Abstract:
A lapping machine includes upper and lower lapping wheels and a sprocket having a common centered rotational axis. A rotational drive source for at least one of the upper and lower lapping wheels provides rotational movement about the axis. At least two independently locatable gears or sprockets disposed radially exterior of the upper and lower lapping wheels rotatably carry a carrier between the upper and lower lapping wheels, in which a material carried within an opening formed in the carrier travels at least partially radially exterior of both lower and upper lapping wheels during operation of the machine.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to lapping machines and, more particularly, to lapping machines capable of accommodating differently sized carriers. 
       BACKGROUND OF THE INVENTION 
       [0002]    Lapping machines, such as lapping machine  10  shown in  FIG. 1 , typically include at least a ring sprocket  16  having a lower lapping wheel  128  and a center sprocket  12 . The ring sprocket  16  has a radius  18  and center sprocket  12  has a radius  14 . During operation of lapping machine  10 , center sprocket  12  rotates about a center axis  24 . Teeth of a carrier  20  mesh with the teeth of ring sprocket  16  and the teeth of center sprocket  12  so that carrier  20  is urged into simultaneous rotational movement about its center axis  26  and planetary movement between radius  14  and radius  18 . Carrier  20  includes one or more openings  22  for carrying a work piece  28 , such as a disk that is exposed to lower lapping wheel  128  during operation. The diameter  30  of carrier  20  is a fixed distance, equal to the difference between radius  18  of ring sprocket  16  and radius  14  of center sprocket  12 . As a result, if a carrier  20  having a diameter greater than diameter  30  is desired, it would be necessary to replace at least one of the center sprocket  12  and ring sprocket  16 , which is a costly proposition. In addition, with the construction of lapping machine  10 , it is similarly apparent that the maximum size of a disk work piece  28  must be less than diameter  30 . 
         [0003]    Such known machines suffer from the drawback that to accommodate a larger size carrier, the machine must be significantly enlarged, taking up a similarly increased amount of space in a manufacturing facility, thereby reducing production efficiencies. In addition, storage provisions must be made to store differently sized lapping wheel not in use. Further, in the event larger carriers, even only incrementally larger carriers, can be used for applications previously unknown, these machines lack the flexibility to accommodate the marginally larger carrier, unless further sizable investment in a larger lapping wheel is made. 
         [0004]    What is needed is a lapping machine that can accommodate differently sized carriers, and further, can accommodate carriers, and even work pieces, having a dimension greater than the difference between the radius of the ring sprocket and the radius of the center sprocket. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention relates to a lapping machine including upper and lower lapping wheels and a sprocket having a common centered rotational axis. A rotational drive source for at least one of the upper and lower lapping wheels provides rotational movement about the axis. At least two independently locatable gears or sprockets disposed radially exterior of the upper and lower lapping wheels rotatably carry a carrier between the upper and lower lapping wheels. A material carried within an opening formed in the carrier travels at least partially radially exterior of both lower and upper lapping wheels during operation of the machine. 
         [0006]    The present invention further relates to a lapping machine including upper and lower lapping wheels and a sprocket having a common centered axis. A rotational drive source for at least one of the upper and lower lapping wheels provides rotational movement about the axis. At least two independently locatable gears or sprockets are disposed radially exterior of the upper and lower lapping wheels for rotatably carrying a carrier between the upper and lower lapping wheels, in which a work piece composed of a semiconductor material or rigid material carried within an opening formed in the carrier travels at least partially radially exterior of both lower and upper lapping wheels during operation of the machine. 
         [0007]    The present invention yet further relates to a lapping machine including upper and lower lapping wheels and a sprocket having a common centered axis. A rotational drive source for at least one of the upper and lower lapping wheels provides rotational movement about the axis. At least two independently locatable idler gears or sprockets are disposed radially exterior of the upper and lower lapping wheels for rotatably carrying a carrier between the upper and lower lapping wheels. The carrier travels at least partially radially exterior of both lower and upper lapping wheels during operation of the machine. 
         [0008]    An advantage of the present invention is it can accommodate differently sized carriers. 
         [0009]    A further advantage of the present invention is that it can accommodate work pieces larger than the difference between the radii of the center sprocket and the ring sprocket. 
         [0010]    A still further advantage of the present invention is that it can accommodate larger work pieces without significantly increasing the footprint of the lapping machine, as compared to prior art lapping machines. 
         [0011]    A yet further advantage of the present invention is that it can reduce the number of operating cycles required to produce a predetermined amount of surface area of work pieces. 
         [0012]    A still yet further advantage of the present invention is that it can accommodate customized carrier sizes for more efficient manufacturing operations. 
         [0013]    Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a plan view of a prior art lapping machine. 
           [0015]      FIG. 2  is a top perspective view of a lapping machine of the present invention. 
           [0016]      FIG. 3  is a plan view taken along line  3 - 3  of  FIG. 2  of an embodiment of a lapping machine of the present invention. 
           [0017]      FIG. 4  is a plan view taken along line  3 - 3  of  FIG. 2  of an embodiment of a lapping machine of the present invention with the carrier rotated 180 degrees about its center axis with respect to  FIG. 3 . 
           [0018]      FIG. 5  is a plan view of an embodiment of a lapping machine of the present invention. 
           [0019]      FIG. 6  is a plan view of an embodiment of the lapping machine of  FIG. 5  with the carrier rotated an additional 180 degrees of its center axis, of the present invention. 
       
    
    
       [0020]    Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Referring to  FIGS. 2-4 , a lapping machine  100  ( FIG. 2 ) according to the present invention includes an upper portion  104  that is supported above a lower portion  102  by support columns  106 . As shown, an annular base  108  extends outwardly from lower portion  102  toward upper portion  104  and encloses a lower lapping wheel  128  ( FIG. 2 ) and a center sprocket  122  ( FIG. 2 ). An upper lapping wheel  116  extends toward lower lapping wheel  128 , upper lapping wheel  116  being rotatably carried by shaft  118  about an axis  120  and selectively raised and lowered with respect to lower lapping wheel  128 . In one embodiment, center sprocket  122 , upper lapping wheel  116  and lower lapping wheel  128  are centered with respect to axis  120 . Controller  110  controls the operations of lapping machine  100  and includes a display device  112  and input device  114 . Drive devices (not shown) contained within upper portion  104  and lower portion  102  urge upper lapping wheel  116 , lower lapping wheel  128  and center sprocket  122  into an appropriate combination of rotational/translational movement required for efficient operation of lapping machine  100 . That is, one or both of upper and lower lapping wheels  116 ,  128  can rotate, either in the same or opposite directions, and center sprocket  122  can also rotate, if desired. In addition, upper and lower lapping wheels  116 ,  128  can be selectively directed toward and away from each other during operation of lapping machine  100 . As will be discussed in further detail below, lapping machine  100  can accommodate differently sized carriers  144  ( FIG. 3 ). 
         [0022]    In one embodiment, center sprocket  122  includes teeth  124  disposed along its periphery, center sprocket  122  having a radius  126  for meshing with corresponding teeth  125  of a carrier  144 . As shown in  FIG. 3 , radius  126  of center sprocket  122  is less than an inner radius  130  of lower lapping wheel  128 , with both sprocket  122  and lower lapping wheel  128  concentrically centered along axis  120 . Lower lapping wheel  128  has an outer radius  132 . Abrasive material (not shown) is disposed along the surface of upper lapping wheel  116  between inner and outer radii  130  and  132 . In one embodiment, the inner and outer radii of the upper and lower lapping wheels  116 ,  128  are substantially the same. 
         [0023]    As further shown in  FIG. 3 , gear or idler sprocket  134  is rotatably carried about an axis  136  and a gear or idler sprocket  138  is rotatably carried about an axis  140 , each axis formed in cradle  142  so that cradle  142  rotatably carries idler sprockets  134 ,  138 . Although not shown in  FIG. 3 , cradle  142  can contain independently positionable idler sprockets  134 ,  138  to be rotatably carried about parallel axes along different positions of cradle  142 . In another embodiment, cradle  142  is not used, with additional axes (not shown) formed in lower portion  102 . In one embodiment, idler sprocket  134  includes teeth  156  peripherally disposed along a radius  158  for meshing with teeth  125  of carrier  144 . Similarly, idler sprocket  138  includes teeth  160  peripherally disposed along a radius  162  for meshing with teeth  125  of carrier  144 . That is, carrier  144  is rotatably carried by virtue of teeth  156 ,  160 ,  124  of respective idler sprockets  134 ,  138  and center sprocket  122  meshing with teeth  125  of carrier  144 . In one embodiment, idler sprockets  134 ,  138  are not directly associated with driving sources of lower portion  102  ( FIG. 1 ), so that sprockets  134 ,  138  do not rotatably drive carrier  144 . In another embodiment, sprockets  134 ,  138  are idler gears. 
         [0024]    Referring to  FIGS. 3 and 4 , carrier  144  having a diameter  146  includes an opening  148  that is configured to carry a work piece  150 , such as a semiconductor material constructed of silicon, silicon carbide, glass, quartz, metal or ceramic or a combination thereof. However, it is to be understood that semiconductor materials can also be constructed of or include other materials. Further, it is to be understood that work pieces, which are constructed of other suitable rigid materials, can also be used. As shown, carrier  144  includes one opening  148 , but it is to be understood that carrier  144  can include more than one opening  148 , each configured to carry a work piece  150 . In one embodiment, opening  148  is eccentrically disposed with respect to the center  166  of carrier  144 . As shown in  FIG. 3 , work piece  150  has a diameter  164  that is greater than the difference between inner and outer radii  130  and  132  of lower lapping wheel  128 . In this embodiment, work piece  150  has an overhang  152  that extends outside of outer radius  132  of lower lapping wheel  128 . Similarly, carrier  144  has an overhang  154  that extends outside of outer radius  132  of lower lapping wheel  128 . 
         [0025]    Overhang  152  as shown in  FIG. 3  represents a minimum overhang  152 , and that  FIG. 4  represents a maximum overhang  152 , as carrier  144  is rotated about its center  166 , 180 degrees with respect to  FIG. 3 . The minimum and maximum overhangs  152  correspond with the minimum and maximum extreme positions of work piece  150  with respect to radius  132  of lower lapping wheel  128  due to eccentricity of opening  148 , as is appreciated by those skilled in the art. In one embodiment, it is possible to have a maximum overhang of the work piece  150  that is about 33% of the surface area of one side of the work piece  150 . However, depending upon the operating parameters of lapping machine  100 , including work piece material type, rotational speeds, the amount of compressive forces applied to opposite surfaces of work piece  150  by upper and lower lapping wheels  116 ,  128 , and the shape of work piece  150 , it may be possible to increase the previously identified maximum overhang  152 . 
         [0026]    Lapping machine  100  can accommodate carriers  144  of increased diameter by virtue of locating idler sprockets  134 ,  138  further outwardly of radius  132 , the resulting increase in footprint of lapping machine  100  is minimally increased, if increased at all, compared with prior art lapping machine  10  (see  FIG. 1 ) in which an increase of radius  18  of ring sprocket  16  is required to accommodate carrier  20 . In addition, with the ability to selectively locate idler sprockets  134 ,  138 , lapping machine  100  provides flexibility and adaptability to seamlessly accommodate a wide range of carriers  144  and corresponding work pieces  150 . It is also to be understood that more than one set of idler sprockets  134 ,  138  can be used with lapping machine  100 , permitting operation with a plurality of differently sized carriers  144  and corresponding work pieces  150 . Therefore, not only can lapping machine  100  accommodate larger carriers  144  and work pieces  150  than is possible for similarly sized lapping wheels of prior art lapping machine  10 , lapping machine  100  can simultaneously accommodate differently sized, smaller carriers  144  capable of more quickly and efficiently producing work pieces than previously possible. 
         [0027]    It is to be understood that although an overhang  152  is always present during operation of lapping machine  100  as shown in  FIGS. 3 ,  4 , the relative sizing of carrier  144 , opening(s)  148  and work piece  150  dictate the existence of and/or extent of overhang  152 . 
         [0028]    It is also to be understood that although center sprocket  122  and idler sprockets  134 ,  138  can be formed of unitary construction, i.e., that teeth  124 ,  156 ,  160  are formed by machining a solid disk of material (spur gear design), in another embodiment, teeth  124 ,  156 ,  160  can be formed by pins disposed along the periphery so that the pins become the teeth of sprocket  122  and gears  134 ,  138 . That is, the pins can be affixed at a desired radius substantially perpendicular to the respective sprocket  122 ,  134 ,  138 . 
         [0029]      FIGS. 5 ,  6  shows an embodiment of lapping machine  100  which is otherwise similar to  FIGS. 3 ,  4 , except that carrier  144  and center sprocket  122  are sized differently, idler sprockets  134 ,  138  are thus located at different respective axes  168 ,  170 , and cradle  142  is configured to receive differently sized carriers. It is to be understood that idler sprockets  134 ,  138  can be positioned at even different axis positions and that gears  134 ,  138  are not necessarily the same diameter. It is also to be understood that the lapping machine can be configured for use without a cradle, making use of hole patterns formed in the lower portion  102  to receive and secure the idler sprockets to the lower portion  102 . 
         [0030]    It is to be understood that lapping machine  100  can be used without work pieces  150  installed in carriers  144 . That is, in one embodiment, no work piece  150  is placed in any of the carriers  144 , so that carriers  144  are exposed to upper and lower lapping wheel  116 ,  128  during operation of lapping machine  100 . 
         [0031]    While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.