Automatic lapping method and a lapping apparatus using the same

The present invention relates to an automatic lapping method for lapping a work piece and a lapping apparatus using the same. The lapping apparatus laps a work piece by moving the mounting base 103 relatively to a lapping plate 104. On a coarse processing step, the lapping plate 104 is controlled with high speed as detecting a remaining amount for lapping the work piece. Then, on a fine processing step, said lapping plate 104 is controlled with low speed by detecting that the remaining amount h for lapping said work piece has reached to a predetermined amount H0. Thereby, it becomes possible to continuously execute the coarse processing and the fine processing in one lapping apparatus.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a method for automatically lapping a work
 piece and a lapping apparatus using the same. More particularly, it
 relates to a lapping method for continuously lapping the work piece and a
 lapping apparatus using the same.
 For example, after forming a magnetic head thin film, the magnetic head
 thin film is lapped on the process of manufacturing a magnetic head.
 Heights of a magnetic resistance layer and a gap of the magnetic head thin
 film of the magnetic head are made to have a certain constant by lapping
 on the manufacturing process of the magnetic head.
 For the heights of the magnetic resistance layer and the gap, sub-micron
 order of accuracy is required. Therefore, it is necessary to lap work
 pieces or magnetic thin films with high accuracy.
 2. Description of the Related Art
 FIGS. 21A and 21B are explanatory diagrams of a composite type magnetic
 head.
 As shown in FIG. 21A, the composite type magnetic head includes a magnetic
 resistance element 82 formed on a base plate 81 and a writing element 85.
 The magnetic resistance element 82 is formed of a magnetic resistance film
 83 and a pair of conducting films 84 as shown in FIG. 21B. A resistance
 value of the magnetic resistance element 82 is varied by an external
 magnetic field. The magnetic resistance element 82 has a function to read
 out an electric current having a value according to magnetic field
 strength of a track 90 on a magnetic disk.
 As the magnetic resistance element 82 is an element for reading out the
 current, it is required to provide a different element 85 for writing. The
 writing element 85 includes an inductive head. The inductive head is
 comprised of a lower magnetic pole 86, an upper magnetic pole 88 faced to
 the lower magnetic pole 86 with a certain gap, and a coil 87 provided
 between the lower and upper magnetic poles 86 and 88 to magnetically
 excite them. A non-magnetic insulating layer 89 is provided around the
 coil 87.
 In such the composite type magnetic head, it is required to have a constant
 resistance value of the magnetic resistance film 83 in the magnetic
 resistance element 82 for each magnetic head. However, it is difficult to
 make the resistance value be constant or uniform on the process of
 manufacturing the thin film for the magnetic head. Therefore, after
 forming the thin film of the magnetic head, a height (width) h of the
 magnetic resistance film 83 is adjusted so that a resistance value may be
 uniformed.
 FIGS. 22A, 22B, 23A, 23B, 23C and 23D are diagrams explaining the process
 of manufacturing the composite type magnetic head.
 As shown in FIG. 22A, a plurality of composite type magnetic heads are
 formed on a semiconductor wafer 100 by a thin film technique. Next, as
 shown in FIG. 24B, the wafer 100 is cut into strips to make a plurality of
 row bars 101. A row bar 101 includes a plurality of the magnetic heads 102
 arranged in one row. Resistance elements 102a are provided on the left and
 right ends, and at the center of the row bar 101 for monitoring the
 process of the manufacturing.
 As described above, the height of the magnetic resistance film 83 for the
 magnetic head 102 is lapped to be constant or uniform. However, the row
 bar 101 is extremely thin, for example, about 0.3 mm. It is, therefore,
 difficult to mount the row bar 101 directly to a lapping jig, and as shown
 in FIG. 22C, the row bar 101 is bonded to a mounting tool or base 103 with
 heat dissoluble wax.
 Then, as shown in FIG. 23A, the row bar 101, which is bonded to the
 mounting base 103, is placed on a lapping plate 104 for lapping the row
 bar 101. As known in Japanese Unexamined patent application published No.
 2-124262 (U.S. Pat. No. 5,023,991) or Japanese Unexamined patent
 application published No. 5-123960, the resistance value of the resistance
 element 102a for monitoring is always measured while lapping the row bar
 101. Then, it can be detected whether or not the magnetic resistance film
 of the magnetic head 102 has become a targeted height.
 When it is detected by the measurement of the resistance value that the
 magnetic resistance film has been lapped to the targeted height, the
 lapping processing is stopped. After that, a slider can be formed on a
 bottom surface 101-1 of the row bar 101, as shown in FIG. 23B.
 The row bar 101 is further cut into a plurality of magnetic heads 102, as
 the row bar 101 is mounted on the mounting base 103 as shown in FIG. 23C.
 Each magnetic head 102 is taken out from the mounting base 103 by heating
 and melting the heat dissoluble wax, as shown in FIG. 25D.
 In this way, a row bar 101 including a plurality of the magnetic heads 102
 is prepared, and lap processing is performed for the row bar 101.
 Therefore, the magnetic resistance film on the plurality of magnetic heads
 102 can be lapped by one step.
 FIG. 24 is an explanatory diagram of a conventional lapping apparatus.
 The lapping apparatus has a rotary lapping plate 104, as shown in FIG. 24.
 A supporting block 105 has three pads 105a contacting to the lapping plate
 104. The pads 105a smoothly spread slurry (abrasive liquid) on the lapping
 plate 104 and fill the slurry into the lapping plate 104. The pads 105a,
 further, may soften pressure of the supporting block 105 to the surface of
 the lapping plate 104.
 The supporting block 105 is swung on the lapping plate 104 by a swing
 mechanism 106. The supporting block 105 supports the mounting base 103.
 Therefore, the row bar 101, which is bonded to the mounting base 103, is
 lapped by the rotation of the lapping plate 104 and the swing of the block
 105.
 In the conventional lapping apparatus, speed and pressure on lapping
 process are set as to be constant from starting to finishing the process.
 It has been possible to reduce the time required for the processing by
 increasing rotating times of a lapping plate or giving higher pressure.
 Thereby, it becomes possible to save the time for the lapping process.
 However, there has been a problem to lower quality of lapping when the
 processing speed is increased.
 On the other hand, when the speed for the lapping process is decreased to
 obtain good quality of lapping, there would be another problem to take
 much time for the lapping process.
 It may be considered that a first lapping apparatus for speeding the
 processing up and a second lapping apparatus for speeding the processing
 down are employed together. After executing a coarse processing in the
 first lapping apparatus, a fine processing is performed by the second
 lapping apparatus. However, the work piece has to be set on the lapping
 apparatus twice according to the method, and therefore, troublesome for an
 operator and take much time. Therefore, it is unsuitable for mass
 production of the work pieces.
 SUMMARY OF THE INVENTION
 Accordingly, it is an object of the present invention to provide an
 automatic lapping apparatus to save processing time and realize quality of
 lapping process and a lapping apparatus using the same.
 It is another object of the present invention to provide a lapping method
 for automatically changing coarse processing and fine processing and a
 lapping apparatus using the same.
 It is further object of the present invention to provide a lapping method
 for automatically changing coarse processing and fine processing according
 to a remaining amount of processing the work piece and an apparatus using
 the same.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Embodiments according to the present invention will be now explained in
 accompanying with the attached drawings. Throughout the following
 descriptions, the same reference numerals and symbols are used to denote
 and identify corresponding or identical components.
 FIG. 1 is an principle diagram of the present invention.
 A lapping apparatus according to the present invention laps a work piece by
 relatively moving a mounting base 103 and a lapping plate 104. In a coarse
 processing, the lapping plate 104 is controlled with a high processing
 speed, as detecting a remaining amount h for lapping the work piece. In a
 fine processing, the remaining amount h for lapping the work piece is
 detected as reached to a predetermined amount H0, and the lapping plate
 104 is controlled with a low processing speed.
 Further, the lapping apparatus according to the present invention has a
 lapping plate 104, which relatively moves to the mounting base 103, a
 detecting part 14 for detecting a remaining amount h for lapping a work
 piece, and a control part 183 for detecting the remaining amount h for
 lapping the work piece becomes a predetermined amount H0 and controlling
 the lapping plate 104 with a low speed, after controlling the lapping
 plate 104 with a high speed.
 According to the present invention, it is possible to automatically shift
 the coarse processing to the fine processing according to the remaining
 amount for lapping the work piece in one lapping apparatus. It is also
 possible to save the time required for lapping the work piece as the
 coarse processing is performed. The fine processing is also performed,
 thus realizing good quality of lapping the work piece. Additionally, as
 the coarse processing and the fine processing are performed in one lapping
 apparatus, an operator has to set the work piece to the lapping apparatus,
 one time. Thereby, it is possible to save the time for operation. In the
 apparatus, the processing is automatically shifted from the coarse
 processing to the fine processing, as detecting a remaining amount for
 lapping. Therefore, it is also possible to move from the coarse processing
 to the fine processing in an appropriate time.
 FIG. 2 is a perpendicular view of one example of a lapping apparatus
 according to the present invention, FIG. 3 is a top view of the lapping
 apparatus of one embodiment according to the present invention, FIG. 4 is
 a side view of the lapping apparatus shown in FIG. 2, and FIG. 5 is a
 cross sectional view of the lapping apparatus shown in FIG. 2.
 As shown in FIGS. 2, 3 and 4, the lapping plate 104 is rotated by a motor,
 not shown in the diagrams. Six pads 111 are provided under a lapping base
 10. The lapping base 10 is set on a rotary shaft 150 fixed on the
 apparatus, so that the base 10 can be rotated around the shaft 150. A cam
 118 is provided on other end of the lapping base 10.
 A swinging mechanism 15 swings the lapping base 10. The swinging mechanism
 15 has a swinging motor 155, a cam pulley 152 rotated by the swing motor
 155, and a swing cam 151 provided on the cam pulley 152. A swinging cam
 151 is engaged with a cam hole 118 of the lapping base 10, as shown in
 FIGS. 3 and 4.
 Therefore, the lapping base 10 swings toward an arrow having both
 directions shown in FIG. 3 according to the rotation of the swinging motor
 155. Two sensor actuators 153 are provided on a cam pulley 152. The sensor
 154 detects the sensor actuators 153. The sensor actuators 153 are
 positioned so as to be detected by the sensor 154 when the lapping base 10
 is located on a point P, i.e., a central point of swinging, shown in FIG.
 3.
 Returning back to FIG. 2, a pressure mechanism 13, which is explained
 later, is provided on the lapping base 10. The pressure mechanism 13 puts
 pressure on the adapter 11. The adapter 11 is set on the lapping base 10.
 The adapter 11 is formed like a L formation as illustrated in FIG. 4. A
 mounting base 103 to which a work piece 101 is bonded is set on a first
 surface 11a of the adapter 11. The mounting base 103 is fixed to the first
 surface 11a of the adapter 11 by a fixing mechanism 112.
 The adapter 11 has a second surface 11b. A holder 113 is provided on an end
 of the second surface 11b. A supporting mechanism 110 provided on the
 lapping base 10 has a screw 110b for adjusting the height, and a spherical
 supporting section 110a. The holder 113 of the adapter 11 is engaged with
 the supporting section 110a.
 Therefore, the adapter 11 is supported by the lapping base 10 at one point.
 The adapter 11 contacts to a lapping plate 104 via the processing surface
 of the work piece 101. That is, the adapter 11 is supported by one point
 position of the supporting mechanism 110, and other two point positions,
 which are provided on both edges of the mounting base 103, to which the
 work piece 101 is bonded. Thereby, the mounting base 103 can be rotated
 around the center of the supporting mechanism so that the mounting base
 103 can follow the lapping plate 104 independently from the lapping base
 10.
 Accordingly, the work piece 101 bonded to the mounting base 103 can be
 lapped by referencing the lapping plate 104 as a standard regardless of
 the accuracy of the lapping base 10. Thereby, it becomes possible to
 uniformly lap the work piece 101.
 Returning back to FIG. 2, an unload mechanism 12 is provided on the lapping
 base 10. The unload mechanism 12 pushes the adapter 11 as shown in FIG. 4
 so that the adapter 11 rotates around the supporting section 110a to
 evacuate the work piece 101 from the lapping plate 104. This unload
 mechanism 12 has an unload block 121 and an unload cylinder 120.
 Unload operation will be now explained in accompanying with FIGS. 7A and
 7B. When a value of a resistance for monitoring the lapping of the row bar
 101 becomes a 15 predetermined value, it is required to stop the lapping.
 When the rotation of the lapping plate 104 is stopped, lapping is stopped.
 However, the lapping plate 104 is stopped after reducing the speed by a
 stopping instruction. Therefore, the work piece should be lapped until the
 lapping plate 104 is finally stopped, thus causing dispersion of accuracy
 of the size of the work piece, that is, a row bar 101. Additionally, there
 is a case where a mark of the surface plate is put on the work piece.
 Therefore, an unload cylinder 120 and an unload block 121 are provided on
 the lapping base 10 as shown in FIGS. 7A and 7B. As shown in FIG. 7B, the
 unload cylinder 120 is activated to stick the unload block 121 out when
 the value of the resistance for monitoring the lapping becomes the
 predetermined value. Then, the adapter 11 rotates above around the
 supporting section 110a to separate the row bar 101 from the lapping plate
 104. Thereby, when the value of the resistance for monitoring the lapping
 becomes the predetermined value, lapping may be immediately stopped.
 Therefore, accuracy of the size of the row bar 101 can be realized.
 Further, as the adapter 11 is set on the lapping base 10, unloading of the
 work piece, that is, a row bar 101 becomes easy.
 As shown in FIG. 3, when the sensor 154 detects that the actuators 153 are
 positioned at the point P, i.e., the central point of swinging, the
 unloading is performed. This is because the mark of the lapping plate 104
 is put on the surface plate of the work piece according to the stopped
 position if the stop position of the swinging mechanism is random.
 It is inclined to put the mark of the surface 104 on the work piece because
 speed of swinging becomes lower on both ends of swinging portion. On the
 contrary, the speed of swinging becomes highest at the center position P
 of swinging. Therefore, it is not easy to put the mark of the surface
 plate 104 on the work piece. The sensor 154 detects that the actuator 153,
 i.e., the sensor 154 detects that the lapping base 10 reaches to the
 center position P of swinging, unloading of the work piece is performed as
 described above. Thereby, it is possible to prevent from putting the mark
 of the surface plate 104 on the work piece 101 when the swinging mechanism
 stops.
 The probe mechanism 14 is provided on the end of the lapping base 10. The
 probe mechanism 14 electrically contacts to an resistance element for
 monitoring processing of the work piece, that is, the row bar 101 mounted
 to the mounting base 103, as shown in FIG. 4. The probe mechanism 14 has a
 probe 140 electrically, which contacts to an resistance element for
 monitoring the processing.
 Returning back to FIG. 2, a correction ring 160 is rotated by a modified
 ring rotary mechanism 161. The correction ring 160 expands slurry
 (abrasive liquid) and fills the slurry into the lapping plate 104, so that
 the flatness of the lapping plate 104 may be kept.
 As shown in the cross sectional view of FIG. 5, the pressure mechanism 13
 includes three pressure cylinders 13L, 13C and 13R. The pressure cylinders
 13L, 13C and 13R are supported by a supporting plate 132. The supporting
 plate 132 can rotate around a rotary shaft 133. Therefore, when setting
 the adapter 11 to the lapping base 10, it is possible to release upper
 space of the lapping base 10 and set the adapter 11 to the lapping base 10
 by rotating the supporting plate 132.
 The pressure cylinder 13L on the left side puts pressure to a left portion
 of the adapter 11. The pressure cylinder 13C on center puts pressure on a
 center of the adapter 11. Further, the pressure cylinder 13R on the right
 portion puts pressure on a right portion of the adapter 11. A pressure
 block 130 is provided on the end of each of the pressure cylinders 13L,
 13C and 13R. The pressure blocks 130 are supported by a spherical section
 131. Accordingly, it is possible to uniformly put pressure power of the
 pressure cylinders onto the adapter 11.
 A pressure mechanism will be now explained in accompanying with FIG. 6. As
 shown in FIG. 6, solenoid valves 135-1, 135-2 and 135-3, and regulators
 134-1, 134-2 and 134-3 are provided on cylinders 13L, 13C and 13R,
 respectively.
 As the lapping plate 104 is rotated, the speed for rotating on a position
 P1 of an inner side of the mounting base 103 is different from that on a
 position P0 of an outer side. That is, the speed V0 on the position P0 of
 the outer side is higher than the speed V1 on the position P1 of the inner
 side. Therefore, the processing speed on the outer side becomes higher
 than that on the inner side.
 To correct the difference, supply pressure of the outer cylinder 13L is set
 different from that of the inner cylinder 13R. That is, the supply
 pressure of the outer cylinder 13L is set lower than that of the inner
 cylinder 13R. Therefore, the set pressure of the outer regulator 134-1 is
 made lower than that of the inner regulator 134-3.
 Thereby, the processing pressure on the outer side becomes lower than that
 on the inner side. Therefore, it becomes possible to control the
 processing speed on the outer side equal to that on the inner side.
 FIGS. 7A and 7B are explanatory diagrams of the work, FIG. 8 is an
 explanatory diagram of a row bar, FIG. 9 is a structural diagram of an ELG
 element shown in FIG. 10, and FIGS. 10A and 10B are explanatory diagrams
 of the ELG element shown in FIG. 9.
 As shown in FIG. 7A, the mounting base 103 has a mounting hole 103a. The
 row bar 101 is bonded on the mounting base 103. A terminal printed circuit
 board 142 is provided on the mounting base 103. The terminal printed
 circuit board 142 has a large space. The terminals of resistance elements
 for monitoring on the row bar 101 described later, i.e., ELG elements, are
 connected to terminals of the terminal printed circuit board 142 by
 bonding wires 142a.
 The terminal space of ELG elements on the row bar 101 is small.
 Additionally, the terminals of the ELG elements are covered with the
 abrasive liquid. Therefore, even if the terminals are directly contacted
 to the probe 140, resistance measurements can not be stably executed.
 Therefore, in the present invention, the probe 140 is contacted to the
 terminal printed circuit board 142. As the terminal printed circuit board
 142 can be provided on the position away from the lapping surface 104, and
 it may have a large terminal spare thereon. It becomes possible to execute
 stable resistance measurement.
 As shown in FIG. 7B, the mounting base 103 may be mounted to the adapter
 11. The adapter 11, which engages to a hole 103a of the mounting base 103
 has protrusions 114 for supporting the mounting base 103, and a fixing
 block 112. The mounting base 103 is positioned by the protrusions 114, and
 is set between the first surface 11a and the fixing block 112.
 As shown in FIG. 8, the row bar 101 includes a plurality of magnetic heads
 102 and ELG elements 102a. The ELG elements 102a are provided on three
 positions of left, center, and right of the row bar 101.
 As shown in FIG. 9, the ELG element is formed of an analog resistance 102-1
 and a digital resistance 102-2. The analog resistance 102-1 has a pattern
 in which value of resistance becomes larger according to the reduction of
 the resistance film. The digital resistance 102-2 includes a pattern in
 which value of resistance becomes off when the resistance film is reduced
 until becoming to a constant value.
 Therefore, an equivalent circuit is expressed as shown in FIG. 10A, and the
 analog resistance 102-2 is expressed as a variable resistance Ra. As shown
 in FIG. 10B, as reducing the height of the ELG element, the resistance
 values increases. The digital resistance 102-2 is expressed by five switch
 resistances as shown in FIG. 10A. Then, FIG. 11B shows a line graph
 showing variation on each of off positions of the resistances.
 The value of the ELG element corresponds to a height of the ELG element.
 The relationship between the resistance value Ra of the ELG element and
 the height h of the ELG element can be nearly expressed in the following
 equation:
 Ra=a/h+b (1)
 Coefficients a and b can be obtained by an experiment in advance. However,
 the characteristic is varied depending on each ELG element. The digital
 resistance is provided to compensate such the problem. The off positions
 h1 to h5 of the digital resistances are predetermined in advance. The off
 position of a digital resistance is detected and the measured resistance
 values and the off position are substituted for the equation (1). If two
 of the off points on the digital resistances can be detected, coefficients
 a and b in the equation (1) can be obtained.
 The resistance values of the ELG element comes to the height of the ELG
 element in this equation (1). Thereby, it is possible to obtain the height
 of the ELG element by measuring the resistance values of the ELG element.
 Therefore, it can be judged whether or not the height of the ELG element
 has reached to a targeted value. As mentioned later, as the height of the
 ELG element is reached to the targeted value, lapping is stopped.
 FIG. 11 is an explanatory diagram of a probe mechanism shown in FIG. 2.
 As shown in FIG. 11, the probe block 140 supports a plurality of probes
 140a. The probe block 140 is moved by a probe cylinder 141. The probe
 cylinder 141 pushes the probe block 140, so that the probe 140a may
 contact the terminal printed circuit board 142. On the other hand, the
 probe 140a is evacuated to easily set the adapter 11 on the lapping base
 10.
 FIG. 12 is a cross sectional view of a bending mechanism shown in FIGS. 7A
 and 7B. FIGS. 13A and 13B are explanatory diagrams of a bending operation,
 and FIG. 14 is an explanatory diagram of a bending mechanism.
 As shown in FIG. 13A, there is a case where the row bar 101 is warped and
 bonded to the mounting base 103. It is difficult to uniformly lap the work
 piece, that is the row bar 101, even when the warp is present in
 sub-microns.
 A bending mechanism is provided on the adapter 11 in order to correct the
 warp. As shown in FIGS. 7B and 12, the bending mechanism includes a
 bending arm 115 and a screw for controlling bending. The bending arm 115
 pushes a wall of the mounting hole 103a of the mounting base 103. The
 screw 116 controls the amount of pushing the wall by the bending arm 115.
 As shown in FIGS. 13B, when the bending arm 115 pushes a center position of
 the lower section of the wall of the hole 103a, the mounting base 103 is
 warped and the warp of the row bar 101 is compensated. A mount of
 compensation is controlled by rotating the screw 116. In here, after
 bonding the work piece to the row bar 101, the row bar 101 is traced by
 the measure to measure the warp amount. Then, the correcting ratio is
 determined according to the warp amount.
 As shown in FIG. 14, an automatic bending mechanism 17 is provided on the
 lapping base 10. A wrench 172 is engaged with the screw 116 for
 controlling bending, as shown in FIG. 15. A motor 171 rotates the wrench
 172. A bending cylinder 170 drives the wrench 172 and the motor 171 toward
 the bending control screw 116.
 In this example, the rotation amount of the motor 171 is controlled
 according to the measured warp amount to rotate the screw 116. Thereby, it
 becomes possible to automatically compensate the warp.
 FIG. 15 is a block diagram of one embodiment according to the present
 invention, FIGS. 16 and 17 are operational flowing charts of lapping the
 work in the one embodiment, FIG. 18 is an operational flowing chart of a
 MR-h measurement, FIG. 19 is an explanatory diagram of a resistance value
 measurement operation, and FIG. 20 is an explanatory diagram of lapping
 processes.
 As shown in FIG. 15, a scanner 180 switches channels of each probe 140a. A
 constant current supply 181 supplies a constant current for resistance
 measurement. A digital multi meter 182 measures a voltage according to an
 output from the scanner 180 and converts the voltage into the value of
 resistance. A rotary motor 104a on the lapping plate rotates the lapping
 plate 104.
 A personal computer (hereinafter called as a controller) 183 converts the
 measured value of resistance outputted from the digital multi-meter 182
 into the height of the ELG element (MR-h) to control each section. That
 is, the controller 183 controls a swing motor 155 on a lapping plate 104,
 a bending motor 171, a correction ring motor 161, and a rotary motor 104a.
 The controller 183 controls each of the pressure cylinders 13L, 13C and
 13R. The controller 183 further controls a cylinder 120 for the unload
 mechanism 12 and a cylinder 141 for the probe mechanism 14. The controller
 183 receives an output of the swing sensor 15 of the swing mechanism to
 control the unload mechanism 12.
 Hereinafter, a processing by the controller 183 will be explained in
 accompanying with FIGS. 16 and 17.
 At first, initial values are inputted by employing an input unit of the
 controller 183 (STEP S1). The initial values are, for example, the number
 of a semiconductor wafer, a row bar address or the like. After inputting
 the initial values, an operator sets the adapter 11 on the lapping base
 10, and then, turns a start switch on (STEP S1-1).
 The controller 183 activates the lapping plate 104 to be rotated (STEP S2).
 That is, the controller 183 makes the motor 104a rotate in order to rotate
 the lapping plate 104 with high speed. The controller 183 rotates a swing
 motor 155 for swing operation. The controller 183 further rotates the
 modified ring motor 161. The controller 183 starts to supply slurry.
 Then, the controller 183 turns the center cylinder 13C on (STEP S2-1).
 Thereby, coarse processing (STAGE 1) is performed with the load of the one
 pressure cylinder. Burrs are removed from the row bar 101 by the coarse
 processing.
 The controller 183 reads the resistance value from the digital multi meter
 182 to measure MR-h explained in FIG. 22 (STEP S3). The controller 183
 starts a timer to count from the starting of lapping the work piece, and
 judges whether or not the value of the timer has become 60 seconds. If the
 value of the timer is within 60 seconds, the controller 183 measures MR-h
 (STEP S3-1). That is, coarse processing is performed for 60 seconds. While
 coarse processing, the controller 183 measures MR-h to detect off
 positions of the digital resistance described above.
 The controller 183 finishes coarse processing after elapsing 60 seconds.
 Then, the controller 183 turns all cylinders 13L, 13C and 13R of the
 pressure mechanism 13 on (STEP S4). That is, the controller 183 chamfers
 the surface of the work piece 101 by adding the load (STAGE 2). The
 chamfering may prevent the ELG element 102a on the row bar 101 from being
 shorted.
 The controller 183 reads the resistance value from the digital multi meter
 182 to measure MR-h explained in FIG. 18 (STEP S5). The controller 183
 judges whether or not MR-h of all ELG elements positioned on the left
 side, the center and the right side are less than 8.0 microns (STEP S5-1).
 If the MR-h of all ELG elements are not less than 8.0 microns, the
 controller 183 continues measuring the MR-h.
 As shown in FIGS. 19A and 19B, when a partial short status occurs on the
 ELG element on a grinding step performed before the lapping process, the
 value of the analog resistance Ra (ELG-R) becomes abnormal. Therefore, the
 converted height MR-h also becomes abnormal. When all of MR-h reach to 8.0
 microns, a partial short status can be removed and the abnormal value is
 canceled. In here, the next step for controlling the process by employing
 the value of the analog resistance is executed.
 After removing the short status, the warp compensation and light-left
 difference compensation (STAGE 3) are performed (STEP S6). The controller
 183 rotates the bending motor 171 described in FIG. 18 to compensate the
 warp. The amount of the compensation is inputted to the controller 183 by
 measurement operation explained in FIG. 17. The controller 183 controls
 the bending motor 171 by the use of the compensation value.
 The controller 183 reads the resistance value from the digital multi meter
 182 and measures MR-h, as explained in FIG. 18 (STEP S7).
 The controller 183, in order to obtain the height of the ELG element at the
 center of gravity, calculates an average value between the MR-h (L) which
 is the height of the left ELG element and the MR-h (R) which is the height
 of the right ELG element. Then, the controller 183 calculates an average
 value between the average value obtained from the above-described
 calculation and the MR-h (C) which is the height of the center ELG element
 to obtain the MR-h (G) which is the height of the ELG element on the
 center of gravity. The controller 183 judges whether or not the MR-h(G) on
 the center of gravity is less than (the targeted MR-h--the finishing
 width) (STEP S8). If the MR-h (G) of the ELG element on the center of the
 gravity is not less than (the targeted MR-h--the finishing width),
 left-right difference modification is performed. The controller 183 finds
 a difference X between the MR-h (L) which is the height of the left ELG
 element and the MR-h (R) which is the height of the right ELG element
 (STEP S8-1).
 If the difference X is more than -0.03 microns, the right end of the row
 bar 101 is 0.03 microns (allowable amount) higher than the left end.
 Therefore, the left pressure cylinder 13L in the pressure mechanism 13 is
 turned to off to lighten the load on the left end, and then returning back
 to the step S7 (STEP S8-2).
 On the other hand, the difference X is more than 0.03 microns, the left end
 of the row bar 101 is 0.03 microns (allowable amount) higher than the
 right end. Therefore, the right cylinder 13R is turned to off to lighten
 the load on the right end, and then, returning back to the step S7 (STEP
 S8-3).
 When the difference X is between -0.03 microns and 0.03 microns, the
 left-right difference of the row bar 101 is in the allowable range. Then,
 all of the pressure cylinders 13L, 13C and 13R are turned to on, and
 returning back to the step S7 (STEP S8-4).
 The controller 183 confirms the warp amount (STEP S9). At first, a
 difference Y between of the MR-h (C) which is the height of the center ELG
 element and the average value between the MR-h of the heights of the ELG
 elements on the left and right ends is obtained. The controller 183 judges
 whether or not the difference Y is more than the allowable value 0.03
 microns. If the difference is not more than 0.03 microns, going to the
 next step S10. On the other hand, the difference Y is more than the
 allowable value, the warp compensation amount explained in the step S6 is
 performed (STEP S9-1). The compensation amount is obtained from the
 above-described difference Y.
 The controller 183 goes to the fine processing (STAGE 4). Then, the
 controller 183 controls the motor 104a to reduce the rotation speed of the
 surface plate 104. The controller 183 turns all of the pressure cylinders
 13L, 13C and 13R in the pressure mechanism 13 to off. The fine processing
 is performed without giving the load (STEP S10).
 The controller 183 reads the resistance value from the digital multi meter
 182 to measure the MR-h described in FIG. 22 (STEP S11). The controller
 183 judges whether or not the MR-h (G) that is the height of the ELG
 element on the center of gravity is less than the targeted value (STEP
 S11-1).
 When the controller 183 detects that the height MR-h (G) is less than the
 targeted value, the processing is controlled for finishing. The controller
 183 judges whether or not the swing sensor 153 described in FIG. 3 is
 turned to on (STEP S12). When the swing sensor 153 is turned to on, as
 described above, the lapping base 10 is positioned on the predetermined
 position P.
 The controller 183 activates the probe cylinder 141 to evacuate the probe
 140 (STEP S12-1). Next, the controller 183 activates the unload cylinder
 120 of the unload mechanism 12 to evacuate the mounting base 103 from the
 lapping plate 104 (STEP S12-2). Then, the controller 183 stops the lapping
 plate 104 and finishes the processing (STEP S12-3).
 In this way, the coarse processing and the fine processing are continuously
 executed by changing conditions for the lapping. Therefore, it is possible
 to realize high productivity differently in comparison with the apparatus,
 in which coarse and fine processings are discontinuously or separately
 executed. Further, it is also possible to save an operator from
 troublesomeness.
 The MR-h measurement will be explained according to FIG. 18.
 The controller 183 reads the resistance value from the digital multi meter
 182 (STEP S20).
 The controller 183 compares the previously measured resistance value R0
 with the just measured resistance value R1 (STEP S21). If the previously
 measured resistance value R0 is larger than the value R1, the previously
 measured value R0 is employed as the resistance value R (STEP S21-1). If
 the value R0 is not larger than the value R1, the value R1 is employed as
 the value R (STEP S21-2).
 As explained in FIG. 10B, the value of resistance becomes larger, depending
 on the reduction of the height of the element. Accordingly, if it is
 normal, a value on a later sampling is larger than a value of resistance
 on a previously measured sampling. However, there is a case where the
 value of resistance becomes abnormal due to a partial short status of the
 element or influence of abrasive liquid. To remove the abnormal value of
 resistance, the following processing is performed:
 The controller 183 judges whether or not the resistance values of all ELG
 elements have been measured (STEP S22). If the measurement has not been
 finished for all ELG elements, a channel of the scanner 180 is switched,
 and the processing is returned to the step s20 (STEP S22-1).
 When the controller 183 finishes the measurement of the resistance values
 for all ELG elements, the controller 183 detects an off position of the
 digital resistance element from the variation of the resistance value
 (STEP S23). As described above, when the controller 183 detects the off
 position of the digital resistance element, the controller 183 obtains
 coefficients shown in the equation (1). The controller 183 converts the
 measured resistance value R into the height MR-h and finishes the
 processing (STEP S23-1).
 As shown in FIG. 20, on the coarse processing on the stage 1, the cambering
 process on the stage 2 for removing an abnormal value, and the left-right
 difference modifying process on the stage 3, the rotary number of the
 lapping plate is large (50 rpm), and additionally, the pressure process is
 also performed by the pressure mechanism 13. Therefore, it is possible to
 process with high speed.
 On the other hand, when the remaining amount for lapping the work piece
 reaches to the predetermined value, the fine processing is performed on
 the stage 4. On the fine processing, the rotary time of the lapping plate
 is small (15 rpm), and the pressure process is not performed by the
 pressure mechanism 13. Therefore, the speed for processing becomes low.
 As coarse processing and fine processing are continuously executed in one
 lapping apparatus by varying the processing speed in this way, it is
 realized to greatly increase the productivity. Further, as an operator
 sets the work piece only one time, the operator can save the time.
 Although the present invention has been described with reference to
 embodiments, the invention is not restricted to those. The following
 modification can be applicable.
 (1) In the above-described embodiments, a row bar formed of a row of the
 magnetic heads as lapped parts is explained as one example. However, it is
 possible to apply the present invention to lap other parts.
 (2) Other elements can be used as the elements for monitoring.
 As explained above, the present invention takes effect as follows:
 (1) As automatically going from the coarse processing to the fine
 processing according to the remaining amount for lapping the work piece in
 one lapping apparatus, it is realized to save time of lapping the work
 piece and improve the quality for the processing.
 (2) The coarse processing and the fine processing are executed on one
 lapping apparatus. Therefore, an operator sets the work piece only one
 time, thus reducing time for operation.
 (3) As automatically going from the coarse processing to the fine
 processing by detecting the remaining amount for lapping the work piece,
 it is possible to automatically proceed from the coarse processing to the
 fine processing on the appropriate time.
 The present invention may be embodied in other specific forms without
 departing from the sprit or essential characteristics thereof. It should
 of course be understood that those which are the same as the technical
 concept of the invention are within the protective scope of the present
 invention.