Abstract:
The apparatus for lapping a magnetic head slider includes a lapping plate to which a bar of the magnetic head slider makes a contact by a predetermined lapping pressure, a primary oscillating mechanism that makes a primary oscillating of the bar in a radial direction of the lapping plate, and a secondary oscillating mechanism that makes a secondary oscillating of the bar in a direction perpendicular to a direction of the primary oscillating. A coarse lapping of the bar is performed by a combined oscillating of the primary oscillating and the secondary oscillating, and upon completion of the coarse lapping, the apparatus switches to the primary oscillating to finish lapping of the bar.

Description:
BACKGROUND OF THE INVENTION 
     1) Field of the Invention 
     The present invention relates to a method of and an apparatus for lapping a magnetic head slider, and more particularly, to a method of and an apparatus for lapping a magnetic head slider that further enhances lapping precision and prevents formation of a scratch or a smear in gaps of magnetoresistive (MR) elements or electrical lapping guide (ELG) elements. 
     2) Description of the Related Art 
     Recently, with increase in capacity of a hard disk drive, it is required to reduce a size and a width of a track and a gap of a combined type magnetic head having a slider. Since a thin magnetic film becomes more popular, precise control with excellent productivity is required also in lapping process of the magnetic head slider. 
     Generally, in a conventional working process of the magnetic head slider, since a row bar in which a plurality of magnetic head elements are aligned in a line is cut out from a wafer and the cut out row bar is lapped into a desired size, the row bar is pushed against a lapping plate under a predetermined pressure and the row bar is lapped. 
       FIG. 20  is a schematic diagram of a row bar as viewed from a surface of the row bar to be lapped. That is, on the row bar  10 , magnetic head sliders  11  and work-monitoring resistive elements, electrical lapping guide (ELG) elements  12 , are alternately arranged. Each of the magnetic head sliders  11  comprises an alumina section  13  and an alumina carbonized-titanium section  14 . The alumina section  13  includes an upper magnetic pole  15 , an upper shield (lower magnetic pole)  16 , an MR film  17  and lower shield  18 . 
     As means for precisely lapping such a row bar  10 , the present inventor, for example, proposed a lapping method and a lapping apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-162526. A lapping direction component of the row bar  10  by this lapping apparatus will be explained with reference to FIG.  21 .  FIG. 21  is a schematic diagram of the lapping direction component as viewed from the surface of the row bar to be lapped.  FIG. 21  depicts the surface  10   a  of the row bar  10  to be polished and a turning and oscillating center  19  of the row bar  10 . A lapping direction component and a surface plate rotation direction are shown with arrows in FIG.  21 . 
     The lapping apparatus includes a rotating lapping plate, first oscillating mechanism which simply primary oscillates the mounted row bar  10  such that the row bar  10  reciprocates in the radial direction of the lapping plate, and a second oscillating mechanism which turns and secondary oscillates the mounted row bar around itself. A oscillating period of the row bar by the first oscillating mechanism and a oscillating period of the row bar by the second oscillating mechanism are set differently so that the row bar is oscillated in a combined manner. 
     According to a lapping method by means of this lapping apparatus, the row bar is subjected to a rough lapping first by the simple oscillating and then by the combined oscillating. A resistance ELG-R of the work-monitoring resistor is monitored, and the ELG-R is converted into an MR element height MRh. If the converted value MRh reaches a predetermined value, a supply of coarse slurry is stopped, finishing slurry is supplied, and the row bar is subjected to a finishing lapping by means of the combined oscillating. During the lapping operation, the working pressure and the rotation speed of the lapping plate are reduced in accordance with the proceeding state of the lapping based on the converted value MRh. 
     In the lapping operation by means of the combined oscillating, the row bar  10  is always moving, there is no moment at which a relative speed between the lapping plate and the surface  10   a  of the row bar  10  to be polished becomes zero. Therefore, a lapped surface is not scratched by the lapping plate. Further, since the lapping direction is not uniform, the row bar can be lapped uniformly and precisely. 
     Recently, however, gaps, for example, between the MR film  17  and the lower shield  18  of the MR elements of the magnetic head slider  11  or the ELG elements  12  are extremely small, and if the finishing lapping using the combined oscillating is carried out, there is a problem that scratches or smears are formed in the gaps, and the sensitivity of the element may be deteriorated due to a short circuit or the like. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to solve at least the problems in the conventional technology. 
     The apparatus for lapping a magnetic head slider according to one aspect of the present invention includes a lapping plate to which a bar of the magnetic head slider makes a contact by a predetermined lapping pressure, a primary oscillating mechanism that makes a primary oscillating of the bar in a radial direction of the lapping plate, and a secondary oscillating mechanism that makes a secondary oscillating of the bar in a direction perpendicular to a direction of the primary oscillating. A coarse lapping of the bar is performed by a combined oscillating of the primary oscillating and the secondary oscillating, and upon completion of the coarse lapping, the apparatus switches to the primary oscillating to finish lapping of the bar. The method of lapping a magnetic head slider according to another aspect of the present invention includes oscillating a bar of the magnetic head slider while the bar is making a contact with a lapping plate by a predetermined lapping pressure. The oscillating includes primary oscillating the bar in a radial direction of the lapping plate, and secondary oscillating the bar in a direction perpendicular to a direction of the primary oscillating. Upon completion of a coarse lapping by the oscillating, performing the primary oscillating to finish lapping of the bar. 
     The other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed descriptions of the invention when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a lapping apparatus according to a first embodiment of the present invention; 
         FIG. 2  is a schematic diagram of the lapping apparatus; 
         FIG. 3  is a plan view of a combined oscillating mechanism; 
         FIG. 4  is a front view of the combined oscillating mechanism; 
         FIG. 5  is a front view of a secondary oscillating mechanism; 
         FIG. 6  is a plan view for illustrating a loading motion (before turning of the combined oscillating mechanism); 
         FIG. 7  is a plan view for illustrating the loading motion (after turning of the combined oscillating mechanism); 
         FIG. 8  is a front view for illustrating the loading motion (before an elevating sub-base moves downward); 
         FIG. 9  is a front view for illustrating the loading motion (after the elevating sub-base moves downward); 
         FIGS. 10A  to  10 H are schematic diagrams for illustrating a process of a combined oscillating motion; 
         FIG. 11  is a flowchart of a lapping process; 
         FIG. 12  is a flowchart of a loading process; 
         FIG. 13  is a flowchart of an unloading process; 
         FIG. 14  is a front view for illustrating a loading motion of a bend unit according to a second embodiment of the present invention; 
         FIG. 15  is a front view for illustrating the loading motion using an extension coil spring; 
         FIG. 16  is a flowchart of a control for reducing a working pressure at both an initial and final positions of the primary oscillating motion; 
         FIG. 17  is a graph of a relation between a oscillating stroke and a load; 
         FIG. 18  is a flowchart of a control to stop a lapping plate at both an initial and a final position of the primary oscillating motion according to a third embodiment of the present invention; 
         FIG. 19  is a graph of a relation between a oscillating stroke and percentage revolutions per minute (rpm) of the lapping plate; 
         FIG. 20  is a schematic diagram of a row bar as viewed from a surface the row bar to be lapped; and 
         FIG. 21  is a schematic diagram of the lapping direction component as viewed from the surface of the row bar to be lapped. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of a method of and an apparatus for lapping magnetic head slider according to the present invention will be explained in detail with reference to the accompanying drawings. The invention is not limited by the embodiments. 
       FIG. 1  is a block diagram a lapping apparatus according to a first embodiment of the present invention.  FIG. 2  is a schematic diagram of the lapping apparatus.  FIG. 3  is a plan view of a combined oscillating mechanism.  FIG. 4  is a front view of the combined oscillating mechanism.  FIG. 5  is a front view of a secondary oscillating mechanism. 
       FIG. 6  is a plan view for illustrating a loading motion (before turning of the combined oscillating mechanism).  FIG. 7  is a plan view for illustrating the loading motion (after turning of the combined oscillating mechanism).  FIG. 8  is a front view for illustrating the loading motion (before an elevating sub-base moves downward).  FIG. 9  is a front view for illustrating the loading motion (after the elevating sub-base moves downward).  FIGS. 10A  to  10 H are schematic diagrams for illustrating a process of the combined oscillating. In the following explanation, the same members as those explained above and members corresponding thereto are designated with the same reference symbols, and redundant explanation will be omitted or simplified. 
     The entire configuration of a lapping apparatus  20  will be explained based on  FIGS. 1  to  9 . The configuration of the lapping apparatus  20  according to the first embodiment is substantially the same as that shown in the Japanese Patent Application Laid-Open No. 2001-162526, therefore the configuration will be explained briefly. The lapping apparatus  20  comprises a lapping machine  21  and a control device  22 . 
     As illustrated in  FIGS. 1 and 2 , the lapping machine  21  comprises a table  24  of a table structure  23 , a lapping plate  25  which rotates in the counterclockwise direction on an upper surface of the table  24 , a pair of left and right lap units  26  and  26  which hold the a row bar  10  through a row tool  31  to push the row bars  10  against the lapping plate  25  by the bend unit  35 , a slurry supply unit (not shown) which supplies a slurry to the lapping plate  25 , a facing unit  27  that dresses the lapping plate  25 , and a wiper unit  28  which scrapes the slurry off the lapping plate  25 . 
     The lapping plate  25  is provided at its upper surface with a correcting ring (not shown) which rotates in a constant direction to spread the slurry on the lapping plate  25 . A compressed air source (not shown) which is an actuation source of pressurizing cylinders  50  and  80  of a later-described lap unit  26  is also provided. 
     As illustrated in  FIG. 1 , the control device  22  comprises a personal computer  30  which is operated by device control software  29 . The control device  22  controls a measuring circuit  32  of a work-monitoring resistance element  12  and a controller  33  which drives the lap unit  26  and the wiper unit  28 . Various setting parameters  34  required for controlling the lapping operation such as a converted value MRh in which a resistance ELG-R of the work-monitoring resistance element  12  is converted into an MR element height MRh, and a target value of the converted value MRh are input into the device control software  29 . 
     The lap unit  26  will be explained mainly based on  FIGS. 6  to  9 . As illustrated in  FIGS. 8 and 9 , the lap unit  26  comprises a base  40  fixed on the table  24 , a turning support plate  42  which is turnably supported on the base  40  by a bearing  41 , and an elevating sub-base  43  which moves up and down on the turning support plate  42 . The turning support plate  42  turns around a shaft  47  through 90° by a turning mechanism  46  that comprises an air cylinder, a rack and a pinion. The elevating sub-base  43  turns integrally with the turning support plate  42 , and moves up and down with respect to the turning support plate  42  by an elevation mechanism  51  while being guided by four guides  49 . The elevation mechanism  51  includes a pressurizing cylinder  50 . 
     A combined oscillating mechanism  60  of the lap unit  26  will be explained. The combined oscillating mechanism  60  is provided on the elevating sub-base  43 , and oscillates the row bar  10  in a combined manner with respect to the lapping plate  25 . That is, the combined oscillating is obtained by combining primary oscillating (simple oscillating) which reciprocates the row bar  10  as a work in the radial direction of the rotating lapping plate  25 , and a secondary oscillating (swivel oscillating) which reciprocates the row bar  10  in a direction intersecting with the primary oscillating direction. With the combined oscillating, a moving locus of the row bar  10  in one period draws substantially a letter of 8 as illustrated in  FIGS. 10A  to  10 H. 
     Phases of a primary oscillating shaft illustrated in  FIGS. 10A  to  10 H can be detected by an origin sensor (not shown) provided on a rotation shaft of a pulley  67 . In each phase, a primary oscillating direction and a secondary oscillating direction of the row bar  10  and a rotation direction of the lapping plate  25  are shown with arrows. 
     As illustrated in  FIG. 3 , the combined oscillating mechanism  60  comprises a primary oscillating mechanism  61  which primary oscillates the row bar  10  and a secondary oscillating mechanism  62  which secondary oscillates the row bar  10 . The primary oscillating mechanism  61  comprises an arm  64  which is turnably supported by a shaft  63  on the elevating sub-base  43 , a motor  65  provided on the elevating sub-base  43 , a pulley  67  which is rotatably provided on the elevating sub-base  43  and is rotated via a timing belt  66  by a pulley  65   a  of the motor  65 , and an eccentric cam  68  which is integrally rotated with the pulley  67  and is provided in a long hole  64   a  of the arm  64 . Thus, if the motor  65  is driven, the pulley  67 , a later-described pulley  72  and the eccentric cam  68  are rotated, and the arm  64  is primary oscillated by the cam function. 
     As illustrated in  FIG. 3 , the secondary oscillating mechanism  62  comprises an arc guide rail  70  provided on the arm  64 , a slide structure  71  which is slidably supported on the guide rail  70 , a pulley  72  which is rotatably supported by the elevating sub-base  43  and around which the timing belt  66  is wound, a rotation arm  73  which is coaxially provided on the pulley  72 , an electromagnetic clutch  74  having a rotation arm  73  connected such that the rotation arm  73  moves in association with rotation of the pulley  72  in its ON state, and a link  75  which connects the rotation arm  73  and the slide structure  71  to each other. 
     As illustrated in  FIG. 5 , the rotation arm  73  is provided with a detection piece  73   a  which detects an origin position (reference position) of the rotation arm  73  by an origin sensor  76 . Similarly, an origin position (reference position) of the arm  64  is detected by an origin sensor (not shown) provided on a rotation shaft of the pulley  67 . These origin sensors can also detect a oscillating phase. 
     According to the combined oscillating mechanism  60  having the above-described configuration, when the electromagnetic clutch  74  is in its ON state, since the pulley  72  and the rotation arm  73  are connected to each other, the rotation arm  73  is rotated by rotation of the pulley  72 , the slide structure  71  is secondary oscillated through the link  75  and with this, the row bar  10  is oscillated in the combined manner. 
     When the electromagnetic clutch  74  is in its OFF state, since the pulley  72  and the rotation arm  73  are not connected to each other, the rotation arm  73  does not rotate even if the pulley  72  rotates, and since the slide structure  71  does not turn and oscillate, the arm  64  is primary oscillated only. 
     As illustrated in  FIGS. 4 ,  8  and  9 , the slide structure  71  comprises a slide body  77  and a connecting member  78  which is fitted to the slide body  77 . As will be explained later, a support frame  79  which turnably supports the bend unit  35  is connected to the connecting member  78  by a pin  79   a.    
     A rear end of the bend unit  35  is turnably supported by a bearing section  82 , and the bend unit  35  is vertically turned by a pressurizing cylinder  80 . With this configuration, the bend unit  35  is pushed or lifted with respect to a direction of the lapping plate  25 . 
     The lapping method will be explained next mainly based on  FIGS. 11  to  13 .  FIG. 11  is a flowchart of a lapping process.  FIG. 12  is a flowchart of a loading process.  FIG. 13  is a flowchart of an unloading process. 
     As illustrated in  FIG. 11  the loading motion is carried out (step S 1 ).  FIG. 12  illustrates details of the loading motion. First, the combined oscillating mechanism  60  is allowed to turn (step S 30 ). As illustrated in  FIGS. 6 and 7 , in this turning motion, the turning mechanism  46  is driven, the turning support plate  42  and the elevating sub-base  43  are turned through 90°, and the bend unit  35  is disposed above the lapping plate  25  (see FIG.  8 ). 
     It is then checked whether the lapping plate  25  is rotating. If the lapping plate  25  is rotating, the lapping plate  25  is stopped (steps S 31 , S 32 ). Then, the arm  64  of the lap unit  26  is loaded (step S 33 ). That is, as illustrated in  FIGS. 8 and 9 , the pressurizing cylinder  50  is driven, the elevating sub-base  43  is lowered while being guided by the four guides  49  and the arm  64  is lowered. 
     The bend unit  35  is then loaded (step S 34 ). The pressurizing cylinder  80  is driven, the bend unit  35  is downwardly turned around the bearing section  82  and is lowered, and the row bar  10  comes into contact with the upper surface of the lapping plate  25 . As illustrated in  FIG. 7 , the row bar  10  is disposed in such a direction that a longitudinal direction of the row bar  10  coincides with a radial direction of the lapping plate  25 , and this position is defined as an origin (reference) position. 
     As illustrated in  FIG. 11 , a working pressure by the pressurizing cylinder  80  is reduced (step S 2 ) and then, rough slurry including diamond powder is supplied (step S 3 ), and the lapping plate  25  is allowed to rotate at high speed (e.g., 50 revolutions per minute) (step S 4 ). 
     The combined oscillating is then started (step S 5 ). At that time, the oscillating periods of the secondary oscillating and the primary oscillating are brought into synchronization with each other (steps S 6  to S 9 ). That is, if the origin sensor  76  of the secondary oscillating checks the origin position, the electromagnetic clutch  74  is turned OFF (steps S 6  and S 7 ). If the origin sensor (not shown) of the primary oscillating provided on the rotation shaft of the pulley  67  checks the origin position, the electromagnetic clutch  74  is turned ON to carry out the combined oscillating (steps S 8  and S 9 ). With this, it is possible to continuously and precisely manage the timing of the lapping, and to enhance the profile regularity. 
     In order to carry out the rough lapping by the combined oscillating, the working pressure by the pressurizing cylinder  80  is set greater (step S 10 ). If the converted value MRh becomes equal to a first set value, the lapping operation proceeds to the finishing lapping (steps S 11  and S 12 ). 
     That is, finishing slurry without diamond powder is supplied (step S 12 ), and the wiper unit  28  is turned ON to start scraping off the rough slurry from the lapping plate  25  (step S 13 ). If a given time is elapsed or a predetermined lapping operation is completed, the wiper unit  28  is turned OFF (steps S 14  and S 15 ). With these steps, the finishing slurry spreads on the lapping plate  25 , and the lapping plate  25  is suitable for the finishing lapping. 
     If the converted value MRh becomes equal to a second set value (step S 16 ), the working pressure is reduced (step S 17 ), and the rotation speed of the lapping plate  25  is changed to a medium speed (e.g., about 25 revolutions per minute) (step S 18 ). Next, if the converted value MRh becomes equal to a third set value (step S 19 ), the rotation speed of the lapping plate  25  is set to a low speed (step S 20 ). This rotation speed is 5 revolutions per minute or lower and, more preferably, 1 revolution per minute or lower. 
     Next, if the origin sensor  76  of the secondary oscillating checks the origin position (step S 21 ), the electromagnetic clutch  74  is turned OFF (step S 22 ), the oscillating manner is switched to the primary oscillating manner and the finishing lapping is carried out. If the converted value MRh becomes equal to the target value (Target) (step S 23 ), the unloading motion is carried out (step S 24 ). 
       FIG. 13  depicts the details of the unloading motion. It is checked that the working is completed, and the unloading motion of the bend unit  35  is carried out (steps S 40  and S 41 ). That is, the pressurizing cylinder  80  is driven, the bend unit  35  is upwardly turned around the bearing section  82  and lifted up, and the row bar  10  is separated from the upper surface of the lapping plate  25 . 
     The rotation of the lapping plate  25  is stopped (step S 42 ), and the lap unit  26  is unloaded in a manner which is the reverse of the loading motion. The lap unit  26  is turned and returned to its initial position (steps S 43  and S 44 ). With the above operation, the lapping operation is completed. 
     As described above, according to the lapping apparatus  20  and the lapping method of the first embodiment, after the rough lapping by means of the combined oscillating is carried out, the oscillating manner is switched to the primary oscillating manner in the finishing state which is close to the target value, and the finishing lapping is carried out at low speed under the small working pressure. Therefore, the lapping precision can further be enhanced, and scratch or smear can be prevented from being generated between the gaps of the MR elements or ELG elements. 
     The lapping apparatus  20  is not limited to the lapping operation of the row bar  10  to obtain the combined type magnetic head having a slider as a final product, and the lapping apparatus  20  can also be applied to a lapping operation of other members. 
       FIG. 14  is a front view for illustrating a loading motion of a bend unit according to a second embodiment of the present invention.  FIG. 15  is a front view for illustrating the loading motion using an extension coil spring.  FIG. 16  is a flowchart of a control for reducing a working pressure at both an initial and final positions of the primary oscillating motion.  FIG. 17  is a graph of a relation between a oscillating stroke and a load. 
     In the second embodiment, the lapping pressure at a dead center of the primary oscillating speed is set to zero or about zero at the time of the finishing lapping by means of the primary oscillating explained in the first embodiment. That is, as illustrated in  FIGS. 14 and 15 , the bend unit  35  is hoisted and the working pressure by the weight of the bend unit  35  itself is set to zero or about zero by disposing an extension coil spring  85  having a predetermined strength, the working pressure of the pressurizing cylinder  80  is controlled at the dead center of the primary oscillating speed and the working pressure is set to zero or about zero. 
     An upper end of the extension coil spring  85  is connected to a base or the like of the pressurizing cylinder  80 , and a lower end of the extension coil spring  85  is connected to an upper portion of the bend unit  35 . If the same pressure reducing effect as that of the extension coil spring  85  can be exhibited, the means is not limited to the extension coil spring, and other means such as an oil damper may be used. 
     The control operation of the working pressure of the pressurizing cylinder  80  will be explained based on  FIGS. 16 and 17 . First, the origin position is checked by the primary oscillating origin sensor (not shown) provided on the rotation shaft of the pulley  67 , and if a given time is elapsed (steps S 50  and S 51 ), the dead center of the primary oscillating speed (position where the oscillating stroke in  FIG. 17  is 0 to 10% and 90 to 100%) can be detected. Therefore, the pressurizing pressure by the pressurizing cylinder  80  is set to zero or about zero (step S 52 ). If another given time is elapsed, i.e., at speed other than the dead center of the primary oscillating speed, an appropriate pressurizing pressure is set by the pressurizing cylinder  80  (steps  53  and S 54 ). 
     According to the lapping apparatus  20  and the lapping method of the second embodiment, as described above, since the lapping pressure is set to zero or about zero at the dead center of the primary oscillating speed at the time of the finishing lapping by the primary oscillating, the lapping is barely carried out at the dead center, and the scratch or smear can be prevented from being generated between the gaps of the MR elements or ELG elements. 
       FIG. 18  is a flowchart of a control to stop a lapping plate at both an initial and a final position of the primary oscillating motion according to a third embodiment of the present invention.  FIG. 19  is a graph of a relation between a oscillating stroke and percentage revolutions per minute (rpm) of the lapping plate. 
     According to the third embodiment, in the finishing lapping by the primary oscillating explained in the first embodiment, the lapping apparatus  20  is controlled such that the number of rotation of the lapping plate  25  is set to zero at the dead center of the primary oscillating speed. 
     Next, the control of the rotation number of the lapping plate  25  will be explained based on  FIGS. 18 and 19 . First, the origin position is checked by the primary oscillating origin sensor (not shown) provided on the rotation shaft of the pulley  67 , and if a given time is elapsed (steps S 60  and S 61 ), the dead center of the primary oscillating speed (position where the oscillating stroke in  FIG. 19  is 0 to 10% and 90 to 100%) can be detected. Therefore, the rotation of the lapping plate  25  is stopped, and a relative speed between the surface to be polished and the lapping plate  25  is set to zero (step S 62 ). If another given time is elapsed, i.e., at speed other than the dead center of the primary oscillating speed, the lapping plate  25  is allowed to rotate again, and the lapping is carried out (steps S 63  and S 64 ). 
     According to the lapping apparatus  20  and the lapping method of the third embodiment, as described above, since the lapping plate  25  is controlled such that its rotation number is set to zero at the dead center of the primary oscillating speed at the time of the finishing lapping by the primary oscillating, the lapping operation by the rotation component of the lapping plate  25  is not carried out at the dead center, and the scratch or smear can be prevented from being generated between the gaps of the MR elements or ELG elements. 
     Although the rotation of the lapping plate  25  is stopped in the third embodiment, the present invention is not limited to this only, and the lapping plate  25  may be controlled such that the rotation number is close to zero (e.g., 0.5 revolution per minute). 
     As explained above, according to the present invention, the lapping precision can further be enhanced, and the scratch or smear can be prevented from being generated between the gaps of the MR elements or ELG elements. 
     Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.