GRINDING DEVICE AND METHOD OF GRINDING

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a grinding device and a method of grinding, utilized to grind an elongated wafer bar, for example.

2. Description of the Prior Art

A piezoelectric element is employed in a gyro sensor. An angular velocity is detected based on vibration in the piezoelectric element. The top end of the piezoelectric element is divaricated like a tuning folk. The piezoelectric element is held on an attachment member. The bottom and back surfaces of the piezoelectric element are adhered to the attachment member. A chamfer is formed at the edge defined between the bottom and back surfaces. The chamfer enables a close contact of the bottom and back surfaces against the attachment member. The piezoelectric element is thus firmly fixed on the attachment member.

Such a piezoelectric element is cut out of an elongated wafer bar. The aforementioned chamfer is formed at the edge of the wafer bar before the piezoelectric element is cut off. A first blade is first utilized to form a notch on the surface of the wafer bar. A second blade thinner than the first blade is then utilized to divide the wafer bar along the notch. The notch serves to define a chamfer at the edge of the divided wafer bar. The piezoelectric element is then cut out of the wafer bar.

The wafer bar is made of a single-crystal piezoelectric material having brittleness, such as a lithium niobate (LiNbO₃), for example. Accordingly, the contact of the first and second blades may cause damages such as microcracks and chipping, for example. Such damages remain on the piezoelectric element cut out of the wafer bar. The damages may cause fracture of the piezoelectric element during the operation of the gyro sensor.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide a grinding device and a method of grinding, contributing to establishment of a chamfer on a work with a high accuracy.

According to a first aspect of the present invention, there is provided a grinding device comprising: a base defining a flat abrasive surface; a holding member defining an elongated holding surface, for holding an object, opposed to the flat abrasive surface; and a movable block having a spherical receiving body for supporting the holding member for change in its attitude around the spherical receiving body, the movable block designed to move in parallel with the flat abrasive surface.

An elongated work is attached to the elongated holding surface opposed to the flat abrasive surface in the grinding device. The holding member is supported on the spherical receiving body so that the holding member changes its attitude around the spherical receiving body. The change of the attitude of the holding member reliably enables the work to uniformly contact with the flat abrasive surface of the base. When the movable block moves in parallel with the flat abrasive surface, a chamfer is formed on the work with a high accuracy. The work is prevented from suffering from generation of microcracks and chipping. In addition, if the work moves on the flat abrasive surface only in one direction, the probability of generation of microcracks and chipping is considerably reduced.

The grinding device may further comprise a detector for detecting a variation in the angle of the holding member around the spherical receiving body. A change in the angle of the holding member determines the grinding amount of the work. In this case, the grinding device may further comprise a distance adjusting mechanism designed to adjust the distance between the elongated holding surface and the spherical receiving body. An increase in the distance between the elongated holding surface and the spherical receiving body leads to a reduced variation in the angle of the holding member around the spherical receiving body during a grinding process. Deviation is thus suppressed in the inclination angle of the work. This results in suppression in the dimensional errors. A decrease in the distance between the elongated holding surface and the spherical receiving body leads to an increased variation in the angle of the holding member during a grinding process. This results in an enhanced resolution of the varied angle. The distance between the elongated holding surface and the spherical receiving body may be determined in view of the dimensional accuracy of the work.

The elongated holding surface may be inclined relative to the flat abrasive surface by a predetermined inclination angle in the grinding device. The spherical receiving body may be coupled to the movable block for relative movement in a perpendicular direction normal to an imaginary plane including the flat abrasive surface. The movement of the spherical receiving body enables establishment of the horizontal attitude of the holding member, for example. The flat abrasive surface is defined on a non elastic body.

According to a second aspect of the present invention, there is provided a grinding device comprising: a receiving support defining a flat receiving surface; an abrasive member placed on the receiving surface of the receiving support, the abrasive member defining a flat abrasive surface; a feeding mechanism designed to move the abrasive member along the receiving surface of the receiving support; a holding member defining an elongated holding surface, for holding an object, opposed to the flat abrasive surface, and a supporting member having a spherical receiving body for supporting the holding member for change in its attitude around the spherical receiving body.

An elongated work is attached to the elongated holding surface opposed to the flat abrasive surface in the grinding device. The holding member is supported on the spherical receiving body so that the holding member changes its attitude around the spherical receiving body. The change of the attitude of the holding member reliably enables the work to uniformly contact with the flat abrasive surface of the abrasive member. When the abrasive member is fed along the flat receiving surface, a chamfer is formed on the work with a high accuracy. The work is prevented from suffering from generation of microcracks and chipping. In addition, if the abrasive member moves only in one direction, the probability of generation of microcracks and chipping is considerably reduced. Moreover, since the feeding mechanism enables the movement of the abrasive member, the grinding process contributes to an enhanced efficiency.

The elongated holding surface may be inclined relative to the flat abrasive surface by a predetermined inclination angle in the grinding device. The spherical receiving body may be coupled to the supporting member for relative movement in a perpendicular direction normal to an imaginary plane including the flat abrasive surface in the same manner as the aforementioned grinding device. The grinding device may further comprise a detector for detecting a variation in the angle of the holding member around the spherical receiving body. The flat receiving surface of the receiving support may be defined on a non elastic body.

According to a third aspect of the present invention, there is provided a method of grinding, comprising: setting a holding member on a spherical receiving body for change in the attitude of the holding member for contacting the edge of a work with a flat abrasive surface, the holding member defining an elongated holding surface, for holding the work, opposed to the flat abrasive surface; and subjecting the edge of the work to a grinding process through relative movement between the work and the flat abrasive surface in one direction.

An elongated work is attached to the elongated holding surface opposed to the flat abrasive surface in the method of grinding. The holding member is supported on the spherical receiving body so that the holding member changes its attitude around the spherical receiving body. The change of the attitude of the holding member reliably enables the work to uniformly contact with the flat abrasive surface. When relative movement is induced between the work and the flat abrasive surface, a chamfer is formed on the work with a high accuracy. The work is prevented from suffering from generation of microcracks and chipping. In addition, if the work moves on the flat abrasive surface only in one direction, the probability of generation of microcracks and chipping is considerably reduced.

The work defines: a first surface extending from the edge in one direction, the first surface having a first surface roughness; and a second surface extending from the edge in other direction, the second surface having a second surface roughness smaller than the first surface roughness. In this case, the second surface follows after the first surface during the relative movement of the flat abrasive surface and the work. Since the first surface precedes the second surface during the relative movement between the work and the flat abrasive surface, the work is prevented from generation of microcracks and chipping. The grinding amount of the work may be specified in accordance with the detected variation in the angle of the holding member around the spherical receiving body. The flat abrasive surface may be defined on a non elastic body.

According to a fourth aspect of the present invention, there is provided a method of fixing a work, comprising: applying a hotmelt to a holding surface defined on a holding member having been heated and thereafter setting a work on the holding surface; causing relative movement of the work along the holding surface, thereby spreading the hotmelt between the work and the holding surface; cooling the work and the holding member down to harden the hotmelt with the work urged against the holding surface by a predetermined urging force; and heating the work and the holding member after the work has been released from the predetermined urging force.

When the work is placed on the holding surface, the relative movement of the work is caused along the holding surface. The relative movement of the work forces the hotmelt to spread uniformly between the work and the holding surface by an equal thickness. The work is urged against the holding member with a predetermined urging force. The work and the holding member are then cooled down so that the hotmelt gets cured or hardened. After the work has been released form the predetermined urging force, the work and the holding member are again heated. The hotmelt melts again. Since the work is released from the urging force, the work is released from the stress resulting from the adhesion of the hotmelt. Warp of the work can thus be eliminated.

BRIEF DESCRIPTIONS OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments in conjunction with the accompanying drawings, wherein:

FIG. 1 is a perspective view schematically illustrating a grinding device according to a first embodiment of the present invention;

FIG. 2 is a perspective view schematically illustrating a holding member;

FIG. 3 is a partially exploded view schematically illustrating a spherical receiving body;

FIG. 4 is an enlarged partial sectional view of the grinding device for schematically illustrating the spherical receiving body;

FIG. 5 is a perspective view schematically illustrating a gyro sensor;

FIG. 6 is a perspective view schematically illustrating a work set on a holding surface of the holding member;

FIG. 7 is a perspective view schematically illustrating a weight placed on the work;

FIG. 8 is an enlarged partial sectional view of the grinding device for schematically illustrating the edge of the work contacting with an flat abrasive surface;

FIG. 9 is an enlarged partial side view schematically illustrating the edge of the work sliding on the flat abrasive surface;

FIG. 10 is a perspective view schematically illustrating a grinding device according to a second embodiment of the present invention; and

FIG. 11 is a side view schematically illustrating a grinding device according to a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically illustrates a grinding device 11 according to a first embodiment of the present invention. The grinding device 11 includes a base 12. The base 12 includes a base body 13 defining a flat surface. The base body 13 is made of a non elastic body, namely a metallic mass. An abrasive sheet 14 is bonded to the flat surface of the base body 13. The abrasive sheet 14 includes abrasive grains adhered to a resin sheet. The abrasive grains may be made of alumina, for example. An alcoholic solution is utilized to firmly bond the abrasive sheet 14 to the flat surface of the base body 13, for example. A flat abrasive surface 15 is defined on the surface of the abrasive sheet 14. Since the base body 13 is made of a metallic mass, the flat abrasive surface 15 is defined on a non elastic body.

A movable block 16 is placed behind the abrasive sheet 14. The movable block 16 includes a block body 18 coupled to a guiding rail 17. The guiding rail 17 extends in the longitudinal direction of the base 13. The block body 18 is designed to move in the longitudinal direction of the base body 13 along the guiding rail 17. The block body 18 moves in parallel with the flat abrasive surface 15. A knob 19 is formed on the block body 18. The knob 19 stands upright from the surface of the block body 18. An operator pinches the knob 19 with fingers to move the block body 18 in the longitudinal direction. The guiding rail 17 and block body 18 is structured as a so-called LM (linear motion) guide.

A pair of stops 21 is placed on the base body 13 on the movement path of the block body 18. The stops 21 may be made of an elastic body. The elastic body may be attached to a support column standing upright from the surface of the base body 13. The stop 21 closer to the abrasive sheet 14 is designed to receive the front end of the block body 18 to restrain the forward movement of the block body 18. The stop 21 farther from the abrasive sheet 14 is designed to receive the rear end of the block body 18. The backward movement of the block body 18 is thus restrained. The stops 21 serve to limit the longitudinal movement of the block body 18 within a predetermined range.

A supporting unit 22 is placed on the block body 18 for supporting a holding member 23. The holding member 23 includes a block member 24 extending forward from the movable block 16. A reflecting mirror 25 is attached to the surface of the block member 24. The reflecting mirror 25 defines a reflecting surface. A clamp 26 is attached to the front end of the block member 24. A holding block 27 is held between the clamp 26 and the front end of the block member 24. A screw 28 exhibits a fastening force to stationarily hold the holding block 27 between the clamp 26 and the block member 24. The screw 28 is screwed into the block member 24. The holding block 27 is elongated in the lateral direction, perpendicular to the longitudinal direction, of the base body 13 along the flat abrasive surface 15 of the abrasive sheet 14. The bottom of the holding block 27 is received on the flat abrasive surface 15.

A detector, namely an autocollimator 29, is opposed to the reflecting mirror 25. The autocollimator 29 may be supported on a support arm. The support arm may be fixed to the base body 13, for example. The autocollimator 29 includes a light source emitting a laser beam to the reflecting mirror 25. The emitted laser beam is reflected on the reflecting mirror 25. The reflected laser beam is supplied to a CCD (charge-coupled device) sensor incorporated in the autocollimator 29. The inclination of the reflecting mirror 25 generates a shift between the angle of the reflected light and the angle of the emitted light. The CCD sensor is designed to detect a change in the angle of the reflecting mirror 25, or the holding member 23, based on the shift between the angles of the emitted light and the reflected light.

As shown in FIG. 2, a bottomed bore 31 is formed in the lower surface of the block member 24. The bottomed bore 31 defines a cylindrical space. The supporting unit 22 is received in the cylindrical space as described later in detail. The central axis of the cylindrical space is set perpendicular to the surface of the reflecting mirror 25. A holding surface 32 is defined on the bottom of the holding block 27. The holding surface 32 extends along an imaginary plane. A work is received on the holding surface 32 as described later. The holding surface 32 is elongated in the longitudinal direction of the holding block 27. A guiding wall 33 is formed on the holding block 27. The guiding wall 33 stands upright from the holding surface 32. The guiding wall 33 is designed to extend in the longitudinal direction of the holding surface 32 along the edge of the holding surface 32.

As shown in FIG. 3, the supporting unit 22 includes a lock nut 34. A spherical receiving body 35 is placed above the lock nut 34. As shown in FIG. 4, the spherical receiving body 35 is received in the bottomed bore 31 of the holding member 23. The spherical receiving body 35 receives the bottom of the bottomed bore 31. The spherical receiving body 35 simultaneously contacts with the inward wall surface of the bottomed bore 31. The spherical receiving body 35 in this manner supports the holding member 23 for change in the attitude of the holding member 23 around the spherical receiving body 35. A screw shaft 36 is formed integral with the spherical receiving body 35. The screw shaft 36 is screwed into a screw bore 37 formed in the block body 18. The rotation of the screw shaft 36 around its central axis enables movement of the spherical receiving body 35 in the perpendicular direction normal to an imaginary plane including the flat abrasive surface 15. The spherical receiving body 35 thus enjoys change in the height from the surface of the block body 18.

The lock nut 34 is engaged with the screw shaft 36. The rotation of the lock nut 34 enables the movement of the lock nut 34 in the perpendicular direction along the screw shaft 36. When the lock nut 34 is tightened toward the block body 18, the screw shaft 36 and the spherical receiving body 35 are prevented from rotating. The height of the spherical receiving body 35 is maintained. When the lock nut 34 is loosened, the screw shaft 35 is allowed to rotate. The rotation of the screw shaft 36 enables adjustment of the height of the spherical receiving body 35. The lock nut 34 is tightened toward the block body 18 after the adjustment. The height of the spherical receiving body 35 is maintained in this manner.

When the holding member 23 is set in the horizontal attitude, the reflecting mirror 25 extends within a horizontal plane. The autocollimator 29 determines zero degree for the angle of the holding member 23. The height of the spherical receiving body 35 is adjusted depending on the detection result of the autocollimator 29. The adjustment of the height of the spherical receiving body 35 causes the attitude of the holding member 23 around the spherical receiving body 35. The holding surface 32 is opposed to the flat abrasive surface 15. The holding surface 32 is elongated in parallel with the flat abrasive surface 15. An imaginary plane 32a including the holding surface 32 intersects with an imaginary plane 27a including the rear end of the holding block 27 by an inclination angle α approximately equal to 60 degrees, for example. Here, the imaginary plane 27a is set perpendicular to a horizontal plane. The imaginary plane 32a intersects with the flat abrasive surface 15 at an inclination angle β approximately equal to 30 degrees, for example.

FIG. 5 schematically illustrates the structure of a gyro sensor 41. The gyro sensor 41 includes a first substrate 42. A package 43 covers over the first substrate 42. A second substrate 44 stands on the surface of the first substrate 42 in the inner space of the package 43. An L-shaped attachment member 45 is stationarily attached to the second substrate 44, for example. The attachment member 45 receives the root end of a piezoelectric element 46 in the shape of a tuning fork. Pin terminals 47 are fixed to the first substrate 42. The front end of the piezoelectric element 46 vibrates in one predetermined direction for detection of angular velocity. When the gyro sensor 41 rotates, the direction of the vibration of the front end changes based on the Coriolis force. Such a change in the direction of the vibration is electrically detected. The angular velocity of an object is detected in this manner.

As is apparent from FIG. 5, the piezoelectric element 46 is attached to the attachment member 45 in the gyro sensor 41. The bottom and back surfaces of the piezoelectric element 46 are partly adhered to the attachment member 45. An oblique surface 48 is formed on the attachment member 45 at the inside corner. A chamfer 49 is formed on the piezoelectric element 46 at the edge defined between the bottom and back surfaces of the piezoelectric element 46. The chamfer 49 serves to reliably allow the bottom and back surfaces of the piezoelectric element 46 to closely contact with the surfaces of the attachment member 45 irrespective of the oblique surface 48. The piezoelectric element 46 is firmly fixed to the attachment member 45. The gyro sensor 41 thus allows an accurate detection of an angular velocity based on the vibration of the piezoelectric element 46.

A brief description will be made on a method of making the piezoelectric element 46. The holding member 23 is heated on a hotplate up to 80 degrees Celsius approximately, for example. A hotmelt is applied to the holding surface 32. As shown in FIG. 6, a work, namely a wafer bar 51, is placed on the holding surface 32. The wafer bar 51 has previously been prepared. The wafer bar 51 is made of a thin plate. The piezoelectric elements 46 are defined in the wafer bar 51. The piezoelectric elements 46 are arranged in the longitudinal direction. The wafer bar 51 is allowed to move relative to the holding block 27 along the holding surface 32. The relative movement of the wafer bar 51 serves to uniformly spread the hotmelt between the wafer bar 51 and the holding surface 32 by an equal thickness. One of the side edges of the wafer bar 51 is abutted against the guiding wall 33. The wafer bar 51 is in this manner set at a predetermined position.

As shown in FIG. 7, a weight 52 is placed on the holding block 27. The weight 52 acts equally on the wafer bar 51. The wafer bar 51 is thus urged against the holding surface 32 by a predetermined urging force. The holding member 23 is thereafter cooled down to a room or normal temperature so that the hotmelt gets cured or hardened. The weight 52 is then removed from the holding member 23. The holding member 23 is thereafter again heated on the hotplate. The hotmelt again melts. Since the wafer bar 51 is released from the weight 52, the wafer bar 51 is released from the stress resulting from the adhesion of the hotmelt. Warp of the wafer bar 51 is eliminated. The holding member 23 is then again cooled down to the room or normal temperature so that the hotmelt gets cured or hardened. The wafer bar 51 is in this manner finally fixed on the holding surface 32.

As shown in FIG. 8, the holding member 23 is mounted on the movable block 16. The spherical receiving body 35 is received in the bottomed bore 31 of the holding member 23. The wafer bar 51 is received on the flat abrasive surface 15 at the edge 51c extending straight between the front surface 51a and the side surface 51b. The height of the spherical receiving body 35 is adjusted in view of the detection result of the autocollimator 29. The adjustment of the height is utilized to set the inclination angle of the holding member 23 at a predetermined angle. The predetermined angle may previously be calculated. A change in the angle of the holding member 23 determines the grinding amount of the wafer bar 51. In the present embodiment, the predetermined angle is set at 0.043 degrees. Specifically, the surface of the holding member 23 extends within an imaginary plane intersecting with a horizontal plane by 0.043 degrees. The rear end of the holding member 23 gets closer to the base body 13 rather than the front end of the holding member 23. In this case, since the holding member 23 is supported on the spherical receiving body 35 for change in the attitude around the spherical receiving body 35, the edge 51c of the wafer bar 51 is reliably allowed to uniformly and thoroughly contact with the flat abrasive surface 15. A predetermined inclination angle is established between the holding surface 32 and the flat abrasive surface 15.

As shown in FIG. 9, the front surface 51a of the wafer bar 51 intersects with the flat abrasive surface 15 by an inclination angle of 30 degrees approximately. The side surface 51b of the wafer bar 51 intersects with the flat abrasive surface 15 by an inclination angle of 60 degrees approximately. The diameter or size of the abrasive grains 14a of the abrasive sheet 14 is set at 10 μm approximately, for example. The surface roughness of the side surface 51b is set larger than that of the front surface 51a in the wafer bar 51. The movable block 16 moves only in one direction along the guiding rail 17, namely toward the rear end of the base body 13. The movable block 16 moves in parallel with the flat abrasive surface 15. The front surface 51a follows after the side surface 51b during the movement. The edge 51c slides on the flat abrasive surface 15. The edge 51c is subjected to a grinding process in this manner. The rear end of the block body 18 is finally received on the stop 21 of the rear.

An operator then lifts the holding member 23. The wafer bar 51 is moved away from the flat abrasive surface 15. The operator brings the block body 18 forward toward the front end of the base body 13. The edge 51c is prevented from contacting with the flat abrasive surface 15 during the forward movement. When the block body 18 is set at a predetermined position, the edge 51c is placed on the flat abrasive surface 15. The angle of the holding member 23 is measured by use of the autocollimator 29. The measured angle specifies the grinding amount of the wafer bar 51. Unless the measured angle reaches zero degree, the operator again moves the movable block 16 backward. The wafer bar 51 slides on the flat abrasive surface 15. The operator repeats the grinding process until the angle of the holding member 23 reaches zero degree. When the angle of the holding member 23 becomes zero degree, a predetermined chamfer is formed on the wafer bar 51.

When the predetermined chamfer is formed, the holding member 23 is detached from the supporting unit 22. The holding member 23 is set on the hotplate. The holding member 23 is heated. The hotmelt melts. The wafer bar 51 is thus easily detached from the holding member 27. The wafer bar 51 is then washed by use of an ultrasonic washer. The hotmelt is removed from the wafer bar 51. The piezoelectric elements 46 are then individually cut out of the wafer bar 51. The production of the piezoelectric elements 46 is in this manner realized. The individual piezoelectric element 46 is adhered to the attachment member 45. The production of the gyro sensor 41 is in this manner completed.

The holding member 23 is supported on the spherical receiving body 35 so that the holding member 23 changes its attitude around the spherical receiving body 35 in the grinding device 11. The edge 51c of the wafer bar 51 is reliably allowed to uniformly contact with the flat abrasive surface 15. A chamfer is formed on the wafer bar 51 with a high accuracy. The wafer bar 51 is prevented from suffering from generation of microcracks and chipping. In addition, the wafer bar 51 is designed to move on the flat abrasive surface 15 only in one direction. The side surface 51b of a first surface roughness moves precedes the front surface 51a of a second surface roughness smaller than the first surface roughness in the grinding process of the wafer bar 51. The inventors have revealed based on an observation that such a grinding process enables a significant reduction in the probability of generation of microcracks and chipping. In the observation, the possibility of chipping was reduced from 3% approximately to 1% approximately, for example.

FIG. 10 schematically illustrates a grinding device 11a according to a second embodiment of the present invention. A holding unit 23a is utilized in place of the aforementioned holding member 23. The holding unit 23a includes a first block member 24a and a second block member 24b. The aforementioned bottomed bore 31 is formed in the first block member 24a. The first block member 24a is coupled to the supporting unit 22 at the bottomed bore 31. The clamp 26 is attached to the front end of the second block member 24b. The clamp 26 is utilized to stationarily attach the holding block 27 on the second block member 24b. Like reference numerals are attached to the structure and components equivalent to those of the aforementioned grinding device 11.

A screw 61 is utilized to couple the first block member 24a to the second block member 24b. Connecting shafts 62 are provided in parallel with the screw 61. The connecting shafts 62 are designed to extend from the first block member 24a into the second block member 24b. One ends of the connecting shafts 62 are fixed to the first block member 24a. The other ends of the connecting shafts 62 are respectively received in corresponding bores, not shown, formed in the second block member 24b, for example. When the screw 61 turns around its longitudinal axis in a first direction, the distance can be reduced between the first and second block members 24a, 24b. When the screw 61 turns around its longitudinal axis in a second direction opposite to the first direction, the distance increases between the first and second block members 24a, 24b. The screw 61 serves as a distance adjusting mechanism according to the present invention.

An increase in the distance between the first and second block members 24a, 24b causes an increase in the distance between the holding surface 32 and the contact point established between the spherical receiving body 35 and the first block 24a in the grinding device 11a. Such an increase in the distance leads to a reduced variation in the angle of the holding member 23 during the grinding process. Deviation is thus suppressed in the inclination angle of the wafer bar 51 relative to the flat abrasive surface 15. This results in suppression in the dimensional error. On the other hand, a decrease in the distance between the first and second block members 24a, 24b causes a reduction in the distance between the holding surface 32 and the contact point established between the spherical receiving body 35 and the first block 24a. Such a reduction in the distance leads to an increased variation in the angle of the holding member 23 during the grinding process. This results in an improved resolution of the varied angle. The angle of the holding member 23 is thus set at zero degree with a high accuracy. Dimensional accuracy is in this manner enhanced. The distance between the holding surface 32 and the contact point established between the spherical receiving body 35 and the first block member 24a may be determined in view of the dimensional accuracy of the wafer bar 51.

FIG. 11 schematically illustrates a grinding device 11b according to a third embodiment of the present invention. The supporting unit 22 is placed on a stationary support 71 in the grinding device 11b. The edge 51c of the wafer bar 51 contacts with a flat receiving surface 73 defined on a stationary receiving support 72. The receiving support 72 is made of a non elastic body such as a metallic mass. A pair of rollers 74 is placed below the receiving support 72. An abrasive belt 75 is wound around the receiving support 72 and the rollers 74. A predetermined tension is applied to the abrasive belt 75 between the receiving support 72 and the rollers 74. Accordingly, a flat abrasive surface 76 is defined on the abrasive belt 75 on the receiving support 72. Since the receiving support 72 is made of a non elastic metallic material, the flat abrasive surface 76 is defined on the non elastic body. The abrasive belt 75 has the structure similar to that of the abrasive sheet 14.

The abrasive belt 75 is interposed between a pair of feed rollers 77 at a position between the rollers 74. The feed rollers 77 rotate in opposite directions from each other. A driving motor may be coupled to the feed rollers 77 for the rotation of the feed rollers 77. The feed rollers 77 realize the circulation of the adhesive belt 75 around the rollers 74 and the flat receiving surface 73. The abrasive belt 75 is fed in one direction along the receiving surface 73 of the receiving support 72. The feed rollers 77 serve as a feeding mechanism according to the present invention. The feed rollers 77 in this manner realize relative movement between the wafer bar 51 and the abrasive belt 75. The wafer bar 51 is received on the flat abrasive surface 76 of the abrasive belt 75. The direction of the circulation of the abrasive belt 75 allows the side surface 51b of the wafer bar 51 to precede the front surface 51a of the wafer bar 51. Like reference numerals are attached to the structure and components equivalent to those of the grinding device 11.

A description will be made on the operation of the grinding device 11b. The wafer bar 51 is adhered to the holding surface 32 in the same manner as described above. The holding member 23 is mounted on the supporting unit 22. The height of the spherical receiving body 35 is adjusted to set the holding member 23 in the attitude defined by a predetermined angle. The edge 51c of the wafer bar 51 uniformly contacts with the flat abrasive surface 76. The feed rollers 77 turn to drive the abrasive belt 75. The abrasive belt 75 is fed in one direction along the receiving surface 73. The edge 51c slides on the flat abrasive surface 76. The edge 51c is thus subjected to a grinding process. The autocollimator 29 continuously measures the angle of the holding member 23 during the grinding process. When the angle of the holding member 23 reaches zero degree, the abrasive belt 75 stops circulating. A predetermined chamfer is formed on the wafer bar 51 in this manner.

The holding member 23 is supported on the supporting unit 22 for change in the attitude around the spherical receiving body 35 in the grinding device 11b in the same manner as the grinding devices 11, 11b. The edge 51c of the wafer bar 51 reliably and uniformly contacts with the flat abrasive surface 76. A chamfer is formed on the wafer bar 51 with a high accuracy. The wafer bar 51 is prevented from suffering from generation of microcracks and chipping. In addition, the abrasive belt 75 is driven to circulate in one direction. The wafer bar 51 slides on the flat abrasive surface 76 in one direction. The side surface 51b of a first surface roughness precedes the front surface 51a of a second surface roughness smaller than the first surface roughness. This enables a significant reduction in the probability of generation of microcracks and chipping. Moreover, the abrasive belt 75 automatically moves relative to the wafer bar 51 based on the action of the feed rollers 75. A manual movement of the holding member 23 is thus not required. Efficiency of the grinding process is thus enhanced.

A vacuum pump may be mounted on the holding block 27 in the grinding devices 11, 11a, 11b. Air inlets may be formed in the holding surface 32 of the holding block 27. The vacuum pump operates to suck air through the air inlets. The negative pressure at the air inlets serves to hold the wafer bar 51 on the holding surface 32. A heating process can thus be omitted for fixation of the wafer bar 51. In addition, an electric actuator may be utilized to enable the vertical movement of the spherical receiving body 35, for example. An abrasive sheet 14 and abrasive belt 75 having abrasive grains of a smaller dimension may be utilized for a finishing grinding process of the chamfer. The dimension of the abrasive grains may be set at approximately 5 μm, for example.

GRINDING DEVICE AND METHOD OF GRINDING

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Priority Claims (1)