Cutting – With means to monitor and control operation – Including means to correct the sensed operation
Reexamination Certificate
1999-10-13
2001-05-01
Rachuba, M. (Department: 3724)
Cutting
With means to monitor and control operation
Including means to correct the sensed operation
C083S076700, C083S367000
Reexamination Certificate
active
06223638
ABSTRACT:
This application is based on Japanese Patent Application No. 8-311300, filed on Nov. 6, 1996, which is incorporated herein in its entirety by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a slicing method and slicing apparatus adaptable for use in cutting and separating an object to be machined, such as a ceramics wafer, for example.
2. Description of the Prior Art
Conventionally, in order to obtain a great number of chips by cutting and separating a ceramics wafer, a slicing apparatus shown in
FIG. 1
has been employed. This slicing apparatus is constructed such that a wafer
2
comprising an object to be machined is bonded onto a self-adhesive sheet
1
, which sheet is held by suction force above a slicing table
3
. While causing a slicing blade
4
consisting of a rotary blade to rotate at a predetermined position, the table
3
is driven by a ball screw mechanism or the like to move in the x-axis direction, thereby cutting the wafer
2
.
In the case of employing the slicing apparatus for cutting the wafer
2
, it can happen that the actual polishing/cutting amount of wafer
2
varies due to decentering D of the slicing blade
4
and/or due to x- and y-axis directional vibrations of a principal shaft
5
which drives the slicing blade
4
. This can result in an increase in variation of the load as applied to the wafer
2
. Accordingly, the apparatus has a problem in that the wafer
2
can crack or suffer from a “chipping” phenomenon. One available approach to avoid this problem is to reduce the machining speed; however, this has the negative consequence of reducing productivity.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a slicing method and slicing apparatus capable of eliminating cracking and chipping of a to-be-machined object without having to reduce the machining speed.
To attain the foregoing object, the slicing method of the instant invention comprises a slicing method for cutting an object to be machined by supporting the to-be-machined object on a table, causing this table to travel in an x-axis direction, and causing a slicing blade to rotate at a predetermined position. The method features the steps of detecting a variable load as received by the to-be-machined object during slicing, and deforming, responsive to the variable load as detected in the above step, the to-be-machined object in a direction in which this variable load decreases.
The to-be-machined object is cut into portions by holding it on the table which is driven to travel in the x-axis direction while causing the slicing blade to rotate at a predetermined position. At this time, the to-be-machined object might vary in cutting amount due to occurrence of decentering of such slicing blade and/or possible vibrations of the principal rotatory shaft, which would result in variation of a load as applied to the to-be-machined object. To avoid this, with respect to a variable load that this to-be-machined object receives, the to-be-machined object is forced to deform in a specific direction which permits reduction of the load. As a result, the cut-away speed of such to-be-machined object is rendered stable, thus stabilizing any load applied to the to-be-machined object. As a result, it becomes possible to increase the machining speed while eliminating occurrence of cracking and chipping of the to-be-machined object, which in turn enables achievement of high-speed slicing operations.
As an apparatus for practicing the above slicing method, it is desirable that a sensor for detection of a variable load received by the to-be-machined object during slicing is provided between the to-be-machined object and the table while providing an actuator, which is operatively responsive to a detection signal generated by the sensor, for deforming the to-be-machined object in the direction which reduces the variable load between the sensor and the table or alternatively between the to-be-machined object and the sensor.
As the actuator of the aforesaid slicing apparatus, a piezoelectric actuator can be used having excellent responsiveness.
In accordance with one aspect of the invention, the direction of the variable load that the to-be-machined object receives may include three directions: a y-axis direction (cut-in depth direction), z-axis direction (principal-shaft thrust direction), and x-axis direction (cutting-forward direction). In view of this, it would be desirable to employ a sensor which detects at least one of the x- and y-axis directional load components of the load components the to-be-machined object receives, because of the fact that the principal-shaft thrust load may be almost negligible.
In other embodiments, the slicing apparatus is also provided with a filter for extracting from a detection signal of the sensor only those variable components of the load applied to the to-be-machined object, and phase inversion means for phase-inverting an output of the filter and for outputting this phase inverted signal to the actuator. More specifically, since the detection signal of the sensor contains therein various kinds of signals other than the load received by the to-be-machined object, a frequency filter having a desired pass-through band is employed to exclusively extract a variable component of cut-away resistance (load) as produced by such slicing. (The term “cut-away resistance” generally refers to a resistance force applied to a cutting device when the device applies force to a material in the course of processing the material). If the resulting variable component of cut-away resistance thus extracted is directly output to the actuator, then the actuator will operate in the direction which causes the cut-away resistance to increase. Accordingly, the output of the filter is subjected to phase inversion before outputting to the actuator thereby enabling the actuator to operate in a direction which permits reduction of the cut-away resistance.
A method of reducing the variable load that the to-be-machined object receives includes the steps of attaching onto the table a sensor for detection of a y-axis directional load applied to the to-be-machined object, and providing a vertical drive actuator between the sensor and table or alternatively between the sensor and the to-be-machined object, which actuator is operatively responsive to a detection signal of the sensor for causing the to-be-machined object to deform in the y-axis direction. In this case, it becomes possible to reduce the variable load by deforming the to-be-machined object in the y-axis direction.
In accordance with a further aspect of the invention, a method is also available which includes the steps of providing an x-axis directionally deformable support base on the table, attaching to this support base a sensor which detects an x-axis directional load component, and providing a drive actuator for driving the support base in the x-axis direction between the table and the support base. In this case, it is possible to reduce the variable load by forcing the to-be-machined object to deform in the forward and backward directions.
In either case, high-precision control is attainable with an associative circuit configuration simplified because of the fact that the direction of the load received by the to-be-machined object and the actuator's deformation direction are identical to each other.
These and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.
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paten
Burns Doane , Swecker, Mathis LLP
Murata Manufacturing Co. Ltd.
Rachuba M.
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