Abrading – Machine – Rotary tool
Reexamination Certificate
2003-08-25
2004-12-14
Nguyen, Dung Van (Department: 3723)
Abrading
Machine
Rotary tool
C451S269000, C451S270000
Reexamination Certificate
active
06830505
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a polishing machine, more precisely relates to a polishing machine capable of polishing both sides (faces) of work pieces, e.g., silicon wafers, by an upper polishing plate and a lower polishing plate.
A conventional polishing machine for polishing both sides of work pieces, e.g., silicon wafers, is shown in FIG.
16
. In
FIG. 16
, a lower polishing plate
200
and an upper polishing plate
202
are rotated in predetermined directions. Carriers
208
, which are driven by an internal gear
204
and a sun gear
206
, are provided between the polishing plates
200
and
202
. Through-holes (not shown), in each of which a work piece to be polished is held, are bored in the carriers
208
. Both sides (faces) of the work pieces held in the through-holes are simultaneously polished by the polishing plates
200
and
202
.
The lower polishing plate
200
is mounted on a lower board
209
and rotated together with the lower board
209
. The lower board
209
is rotatably mounted on a base
210
with a bearing
212
. Torque of an electric motor
214
, which rotates the lower board
209
, is transmitted to the lower board
209
by transmission gears
216
and a cylindrical shaft
217
.
The upper polishing plate
202
is rotated by torque of an electric motor
224
, which is transmitted by transmission gears
218
and a shaft
219
. The internal gear
204
is rotated by torque of an electric motor
226
by transmission gears
220
and a cylindrical shaft
221
. Further, the sun gear
206
is rotated by torque of an electric motor
228
by transmission gears
222
and a shaft
223
.
As shown in
FIG. 17
, a plurality of carriers
208
are mounted on the lower polishing plate
200
, and a plurality of the through-holes
230
, in which the work pieces will be accommodated and held, are bored in each carrier
208
.
Gear teeth for engaging with the internal gear
204
and the sun gear
206
are formed on an outer edge of each carrier
208
. By rotating the internal gear
204
and the sun gear
206
, the carriers
208
are revolved and orbited around the sun gear
206
by difference of rotational speeds of the two gears
204
and
206
.
The carriers
208
, in each of which the work pieces are held in the through-holes
230
, are sandwiched between the polishing plates
200
and
202
, then the polishing plates
200
and
202
, the internal gear
204
and the sun gear
206
are respectively rotated at predetermined rotational speeds. The work pieces are revolved and orbited around the sun gear
206
together with the carriers
208
, so that the both sides of the work pieces can be polished simultaneously.
However, in the polishing machine shown in
FIGS. 16 and 17
, each of the carriers
208
is revolved on its own axis, so a peripheral speed of an inner part of the carrier
208
is different from that of an outer part. Further, the work piece held in the through-hole
230
of the carrier
208
is also revolved, so a peripheral speed of an inner part of the work piece is different from that of an outer part.
By the difference of the peripheral speeds of the carrier
208
, the work pieces held in the inner part and the outer part of the carrier
208
cannot be polished uniformly, and abrasion spots are sometimes formed in the work pieces. Further, by the difference of the peripheral speeds of the work piece, the inner part and the outer part of each work piece cannot be polished uniformly, and abrasion spots are sometimes formed in the work piece.
Since the gear teeth of the carriers
208
are engaged with the internal gear
204
and the sun gear
206
, abrasion dusts formed therebetween stick onto not only the carriers
208
but also polishing faces of the polishing plates
200
and
202
.
To solve the above described disadvantages, an improved polishing machine, which is capable of polishing both sides of work pieces without revolving and orbiting carriers, was disclosed in U.S. Pat. No. 6,080,048. It is shown in FIG.
18
.
In
FIG. 18
, an upper polishing plate
302
is rotated by a rotating unit
304
and vertically moved by a lifting unit
306
. A lower polishing plate
310
is rotated by a rotating unit
308
. One carrier
300
is sandwiched between the polishing plates
302
and
310
. A plurality of through-holes
230
, in each of which a work piece
100
is accommodated and held, are formed in the carrier
300
.
The carrier
300
has a plurality of holes bored along an outer edge. By inserting pins
316
, which are upwardly extended from a carrier holder
312
, into the holes, the carrier
300
can be attached to the carrier holder
312
.
The carrier holder
312
has a circular motion mechanism
320
. The circular motion mechanism
320
includes: four bearing sections
318
outwardly extended from an outer circumferential face of the carrier holder
312
; cranks respectively provided to the bearing sections
318
; and a driving unit
340
capable of synchronously driving the cranks.
Each of the cranks includes: a rotatable eccentric arm
324
formed into a circular disk; and a shaft
322
a
arranged parallel to axial lines of the polishing plates
302
and
310
and having one end attached to the bearing section
318
and the other end eccentrically attached to the circular eccentric arm
324
.
The driving unit
340
includes: shafts
322
b
, whose one ends are respectively attached to centers of the circular eccentric arms
324
; sprockets
342
respectively attached to the other ends of the shafts
322
b
; a timing chain engaged with the sprockets
342
; a gear
346
attached to one of the shafts
322
b
; a gear
350
engaged with the gear
346
; and a motor
348
for rotating the gear
350
.
In the polishing machine shown in
FIG. 18
, the polishing plates
302
and
310
are rotated in the predetermined directions by the motor
348
of the circular motion mechanism
320
. Therefore, the carrier holder
312
sandwiched between the polishing plates
302
and
310
performs small circular motion, without revolving on its own axis, in a plane including the carrier
300
. The peripheral speed differences of the carrier and the work pieces
100
, which are caused by revolution of the carrier, can be solved.
Unlike the polishing machine shown in
FIGS. 16 and 17
, the carrier
300
has no gear teeth engaging with the internal gear and the sun gear. Therefore, no abrasion dusts are formed and stuck onto the carrier
300
. Further, no abrasion dusts are stuck onto polishing faces of the polishing plates
302
and
310
.
However, in the polishing machine shown in
FIG. 18
, the center of the carrier
300
is shifted a distance “M” from a coaxial line “L” of the polishing plates
302
and
310
. The carrier
300
orbits around the line “L” without revolving its own axis. A radius of the circular orbit motion of the carrier
300
is equal to a distance between the shafts
322
a
and
322
b
(=”M”).
Since the carrier
300
, whose center is shifted the distance “M” from the line “L”, performs the circular orbit motion without revolving, centers of gravity of the work pieces held in the through-holes
230
of the carrier
300
are located at different positions with respect to a center of gravity or a center of rotation of the upper polishing plate
302
. Accordingly, uneven forces are applied to the work pieces
100
from the polishing plates
302
and
310
, vibrations are generated while polishing, and polishing accuracy is lowered.
Since the carrier
300
must be broader than the polishing faces of the polishing plates.
302
and
310
, the polishing machine must be large, and its manufacturing cost must be high. Namely, increasing efficiency by large-sized polishing machines is limited.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a compact polishing machine capable of evenly applying a pressing force from an upper polishing plate to work pieces accommodated in through-holes of carriers.
To solve the problems of the conventional polishing machines, the inventors studied and found that polishing e
Kajikura Atsushi
Kanda Satoki
Kobayashi Takumi
Moriya Norihiko
Fujikoshi Machinery Corp.
Jordan and Hamburg LLP
Nguyen Dung Van
LandOfFree
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