  can be generally similar to the stack  100 , as shown and described with respect to  FIG. 6A . However, the stack  200  does not include a bonding layer, and therefore the wick-stop layer  112  covers the top of the upper most layer (i.e., the upper diffusion bonding layer  108 ). Making the layers of the stack  200  similar to the stack  100  can simplify fabrication of an interconnect structure of a slider assembly, by permitting use of substantially the same fabrication process to construct both stacks  100  and  200 . The stack  200  can further differ from the stack  100  in other embodiments. For instance, the upper diffusion barrier layer  108  is optional, and can be omitted from the stack  200 . 
         [0040]    The structures of the present invention described above can be fabricated using conventional techniques known to those of ordinary skill in the art of thin film head design and manufacture, including techniques such as photolithography, etching, plating, variable-angle deposition, and techniques similar to, but not limited by, those described in commonly-assigned U.S. Pat. Nos. 5,610,783 and 5,774,975. 
         [0041]      FIG. 8  is a simplified schematic side view of a slider assembly  300  supported by a suspension assembly  302 , which is illustrated as having integral electrical traces. A number of solder connections  304  are provided to both mechanically and electrically connect (i.e., to electromechanically connect) the slider assembly  300  to the suspension assembly. The solder connections can be made at top bond pads of the slider assembly  300 , which can be arranged for cooperative engagement with electrical connection pads on the suspension assembly  302 . in the configuration shown in  FIG. 8 , there is no need for separate electrical and mechanical connections between the slider assembly  300  and the suspension assembly  302 , and, thus, fabrication can be simplified. 
         [0042]    It should be recognized that the present invention provides numerous advantages. For example, top bond pads located relative to the back side of a slider assembly promote reliable fabrication. Because more space is available at the back side of a slider than at its sides or edges, top bond pads can be larger in size than might otherwise be feasible at side or edge locations. Top bond pads thereby permit the reliable use of conventional connection methods (and corresponding equipment) to electrically and mechanically connect the top bond pads of the slider to other support and/or interconnect components. Also, localized insulators can be fabricated without the need to etch away portions of the insulator and redeposit conductor materials. Fabrication is further benefited in that thick, unitary sheet insulators make alignment in reference to the slider body more difficult. Thus, the present invention provides advantages over other possible means of providing top bond pads at a back side of a slider. 
         [0043]    Moreover, the use of a plurality of discrete, localized insulators as part of interconnect structures along the back side of a slider assembly provides additional benefits. The relatively small areas of these structures isolate film stress, such as residual stress from deposition and thermal stress induced by differing coefficients of thermal expansion of components of the slider assembly, because film stress is proportional to area. 
         [0044]    Although the present invention has been described with reference to several alternative embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For instance, the particular materials of each layer of the multi-layer interconnect structures can vary from the examples given above. Moreover, the particular layout, positioning and arrangement of the slider assembly of the present invention will vary according to the particular application, as desired.