Flattening machine

Details Flattening machine Flattening machine

1999-11-01

2002-02-05

Rose, Robert A. (Department: 3723)

Abrading

Machine

Rotary tool

C451S340000

Reexamination Certificate

active

06343980

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a flattening machine for grinding or polishing a disc-shaped work piece such as a semiconductor wafer or a glass disc.
1. Field of the Invention
A conventional vertical spindle type surface grinding machine has a grinding wheel fixed to a slider which is provided movably along a column of a cantilever or gantry-type frame. The grinding wheel is fed along a vertical axis by cylindrical linear actuator, a ball screw or the like so as to descend the slider.
2. Brief Description of the Prior Art
When the slider which a main spindle is fixed thereto is fed along the column of the cantilever-type frame, the slider is likely to take pitching or yawing motion with respect to a guide way of the column due to disturbances such as offset between the guide way and the slider or fluctuation of an external force applied to the slider. Such motion causes even slight inclination of the main spindle. Thermal unbalance also causes inclination of the main spindle. Due to the inclination of the main spindle, the grinding wheel irregularly deviates from a position facing to a work piece, so as to deteriorate dimensional accuracy of a ground work piece such as a semiconductor wafer or an optical glass disc which is expected to be finished with high flatness.
Inclination of the main spindle occurs, when a central axis of a guide way system, a direction of a driving force of a slider feeding member and a rotation axis of the main spindle are not aligned on the same line.
In this regard, Japanese Patent Application Laid-Open 8-276358 proposed the structure that a direction of a driving force of a slider feeding member is held on nearly the same line with a central axis of a guide way. According to this structure, a slider is hardly inclined with respect to a feeding direction. Even when the slider is inclined, its inclination angle is suppressed to a small value. In addition, a rotation axis of a grinding wheel is preferably aligned on nearly the same line with a scale line of a detector for detecting a position of the grinding wheel. Such alignment enables accurate detection of a position of the grinding wheel without substantial errors even when the main spindle is inclined.
Japanese Patent Application Laid-Open 6-155257 proposed the structure that a tripodal outer frame for supporting a main spindle is supported at the apex of a trigonal pyramid under the condition that a direction of a resultant of machining forces applied to the grinding wheel is aligned with a rotation axis. According to this structure, a supporting member for the grinding wheel can be designed to a constitution rigid enough to suppress distortion or deformation caused by various machining forces to a minimum level. A rotation axis of a motor for rotating a work piece and a grinding wheel can be concentrically aligned with axes of the work piece and the grinding wheel, so as to effectively eliminate bending moments or vibrations which likely occur during feeding.
However, when a center line of a guide way, a direction of a driving force of a slider feeding system, a rotation axis of a grinding wheel and a scale line of a detector for detecting a position of a grinding wheel are aligned on the same line as disclosed in Japanese Patent Application Laid-Open 8-276358, the grinding wheel is located at a position surrounded with a gantry-type frame at both sides. Therefore, troublesome operations are obliged to maintain and check the grinding wheel, and a space necessary for changing an abraded grinding wheel to a new one is hardly kept. Consequently, it is difficult to improve both performance of the grinding machine and workability during change of grinding wheels. Frontward or backward inclination of a main spindle also puts harmful influences on grinding results, since the main spindle is supported with the gantry-type frame having tow columns standing up on a bed.
On the other hand, with a grinding machine wherein supporting columns are constructed to a trigonal pyramid as disclosed in Japanese Patent Application Laid-Open 6-155257, it is impossible to design the trigonal pyramid frame so as to support a main spindle unit with an area broad enough to guarantee the stiffness necessary for supporting the main spindle. Inferior stiffness causes inclination of the main spindle and deterioration of dimensional accuracy of a ground work piece, especially when a wafer or the like is machined by a rotary grinder which is likely to be affected by an unbalanced load.
SUMMARY OF THE INVENTION
The present invention is aimed at machining wafers or the like to precisely flattened surface with extremely high accuracy while inhibiting inclination of a main spindle. The precise working is attained by setting the main spindle at a geometric gravity center of a triangle defined by three columns which are located near a work piece loading-unloading equipment, so as to uniformly distribute machining force to each of the three columns during machining and to hold a space necessary for operations such as maintenance and checking, change of work pieces.
The flattening machine according to the present invention comprises three columns set up in triangular relationship, a saddle which can move along a vertical direction in state direct or indirect contact with a side face of one column, a main spindle fixed to the saddle at a position equal to a geometrical gravity center of a triangle defined by the three columns, and an indexing table which provides a plurality of chucking tables thereon. When a single or a plurality of chucking tables carries a work piece(s) at a position below the saddle, the other chucking table(s) is located at a loading-unloading position(s).
The indexing table may be either a rotary or reciprocative type. In the case where the indexing table is a rotary type, one of the three columns may be set up through a central opening of the indexing table, while the other two columns are set up near a periphery of the indexing table. In another case of rotary type, two columns may be constructed to a gantry-type frame encompassing a rotary indexing table which is located at a position on a loading-unloading line. In the case where the indexing table is a reciprocative type, two columns are constructed to a gantry-type frame, and the indexing table is provided in reciprocative state between the gantry-type frame and the rest column.
The other features of the present invention will be apparent from the following explanation consulting with the attached drawings.


REFERENCES:
patent: 5718619 (1998-02-01), Merrill et al.
patent: 5784932 (1998-07-01), Gilberti
patent: 5950503 (1999-09-01), Amendolea
patent: 05309535 (1993-11-01), None
patent: 06155257 (1994-06-01), None
patent: 08276358 (1996-10-01), None
patent: 99044787 (1999-09-01), None

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