Abstract:
The abrasive machine is capable of feeding a proper amount of slurry and preventing a work piece from sticking on an upper abrasive plate. The abrasive machine comprises: the upper abrasive plate abrading an upper face of the work piece and having a plurality of slurry holes for feeding the slurry to the work piece; a lower abrasive plate abrading a lower face of the work piece; a slurry feeding unit pressurizing and feeding the slurry; a plurality of slurry paths respectively connecting the slurry holes to the slurry feeding unit; a plurality of valve mechanisms respectively provided to the slurry paths so as to control flows of the slurry; and a control section for controlling the valve mechanisms.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to an abrasive and a method of abrading a work piece, more precisely relates to an abrasive machine, which has an upper abrasive plate and a lower abrasive plate for abrading both faces of a work piece, and a method of abrading a work piece with said machine.  
           [0002]    In a conventional abrasive machine having an upper and a lower abrasive plates, a work piece is sandwiched between the abrasive plates, and the abrasive plates are rotated in the opposite directions with feeding slurry to the work piece, so that both faces of the work piece can be abraded. The conventional abrasive machine (see Japanese Patent Gazette No. 11-262862) is shown in FIG. 5. The abrasive machine includes: an upper abrasive plate  10  and a lower abrasive plate  12 , which are rotated in the opposite directions; a sun gear  14 : an internal gear  16 ; and carriers  18 . The carriers  18  are provided between the abrasive plates  10  and  12 , and a gear (not shown), which engages with the sun gear  14  and the internal gear  16 , is formed along an outer edge of each carrier  18 . With this structure, the carriers  18  are capable of spinning about their own axes and orbiting along the internal gear  16 . By rotating the abrasive plates  10  and  12 , upper faces and lower faces of work pieces  20 , which are respectively held in through-hole of the carriers  18 , can be abraded by the abrasive plates  10  and  12 .  
           [0003]    The lower abrasive plate  12  is held by a lower holder  22 , and the lower holder  22  is rotatably supported by a base  24 . The lower holder  22  is rotated by a rotary shaft  22   a , so that the lower abrasive plate  12  is rotated. The upper abrasive plate  10  is rotated by a drive shaft  26  and engaging members  28  and  29 .  
           [0004]    The sun gear  14  is rotated by a rotary shaft  30 . A casing  32  supports the internal gear  16 .  
           [0005]    In the abrasive machine shown in FIG. 5, a plate  40  is provided above the upper abrasive plate  10 , a slurry ring  42 , whose sectional shape is a U-shape, is provided to the plate  40 , and connecting pipes  44  and connecting tubes  46  are connected to the slurry ring  42 , so that the slurry ring  42  is communicated with slurry holes  48  formed in the upper abrasive plate  10 . Valves  50  for controlling amount of flow are respectively provided to the connecting tubes  46 . The plate  40  is rotated in one direction together with the upper abrasive plate  10 , and slurry supplied to the slurry ring  42  is fed to the work pieces  20  via the connecting pipes  44 , the connecting tubes  46  and the slurry holes  48 . The valves  50  adjust amount of the slurry fed to the slurry holes  48 . For example, much slurry is fed to the slurry holes  48  near the center of the upper abrasive plate  10 .  
           [0006]    In the conventional abrasive machine, the slurry is uniformly fed to the work pieces  20  by adjusting the amount of the slurry supplied to the slurry holes  48  of the upper abrasive plate  10 . However, as shown in FIG. 5, the slurry flows downward from the slurry ring  42  by gravity or own weight. Therefore, it is difficult to control the amount of the slurry because the slurry holes  48  must be properly selected and the flow of the slurry must be precisely controlled.  
           [0007]    In the abrasive machine, the upper abrasive plate  10  is lifted or moved upward until reaching an uppermost position when the work pieces  20  are exchanged, maintenance is taken place, etc. At that time, some work pieces  20  stuck on an abrasive face of the upper abrasive plate  10  are lifted together with the upper abrasive plate  10 . If the work pieces  20  are lifted together with the upper abrasive plate  10 , the work piece  20  fall therefrom, and they are damaged. These days, the work pieces  20  are large and thin, so they are apt to be stuck on the upper abrasive plate  10 . Especially, in the abrasive machine capable of automatically feeding and removing work pieces, sticking the work pieces onto the upper abrasive plate must be prevented.  
           [0008]    To solve the problem of sticking work pieces onto an upper abrasive plate, some methods have been proposed. For example, mist of a fluid is jetted from the upper abrasive plate to work pieces (see Japanese Patent Gazette No. 11-226864); jet holes are formed in the upper abrasive plate, and high pressure air is jetted from the jet holes toward work pieces so as to peel off the work pieces (see Japanese Patent Gazette No. 9-66448); an ejecting member, which is usually located away from the upper abrasive plate, is actuated to mechanically eject work pieces from the upper abrasive plate (see Japanese Patent Gazette No. 6-55436); a compressed fluid, e.g., compressed air, is jetted from the upper abrasive plate so as to peel off work pieces (see Japanese Patent Gazette No. 58-171825).  
           [0009]    However, even if jet holes for jetting a compressed fluid are formed in the upper abrasive plate so as to peel off work pieces, the jet holes are independent of the slurry holes. Thus, if arrangement of the slurry holes has priority over that of the jet holes, the arrangement of the jet holes are restricted so that the jet holes cannot be located at ideal positions. Further, in the abrasive machines capable of abrading various types of work pieces, jet holes cannot be always located at ideal positions because the positions of the jet holes are fixed.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention has been invented to solve the above described problems of the conventional abrasive machines.  
           [0011]    An object of the present invention is to provide an abrasive machine capable of feeding a proper amount of slurry according to arrangement of a work piece so as to precisely abrade the work piece and preventing the work piece from sticking on an upper abrasive plate so as to automatically feeding and removing the work piece.  
           [0012]    Another object of the present invention is to provide a method of abrading a work piece with the abrasive machine of the present invention.  
           [0013]    To achieve the object, the present invention has following structures.  
           [0014]    The abrasive machine of the present invention comprises:  
           [0015]    an upper abrasive plate rotating to abrade an upper face of a work piece, the upper abrasive plate having a plurality of slurry holes for feeding slurry to the work piece;  
           [0016]    a lower abrasive plate rotating to abrade a lower face of the work piece, the lower abrasive plate sandwiching the work piece with the upper abrasive plate so as to abrade the both faces of the work piece;  
           [0017]    a slurry feeding unit pressurizing and feeding the slurry;  
           [0018]    a plurality of slurry paths respectively connecting the slurry holes to the slurry feeding unit;  
           [0019]    a plurality of valve mechanisms being respectively provided to the slurry paths so as to control flows of the slurry; and  
           [0020]    a control section for controlling the valve mechanisms.  
           [0021]    In the abrasive machine, the control section may control degree of opening the valve mechanisms so as to control feeding the slurry to each of the slurry holes.  
           [0022]    In the abrasive machine, the slurry feeding unit may be a pressurizing unit capable of feeding the slurry with fixed pressure,  
           [0023]    the pressurizing unit may be connected to the slurry holes by a distributor, and  
           [0024]    the valve mechanisms may be electromagnetic valves.  
           [0025]    The abrasive machine may further comprise:  
           [0026]    a carrier having a through-hole in which the work piece is set so as to abrade the both faces of the work piece, the carrier being provided between the upper abrasive plate and the lower abrasive plate;  
           [0027]    a carrier holder holding an outer edge of the carrier; and  
           [0028]    a crank mechanism for orbiting the carrier holder.  
           [0029]    The abrasive machine may further comprise:  
           [0030]    a shaft being connected to the upper abrasive plate;  
           [0031]    a rotating mechanism for rotating the shaft; and  
           [0032]    a slurry feeding tube being provided in the shaft,  
           [0033]    wherein the slurry paths are connecting tubes respectively connecting the slurry holes to the slurry feeding tube.  
           [0034]    In the abrasive machine, the shaft may include a water path for feeding water for cooling the upper abrasive plate.  
           [0035]    The abrasive machine may further comprise:  
           [0036]    a carrier having a through-hole in which the work piece is set so as to abrade the both faces of the work piece, the carrier being provided between the upper abrasive plate and the lower abrasive plate;  
           [0037]    a sun gear engaging with an outer edge of the carrier; and  
           [0038]    an internal gear engaging with the outer edge of the carrier,  
           [0039]    wherein the carrier spins and orbits along the internal gear.  
           [0040]    The abrasive machine may further comprise:  
           [0041]    a supporting plate being provided to the upper abrasive plate, the supporting plate supporting a distributor; and  
           [0042]    a plurality of connecting tubes respectively connecting the slurry holes to the distributor.  
           [0043]    The method of the present invention is a method of abrading a work piece in a machine comprising:  
           [0044]    an upper abrasive plate rotating to abrade an upper face of a work piece, the upper abrasive plate having a plurality of slurry holes for feeding slurry to the work piece;  
           [0045]    a lower abrasive plate rotating to abrade a lower face of the work piece, the lower abrasive plate sandwiching the work piece with the upper abrasive plate so as to abrade the both faces of the work piece;  
           [0046]    a slurry feeding unit pressurizing and feeding the slurry;  
           [0047]    a plurality of slurry paths respectively connecting the slurry holes to the slurry feeding unit;  
           [0048]    a plurality of valve mechanisms respectively provided to the slurry paths so as to control flows of the slurry; and  
           [0049]    a control section for controlling the valve mechanisms, the control section controlling the valve mechanisms so as to control amount of the slurry fed from the slurry feeding unit to each of the slurry holes while abrading the work piece.  
           [0050]    In the method, the control section may feed the slurry via the selected slurry hole so as to remove the work piece from the upper abrasive plate by liquid pressure when the upper abrasive plate is moved away from the lower abrasive plate.  
           [0051]    By employing the abrasive machine and the method of the present invention, the slurry can be properly fed to the work piece, so that the work piece can be abraded precisely. Since the control section controls the valve mechanisms of the slurry paths, amount of the slurry fed via each slurry hole can be controlled so that various types of work pieces can be properly abraded. Further, the slurry can be jetted toward the work piece from the slurry holes, so that the work piece can be securely removed from the upper abrasive plate. Therefore, damaging the work piece can be prevented when the upper abrasive plate is moved upward, and reliability of the machine can be improved. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0052]    Embodiments of the present invention will now be described by way of examples and with reference to the accompanying drawings, in which:  
         [0053]    [0053]FIG. 1 is a sectional view of the abrasive machine of a first embodiment of the present invention;  
         [0054]    [0054]FIG. 2 is an explanation view showing an arrangement of slurry holes formed in an upper abrasive plate of the first embodiment;  
         [0055]    [0055]FIG. 3 is a sectional view of the abrasive machine of a second embodiment;  
         [0056]    [0056]FIG. 4 is an explanation view showing an arrangement of the slurry holes formed in the upper abrasive plate of the second embodiment; and  
         [0057]    [0057]FIG. 5 is a sectional view of the conventional abrasive machine. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0058]    Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.  
         [0059]    [0059]FIG. 1 is a sectional view of a main part of an abrasive machine of a first embodiment. A symbol  10  stands for an upper abrasive plate; a symbol  12  stands for a lower abrasive plate; a symbol  18  stands for a carrier; and symbols  20  stand for work pieces. The work pieces  20  are respectively set in through-holes  18   a  of the carrier  18 .  
         [0060]    An outer edge of the carrier  18  is supported by a carrier holder  19 , and the carrier holder  19  engages with cranks  21 , which are rotatably held by a base  100 . The cranks  21  are circularly provided along an outer edge of the base  100  with regular separations. The cranks  21  are connected to a motor  102  with sprockets  104 , so that the cranks  21  can be rotated synchronously.  
         [0061]    When the motor  102  synchronously rotates the cranks  21 , the carrier  18  is orbited without spinning about its own axis. Therefore, the work pieces  20  held by the carrier  18  are also orbited together with the carrier  18 , so that upper faces and lower faces of the work pieces  20 , which have been sandwiched or clamped between the abrasive plates  10  and  12 , can be abraded simultaneously.  
         [0062]    The lower abrasive plate  12  is rotated by a motor  106 . A splined shaft  108  is connected to a center of the upper abrasive plate  10 . The shaft  108  is rotated by a driving mechanism (motor)  108   a  for rotating the upper abrasive plate  10 . The upper abrasive plate  10  and the lower abrasive plate  12  are rotated in the opposite directions by the motor  106  and the driving mechanism  108   a.    
         [0063]    Slurry holes  48  are through-holes vertically extending in the upper abrasive plate  10 . A pipe  110  for feeding slurry and a water path  108   b , through which water for cooling the upper abrasive plate  10  is supplied, are formed in the shaft  108 . The pipe  110  is communicated to the slurry holes  48  by connecting tubes  112  respectively. With this structure, the slurry supplied to the pipe  110  can be fed to each slurry hole  48  via the connecting tube  112 .  
         [0064]    A characteristic point of the abrasive machine of the first embodiment is that the slurry is pressurized when it is supplied to the work pieces  20 . A pressurizing unit (slurry feeding unit)  60  pressurizes the slurry and sends it to the pipe  110 . A distributor  61  is provided to an upper end of the shaft  108 , communicated to the pipe  110  and liquid-tightly sealed by a rotary seal unit (not shown). The slurry feeding unit  60  is communicated to the pipe  110  via the distributor  61 . By communicating the slurry feeding unit  60  to the pipe  110  via the distributor  61 , the slurry can be always supplied while the upper abrasive plate  10  is rotated. Note that, the cooling water is also supplied and discharged via the distributor  61 .  
         [0065]    In the first embodiment, adjust valves  70 , which act as valve mechanisms, respectively correspond to the slurry holes  48  of the upper abrasive plate  10 . Flows of the slurry from the slurry feeding unit  60  to the slurry holes  48  are respectively controlled by the valves  70 .  
         [0066]    The valves  70  are, for example, electromagnetic valves, and degree of opening the valves  70  are respectively controlled by a control section  71 . By controlling the degree of opening the valves  70 , amount of feeding the slurry can be controlled; by closing the valves  70 , feeding the slurry can be stopped. The valves  70  can be optionally controlled while the abrasive plates  10  and  12  abrade the work pieces  20 .  
         [0067]    A planar arrangement of the upper abrasive plate  10 , the carrier  18  and the work pieces  20  is shown in FIG. 2. In the present embodiment, the work pieces  20  are semiconductor wafers, and eight wafers  20  are arranged in the circumferential direction. As described above, the work pieces  20  are set in the through-holes  18   a  of the carrier  18 . The work pieces  20  are orbited and abraded with the orbital movement of the carrier  18 .  
         [0068]    A plurality of the slurry holes  48  are formed in the upper abrasive plate  10  as shown in FIG. 2. The slurry is fed to the work pieces  20  via the slurry holes  48  respectively.  
         [0069]    Positions of the slurry holes  48  in the upper abrasive plate  10  are fixed; relative positions of the slurry holes  48  with respect to the work pieces  20  are varied with the orbital movement of the carrier  18  when the work pieces  20  are abraded. In FIG. 2, the carrier  18  is located at an initial position.  
         [0070]    In the first embodiment, the slurry feeding unit  60  pressurizes and sends the slurry, so amount of the slurry fed through each slurry hole  48  can be properly adjusted by controlling each valve  70 .  
         [0071]    For example, if amount of the slurry fed to an inner part of the upper abrasive plate  10  and that fed to an outer part thereof are different, the valves  70  corresponding to the slurry holes  48  in the inner part and those corresponding to the slurry holes  48  in the outer part are differently controlled so as to uniformly feed the slurry to the whole abrasive plate  10 .  
         [0072]    Further, the slurry can be fed to selected slurry holes  48  only, and no slurry can be fed to the rest slurry holes  48 . Namely, slurry feeding positions in the upper abrasive plate  10  can be controlled.  
         [0073]    In the case of the conventional abrasive machine in which the slurry is flowed downward by its own weight, amount of flowing the slurry varies, so it is difficult to precisely control the amount of feeding the slurry. On the other hand, in the abrasive machine of the first embodiment, the slurry feeding unit  60  sends the slurry with applying prescribed pressure. Therefore, the amount of feeding the slurry can be precisely adjusted by controlling the valves  70 . This is a unique advantage of the first embodiment.  
         [0074]    The amount of feeding the slurry can be adjusted at each slurry hole  48 , further the electromagnetic valves  70 , which respectively correspond to the slurry holes  48 , can be independently turned on and off, so a method of feeding the slurry can be precisely controlled according to types of the work pieces  20 , etc. Therefore, precise abrasion can be performed.  
         [0075]    In the first embodiment, the valves  70  can be controlled while operating the abrasive machine, so the amount of feeding the slurry can be controlled with progress of the abrasion. For example, the amount of feeding the slurry can be gradually increased or reduced with the progress of abrasion. In this case, the slurry can be effectively consumed. Further, the amount of feeding the slurry may be adjusted according to conditions of the work pieces  20 , the abrasive plates  10  and  12 , etc.  
         [0076]    In the first embodiment, a shape of an abrasive face of the upper abrasive plate  10  can be controlled by the pressure of the slurry. For example, if temperature of the upper abrasive plate  10  rises and the shape of the abrasive face thereof is deviated from a prescribed shape, the shape of the abrasive face can be corrected by adjusting the pressure of the slurry. Since the slurry feeding unit  60  sends the slurry with the fixed pressure, the pressure of the slurry, which jets out from the slurry holes  48  and works to the abrasive face of the abrasive plate  10 , is adjusted by the valves  70 .  
         [0077]    When the abrasion is completed, the upper abrasive plate  10  is lifted or moved upward so as to transfer the work pieces  20  abraded. At that time, the slurry is jetted toward the work pieces  20  so as to securely eject the work pieces from the abrasive face of the upper abrasive plate  10 .  
         [0078]    If the carrier  18  returns to the initial position when the abrasion is completed, the slurry may be jetted out from the specific slurry holes  48 , which have been previously selected, when the upper abrasive plate  10  is moved upward.  
         [0079]    In the conventional abrasive machine, the work pieces are ejected by a compressed fluid, e.g., compressed air. On the other hand, in the first embodiment, the slurry for ejecting the work pieces  20  from the upper abrasive plate  10  and the slurry for abrading the work pieces  20  are the same slurry. Therefore, the work pieces  20  are not badly influenced by the slurry for ejecting.  
         [0080]    A second embodiment of the abrasive machine of the present invention will be explained with reference to FIGS. 3 and 4.  
         [0081]    In FIG. 3, a symbol  10  stands for an upper abrasive plate; a symbol  12  stands for a lower abrasive plate; and symbols  18  stand for carriers, which are spun and orbited by a sun gear  14  and an internal gear  16 . Work pieces  20  are held in each carrier  18  and sandwiched or clamped between the abrasive plates  10  and  12 . An upper face and the lower face of the work pieces  20  are simultaneously abraded by the abrasive plates  10  and  12  with the spin and the orbital movement of the carriers  18 .  
         [0082]    The abrasive machine has a lower holder  22 , a base  24 , a rotary shaft  22   a  of the lower holder  22 , a drive shaft  26  for rotating the upper abrasive plate  10 , a shaft  30  for rotating the sun gear  14 , etc. as well as the conventional abrasive machine shown in FIG. 5. Therefore, they are assigned the same symbols and explanation will be omitted.  
         [0083]    A slurry feeding unit  60  pressurizes and sends the slurry. A distributor  62  is communicated to the slurry feeding unit  60 , and slurry holes  48  of the upper abrasive plate  10  are respectively communicated to the distributor  62  via connecting tubes  64 . A support plate  68  is provided to the upper abrasive plate  10 , and valves  70  are provided to the support plate  68 . The valves  70  respectively correspond to the connecting tubes  64  so as to control amount of the slurry fed to each slurry hole  48 .  
         [0084]    In the second embodiment, the valves  70  are provided to the support plate  68  of the upper abrasive plate  10 , means for holding the valves  70  is not limited to the present manner.  
         [0085]    A planar arrangement of the slurry holes  48  is shown in FIG. 4. In FIG. 4, the carriers  18  are located at initial positions.  
         [0086]    In the second embodiment too, amount of feeding the slurry to each slurry hole  48  of the upper abrasive plate  10  can be precisely adjusted by the valves  70 , which are controlled by a control section as well as the first embodiment. Therefore, the work pieces  20  can be precisely abraded. By adjusting the amount of feeding the slurry to each slurry hole  48 , the abrasive machine can properly abrade many types of work pieces. The amount of feeding the slurry to each slurry hole  48  may be defined according to types of work pieces, etc.  
         [0087]    In the second embodiment too, if amount of the slurry fed to an inner part of the upper abrasive plate  10  and that fed to an outer part thereof are different, the valves  70  corresponding to the slurry holes  48  in the inner part and those corresponding to the slurry holes  48  in the outer part are differently controlled so as to uniformly feed the slurry to the whole abrasive plate  10 . The valves  70  can be controlled while operating the abrasive machine, so the amount of feeding the slurry may be controlled with progress of the abrasion. A shape of an abrasive face of the upper abrasive plate  10  may be corrected by adjusting the pressure of the slurry. When the abrasion is completed and the upper abrasive plate  10  is moved upward, the slurry may be jetted toward the work pieces  20  so as to securely eject the work pieces from the abrasive face of the upper abrasive plate  10 .  
         [0088]    The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by he foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.