Patent ID: 12220785

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will be described with reference to the accompanying drawings.FIG.1Ais a top view schematically illustrating one example of a chuck table.FIG.1Bis a side view schematically illustrating the one example of the chuck table. A chuck table2illustrated inFIG.1AandFIG.1Bhas a base part4that is composed of ceramic or the like and has a circular disc shape, for example.

This base part4has a flat upper surface (reference surface)4a. Further, on this reference surface4a, multiple (for example, four) holding parts6,8,10, and12with a rectangular parallelepiped shape are disposed to line up along a first direction (D1) parallel to the reference surface4aand protrude along a second direction (D2) perpendicular to the reference surface4a.

The multiple holding parts6,8,10, and12have frame bodies6a,8a,10a, and12a, respectively, that are composed of ceramic or the like and have a rectangular parallelepiped shape, and a recessed part is formed at the upper part of each of the frame bodies6a,8a,10a, and12a. To these recessed parts, porous plates6b,8b,10b, and12bthat are composed of ceramic or the like and have a rectangular parallelepiped shape are fixed.

Moreover, the porous plates6b,8b,10b, and12bhave upper surfaces parallel to the reference surface4a. In addition, a suction path for allowing the side of the lower surface of the porous plates6b,8b,10b, and12bto communicate with a suction source such as an ejector is made inside each of the base part4and the multiple holding parts6,8,10, and12.

Further, a negative pressure is generated in spaces near the upper surfaces of the porous plates6b,8b,10b, and12bwhen the suction source operates in a state in which this suction path communicates with the suction source. Thus, in each of the multiple holding parts6,8,10, and12, upper surfaces6c,8c,10c, and12cthereof function as holding surfaces that hold a workpiece.

The reference surface4aof the base part4is disposed to surround the upper surfaces (holding surfaces)6c,8c,10c, and12cof the holding parts6,8,10, and12in plan view. Further, each of the multiple holding surfaces6c,8c,10c, and12cis parallel to the reference surface4a.

Moreover, the multiple holding surfaces6c,8c,10c, and12chave the same shape. Specifically, the shape of each of the multiple holding surfaces6c,8c,10c, and12cis a rectangular shape having a pair of short sides that extend along the first direction and a pair of long sides that extend along a third direction (D3) perpendicular to the first direction and the second direction.

However, the heights of the multiple holding surfaces6c,8c,10c, and12cfrom the reference surface4aare different. Specifically, the heights of the multiple holding surfaces6c,8c,10c, and12cfrom the reference surface4aare in increasing order along the first direction. That is, the holding surface6cis lower than the other holding surfaces8c,10c, and12c. Further, the holding surface8cis lower than the holding surfaces10cand12c. In addition, the holding surface10cis lower than the holding surface12c.

Moreover, the difference in the height between the pair of holding surfaces adjacent along the first direction (for example, the holding surface6cand holding surface8c) is decided in consideration of variation in the thickness of the workpiece held in each of the multiple holding surfaces6c,8c,10c, and12c. Specifically, this difference is at least 10 μm and at most 300 μm (for example, 50 μm).

FIG.2is a partially sectional side view schematically illustrating one example of a grinding apparatus including the chuck table2. An X-axis direction (front-rear direction) and a Y-axis direction (left-right direction) illustrated inFIG.2are directions perpendicular to each other on the horizontal plane. Further, a Z-axis direction (upward-downward direction) is the direction (vertical direction) perpendicular to the X-axis direction and the Y-axis direction.

A grinding apparatus14illustrated inFIG.2includes a base16that supports or houses the respective constituent elements. An opening16awith a rectangular parallelepiped shape is made on the side of the upper surface of the base16. Further, an X-axis movement mechanism (first movement mechanism)18is disposed inside the opening16a. This X-axis movement mechanism18has a screw shaft20that extends along the X-axis direction.

A motor22for rotating the screw shaft20is coupled to one end part of the screw shaft20. Further, a nut part24that houses balls that roll on the surface of the screw shaft20that rotates is disposed on the surface of the screw shaft20in which a spiral groove is formed, so that a ball screw is configured.

That is, when the screw shaft20rotates, the balls circulate in the nut part24, and the nut part24moves along the X-axis direction. Moreover, the lower part of the chuck table2is mounted on the upper part of this nut part24in such a manner that the above-described first direction (D1), second direction (D2), and third direction (D3) become parallel to the X-axis direction, the Z-axis direction, and the Y-axis direction, respectively. Thus, when the screw shaft20is rotated by the motor22, the chuck table2moves along the X-axis direction together with the nut part24.

Moreover, the grinding apparatus14incorporates a suction source (not illustrated), and this suction source communicates with the suction path made inside each of the base part4and the multiple holding parts6,8,10, and12through a valve (not illustrated) and so forth. Thus, by opening the valve in a state in which this suction source is operated, workpieces can be held in the holding surfaces6c,8c,10c, and12cof the multiple holding parts6,8,10, and12.

A support structure26with a rectangular parallelepiped shape is disposed on the rear side (right side ofFIG.2) of the chuck table2and the X-axis movement mechanism18. Further, a Z-axis movement mechanism (second movement mechanism)28is disposed on the side of the front surface (front face) of the support structure26. The Z-axis movement mechanism28is coupled to a grinding unit40to be described later and moves the grinding unit40along the Z-axis direction.

The Z-axis movement mechanism28has a pair of guide rails30that are fixed to the side of the front surface of the support structure26and extend along the Z-axis direction. A moving plate32is coupled to the side of the front face of the pair of guide rails30slidably along the pair of guide rails30.

A screw shaft34that extends along the Z-axis direction is disposed between the pair of guide rails30. A motor36for rotating the screw shaft34is coupled to one end part of the screw shaft34. Further, a nut part38that houses balls that roll on the surface of the screw shaft34that rotates is disposed on the surface of the screw shaft34in which a spiral groove is formed, so that a ball screw is configured.

That is, when the screw shaft34rotates, the balls circulate in the nut part38, and the nut part38moves along the Z-axis direction. Moreover, the nut part38is fixed to the side of the back surface (rear face) of the moving plate32. Thus, when the screw shaft34is rotated by the motor36, the moving plate32moves along the Z-axis direction together with the nut part38.

The grinding unit40is disposed on the side of the front surface (front face) of the moving plate32. The grinding unit40has a support component42that is fixed to the side of the front surface of the moving plate32and has a hollow circular column shape. A housing44with a hollow circular column shape is housed in the support component42. The housing44is fixed to the bottom wall of the support component42with the interposition of a connecting component46disposed on the lower surface of the housing44.

In the housing44, a circular columnar spindle48that extends along the Z-axis direction is rotatably housed. The tip (lower end) part of the spindle48is exposed from the housing44and passed through an opening made in the bottom wall of the support component42and protrudes downward from the bottom surface of the support component42. Further, a mount50that is composed of metal or the like and has a circular disc shape is fixed to the tip part of the spindle48.

The diameter of the mount50is shorter than the diameter of the chuck table2(diameter of the reference surface4aof the base part4). InFIG.2, the mount50having a diameter that is approximately half the diameter of the chuck table2is illustrated. Moreover, an annular grinding wheel52is detachably mounted on the side of the lower surface of the mount50.

For example, this grinding wheel52has a circular annular wheel base54composed of a metal such as aluminum or stainless steel, and the outer diameter of the wheel base54is substantially equal to the diameter of the mount50. That is, inFIG.2, the wheel base54having a diameter that is approximately half the diameter of the chuck table2is illustrated.

Further, the side of the upper surface of the wheel base54is fixed to the side of the lower surface of the mount50by a fixing component such as a bolt. Moreover, multiple grinding abrasive stones56annularly disposed in a discrete manner are fixed to the side of the lower surface of the wheel base54. The multiple grinding abrasive stones56each have a rectangular parallelepiped shape, for example, and are disposed at substantially equal intervals along the circumferential direction of the wheel base54.

The grinding abrasive stones56are formed by fixing abrasive grains composed of diamond, cubic boron nitride (cBN), or the like by a binding material (bond material) composed of a metal bond, resin bond, vitrified bond, or the like. However, there is no limitation on the material, shape, structure, size, and so forth of the grinding abrasive stones56. Further, the number of multiple grinding abrasive stones56is optionally set.

Moreover, a rotational drive source (not illustrated) such as a motor for rotating the spindle48is coupled to the base end (upper end) part of the spindle48. When this rotational drive source rotates the spindle48around a rotation axis along the Z-axis direction, the mount50and the grinding wheel52(wheel base54and multiple grinding abrasive stones56) rotate together with the spindle48.

FIG.3is a flowchart schematically illustrating one example of a grinding method for workpieces in which the workpieces are ground by using the grinding apparatus14. In this method, first, each of the multiple holding surfaces6c,8c,10c, and12cof the chuck table2is caused to hold a workpiece (holding step: S1).FIG.4Ais a side view schematically illustrating the state of the holding step (S1).

In this holding step (S1), first, the X-axis movement mechanism18is operated to position the chuck table2to a position at which workpieces11can be carried in to the multiple holding surfaces6c,8c,10c, and12cof the chuck table2(for example, a position separate from the grinding unit40). Subsequently, the multiple workpieces11are each carried in to a respective one of the multiple holding surfaces6c,8c,10c, and12cof the chuck table2.

For example, the workpieces11are package substrates with a rectangular parallelepiped shape, such as CSP substrates or QFN substrates, and the shape of the upper surface and the lower surface thereof is almost the same as the shape of the multiple holding surfaces6c,8c,10c, and12c. Subsequently, in a state in which the suction source that communicates with the suction path made inside the chuck table2through the valve and so forth is operated, this valve is opened. This completes the holding step (S1).

In the grinding method for workpieces illustrated inFIG.3, after the holding step (S1), creep-feed grinding for the workpieces11each held by the respective one of the multiple holding surfaces6c,8c,10c, and12cis executed in states in which the grinding unit40is positioned at different heights (grinding step: S2).

Specifically, in the grinding step (S2), the workpieces11are ground by moving the chuck table2along the X-axis direction (first direction) and bringing the multiple grinding abrasive stones56that rotate into contact with the workpieces11each held by the respective one of the multiple holding surfaces6c,8c,10c, and12cwhile widening the interval between the reference surface4aand the multiple grinding abrasive stones56along the Z-axis direction (second direction) in a stepwise manner to cause the workpieces11each held by the respective one of the multiple holding surfaces6c,8c,10c, and12cto have a predetermined finished thickness.

FIG.4B,FIG.4C,FIG.5A,FIG.5B, FIG.5C,FIG.6A,FIG.6B, andFIG.6Care side views schematically illustrating the state of the grinding step (S2). In this grinding step (S2), first, the Z-axis movement mechanism28lowers the grinding unit40to position the lower surfaces of the multiple grinding abrasive stones56of the grinding wheel52to a position higher than the holding surface6cby the finished thickness of the workpiece11(seeFIG.4B).

Subsequently, while the chuck table2is moved rearward along the X-axis direction, multiple grinding abrasive stones56located on the front side of the grinding wheel52that rotates are brought into contact with the side of the upper surface of the workpiece11held by the holding surface6c. As a result, the side of the upper surface of the workpiece11held by the holding surface6cis ground from the rear end to the front end, and this workpiece11is thinned to the predetermined finished thickness (seeFIG.4C).

Next, the Z-axis movement mechanism28raises the grinding unit40to position the lower surfaces of the multiple grinding abrasive stones56of the grinding wheel52to a position higher than the holding surface8cby the finished thickness of the workpiece11(seeFIG.5A).

Subsequently, while the chuck table2is moved rearward along the X-axis direction, the multiple grinding abrasive stones56located on the front side of the grinding wheel52that rotates are brought into contact with the side of the upper surface of the workpiece11held by the holding surface8c. As a result, the side of the upper surface of the workpiece11held by the holding surface8cis ground from the rear end to the front end, and this workpiece11is thinned to the predetermined finished thickness (seeFIG.5B).

At this time, multiple grinding abrasive stones56located on the rear side of the grinding wheel52that rotates are located over the workpiece11held by the holding surface6cand do not come into contact with this workpiece11. That is, the workpiece11held by the holding surface6cis not ground again by the multiple grinding abrasive stones56.

Next, the Z-axis movement mechanism28raises the grinding unit40to position the lower surfaces of the multiple grinding abrasive stones56of the grinding wheel52to a position higher than the holding surface10cby the finished thickness of the workpiece11(seeFIG.5C).

Subsequently, while the chuck table2is moved rearward along the X-axis direction, the multiple grinding abrasive stones56located on the front side of the grinding wheel52that rotates are brought into contact with the side of the upper surface of the workpiece11held by the holding surface10c. As a result, the side of the upper surface of the workpiece11held by the holding surface10cis ground from the rear end to the front end, and this workpiece11is thinned to the predetermined finished thickness (seeFIG.6A).

At this time, the multiple grinding abrasive stones56located on the rear side of the grinding wheel52that rotates are located over the workpiece11held by the holding surface8cand do not come into contact with this workpiece11. That is, the workpiece11held by the holding surface8cis not ground again by the multiple grinding abrasive stones56.

Next, the Z-axis movement mechanism28raises the grinding unit40to position the lower surfaces of the multiple grinding abrasive stones56of the grinding wheel52to a position higher than the holding surface12cby the finished thickness of the workpiece11(seeFIG.6B).

Subsequently, while the chuck table2is moved rearward along the X-axis direction, the multiple grinding abrasive stones56located on the front side of the grinding wheel52that rotates are brought into contact with the side of the upper surface of the workpiece11held by the holding surface12c. As a result, the side of the upper surface of the workpiece11held by the holding surface12cis ground from the rear end to the front end, and this workpiece11is thinned to the predetermined finished thickness (seeFIG.6C).

At this time, the multiple grinding abrasive stones56located on the rear side of the grinding wheel52that rotates are located over the workpiece11held by the holding surface10cand do not come into contact with the workpiece11. That is, the workpiece11held by the holding surface10cis not ground again by the multiple grinding abrasive stones56. Through the above, the grinding step (S2) is completed.

In the chuck table2, the multiple holding surfaces6c,8c,10c, and12care disposed in such a manner that the heights from the reference surface4aare in increasing order along the first direction parallel to each of them. Thus, in a case of using this chuck table2, the creep-feed grinding for the workpieces11each held by the respective one of the multiple holding surfaces6c,8c,10c, and12ccan be executed in states in which the grinding unit40is positioned at different heights.

In this case, the workpiece11for which the creep-feed grinding has been executed (for example, the workpiece11held by the holding surface6c) is located on the lower side as viewed from the grinding unit40when another workpiece11(for example, the workpiece11held by the holding surface8c) is ground. Due to this, in this creep-feed grinding, the specific workpiece11can be prevented from being ground twice.

Moreover, in the grinding method for workpieces according to the present invention, prior to the above-described holding step (S1), the chuck table2may be processed in the grinding apparatus14in such a manner that the heights of multiple holding surfaces of the chuck table2from the reference surface4aare set to be in increasing order along the first direction. Due to this, for example, the above-described grinding step (S2) can be executed even in a case in which the heights of the upper surfaces of the holding parts6,8, and10from the reference surface4aare equal to the height of the upper surface (holding surface)12cof the holding part12from the reference surface4a.

When the chuck table2is ground, in general, a grinding wheel (grinding wheel for the chuck table) that is different in kind from the grinding wheel used in grinding of the workpiece11(grinding wheel for the workpiece) is used. That is, in general, the chuck table2is ground by using the grinding wheel for the chuck table in which multiple grinding abrasive stones (grinding abrasive stones for the chuck table) that are different in kind from the multiple grinding abrasive stones included in the grinding wheel for the workpiece (grinding abrasive stones for the workpiece) are annularly disposed in a discrete manner.

FIG.7is a flowchart schematically illustrating one example of a grinding method for workpieces in which the chuck table2is processed prior to the holding step (S1). In this method, first, the chuck table2is ground to cause the heights of multiple holding surfaces of the chuck table2to be in increasing order along the X-axis direction (first direction) (holding surface grinding step: S3).

Specifically, in the holding surface grinding step (S3), the chuck table2is ground by moving the chuck table2along the X-axis direction (first direction) and bringing the multiple grinding abrasive stones for the chuck table that rotate into contact with the chuck table2while widening the interval between the reference surface4aand the multiple grinding abrasive stones for the chuck table along the Z-axis direction (second direction) in a stepwise manner to cause the heights of the multiple holding surfaces from the reference surface4ato be in increasing order along the X-axis direction.

FIG.8A,FIG.8B,FIG.8C,FIG.9A,FIG.9B, andFIG.9Care side views schematically illustrating the state of the holding surface grinding step (S3). In this holding surface grinding step (S3), first, the Z-axis movement mechanism28lowers the grinding unit40in such a manner that the lower surfaces of multiple grinding abrasive stones56afor the chuck table annularly disposed in a discrete manner on the side of the lower surface of a wheel base54aof a grinding wheel52afor the chuck table are positioned to a position that is lower than the holding surface12cbut higher than the reference surface4a(seeFIG.8A).

Subsequently, while the chuck table2is moved rearward along the X-axis direction, the multiple grinding abrasive stones56afor the chuck table located on the front side of the rotating grinding wheel52afor the chuck table are brought into contact with the side of the upper surface of the holding part6. As a result, the side of the upper surface of the holding part6is ground from the rear end to the front end, and the upper surface of the holding part6makes a transition to a position lower than the holding surface12c. That is, the holding surface6cis formed (seeFIG.8B).

Next, the Z-axis movement mechanism28raises the grinding unit40to position the lower surfaces of the multiple grinding abrasive stones56afor the chuck table to a position that is lower than the holding surface12cbut higher than the holding surface6c(seeFIG.8C).

Subsequently, while the chuck table2is moved rearward along the X-axis direction, the multiple grinding abrasive stones56afor the chuck table located on the front side of the rotating grinding wheel52afor the chuck table are brought into contact with the side of the upper surface of the holding part8. As a result, the side of the upper surface of the holding part8is ground from the rear end to the front end, and the upper surface of the holding part8makes a transition to a position that is lower than the holding surface12cbut higher than the holding surface6c. That is, the holding surface8cis formed (seeFIG.9A).

Next, the Z-axis movement mechanism28raises the grinding unit40to position the lower surfaces of the multiple grinding abrasive stones56afor the chuck table to a position that is lower than the holding surface12cbut higher than the holding surface8c(seeFIG.9B).

Subsequently, while the chuck table2is moved rearward along the X-axis direction, the multiple grinding abrasive stones56afor the chuck table located on the front side of the rotating grinding wheel52afor the chuck table are brought into contact with the side of the upper surface of the holding part10. As a result, the side of the upper surface of the holding part10is ground from the rear end to the front end, and the upper surface of the holding part10makes a transition to a position that is lower than the holding surface12cbut higher than the holding surface8c. That is, the holding surface10cis formed (seeFIG.9C).

Through the above, the holding surface grinding step (S3) is completed. In the grinding method for workpieces illustrated inFIG.7, after the holding surface grinding step (S3), the above-described holding step (S1) and grinding step (S2) are sequentially executed. As a result, in the grinding method for workpieces illustrated inFIG.7, the specific workpiece11can be prevented from being ground twice as in the grinding method for workpieces illustrated inFIG.3.

The above-described contents are one aspect of the present invention, and the contents of the present invention are not limited to the above-described contents. For example, in the chuck table of the present invention, the shape of each of the multiple holding surfaces is not limited to the rectangular shape and may be a polygonal shape in which three or five or more corners exist or a circular shape or an elliptical shape.

Further, in the chuck table of the present invention, the base part4may have a rectangular parallelepiped shape or an elliptical plate shape. Moreover, in the chuck table of the present invention, the heights from the reference surface4aregarding some of the holding surfaces included in the multiple holding surfaces may be the same.

Specifically, in a case in which the diameter of the grinding wheel52is relatively long (for example, in a case in which the diameter of the grinding wheel52is at least 70% and at most 90% of the diameter of the chuck table2), when the workpiece11held by the upper surface (holding surface) of the holding part8and/or the holding part10is ground by the multiple grinding abrasive stones56located on the front side of the grinding wheel52, the multiple grinding abrasive stones56located on the rear side thereof have not reached the upper side of the holding part6in some cases.

In such a case, for example, the heights of the upper surfaces (holding surfaces) of the holding parts6and8from the reference surface4amay be made the same. Alternatively, the heights of the upper surfaces (holding surfaces) of the holding parts6,8, and10from the reference surface4amay be made the same. That is, in the chuck table of the present invention, the multiple holding surfaces may be classified into lower holding surfaces whose heights are equal to each other (for example, the upper surfaces of the holding parts6and8or the upper surfaces of the holding parts6,8, and10) and holding surfaces higher than these lower holding surfaces (for example, the upper surfaces of the holding parts10and12or the upper surface of the holding part12).

Further, in the grinding apparatus of the present invention, the X-axis movement mechanism18may be replaced by an X-axis movement mechanism that moves the grinding unit40along the X-axis direction. That is, in the grinding apparatus of the present invention, it suffices that the chuck table2and the grinding unit40can relatively move along the X-axis direction, and the constituent element for this purpose is not limited to any kind.

Similarly, in the grinding apparatus of the present invention, the Z-axis movement mechanism28may be replaced by a Z-axis movement mechanism that moves the chuck table2along the Z-axis direction. That is, in the grinding apparatus of the present invention, it suffices that the chuck table2and the grinding unit40can relatively move along the Z-axis direction, and the constituent element for this purpose is not limited to any kind.

Moreover, in the grinding method for workpieces according to the present invention, the grinding wheel for the chuck table and the grinding wheel for the workpiece may be the same grinding wheel. That is, in the grinding method for workpieces according to the present invention, the chuck table2and the workpieces11may be ground by using the same multiple grinding abrasive stones.

Besides, structures, methods, and so forth according to the above-described embodiment can be executed with appropriate changes without departing from the range of the object of the present invention.

The present invention is not limited to the details of the above described preferred embodiment. The scope of the invention is defined by the appended claims and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention.