Abrading – Abrading process – Combined abrading
Reexamination Certificate
2000-03-31
2001-12-25
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
Combined abrading
C451S008000, C451S044000
Reexamination Certificate
active
06332834
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for grinding a workpiece, specifically, for grinding an outer peripheral edge of a workpiece formed of a circular thin plate such as a semiconductor wafer.
2. Description of the Related Art
Conventionally, in a case where this type of workpiece formed of a circular thin plate is ground, a grinding method such as the one shown in
FIG. 16
has been adopted. Namely, in this conventional method, a workpiece
71
is rotated about its center as an axis L
1
, and a forming grinding wheel
72
is moved so as to be fed toward an outer peripheral edge portion
71
a
of the workpiece
71
while being rotated about an axis L
2
which is parallel to the central axis L
1
of the workpiece
71
. As a result, the outer peripheral edge portion
71
a
of the workpiece
71
is ground by a recessed wheel surface
72
a
of the outer periphery of the forming grinding wheel
72
.
However, with this conventional method of grinding a workpiece, since the outer peripheral edge portion
71
a
of the workpiece
71
is arranged to be ground at one time by the recessed wheel surface
72
a
of the forming grinding wheel
72
, the recessed wheel surface
72
a
of the forming grinding wheel
72
has been liable to become worn, and the deformation of its profile has been liable to occur as a result. For this reason, particularly in finishing, it is extremely difficult to maintain constant the machining accuracy of the profiles of the outer peripheral edge portions
71
a
of a multiplicity of workpieces
71
by a single forming grinding wheel
72
, and it has been necessary to replace the forming grinding wheel
72
frequently, so that there have been problems in terms of the machining accuracy and machining cost.
SUMMARY OF THE INVENTION
The invention has been devised in light of the above-described problems which are present in the conventional art. Its object is to provide a method of and an apparatus for grinding a workpiece which make it possible to grind outer peripheral edge portions of workpieces while maintaining constant machined shape accuracy, and which make it unnecessary to replace the grinding wheel frequently.
To solve the above object, according to a first aspect of the invention, there is provided a method of grinding a workpiece, a workpiece formed of a circular thin plate is rotated about its center as an axis, and each of the disk-shaped rotating grinding wheels, while being rotated about an axis substantially parallel to the plane of the workpiece, is made to undergo relative feeding movement on both obverse and reverse surf ace sides of the workpiece along the outer peripheral edge portion of the workpiece. Consequently, the outer peripheral edge portion of the workpiece is ground by the outer peripheral wheel surface of each of the rotating grinding wheels.
In this connection, the wording “the rotating grinding wheel” includes a pad, and the wording “grinding” includes polishing. And, these wordings are used as well in the below description.
In addition, the above relative feeding movement is performed such that the grinding wheel continuously moves on at least one part of a predetermined configuration of the edge portion to be ground along a thickness direction of the workpiece.
For this reason, as compared with the conventional grinding method in which the outer peripheral edge portion of the workpiece is ground by a forming grinding wheel, the profile of the wheel surface of each of the rotating grinding wheels is less prone to deformation, so that it be comes unnecessary to replace the rotating grinding wheels frequently. Accordingly, it is possible to reduce the material cost of the rotating grinding wheels, and hence the machining cost. Furthermore, since the profile of the wheel surface of each of the rotating grinding wheels is less prone to deformation, the outer peripheral edge portions of the workpieces can be ground into constant machined shapes with high accuracy.
In addition, the edge portion of the workpiece can be finished into an arbitrary shape by the same grinding wheels through the relative feeding control of the workpiece and the rotating grinding wheels.
In the method of grinding a workpiece according to the invention, the axis of the rotating grinding wheels is disposed in such a manner as to be perpendicular to the radial direction of the workpiece. For this reason, the rotation of the workpiece is effected so as to traverse the outer peripheral surface of each of the rotating grinding wheels. In other words, the workpiece undergoes relative movement in the widthwise direction of the rotating grinding wheels. Accordingly, it becomes possible to effectively grind all over the outer peripheral edge portion of the workpiece by making effective use of the overall width of the outer peripheral wheel surfaces of the rotating grinding wheels.
In the method of grinding a workpiece according to the invention, the rotating grinding wheels consist of the two grinding wheels for rough grinding and finish grinding, and rough grinding and finish grinding are performed by the grinding wheels, respectively. For this reason, the grinding of the outer peripheral edge portion of the workpiece can be effected separately for rough grinding and finish grinding and continuously and efficiently with high accuracy.
In the method of grinding a workpiece according to the invention, the rough grinding and finish grinding of the outer peripheral edge portion of the workpiece are performed by the same station. For this reason, it becomes unnecessary to transport the workpiece into another station or shift the holding of the workpiece, and it is possible to continuously perform rough grinding and finish grinding for the outer peripheral edge portion in the state of being disposed in the same station. Hence, it is possible to maintain the positional accuracy of the workpiece and improve the operating efficiency. Further, stations for rough grinding and finish grinding need not be provided separately, the arrangement of the grinding apparatus can be simplified, and the grinding apparatus can be made compact.
In the method of grinding a workpiece according to the invention, a rotating grinding wheel which is formed by binding the grains of silicon dioxide into fixed abrasive grains is used as the rotating grinding wheel for finishing. For this reason, the outer peripheral edge portion of the workpiece can be ground with good finish-ground surface roughness by virtue of the chemical action based on the reducing action of silicon dioxide.
In the method of grinding a workpiece according to the invention, after the outer peripheral edge portion of the workpiece is subjected to rough grinding and finish grinding by using the rotating grinding wheels; final finishing is performed by using the disk-shaped polishing pad and slurry. For this reason, the relatively soft polishing pad are applied, and the slurry always cools the machined portion of the workpiece. Hence, it is possible to further enhance the ground surface roughness of the outer peripheral edge portion of the workpiece and effect super-finish grinding.
In the method of grinding a workpiece according to the invention, an outer peripheral edge portion of the workpiece is ground.
Accordingly, it is possible to obtain the aforementioned operational advantages in the grinding of the outer peripheral edge portion.
In the method of grinding a workpiece according to the invention, an inner peripheral edge portion of the workpiece having a circular hole in its center is ground.
Accordingly, it is possible to obtain the aforementioned operational advantages in the grinding of the inner peripheral edge portion.
In the method of grinding a workpiece according to the invention, a rotating grinding wheel for cylindrical grinding is rotated about an axis parallel to the central axis of the workpiece in a process preceding the grinding by the disk-shaped rotating grinding wheel, so as to effect the rough cutting of the edge portion of the workpi
Kaga Muneaki
Murai Shirou
Nukui Mitsuru
Okuyama Tetsuo
Takata Michihiro
Hail III Joseph J.
Nippei Toyama Corporation
Sughrue & Mion, PLLC
Thomas David B.
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