Abstract:
A lapping row tool comprising a plurality of bending nodes having a space between adjacent ones of said nodes and each of which has an end surface to manipulate a row of magnetic heads during lapping. A bridge extends along the end surfaces of the bending nodes and across the space between the adjacent bending nodes. The bridge provides a surface for holding the row of magnetic heads that prevents the flexing of the row into the space between the bending nodes during lapping while allowing the bending nodes to manipulate the row during lapping.

Description:
This application claims the benefit of provisional application Ser. No. 60/523,238 to Schuh et al., which was filed on Nov. 18, 2003. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to lapping systems for hard drive magnetic heads, and more particularly to row tools used in lapping systems. 
     2. Description of the Related Art 
     Magnetic heads (also called sliders) for hard drives read data from the media (platter/disk) by sensing changes in magnetic field strength emanating from magnetic grains in the media. A writer is also included in the head that generates a magnetic field orienting the grains based on whether a one or zero is stored. The data is stored magnetically by alternating magnetic fields created by the writer as the gap (space between the poles) of the electromagnetic element glides (or slides) over the surface of the disk. The data is stored on the disk in a circular pattern with data tracks spaced as close as ten millionths of an inch apart, with as many as one hundred thousand tracks per inch. The data is stored by the writer in a track as individual “bits” at as many as five hundred thousand bits per inch, or as close together as two millionths of an inch. The data can then be read back by the reader-part of the head which contains a “magneto-resistive” material between two shields, with the magneto-resistive material changing resistance based on the magnetic orientation of a magnetic field. 
     Magnetic heads go through a number of processes before being lapped (or polished) to obtain the proper magnetic performance. The magnetic heads are typically deposited in rows on a wafer using fabrication and deposition techniques similar to those developed in the semiconductor industry. The wafer is then sliced into individual rows or a block of several rows of magnetic heads that are then bonded onto a row tool for the lapping operation. The row tool is then mounted in a lapping system/machine that laps the row of magnetic heads. Depending on the size of the heads and the length of the rows, there may be from 30 to 80 heads that are lapped simultaneously. 
     This lapping procedure removes material from the lower surface of the row and is one of the final procedures in manufacturing the magnetic heads/sliders. Using conventional lapping processes and row tools there was little to no control over the lapping of individual heads or groups of heads. As a result, all heads in the row had to meet the end performance target at the same time. Often times, however, the individual heads exhibit different performance characteristics at the end of lapping, and some of the heads characteristics are outside the acceptable range. These unacceptable heads are typically discarded which leads to waste that can increase the overall cost of the acceptable heads. 
     More recently, row tools have been developed that have control points that are designed to influence the row on the row tool to allow the lapping process to define the primary shape of the row of sliders. This also allows some control over the primary surface finish, device dimensions (distance from reading and writing elements to machined surface), and the shape and condition of the exposed surfaces. See U.S. Pat. Nos. 5,607,340 and 5,620,356 to Lackey et al. 
       FIG. 1  shows a more recent row tool  10  having a row of sliders  12  bonded on its lapping surface  14  that provides limited control over the lapping of the magnetic heads. Tool  10  includes seven “nodes”  16 , or control points, and a lapping surface  14  to which a row of magnetic heads  12  can be mounted. The nodes  16  allow the lapping machine to alter the lapping surface  14  and thereby control the shape of row  12  mounted on lapping surface  14 . The lapping machine manipulates the nodes by applying bending force (positive or negative force) at each node  16 , which essentially bends the lapping surface  14 . This bending provides the control of the shape of the lapping surface  14  row during the lapping which in turn controls the shape of row  12 . 
     One of the primary disadvantages of row tool  10  is that each of the rows can have between approximately and 80 magnetic heads so that each of the seven control nodes  16  bends the lapping surface  14  under several magnetic heads. Force interpolation is required at nodes  16  to “estimate” a best fit line between the heads on the row for which a discrete bending node is not available. This results in a less than optimum dimensional control for the population of heads on a row. 
     A relatively recent advancement in row tool technology has been the development of row tools with bending nodes along the entire row of heads. This increases the number of control nodes from the previously conventional seven, to forty-eight (48) or more. For a row with forty-eight heads, each head can have its own bending node; referred to as Single Slider Level Lapping Technology (SLLT).  FIG. 2  shows one embodiment of a SLLT row tool  20  having forty-eight nodes  22 , each of which has a top surface, with the node top surfaces together serving as lapping surface  24 . A row  26  of heads is arranged on lapping surface  24 , preferably with one of the heads in row  26  over a respective one of nodes  22 . Applying the required bending force (positive or negative force) at each head location in row  26  results in much better control over dimensional features of the full population of devices on row  26 . 
     The row tool  20 , however, has a lapping surface that is interrupted along its length by the spaces between the bending nodes  22 .  FIG. 3  shows row  26  mounted to nodes  22  with a respective head  28  arranged over a respective one of nodes  22 . During lapping, the pressure of the lapping surface can cause row  26  to flex into the space between nodes  22 . After the pressure is removed, row  26  flexes back such that the resulting lapped row  26  can have bumps  30  or other imperfections on its lapped surface. 
     Another disadvantage is that the bonding surface of the row tool can be ductile. As a result, the bonding surface can be altered such that the slider dimensions and geometry are undesirably changed. This can easily happen during the lapping process without detection so that many defective sliders will be fabricated. These defective sliders may not be usable, which leads to waste and increases costs. 
     SUMMARY OF THE INVENTION 
     One embodiment of a lapping row tool according to the present invention comprises a plurality of bending nodes having a space between adjacent ones of the nodes and each of which has an end surface to manipulate a row of magnetic heads during lapping. A bridge extends along the end surfaces of the bending nodes and across the space between the adjacent bending nodes. The bridge provides a surface for holding the row of magnetic heads that prevents the flexing of the row into the space between the bending nodes during lapping while allowing the bending nodes to manipulate the row during lapping. 
     Another embodiment of a lapping row tool according to the present invention comprises a plurality of bending nodes to manipulate a row of magnetic heads during lapping. An uninterrupted surface holds the row of magnetic heads with the bending nodes engaging the uninterrupted surface and manipulating the magnetic heads during lapping by applying a force to the uninterrupted surface to alter the orientation of the surface and in turn, the row. 
     One embodiment of a lapping system control head according to the present invention comprises a mounting post for mounting into a lapping machine. A row tool is mounted within the control head with the row tool including a plurality of bending nodes with a bridge on the bending nodes providing a surface for holding a row of magnetic heads. A control voice coil manipulates the bending nodes with the bending nodes engaging the bridge to manipulate the shape of the surface of the bridge. This in turn controls the shape of the row on the surface to control lapping of the heads in said row. 
     These and other further features and advantages of the invention would be apparent to those skilled in the art from the following detailed description, together with the accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a conventional seven node row tool; 
         FIG. 2  is a perspective view of a conventional SLLT  48  point row tool; 
         FIG. 3  is a sectional view of a row mounted to a conventional row tool showing bumps that can form on a row the lapping process; 
         FIG. 4  is a perspective view of one embodiment of a row tool according to the present invention; 
         FIG. 5  is a perspective exploded view of the row tool in  FIG. 4 ; 
         FIG. 6  is an end elevation view of the row tool in  FIG. 4 ; 
         FIG. 7  is a front elevation view of the row tool in  FIG. 4 ; 
         FIG. 8  is a top view of the row tool in  FIG. 4 ; 
         FIG. 9  is a sectional view of the row tool in  FIG. 4  taken along section lines  9 - 9 ; 
         FIG. 10  is a sectional view of a row mounted to a row tool according to the present invention showing the bridge between bending nodes; 
         FIG. 11  is a perspective view of another embodiment of a row tool according to the present invention; and 
         FIG. 12  is machine view of a lapping machine head using one embodiment of a row tool according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides row tools that can be used in magnetic head lapping machines to more efficiently lap rows of magnetic heads. The row tools include numerous bending/control nodes to control the heads such that the heads can be lapped using SLLT. In other embodiments of the row tool the bending nodes can be used to control more than one of the heads in a row during lapping. The row tool also proves an uninterrupted surface with the row of magnetic heads mounted to the surface for lapping. The uninterrupted surface allows the row to be lapped without the row flexing into the space between the bending nodes. The surface also allows the control force of the bending nodes to transfer through the bridge to the row during lapping. As a result, the bumps and imperfections associated with lapping using conventional row tools can be avoided. The arrangement provides the desired control over lapping of the heads in the row while reducing waste and providing heads having a higher quality. 
     Row tools according to the present invention comprise a bridge across the space between the bending nodes, with the bridge having a width sufficient to hold the row of magnetic heads, and a sufficient thickness to support the row under the force of lapping while still allowing for lapping control by the bending nodes. The bridge can be used in many different row tools and can be formed integral to the bending nodes or mounted to the bending nodes. 
       FIGS. 4-9  show one embodiment of a row tool  40  according to the present invention that can be mounted within a lapping machine for lapping a row of magnetic heads. The row tool  40  comprises three primary components including the base  42 , bridge carrier  44 , and clamp  46 , all of which are arranged in the assembled row tool such that the bridge carrier  44  is held between the base  42  and clamp  46 . 
     The base  42  provides the mounting points to a lapping machine, and many different mounting methods can be used that can be arranged in different locations on the base  42 . In a preferred embodiment, the base  42  has first and second mounting tabs  48 ,  50  that extend from the ends of the base  42 , with first and second mounting holes  52 ,  54  passing through. Mounting screws or bolts (not shown) pass through the mounting holes  52 ,  54  and into threading holes in the lapping machine to provide a strong and stable connection to the lapping machine so that the row tool  40  is held firmly in place during lapping of the row. 
     The base  42  also has a bridge carrier surface  55  (shown in  FIG. 5 ) for the bridge carrier to rest in the assembled tool  40 . As more fully described below, the bending nodes are arranged to move freely over the surface  55 . Threaded base mounting holes  56   a - d  are provided to accept a screw or bolt for mounting the clamp  46  to the base  42 . The base  42  can be made of many different rigid materials such as metals and ceramics, with a preferred material being stainless steel, such as commercially available 17-4 PH900 stainless steel. The base can be fabricated using known methods including but not limited to electro discharge machining (EDM). 
     The bridge carrier  44  comprises the bridge  64 , along with bending nodes  66  that control the flexing of the bridge  64  during lapping. The bridge  64  provides an uninterrupted surface onto which row  57  (shown in  FIG. 4 ) is bonded for lapping. Many different bonding methods and materials can be used that provide the necessary adhesive force during lapping and also allow for the row  57  to be easily removed from bridge  64  after lapping. A suitable bonding material is commercially available thermo-plastic adhesive that when heated releases the row from the bridge  64 . Different adhesives can be used depending on the type of magnetic heads being lapped. The adhesive typically has a melting temperature of approximately 100° to release the row. The adhesive should also have minimal surface tension and uniform thickness under the row  57 . In some embodiments the adhesive can be conductive by including conductive particles, such as silver particles. 
     The bridge carrier  44  can have different numbers of bending nodes depending on the number of heads in the row that is being lapped and whether the row tool is providing SLLT, as described above. In the embodiment shown the bridge carrier  44  has forty-eight (48) bending nodes  66  each of which can be independently manipulated forward or back as shown by arrow  68 . As best shown in  FIG. 9  the bridge carrier has a series of hooks  70  on its lateral section  76 , opposite the bridge  64 , with each of the hooks  70  used by the lapping system to manipulate one of the bending nodes  66 . For row tool  40  there are forty-eight hooks corresponding to the forty-eight bending nodes  66 . The lapping machine has a series of controls that engage the hooks  70  when the row tool  40  is mounted to the lapping machine. The controls manipulate flexing of the bridge  64  by moving the particular ones of the bending nodes  66  back or forth to control lapping of the row. 
     The bridge carrier  44  also comprises first and second flexures  72 ,  74  that provide anchors for the bending nodes  66 . As more fully described below, the flexures  72 ,  74  are firmly mounted to the clamp  46  so that the bending nodes  66  can move back and forth under control of the lapping machine, with the flexures  72 ,  74  causing the bending nodes to return to a neutral position when the force from the lapping machine controls is removed. 
     The bridge carrier  44  can be also be made of many different rigid materials such as a metal or ceramic, with the preferred material being 17-4 PH900 stainless steel. It can be fabricated using EDM and can be fabricated from a single piece of material or different pieces that are then assembled. One embodiment of a bridge carrier  44  is made of four different pieces each, of which can be fabricated using EDM or other methods, with the four pieces including the carrier lateral section  76 , the first and second flexures  70 ,  72 , and the stability bar  78 . These pieces are then assembled and bonded together to form the bridge carrier  44 . 
     In row tool  40  the bridge  64  is formed integral to the bending nodes  66  during fabrication of the lateral section  76 . Alternatively, the bridge can be formed separately from the row tool and bonded to the bending nodes  66 . In embodiments where the bridge  64  is separately manufactured, it can be made of the same or different material than the bending nodes  66 . In one embodiment it can be made of ceramic material such as an aluminum oxide or yttrium doped zirconia, which can exhibit improved robustness and can include materials to provide for electro-static discharge (ESD) protection. Separately formed bridges can be mounted to the bending nodes using adhesives or by brazing. 
     The bridge  64  can have many different dimensions and should be long enough to run along and cover all of the bending nodes  66 , and should be wide enough to hold the particular row of magnetic heads that is being lapped. The bridge  64  should also be thick enough so that it does not flex into the space between the bending nodes  66  during lapping and should be thin enough so that movement of the bending nodes is transferred through the bridge  64  to the row being lapped. In a preferred embodiment the bridge is approximately 0.0485 inches (±0.0005 inches) thick as measured where the bridge  64  spans one of the spaces between the bending nodes  66 . 
     The row tool  40  also comprises a clamp  46  that is mounted to the base  42  with the bridge carrier  44  held between the base  42  and clamp  46 . The clamp includes clamp mounting holes  80   a - d  that align with the base mounting holes  56   a - d  in the base  42 . Assembly screws  82   a - d  are included that are sized to pass through the clamp mounting holes  80   a - d  and mate with the threads in the base mounting holes  56   a - d  to mount the clamp  46  to the base  42 . 
     The clamp  46  further comprises first and second longitudinal slots  84 ,  86  that are sized to accept the bridge carrier&#39;s first and second flexures  72 ,  74  respectively. As best shown in  FIG. 9 , when the row tool  40  is assembled, the top portion of the flexures  72 ,  74  are inserted into the slots  84 ,  86  and remain in the slots in the finally assembled row tool  40 . The clamp further comprises threaded first flexure holes  88   a - f  sized to mate with first flexure screws  90   a - f , and threaded second flexure holes (not shown) on the opposite side of the clamp  46 , sized to mate with second flexure screws  94   a - f . Each of the first screws  90   a - f  turns into its respective one of the first flexure holes  88   a - f  to close the first slot  84  on the top portion of the first flexure  72 . Second screws  94   a - f  similarly cooperate with second flexure holes to close the second slot  86  on the top portion of the second flexure  74 . Different numbers of flexures screws can be used according to the present invention, with six being a suitable number to overcome the stiffness of the clamp  46  to reliably clamp the flexures  72 ,  74  in the slots  84 ,  86  such that the flexures  72 ,  74  are solidly held in place. This allows the flexure points  66  to be accurately controlled by the lapping machine as described above. 
     The clamp  46  can be made of the same rigid material and made using the same fabrication process as the base  42  and the bridge carrier  44 . When assembled, a continuous lapping surface for a row is provided at the bridge  64  with the row tool  40  also providing an accurate and reliable mechanism for manipulating the surface of the bridge  64  during lapping. 
       FIG. 10  shows the bridge and bending node arrangement from a row tool  100  according to the present invention. Tool  100  comprises bending nodes  102  with a bridge  104  integral with or mounted to the ends of the bending nodes  102 . A row  106  is mounted to the bridge  104  preferably by a thermo plastic adhesive  108  as described above. The row  106  is positioned on a surface of bridge  104  with each individual magnetic head  110  in the row aligned with one of the bending nodes  102  pursuant to SLLT. 
     This arrangement allows the lapping of each of the heads to be controlled during lapping by the lapping machine individually manipulating the bending nodes  102  back and forth in the direction of arrows  112 . This movement of bending nodes  102  causes movement of bridge  104 , which in turn causes movement of row  106 . This arrangement allows the lapping machine to control the shape of each head  110  in the row  106  during lapping, with bridge  104  preventing flexing of the row into the space between the bending nodes  102  that can result in bumps in row  106  after lapping. 
       FIG. 11  shows another embodiment of a row tool  120  according with the present invention which includes an integrated assembly  122 , formed of previously separate components, and a base assembly  124  that can be made of ceramic. It should be noted that row tool  120  is similar to row tool  40  discussed above in  FIGS. 4-9 , but has some differences in how the components are arranged. Like row tool  40 , row tool  120  includes bending nodes  126  with a bridge  128  mounted across them. Row  130  can then be bonded to bridge  128 , preferably by a thermo plastic adhesive as described above, with bridge  128  providing an uninterrupted surface between the nodes  126  and row  130 . 
     Previous row tools arranged similar to tool  120  included separate subassemblies such as a clamp, bridge carrier, and base mounted together by screws. The clamp holds the bridge carrier and provides reference surfaces for the customer process tooling. The bridge carrier is arranged to allow the bending nodes  126  to move back and forth beneath the clamp subassembly under control of the lapping machine. The base serves as the mounting point to the lapping machine. 
     In conventional row tools these subassemblies are fabricated separately using conventional fabrication methods such as electro-discharge machining. Pursuant to the present invention, the clamp and bridge carrier can be fabricated as an integrated unit. Different fabrication methods can be used, with a preferred method using abrasive sawing technology or chemical etch machining, which are known in the art. The clamp and bridge carrier fabricated in the integrated assembly  122  can be made of many different materials, with a suitable material being a metal such as steel. 
     After integrated assembly  122  is typically formed having an insert assembly that is separated from the remainder of the integrated subassembly, with a preferred method being electro-discharge machining. By separating the insert subassembly, the bending nodes  126  in the final assembly are free to apply a force to bridge  128  and row  130  during lapping. 
     Base  124  can be made of many different materials, with a preferred material being ceramic. Integrated assembly  122  is mounted to base  124  with the bridge carrier properly mounted such that the bending nodes  126  can be manipulated during lapping. Bridge  128  can be made of many ridged materials, with a suitable material being ceramic. Another suitable material is ceramic which has certain desirable properties such as superior hardness and non-ductility. 
     By having portions of the tool  120  made of ceramics row  130  and its magnetic heads can be protected from electro-static discharge (ESD). For ceramic bridges, the ceramic material can serve as an ESD buffer between bending nodes  126  and row  130  with the row  130  being protected from the conductive properties of the row tool components. This design can also improve the reliability and life of the row tool  120  due to the non-ductile properties of ceramic. By having an integrated assembly, row tool  120  also has fewer components to manufacture, which results in decreased manufacturing costs and improved manufacturability due to the inherent superiority of the abrasive sawing technology. Row tool  120  also does not need as many screws during assembly, reducing complexity of manufacturing and the danger of contamination in the lapping process. The ability to match a ceramic&#39;s physical properties to that of the row being lapped also can reduce in-process mechanical stresses in the row. 
     The ceramic bridge  128  can be brazed to the steel surface of bending nodes  126  with the brazing material at the surface of each of bending nodes  126  providing a mechanical connection to the two. In one embodiment, the ceramic bridge  128  is brazed to the steel surface of the bending nodes using a hard solder with a high melting point. 
       FIG. 12  shows a lapping machine control head  140  utilizing a row tool  142  according to the present invention. The control head  140  is mounted to a lapping machine at first and second mounting posts  144 ,  146  so that the control head is firmly held within the lapping machine. The row tool  142  is oriented in the control head so that the row  148  of magnetic heads is facing down. The row  148  is mounted to the row tool&#39;s bridge  149 , pursuant to the present invention. The lapping surface in a typical lapping machine is facing up to engage the row  148  during lapping. The control head  140  further comprises a control voice coil  150  that is arranged to manipulate the row tool&#39;s bending node&#39;s during lapping by engaging the bending nodes at their hooks (shown above). The bending nodes are typically manipulated under control of the lapping machine which can comprise a data processor to determine the appropriate force to be applied by said bending nodes, and a system for generating commands to the control voice coil. In this way, the lapping of the individual heads in the row can be controlled during lapping. 
     Although the present invention has been described in considerable detail with reference to certain preferred configurations thereof, other versions are possible. Numerous modifications, variations and rearrangements can be readily envisioned to achieve substantially equivalent results, all of which are intended to be embraced within the spirit and scope of the invention as defined in the appended claims.