JP2005313316A - Double-side polishing method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high pressure and high speed double-side polishing method without a gear transmission mechanism. <P>SOLUTION: In this double-side polishing method, a workpiece 3 nipped between upper and lower platens of a rotary polishing platen using an upper platen 1 and a lower platen 2 rotating in opposite directions or in the same direction, and held by a carrier 13 is rotated using difference between contact friction forces in radial directions of the workpiece 3 and the platens 1, 2 without rotating the carrier 13, so as to polish the workpiece. A step projecting toward an opposite platen in a radial direction of the platen is formed, and an actual contact area of the workpiece 3 and the platens 1, 2 is changed in a radial direction of the platen, so as to create the difference of the friction forces of the platens 1, 2. The creation of the difference of the friction forces may be produced by changing, in the radial direction of the platen, the actual contact area between the workpiece and the platen. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polishing process for metals (steel, non-ferrous metals), non-metals (ceramics, glass, plastics) and the like.

  Polishing such as lapping that polishes the workpiece and lap by rubbing each other through a polishing agent in which loose abrasive grains are dispersed, and polishing that uses a tool called a polisher that is softer than metal, It is a processing method used in the final finishing process of machining, and is a processing method that is becoming increasingly important as the quality of equipment in recent years has increased. In this machining method, since the surface of the workpiece is removed minutely, the machining efficiency is low and the machining cost is high, so that improvement of the machining efficiency is strongly demanded.

  There are many processing operations such as single-sided, double-sided, and curved surfaces in the polishing process. Basically, as shown in FIG. 10, on the polishing plate (surface plate) 10 (in the case of polishing, it is affixed on the surface plate). The workpiece 3 held in the holder 14 held by the carrier 13 or the like and rotated at the speed of n is pressed against the polishing platen 11 with a pressure P to the polishing surface plate 10 (on the polishing platen 11 in the case of polishing). The polishing platen 10 is rotated at a speed of N while dripping the polishing liquid 15 containing the free abrasive grains 12 on the surface, and the surface of the workpiece 3 is moved to the free abrasive grains 12 by the relative movement between the rotation and the rotation of the work piece 3. This is a processing method in which the surface is removed to make the surface highly smooth. As the polisher, a nonwoven fabric or a suede-type plastic is often used. The current maximum polishing speed in this polishing process is considered to be about 2 m / s.

  On the other hand, in recent years, the present inventor has conducted polishing at a speed several times higher than 2 m / s, which is the highest polishing speed currently generally performed, in research on single-side polishing processing of a magnetic disk substrate. Although the removal speed is remarkably improved, a very useful result has been found that the polishing smoothness is hardly changed (Non-patent Document 1). Also, it is shown that high pressure polishing has a higher removal rate and can be processed with high efficiency. Such high speed and high pressure are considered to be effective in polishing processing such as other polishing operations and lapping operations.

  This high-speed and high-pressure polishing method uses a current double-side polishing method using a gear made up of a sun gear 16 and an internal gear 17 between an upper surface plate 1 and a lower surface plate 2 as shown in FIG. The method cannot be applied because the rotation carrier 13 of the workpiece 3 cannot withstand a high load force generated by high pressure or high-speed rotation. That is, many of the double-side polishing processes currently being performed are carried out in a carrier 13 having a gear blade for holding the workpiece 3 on the outer periphery between parallel rotating surface plates (in the case of polishing, a polisher affixed on the surface plate). The workpiece 3 is polished by rotating and revolving the carrier 13 with a gear. The gear that rotates the carrier 13 is performed by a sun gear 16 at the center of the polishing surface plate and an internal gear 17 at the outer peripheral side of the polishing surface plate. The maximum conditions for the rotation speed and polishing pressure of the polishing platen are determined in consideration of the strength of the carrier 13, but since the carrier 13 is thin and not strong, the sun gear 16, the internal gear 17, the carrier 13, etc. An allowable rotational speed is generated in the gear transmission mechanism constituted by the above, and the rotational speed of the polishing surface plate is limited. In practice, the current double-side polishing speed is limited to about 2 m / s. Also, the polishing pressure cannot be increased.

  Thus, in normal double-side polishing processing, it can be said that the processing is performed with 2 m / s as the polishing speed limit and without increasing the polishing pressure within the polishing speed range. For this reason, development of a high-speed and high-pressure double-side polishing method capable of performing highly efficient polishing is expected.

H.YASUI, T.FUKAMACHI, S.SAKAMOTO, S.TAKAKURA: High Removal Rate Ultra-Smoothness Polishing of NiP Plated Aluminum Magnetic Disk Substrate by Means of High Polishing Speed with High Polishing Pressure, Proc.ASPE 17th Annual Meeting, pp. 689-692, Oct. 20-25, 2002, St. Louis, USA (2002.10)

  The existing double-side polishing machine using gears has a problem with the load resistance of the carrier that rotates the workpiece with the gear mechanism, and cannot perform high-speed and high-pressure polishing that significantly exceeds the polishing pressure and speed currently used. . For this reason, in recent years, it has become impossible to improve the efficiency of polishing by the high-speed and high-pressure polishing method found by the present inventor, and a new concept high-speed double-side polishing method and polishing apparatus for its implementation have been developed. Production is a challenge. In addition, cost reduction of the polishing apparatus is one of the major problems to be solved.

  The present invention is (1) rotating a carrier between workpieces held by a carrier, sandwiched between upper and lower surface plates of a rotary type polishing surface plate using an upper surface plate and a lower surface plate rotating in opposite directions or the same direction. Without rotating, the workpiece is rotated using the difference in the contact frictional force between the surface plate in the radial direction of the surface plate and the surface plate or the polisher affixed to the surface of the surface plate. This is a double-sided polishing method in which the workpiece is polished by relative movement between the workpiece and the workpiece.

  The present invention is (2) by making the actual contact area of the workpiece and the surface plate or polisher different in the surface plate radial direction due to the difference in the surface structure in the surface plate radial direction of the surface plate or the surface plate. The double-side polishing method of (1) above, which creates a difference in contact frictional force.

  Furthermore, the present invention is (3) an apparatus used for carrying out the above method (1) or (2), which is attached to one surface of the upper surface plate or the lower surface plate, or to the surface. The polisher forms a step that protrudes from the outer circumference side to the surface of the mating surface in a circumferential direction from the center of the surface plate to the position of the center of rotation of the surface plate. It is only near the center of rotation of the surface plate, and the other surface, or the polisher affixed to the surface, moves from the center of rotation of the surface plate to the position of a constant distance from the center of rotation of the surface plate to the outer surface. A protruding step is formed, and the position of the edge of this step is closer to the outer peripheral side of the surface plate by a certain distance from the center of the workpiece, and the surface plate where the upper and lower surface plates overlap and contact the upper and lower surfaces of the workpiece Radial width is a double-side polishing device, characterized in that the width allows the rotation of the workpiece

  According to the present invention, (4) the surface plate radius width is within 10% of the diameter of the workpiece starting from the center of the workpiece (in the case of a workpiece having an annular hole in the center). The double-side polishing apparatus according to (3) above, which is characterized.

  The present invention is also (5) an apparatus used for carrying out the above method (1) or (2), having a groove or a hole on the inner peripheral side or outer peripheral side of a circular polisher, This is a double-side polishing device in which the actual contact area between the workpiece and the polisher is changed depending on the direction to create a difference in the contact friction force between the workpiece and the polisher in the radial direction of the surface plate, and the polisher is pasted on the surface of the surface plate.

As described above, the method of the present invention enables high-speed and high-efficiency double-side polishing, which was difficult to achieve with the conventional polishing method using gears, and has the following characteristics and advantages over the conventional method. .
(1) The double-side polishing speed in a polishing apparatus manufactured using the concept of the present invention is theoretically higher than the usual maximum polishing speed of 2 m / s in a double-side polishing machine using a conventional gear mechanism. Can be increased by 10 times or more.
(2) When high-speed and high-pressure double-sided polishing is used, the polishing removal rate can be remarkably high-efficiency polishing compared to the case of polishing at the current normal speed.
(3) Since the polishing rate does not significantly affect the smoothness, the smoothness formed at a high removal rate by this polishing method is not significantly different from the smoothness formed by the conventional double-side polishing machine. .
(4) In the polishing method of the present invention, since the carrier is not driven and no gear is used, the apparatus can be manufactured at a low cost.

  FIG. 1 is a conceptual perspective view of the double-side polishing method of the present invention that does not use a gear mechanism for rotating a carrier. FIG. 2 is a partial sectional view of the upper and lower surface plates of the rotary double-side polishing apparatus of the present invention and a partially enlarged view showing the contact state between the upper and lower surface plates and the workpiece. In the method of the present invention, as shown in FIG. 1, the work piece 3 is polished on both sides only by rotating the parallel rotating double-side polishing surface plate of the upper surface plate 1 and the lower surface plate 2 without using a gear.

  The workpiece 3 held in the hole of the carrier 13 is sandwiched between the upper surface plate 1 and the lower surface plate 2 rotating in the opposite direction or the same direction. 1 and 2, the workpiece 3 is a disk-shaped substrate having an annular hole at the center. At least one hole of the carrier 13 is provided so that the workpiece 3 is positioned near the outer periphery of the surface plate. The carrier 13 is not rotated. The workpiece 3 is rotationally moved by making the contact frictional force between the workpiece 3 and the upper and lower surface plates 1 and 2 (a polisher in the case of polishing) differ in the radial direction of the surface plate. Then, the workpiece 3 is polished by relative movement between the upper and lower polishing surface plates 1 and 2 and the rotating workpiece 3. As shown in FIG. 2, the polishing liquid 15 containing abrasive grains is supplied to the polishing surface through a hole provided in the upper surface plate 1. The polishing liquid may be supplied to the polishing surface through holes provided in the lower surface plate 2 or the upper and lower surface plates.

  FIG. 3 schematically shows a specific example in which the contact friction force is varied. FIG. 3A shows an example in which the upper and lower surface plates are machined to provide circumferential steps. FIG. 3B shows an example in which a step is provided by attaching an annular polisher on both upper and lower surface plates. In the case of providing circumferential steps on the upper and lower surface plates, as shown in FIG. 3 (A), the lower surface plate 2 is circular from the outer peripheral side to the position of a certain distance in the direction of the center of rotation of the surface plate. Is formed with a protruding step toward the mating surface. The position of the edge of the step formed in the circumferential shape is closer to the center of rotation of the lower surface plate 2 by a certain distance (X1) than the center of the workpiece 3. This constant distance (X1) is preferably about 10% or less of the diameter of the workpiece 3. As shown in the figure, in the workpiece 3 having an annular hole in the center, it is about 10% or less of the diameter of the workpiece 3, and is closer to the rotation center of the lower surface plate 2 than the wall surface of the hole of the workpiece (width indicated by X2 in the figure). And The region lowered by the step does not come into contact with the surface of the surface plate or the polisher attached to the surface of the surface plate.

  Contrary to the lower surface plate 2, the upper surface plate 1 is formed with a step projecting circumferentially from the center of rotation of the upper surface plate 1 to a position at a constant distance in the outer circumferential direction. The position of the edge of the step is closer to the outer peripheral side of the surface plate by a fixed distance (X1) than the center of the workpiece. The step formed in the circumferential shape of the upper surface plate 1 is in a position symmetrical to the case of the lower surface plate 2 across the center of the workpiece 3.

  The upper surface plate 1 and the lower surface plate 2 having such a shape are pressed against the workpiece 3 held by the carrier 13 disposed between both surface plates 1 and 2. That is, an upper surface plate 1 having a circumferential step near the outer peripheral side of the surface plate and a lower surface plate 2 having a circumferential step near the rotation center with the vicinity of the center of the workpiece 3 as a boundary. The two surface plates 1 and 2 are pressed against the workpiece 3 while rotating in the opposite direction. Thereby, the difference of the contact frictional force of the surface plate radial direction of the workpiece of a surface plate radial direction and the polisher stuck on the surface plate or the surface of a surface plate is created.

When the upper surface plate 1 and the lower surface plate 2 are rotated in opposite directions, the frictional force between the upper surface plate 1 and the workpiece 3 and the frictional force between the lower surface plate 2 and the workpiece are reversed. A couple of people are born and work piece 3
Can easily rotate. Polishing is performed by the rotational movement of the workpiece 3 and the relative movement between the upper surface plate 1 and the lower surface plate 2 rotated by a motor.

  In this case, as shown in the drawing, the lower surface of the work plate 3 starts from the center of the work piece 3 to the surface of the lower platen 2 up to about 10% of the diameter of the work piece 3 and close to the rotation center of the lower platen 2. To touch. Further, the upper surface of the workpiece 3 starts from the center of the workpiece 3 and contacts the surface of the upper surface plate 2 up to about 10% of the diameter of the workpiece 3 and a portion closer to the outer peripheral side of the upper surface plate 2. Since a fixed width is supported from the center of the workpiece 3 by the upper and lower surface plates, the vertical bending deformation of the workpiece 3 due to the pressing of the surface plates against the workpiece 3 does not occur, and the workpiece A flatness of 3 is maintained.

  The surface plate radius width (overlapping contact radius width) of the region where the upper and lower surface plates contact with each other by overlapping the upper and lower surfaces of the workpiece (referred to as “overlapping contact”) may be any width that allows rotation of the workpiece. However, it is preferably within about 10% of the diameter of the workpiece 3 starting from the center of the workpiece 3 (in the case of a workpiece having an annular hole in the center, the wall surface of the hole). The reason is that in the overlapping contact area of the upper and lower surface plates, the frictional force in the direction opposite to the rotational friction force of the opposite surface plate acts and hinders the rotation of the workpiece, so the overlapping radius width is made as small as possible. This is to eliminate the influence.

  This polishing apparatus can be increased in speed by changing the motor rotation speed, but by using a general-purpose 3600 rpm motor, it is 10 times the normal polishing speed in the case of a platen diameter of 300 mm. A polishing speed of about 20 m / s is theoretically possible.

  In the case of polishing, instead of the level difference of the surface plate shown in FIG. 3 (A), the polisher 11 is stuck on the upper and lower surface plates so as to overlap the workpiece 3 as shown in FIG. 3 (B). To do. Thereby, the workpiece 3 can be rotated and polished in the same manner as in the case of using the surface plate shape shown in FIG. Moreover, a polisher may be affixed to the entire surface of the surface plate shape shown in FIG. 3A to reflect the level difference of the surface plate on the polisher.

  As another example of a specific implementation method, as shown in FIG. 4, a polisher having grooves or holes on the inner peripheral side or outer peripheral side of a circular polisher attached to the surface plate is used, and the surface plate radial direction is used. By creating a difference in the actual contact area between the workpiece and the polisher (referred to as “actual contact area”), a difference in the surface structure in the surface plate radial direction is created, and this is the same as when changing the surface plate shape described above. In addition, it is possible to adopt a method of increasing the rotational force of the workpiece by changing the contact friction force between the workpiece and the polisher in the radial direction of the surface plate.

  The example shown in FIG. 4A is a polisher 11 of an upper surface plate, and a large number of circular holes 21 are formed in an annular shape on the outer surface side of the surface plate, while the round holes are formed on the inner surface of the surface plate. It is not vacant. The polisher does not contact the substrate for the area of the round hole 21. For this reason, when it sees about a fixed width | variety on the line of a radial direction from the rotation center of a surface plate, the actual contact area of the board | substrate 3 and the polisher 11 becomes larger in the inner peripheral part side. On the other hand, the surface structure of the polisher affixed to the lower surface plate side shown in FIG. 4B is opposite to that of the upper surface plate, and the actual contact area between the substrate and the polisher is on the inner peripheral side. Becomes smaller.

  FIG. 5 is a schematic diagram showing the contact state between the polisher and the workpiece when the polisher surface structure applied to the surface plate of the rotary double-side polishing apparatus of the present invention is changed in the surface plate radial direction. As shown in FIG. 5, the actual contact area is different between the workpiece and the polisher. When the upper surface plate 1 and the lower surface plate 2 are rotated in opposite directions, a couple is generated in the workpiece 3, and the workpiece 3 Can easily rotate.

By changing the surface structure of the circular polisher to be attached to this surface plate and using a polisher having grooves or round holes on the inner or outer peripheral side, the above-mentioned surface plate shape is changed depending on the position of the surface plate radius. It is easier than changing the contact area. The advantage of using a polisher is that the method of making a step with the surface plate shape shown above requires high-precision machining, and processing the surface plate in response to various polishing operations Although time and labor are required, changing the surface structure of the polisher makes the polisher soft and easy to process with a blade or the like. In addition, in the case of a structure with a fixed polisher, it can be produced in large quantities depending on the mold.

  In the above method, the upper surface plate and the lower surface plate are examples of reverse rotation, but the surface structure of the surface plate and polisher that both increase the contact friction force between the upper and lower surface plates and the workpiece on the outer peripheral side. Thus, both surfaces can be polished even if the upper surface plate and the lower surface plate are rotated in the same direction.

  The method and embodiments of the present invention are described below with reference to the figures. As shown in FIG. 6, the upper surface of the workpiece (magnetic disk substrate) 3 accommodated in the hole of the carrier 13 is circumferentially raised from the wall surface of the hole to the edge of the step about 5 mm ahead of the rotation center of the lower surface plate 2. From the wall surface of the lower surface plate 2 and workpiece 3 with the step shape protruding toward the platen to the edge of the step 5mm ahead of the outer surface of the upper surface plate 1 from the wall surface of the workpiece 3 protrudes circumferentially toward the lower platen side Polishing of the magnetic disk substrate 3 sandwiched between the polishers 11 and 11 was performed using a double-side polishing apparatus of a type that presses the upper surface plate 1 having a step shape against the workpiece 3.

  FIG. 7 shows a magnetic disk under a polishing condition up to 6 m / s, which is about 4 times higher than the conventional maximum polishing speed of 1.5 m / s, at 24 kPa, which is about twice the maximum polishing pressure of about 10 kPa used conventionally. It shows the relationship between the polishing time and the substrate removal thickness when the substrate is polished. It can be seen that polishing can be performed by this polishing method.

  In addition, when the same experiment was conducted under the experimental conditions of 12 kPa near the conventional maximum polishing pressure and 1.5 m / s near the conventional maximum polishing speed, the removal thickness obtained in 10 minutes of polishing time was about 0.5 μm. Therefore, when the removal thickness obtained under the experimental conditions of polishing pressure of 24kPa and the maximum polishing speed of 6m / s was compared with the polishing time of 10 minutes, the removal speed was about 5 times. Thus, the usefulness of the processing method of the present invention is understood. Therefore, if the polishing rate is further increased, a higher removal rate will be obtained as in the case of single-side polishing.

  FIG. 8 shows a magnetic disk under a polishing condition up to 6 m / s, which is about 4 times higher than the conventional maximum polishing speed of 1.5 m / s, at 24 kPa, which is about twice the maximum polishing pressure of about 10 kPa used conventionally. It shows the relationship between the polishing time and the substrate smoothness when the substrate is polished. The substrate smoothness is smoothed with the polishing time. In any polishing condition, the surface roughness Hra is finally approaching 0.3 nm. This is almost the same as the surface roughness conventionally obtained by single-side polishing, and it can be seen that increasing the polishing pressure and speed has no significant effect.

  FIG. 9 is an example showing the result of FIG. 8, and is an example of measuring the surface roughness of the substrate when polished for 10 minutes at 6 m / s, which is about 4 times or more the conventional maximum polishing speed of 1.5 m / s. In both cases of the polishing pressure of 6 kPa in FIG. 9A and 24 kPa in FIG. 9B, the substrate surface roughness Hra measured two-dimensionally is about 0.25 nm, which is an ultra-smooth surface. It shows that the smoothness is the same as the conventional method.

  Since the method and apparatus of the present invention do not rotate the carrier, a gear for rotating the carrier is not necessary. Therefore, the surface plate is moved at a high speed to a speed and pressure range in which the workpiece can be rotated by a frictional force. It can rotate, enabling high speed and high pressure polishing. Further, since no gear is used, the polishing apparatus can be manufactured at a low cost.

It is a conceptual perspective view of the double-sided grinding | polishing method of this invention which does not use the gear mechanism for rotating a carrier. It is the partial cross section figure of the upper and lower both surface plates of the rotary type double-side polish apparatus of this invention, and the one part enlarged view which shows the contact state of the upper and lower surface plates and a workpiece. It is a schematic diagram which shows the shape (A) of the surface plate of the rotary type double-side polish apparatus of this invention, and the shape (B) of a polisher. It is a schematic diagram which shows the polisher surface structure example (A) affixed on the upper surface plate of the rotary type double-side polish apparatus of this invention, and the polisher surface structure example (B) affixed on the lower surface plate. It is a schematic diagram which shows the contact state of a polisher and a workpiece | work when the polisher surface structure stuck on the surface plate of the rotary type double-side polish apparatus of this invention is changed to the surface plate radial direction. It is a schematic diagram which shows the shape of the surface plate and polisher of the double-side polish apparatus used in the Example. It is a graph which shows the relationship between the polishing time and polishing removal thickness at the time of polishing by polishing conditions up to a polishing speed of 6 m / s with high pressure polishing of 24 kPa, obtained in an example. It is a graph which shows the relationship between the polishing time and workpiece surface roughness at the time of polishing by the high pressure polishing of 24 kPa and polishing conditions up to a polishing speed of 6 m / s, obtained in an example. Using the high-speed polishing of 6m / s obtained in the example, the surface roughness Hra of the workpiece when polishing for 10 minutes under the conditions of polishing pressure of 6kPa and 24kPa is measured with an optical interference type high precision surface measuring instrument (WYKO). It is a drawing substitute photograph which shows the measurement result. It is a schematic diagram showing the principle of normal polishing (example of polishing) It is a schematic diagram which shows the example of the double-side polishing method using the conventional gear mechanism.

Claims (5)

A workpiece that is sandwiched between the upper and lower surface plates of a rotary type polishing surface plate that uses an upper surface plate and a lower surface plate that rotate in opposite directions or in the same direction and that is held by the carrier without rotating the carrier. Relative motion between upper and lower polishing surface plate and workpiece by rotating the workpiece using the difference in contact friction force between the radial workpiece and the surface plate or the polisher affixed to the surface of the surface plate. And double-side polishing method to polish the workpiece. Creates a difference in contact friction force by making the actual contact area in the radial direction of the surface plate between the workpiece and the surface plate or polisher different depending on the surface structure in the radial direction of the surface plate of the surface plate or the surface plate of the polisher. The double-side polishing method according to claim 1, wherein: An apparatus used to carry out the method according to claim 1 or 2, comprising:
One surface of the upper surface plate or the lower surface plate, or the polisher affixed to the surface protrudes circumferentially from the outer periphery side to the position of the fixed surface in the direction of the center of rotation of the surface plate. A step is formed, and the position of the edge of this step is closer to the center of rotation of the surface plate by a certain distance from the center of the workpiece,
The other one surface, or the polisher affixed to the surface, has a protruding step toward the opposite mating surface from the rotation center of the surface plate to a position at a constant distance in the outer circumferential direction. The position of the edge of the plate is closer to the outer periphery of the surface plate by a certain distance from the center of the workpiece,
A double-side polishing apparatus characterized in that the surface plate radius width where the upper and lower surface plates are in contact with the upper and lower surfaces of the work piece is set to a width allowing rotation of the work piece. 4. The double-sided surface according to claim 3, wherein the surface plate radius width is within 10% of the diameter of the workpiece starting from the center of the workpiece (or the wall surface of the hole in the case of a workpiece having an annular hole in the center). Polishing equipment. An apparatus used for carrying out the method according to claim 1 or 2, wherein a groove or a hole is provided on an inner peripheral side or an outer peripheral side of a circular polisher, and an actual contact area between a workpiece and a polisher in a surface plate radial direction. This is a double-side polishing machine in which a polisher is applied to the surface of the surface plate to create a difference in contact friction force between the workpiece and the polisher in the radial direction of the surface plate.

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