Processing method for surface microstructure of polishing pad

Abstract

The invention discloses a method for machining a surface microstructure of a polishing pad, the polishing pad is made of a soft and tough material, and the machining method comprises the following steps: a cutting knife piece extends into the polishing pad, and cuts and advances at a first cutting speed; the cutting knife part cuts the part of the polishing pad until the part is not completely separated, that is, the part is attached to the polishing pad; the cutting knife part cuts along the original cutting track at a second cutting speed and advances in the opposite direction; and the cutting knife part cuts off the part attached to the polishing pad, so that the part is separated from the polishing pad, and a target microstructure is formed. The invention further discloses a polishing pad surface microstructure reprocessing method. By adjusting the cutting mode and increasing the cutting volume, the material is cut off instead of cutter back-off, complete removal of cutting is achieved, and the method is particularly suitable for deepening and reprocessing of the surface microstructure of the polishing pad.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor integrated circuit chip manufacturing and processing, and particularly relates to a method for processing the surface microstructure of a polishing pad. Background Art

[0002] In the manufacturing process of semiconductor integrated circuit chips, planarization technology has become one of the indispensable key technologies. Chemical Mechanical Planarization (CMP) process is currently the most effective and mature planarization technology. CMP equipment is fully automated, ensuring the safety of each module and each link in the production process of the wafer, which is of great significance for safe production, reducing losses, and improving production efficiency. The CMP equipment mainly adsorbs and transports the wafer to the polishing pad through the polishing head for polishing, and then transports the wafer back to the wafer loading bracket by the polishing head for unloading and placing after polishing.

[0003] Generally, the upper surface of the polishing pad has grooves, and the polishing process depends on the grooves on the polishing pad to fill the polishing liquid and other media. When the groove depth becomes shallower, the liquid medium in the grooves of the polishing pad becomes less, which will cause the failure of the function of the polishing head or the deterioration of the stability of the polishing process during polishing, and the loading and unloading stability of the polishing head also becomes worse. If the groove depth is too large in the initial state, there are problems of poor process stability and impurities falling into the grooves and being difficult to discharge. Therefore, in the actual application process, the equipment personnel will determine the service life of the polishing pad by the method of setting the processing amount or the groove depth, and perform the operation of replacing the new polishing pad.

[0004] The polishing pad is made of soft and tough materials such as polyurethane, and there are grooves on its upper surface, and liquids such as polishing liquid are accumulated in the grooves. For the processing of the surface grooves of the polishing pad, the selection of processing parameters usually needs to meet two elements: high cutting rate and low cutting amount, so as to facilitate the cutting of materials and reduce the cutting resistance. For milling cutter processing, high cutting rate corresponds to high sharpness tool and high rotational speed; low cutting amount corresponds to low back engagement of the cutting edge and low feed rate, as Figure 1 shown.

[0005] However, during actual processing, the high rotational speed and low feed rate of the milling cutter can cut and break the polyurethane material well, but due to the softness and toughness of the material, the material tears when broken, so it is very easy to leave burrs at the chip discharge place, as Figure 3 shown. During mechanical processing, such burrs are usually removed by higher rotational speed and lower feed rate (secondary pass - or finish machining), as Figure 2As shown, when removing the flash of soft and flexible materials, this method is not applicable because the flash is more likely to deflect under the friction of the tool (due to the poor stiffness of the material, even if the numerical control tool moves exactly along the designed contour of the part, the soft and flexible material is more likely to deform under the extrusion of the tool, resulting in the failure of the second tool path, and the phenomenon of thick upper part, thin lower part and out-of-tolerance dimensions of the part) rather than being cut off. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, the present invention provides a method for machining the surface microstructure of a polishing pad, which adjusts the cutting method, increases the cutting volume, enables the material to be cut off rather than deflected, and realizes the complete removal of cutting.

[0007] The technical solution adopted by the present invention to solve its technical problems is: a method for machining the surface microstructure of a polishing pad, the polishing pad is made of soft and flexible material, and the machining method includes the following steps:

[0008] The cutting tool extends into the polishing pad and cuts and advances at the first cutting speed;

[0009] The cutting tool cuts a part of the polishing pad to be incompletely separated, that is, this part adheres to the polishing pad;

[0010] The cutting tool cuts and travels in the reverse direction along the original cutting trajectory at the second cutting speed;

[0011] The cutting tool cuts off the part adhering to the polishing pad so that this part detaches from the polishing pad to form the target microstructure.

[0012] Further, before forming the target microstructure, the above steps are repeated two or more times.

[0013] Further, the hardness of the polishing pad is less than 70D, and / or, the fracture strength of the polishing pad is greater than 120 kg / cm 2 , and / or, the elongation rate of the polishing pad is greater than 100%.

[0014] Further, the hardness of the polishing pad is 50 - 65D; the fracture strength of the polishing pad is 180 - 220 kg / cm 2 ; the elongation rate of the polishing pad is 120 - 160%.

[0015] Further, the first cutting speed and the second cutting speed are the same; or, the first cutting speed and the second cutting speed are different.

[0016] Further, the first cutting speed includes the first cutting speed and the first rotational speed of the cutting tool rotating around its own central axis; the second cutting speed includes the second cutting speed and the second rotational speed of the cutting tool rotating around its own central axis.

[0017] Furthermore, the first cutting speed is 400 - 6000 mm / min, and the first rotational speed is 8000 - 80000 rpm; the second cutting speed is 400 - 6500 mm / min, and the second rotational speed is 8000 - 100000 rpm.

[0018] Furthermore, it includes the following steps:

[0019] The cutting tool extends into the polishing pad, travels along a first direction at a first cutting speed, and rotates around its own central axis at a first rotational speed;

[0020] The cutting tool cuts a part of the polishing pad, and this part adheres to the surface of the polishing pad in a mass shape and is connected to the polishing pad;

[0021] The cutting tool travels along the original cutting trajectory, travels along a second direction at a second cutting speed, and rotates around its own central axis at a second rotational speed. The second direction is opposite to the first direction, and the rotational direction of the cutting tool around its own central axis remains unchanged;

[0022] The cutting tool continues to cut to separate the mass-shaped part attached to the polishing pad, and all the mass-shaped parts are connected into a strip and separated from the polishing pad simultaneously;

[0023] A target micro-structure is formed on the surface of the polishing pad.

[0024] Furthermore, the width of the mass-shaped part is approximately equal to the width of the target micro-structure, the thickness of the mass-shaped part is approximately equal to the depth of the target micro-structure, all the mass-shaped parts are connected into a strip, and the volume of this strip part is approximately equal to the volume of the part cut off from the polishing pad.

[0025] Furthermore, the diameter of the cutting tool is D, and the width of the target micro-structure is L, then L ≤ D < 1.5L.

[0026] Furthermore, the micro-structure is a micro-groove or a micro-geometric shape; the width of the target micro-structure is 0.2 - 2.0 mm, and the depth of the target micro-structure is 0.2 - 2.0 mm.

[0027] Furthermore, the cutting tool has two cutting surfaces symmetrically arranged radially; the cutting tool is a double-edge end mill; the cutting tool has a three-edge structure or a multi-edge structure.

[0028] Furthermore, the surface of the polishing pad has a micro-structure, which is used for reprocessing the micro-structure on the surface of the polishing pad to increase the depth of the micro-structure.

[0029] The present invention solves the problem of micro-structure machining of polishing pads made of soft and ductile materials by combining forward and reverse travel and adjusting the cutting speed. It should be emphasized here that for the cutting machining of soft and ductile materials, the key to ensuring the machining accuracy is to control the chip breaking quality, that is, the chips can be quickly cut off without tearing of the material. When machining large-sized structures, larger-sized tools can be used. Such tools can provide higher cutting forces during rotation, making it easier to cut the material. Therefore, it is not an effective applicable scenario for the back-cutting process. When machining micro-structures on soft and ductile materials, the reduction of the tool size limits the improvement of the tool sharpness and cutting force, thus restricting the machining accuracy of micro-structures. The application of the back-cutting process can efficiently remove materials and improve the machining quality, especially suitable for the machining and manufacturing of micro-structures on soft and ductile materials.

[0030] The beneficial effect of the present invention is that by adjusting the relative magnitudes of the rotational speed of the cutting tool and the cutting speed value, during the forward travel of the tool, the rotational cutting of the cutting tool will only lift part of the material along the machining path rather than cut it into debris, keeping it as a continuously structured mass covering the original trajectory. The material cross-section is as Figure 10 shown; at this time, control the cutting tool to travel in the reverse direction, switch the cutting position, and perform secondary cutting on the connecting position of the lifted part of the material, so that the mass of the material can be completely cut off, realizing high-quality groove machining with a smooth contour and no burrs, as Figure 11 shown. At this time, the cut material is in the form of continuous long or short strips, avoiding the problem that it is difficult to machine the burrs left after the material is shredded. In short, the present invention integrates the chip fragments and burr structures by regulating the rotational speed and cutting speed of the cutting tool, increasing the volume of the cut part, and cutting it completely from the workpiece, thereby realizing high-quality machining of micro-structures of soft and ductile materials; due to the soft and ductile material properties of the polishing pad, the side walls of the target micro-structures are pulled by the cutting tool during machining. The diameter of the cutting tool needs to be slightly larger than the width of the target micro-structure to ensure that the width of the target micro-structure remains unchanged after reprocessing.

[0031] The present invention also discloses a method for reprocessing the surface micro-structures of a polishing pad. The polishing pad is made of a soft and ductile material, and the processing method includes the following steps:

[0032] The cutting tool cuts into the polishing pad at a third speed, cuts and travels at a first cutting speed to perform polishing pad cutting;

[0033] The cutting tool cuts part of the polishing pad to be incompletely separated, that is, this part adheres to the polishing pad;

[0034] The cutting tool travels to the target position and cuts off the part adhering to the polishing pad so that this part detaches from the polishing pad to form the target micro-structure.

[0035] Further, the polishing pad is located on a polishing disc, and the polishing disc is movable so that a relatively stationary cutting tool cuts and advances at a first cutting speed.

[0036] Further, the third speed at which the cutting tool cuts into the polishing pad is Vz, and Vz is 0.05 - 0.5 mm / s; the depth at which the cutting tool cuts into the polishing pad is d, and the width of the target microstructure is L, then d > 1 / 4L so that the cut portion of the polishing pad is continuous.

[0037] Further, the cutting tool includes a rake face and a flank face. When the cutting tool advances and cuts, the angle between the rake face and the plumb plane is the rake angle, and the angle between the flank face and the horizontal plane is the flank angle. The rake angle is 5° - 30°, and the flank angle is 10° - 80°.

[0038] Further, the cut portion of the polishing pad accumulates on the rake face.

[0039] Further, when the cutting tool cuts into the polishing pad and cuts and advances at a first cutting speed, the cutting tool itself rotates to adjust the cutting direction.

[0040] Further, the hardness of the polishing pad is less than 70D, and / or the fracture strength of the polishing pad is greater than 120 kg / cm 2 , and / or the elongation rate of the polishing pad is greater than 100%.

[0041] Further, the hardness of the polishing pad is 50 - 65D; the fracture strength of the polishing pad is 180 - 220 kg / cm 2 ; the elongation rate of the polishing pad is 120 - 160%.

[0042] Further, the polishing disc rotates at a rotational speed of 5 - 200 rpm.

[0043] Further, the width of the cutting tool is D, and the width of the target microstructure is L, then L ≤ D < 1.5L.

[0044] Further, the microstructure is a microgroove or a micro geometric shape; the width of the target microstructure is 0.2 - 2.0 mm, and the depth of the target microstructure is 0.2 - 2.0 mm.

[0045] Further, the surface of the polishing pad has a microstructure, which is used for reprocessing the surface microstructure of the polishing pad to increase the depth of the microstructure.

[0046] The beneficial effects of the present invention are as follows: The cutting tool member is relatively fixed and does not rotate, and the broach structure is selected for the cutting tool member, which is relatively simple; the cutting ability of the cutting tool member is provided by the rotation of the workpiece, and it has a high cutting speed, which can effectively reduce the processing time and improve the processing efficiency; since the polishing pad material is soft and tough, it is necessary to make the material to be removed have a certain volume. When the cutting tool member is processing, under the action of the cutting force at the tool tip, the material on the surface of the polishing pad to be processed is removed and accumulates on the rake face. Due to the toughness of the material itself, the cutting does not continuously break at the tool tip. Driven by the already cut material, the material to be cut is removed completely.

[0047] By adjusting the orientation of the rake face of the tool to be consistent with the tangent direction of the groove in real time, the types of microstructures that can be processed can be expanded from concentric circular grooves to micro circular hole arrays, micro waist-shaped hole arrays, involute micro grooves, etc. Brief Description of the Drawings

[0048] Figure 1 It is a schematic diagram of milling in traditional milling technology.

[0049] Figure 2 It is a schematic diagram of the forward feed and reverse feed cutting in traditional milling technology.

[0050] Figure 3 It is a schematic diagram of the milling effect in traditional milling technology.

[0051] Figure 4 It is a schematic diagram of the cooperation structure of the polishing pad, polishing disc and cutting tool member in the first embodiment of the present invention.

[0052] Figure 5 It is a three-dimensional structure schematic diagram of the cutting tool member and the local polishing pad groove in the first embodiment of the present invention. At this time, it is cutting at the first cutting speed and traveling in the direction of the arrow.

[0053] Figure 6 It is a front view structure schematic diagram of the cutting tool member and the local polishing pad groove in the first embodiment of the present invention.

[0054] Figure 7 For Figure 6 The A-A cross-sectional view in

[0055] Figure 8 It is a three-dimensional structure schematic diagram of the cutting tool member and the local polishing pad groove in the first embodiment of the present invention. At this time, it is cutting at the second cutting speed and traveling in the direction opposite to the first cutting speed direction along the arrow.

[0056] Figure 9 For Figure 8 The cross-sectional schematic diagram in the

[0057] Figure 10Schematic diagram of the connection between the mass part and the groove of the polishing pad in Embodiment 1 of the present invention.

[0058] Figure 11 Cross-sectional view of the polishing pad groove after processing in Embodiment 1 of the present invention, with the mass part completely detached.

[0059] Figure 12 Schematic diagram of the effect of processing the polishing pad groove using traditional milling technology.

[0060] Figure 13 Physical diagram of the cutting tool forming a mass part while traveling along the first direction in Embodiment 1 of the present invention.

[0061] Figure 14 Schematic diagram of the cooperation structure of the polishing disc, polishing pad, and cutting tool in Embodiment 2 of the present invention.

[0062] Figure 15 Schematic diagram of the cooperation structure of the cutting tool and the polishing pad in Embodiment 2 of the present invention Figure 1 。

[0063] Figure 16 Schematic diagram of the cooperation structure of the cutting tool and the polishing pad in Embodiment 2 of the present invention Figure 2 。

[0064] Figure 17 Schematic diagram of the three-dimensional structure of the cutting tool in Embodiment 2 of the present invention Figure 1 。

[0065] Figure 18 Schematic diagram of the three-dimensional structure of the cutting tool in Embodiment 2 of the present invention Figure 2 。

[0066] Figure 19 Side view of the cutting tool in Embodiment 2 of the present invention.

[0067] Figure 20 Schematic diagram of the cooperation structure of the polishing disc, polishing pad, and cutting tool in Embodiment 2 of the present invention, with the cutting tool rotating itself at this time.

[0068] Figure 21 Top view of the cooperation structure of the polishing disc, polishing pad, and cutting tool in Embodiment 2 of the present invention, with the cutting tool rotating itself at this time.

[0069] Figure 22 Top view of the cooperation structure of the polishing disc, polishing pad, and cutting tool in Embodiment 2 of the present invention, with the cutting tool rotating itself and the microstructure being a grid-shaped groove at this time.

[0070] Figure 23 Top view of the polishing pad in Embodiment 2 of the present invention, with the microstructure being a concentric circular groove at this time.

[0071] Among them, 1 is a cutting tool, 11 is a cutting surface, 12 is a front cutting surface, 13 is a rear cutting surface, 2 is a polishing pad, 21 is a groove, 22 is a chip, 3 is a polishing disc, and 41 is a lump part. Specific embodiments

[0072] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0073] Under the combined action of the polishing liquid, polishing head, wafer, and polishing pad dresser, the polishing pad will continuously wear and thin, and the groove depth will gradually become shallower. Usually, the polishing pad is bonded to the top surface of the polishing disc; when the polishing pad reaches the replacement node, the polishing head, polishing pad dresser, and liquid supply arm make avoidance movements to create space for removing the polishing pad; the operator tears off the polishing pad from the edge and replaces it with a new one.

[0074] The present invention introduces a cutting tool 1. When the polishing pad 2 is placed on the polishing disc 3 or other working platforms, by the movement of the cutting tool 1, or by the movement of the working platform, or by the movement of both, the cutting tool 1 deepens the cutting of the groove, increasing the depth of the groove, that is, realizing the reprocessing of the micro-structure on the surface of the polishing pad. Without tearing off the polishing pad 2 from the working platform, the reprocessing of the polishing pad 2 can be realized, and the polishing pad 2 can be put back into use after the processing is completed.

[0075] The method of the present invention is not only applicable to the original grooving processing of the grooves of the polishing pad 2, but also more applicable to the reprocessing of the grooves of the polishing pad 2 to increase the groove depth.

[0076] Embodiment 1

[0077] A method for reprocessing the micro-structure on the surface of a polishing pad, used to form a micro-structure on the polishing pad 2. The polishing pad 2 is made of a soft and tough material. Specifically, the hardness of the polishing pad 2 is less than 70D; or, the breaking strength of the polishing pad 2 is greater than 120 kg / cm 2 ; or, the elongation rate of the polishing pad 2 is greater than 100%; or, the hardness, breaking strength, and elongation rate of the polishing pad 2 simultaneously meet the above conditions; or, the hardness, breaking strength, and elongation rate of the polishing pad 2 meet any two of the above conditions, and there is no specific limitation.

[0078] In this embodiment, the hardness of the polishing pad 2 is 50 - 65D; the breaking strength of the polishing pad is 180 - 220 kg / cm 2; The elongation rate of the polishing pad is 120 - 160%. The polishing pad 2 can be a polyurethane (PU) polishing pad, made of a densely foamed polyurethane material with fine air bubbles distributed inside. Preferably, the hardness of the polishing pad 2 is 56D; the breaking strength of the polishing pad is 200 kg / cm 2 ; The elongation rate of the polishing pad is 140%, in other words, the polishing pad 2 is soft and tough, making it difficult to process.

[0079] A method for reprocessing the surface microstructure of a polishing pad. For the polishing pad 2 made of the soft and tough material mentioned above, the processing method includes the following steps:

[0080] The cutting tool 1 extends into the polishing pad 2 and cuts and advances at the first cutting speed; this can be defined as the first tool path.

[0081] The above first cutting speed includes the first cutting velocity V1 and the first rotational speed N1 of the cutting tool 1 rotating around its own central axis; specifically, the first cutting velocity V1 is 400 - 6000 mm / min, preferably, V1 is 2500 - 3500 mm / min, and the first rotational speed N1 is 8000 - 80000 rpm, preferably, N1 is 40000 - 80000 rpm;

[0082] The cutting tool 1 cuts a part of the polishing pad 2 to an incomplete separation, so that this part adheres to the polishing pad 2;

[0083] The cutting tool 1 cuts and travels in the reverse direction along the original cutting trajectory at the second cutting speed; the above cutting trajectory can be any trajectory, that is, the processing method of the present invention has nothing to do with the path of the cutting tool 1 walking, as long as it travels forward and backward along the original path twice; this can be defined as the second reverse tool path, and the combination of the above first tool path and the second reverse tool path is defined as the back - cutting processing;

[0084] The above second cutting speed includes the second cutting velocity V2 and the second rotational speed N2 of the cutting tool 1 rotating around its own central axis; the second cutting speed and the first cutting speed can be the same or different; specifically, the second cutting velocity V2 is 400 - 6500 mm / min, preferably, V2 is 3000 - 4000 mm / min, and the second rotational speed N2 is 8000 - 100000 rpm, preferably, N2 is 60000 - 100000 rpm;

[0085] The cutting tool 1 cuts off the part adhering to the polishing pad 2 so that this part detaches from the polishing pad 2, forming the target microstructure.

[0086] In the above process, the first feed and the second reverse feed are carried out to achieve the machining of the target microstructure. Of course, in other embodiments, it may also take two or more rounds with the first feed and the second reverse feed as one round to achieve the machining of the target microstructure, and specific limitations are not made.

[0087] Furthermore, a method for reprocessing the surface microstructure of a polishing pad, aiming at the polishing pad 2 made of the above-mentioned soft and tough material, the processing method includes the following steps:

[0088] The cutting tool 1 extends into the polishing pad 2, travels along the first direction at the first cutting speed V1, and rotates around its own central axis at the first rotational speed N1; in this embodiment, the cutting tool 1 vertically extends into the polishing pad 2 along the thickness direction; of course, in other embodiments, the cutting tool 1 may also be inclined to extend, and specific limitations are not made;

[0089] The cutting tool 1 cuts a part of the polishing pad 2, and this part adheres to the surface of the polishing pad 2 in a lump, and this lump part 41 is connected to the polishing pad 2;

[0090] The above-mentioned lump part 41 specifically refers to that after being cut by the cutting tool 1, this part does not break the cut material like the traditional milling technology (such as Figure 8 shown), the material will form a lump, that is, the width of the lump part 41 is approximately equal to the width of the target microstructure, the thickness of the lump part 41 is approximately equal to the depth of the target microstructure, and all the lump parts 41 are connected in a strip shape, and the volume of this strip part is approximately equal to the volume of the cut part of the polishing pad 2;

[0091] The cutting tool 1 travels along the original cutting trajectory, travels along the second direction at the second cutting speed V2, and rotates around its own central axis at the second rotational speed N2, the second direction is opposite to the first direction, and the rotational direction of the cutting tool 1 around its own central axis remains unchanged;

[0092] The cutting tool 1 continues to cut to separate the lump part 41 attached to the polishing pad 2, and all the lump parts 41 are connected in a strip shape and separated from the polishing pad 2 at the same time;

[0093] Target microstructures are formed on the surface of the polishing pad 2; in this embodiment, the target microstructures are concentric micro-grooves, or other micro geometric shapes: such as micro-round hole arrays, micro-oval hole arrays, involute micro-grooves, etc.; the width of the target microstructures is 0.2 - 2.0 mm, preferably, the width of the target microstructures is 0.4 - 0.8 mm, that is Figure 7 in which L = 0.4 - 0.8 mm, the depth of the target microstructures is 0.2 - 2.0 mm, preferably, the depth of the target microstructures is 0.4 - 0.8 mm, that is Figure 7 in which d = 0.4 - 0.8 mm.

[0094] Define the diameter of the cutting tool 1 as D and the width of the target microstructure as L, then L ≤ D < 1.5L. Since the material of the polishing pad 2 is soft and tough, the side wall of the target microstructure is pulled by the cutting tool 1 during cutting. To ensure that the width of the target microstructure remains unchanged after reprocessing, the cutting tool 1 needs to be selected with a diameter D slightly larger than the width L of the target microstructure. The specific ratio can be determined according to the parameters of the polishing pad 2. When the hardness of the polishing pad 2 is low and the fracture strength is high, this ratio needs to be increased accordingly.

[0095] The cutting tool 1 has two cutting surfaces 11 arranged radially symmetrically. In this embodiment, the cutting tool 1 can be a double-edge end mill, or a three-edge structure, or a multi-edge structure. The tip shape of the cutting tool 1 is selected according to the specific application scenario: for example, in the processing application of the groove 21 of the polishing pad 2, since the size of the groove 21 is small (0.4 - 0.8 mm), when selecting the cutting tool 1, it is necessary to consider various aspects such as the sharpness of the cutting tool 1, the strength of the cutting tool 1, and the cutting efficiency. Here, a double-edge flat-end mill is selected for processing.

[0096] The displacement of the cutting tool 1 on the workpiece can be realized by controlling the cutting tool 1 through a numerical control platform such as the X - Y axis, or preferably, in the present invention, it is realized by combining the rotational movement of the polishing pad 2 and the linear movement of the cutting tool 1 along the radial direction. In this way, the linear velocity of the milling cutter tip of the cutting tool 1 on the rotating polishing pad 2 following the polishing disc 3 is the traveling speed v of the cutter during milling c , and the traveling speed can be calculated by the rotational speed N pad of the polishing pad 2 and the radius R where the tip is located (v c = 2π * N pad * R).

[0097] In this embodiment, several sets of process parameters with better processing quality of the cutting tool 1 are given as shown in Table 1 below (where √ represents that the inner wall of the groove is smooth after processing and the cut material is not shredded).

[0098] Table 1

[0099]

[0100] As Figure 15 shown, in the processing method of the present invention, when the cutting tool 1 travels along the first direction at the first cutting speed V1 and rotates around its own central axis at the first rotational speed N1, that is, when moving forward, the cutting direction of the cutting edge, that is, the material structure at the cutting position part is cut off, and the material is lifted up, that is, as Figure 10As shown, although most of the agglomerated part 41 has separated from the groove 21, a small part of it still adheres to the groove 21, located at the chip removal position. It should be emphasized that the material is not broken and remains in a connected agglomerated structure. The cutting tool 1 travels along the second direction at the second cutting speed V2 and rotates around its own central axis at the second rotational speed N2. At this time, the positions of the cutting position and the chip removal position are switched, and material cutting occurs at the original chip removal position. The attached agglomerated part of the material 41 is completely cut off and separated from the groove 21, as Figure 11 shown. The inner wall of the groove 21 is relatively smooth and no burrs will be left. Moreover, since the agglomerated part 41 is connected in a band shape and separated from the polishing pad 2 at the same time, no fine materials will have an adverse effect.

[0101] As Figure 1 , Figure 2 shown, the cutting edge of a traditional milling cutter usually moves in one direction (clockwise or counterclockwise). During machining, only the motorized spindle can be controlled to rotate at a high speed in the corresponding direction to provide the cutting force, thus forming a cutting position and a chip removal position on the workpiece. Due to the material properties of the workpiece and insufficient cutting, material burrs often remain at the chip removal position, forming burrs, which is one of the main reasons for the low quality of milling machining.

[0102] During milling machining, to improve the machining quality, it is usually achieved by increasing the rotational speed of the motorized spindle and reducing the cutting speed. However, when machining soft and tough materials such as polyurethane, at a high rotational speed during the forward feed process, the material will be quickly broken, forming fine chips and leaving a large amount of burrs at the chip removal position; due to the soft texture of the material, during the reverse feed process, the burrs will "yield to the tool" under the high-speed rotation and cutting of the tool, making it impossible to be completely cut off, as Figure 3 shown.

[0103] By comparison, the traditional cutting method is not applicable to polishing pads made of soft and tough materials, resulting in burrs remaining in the groove after the final cutting. To effectively remove the burrs, it is necessary to increase the volume of the burrs to increase the stiffness of the material, so as to achieve the separation of the material from the original workpiece under the cutting of the cutting edge. The back-feed machining technology of the present invention (i.e., cutting at the first cutting speed and traveling in the opposite direction at the second cutting speed) effectively removes the material by traveling back and forth. Specifically, by controlling the matching of the rotational speed of the motorized spindle and the traveling speed of the cutting tool, a partial cutting effect is produced during the first pass, that is, the material is partially cut but not dropped, which is equivalent to magnifying the volume of the burrs; during the second reverse pass, the connected part is cut off. At this time, the magnified burrs have no space to "yield to the tool" in the groove, and the connected material is cut off; since the cutting parameters of the two passes are similar and only partial cutting occurs, the generated chips are usually in a continuous long strip or short strip shape, and the edge of the formed groove is smooth without burrs.

[0104] Embodiment Two

[0105] A method for reprocessing the surface microstructure of a polishing pad is used to form a microstructure on the polishing pad 2, which is made of a soft and tough material. Specifically, the hardness of the polishing pad 2 is less than 70D; or, the breaking strength of the polishing pad 2 is greater than 120 kg / cm 2 ; or, the elongation rate of the polishing pad 2 is greater than 100%; or, the hardness, breaking strength, and elongation rate of the polishing pad 2 simultaneously meet the above conditions; or, the hardness, breaking strength, and elongation rate of the polishing pad 2 meet any two of the above conditions, and there is no specific limitation.

[0106] In this embodiment, the hardness of the polishing pad 2 is 50 - 65D; the breaking strength of the polishing pad is 180 - 220 kg / cm 2 ; the elongation rate of the polishing pad is 120 - 160%. The polishing pad 2 can be a polyurethane (PU) polishing pad, and the material is a densely foamed polyurethane material with small air bubbles distributed inside. Preferably, the hardness of the polishing pad 2 is 56D; the breaking strength of the polishing pad is 200 kg / cm 2 ; the elongation rate of the polishing pad is 140%. In other words, the polishing pad 2 is soft and tough and difficult to process.

[0107] A method for reprocessing the surface microstructure of a polishing pad, aiming at the polishing pad 2 made of the above soft and tough material, the processing method includes the following steps:

[0108] The cutting tool 1 cuts into the polishing pad 2 at a third speed and cuts and advances at a first cutting speed, thereby cutting the polishing pad 2;

[0109] In this embodiment, the cutting tool 1 is relatively stationary, the polishing pad 2 is located on the polishing disc 3, and the polishing disc 3 is movable. Specifically, the polishing disc 3 can rotate, and its rotation speed is 5 - 200 rpm, so that the relatively stationary cutting tool 1 cuts and advances at a first cutting speed; at the same time, in order to adjust the cutting direction, the cutting tool 1 can rotate itself, such as Figure 20 shown;

[0110] In this embodiment, the cutting tool 1 is a broach, as Figures 17 - 19 shown, which includes a rake face 12 and a flank face 13. When the cutting tool 1 advances and cuts, the angle between the rake face 12 and the plumb plane is the rake angle, and the angle between the flank face 13 and the horizontal plane is the flank angle. Then, the rake angle α is 5° - 30°, and the flank angle β is 10° - 80°; and, the cut part 22 of the polishing pad 2, that is, the chip 22, accumulates on the rake face 12, such as Figure 15 , Figure 16 shown;

[0111] The third speed is Vz, and this Vz is 0.05 - 0.5 mm / s. Preferably, this Vz is 0.1 - 0.2 mm / s;

[0112] The cutting tool 1 cuts a part of the polishing pad 2 until it is not completely separated, so that the part of the polishing pad 2 that has been cut but not completely separated adheres to the polishing pad 2;

[0113] The cutting tool 1 travels to the target position and cuts off the part adhering to the polishing pad 2, so that this part detaches from the polishing pad 2 to form the target micro-structure;

[0114] Define the width of the cutting tool 1 as D and the width of the target micro-structure as L, then L ≤ D < 1.5L. Since the material property of the polishing pad 2 is soft and tough, the side wall of the target micro-structure is pulled by the cutting tool 1 during cutting. To ensure that the width of the target micro-structure remains unchanged after reprocessing, the cutting tool 1 needs to be slightly wider than the width L of the target micro-structure. The specific ratio can be determined according to the parameters of the polishing pad 2. When the hardness of the polishing pad 2 is low and the fracture strength is high, this ratio needs to be increased accordingly.

[0115] In this embodiment, the target micro-structure is a micro-groove of concentric circles, or other micro geometric shapes such as a micro circular hole array, a micro waist-shaped hole array, an involute micro-groove, etc.; the width L of the target micro-structure is 0.2 - 2.0 mm. Preferably, the width L of the target micro-structure is 0.4 - 0.8 mm, the depth d of the target micro-structure is 0.2 - 2.0 mm. Preferably, the depth d of the target micro-structure is 0.4 - 0.8 mm, and d > 1 / 4L, so as to ensure that the cut part of the polishing pad 2 is continuous, that is, continuous and curly chips 22 are formed, as Figure 15 , Figure 16 shown.

[0116] Since the material property of the polishing pad 2 is soft and tough, it is necessary to make the removed material have a certain volume. When the cutting tool 1 is a broaching tool, under the action of the cutting force at the tool tip, the material on the surface to be machined of the polishing pad 2 is removed and accumulates on the rake face 12. Due to the toughness of the material itself, the cutting does not break continuously at the tool tip. The removed material drives the material to be removed to achieve the complete removal of the material.

[0117] The micro-structure is a non-concentric circle groove, as Figure 20 shown. When using the processing device in the prior art to process the non-concentric circle polishing pad groove, since the cutting tool 1 has significant directionality, it is necessary to ensure that the rake face 12 is perpendicular to the cutting direction during processing. Therefore, when using the cutting tool 1 to process grooves such as a parallel grid, as Figure 21 , a steering device needs to be added to the cutting tool 1. According to the groove shape, the orientation of the cutting tool 1 is adjusted in real time to ensure the cutting direction of the cutting tool 1 and achieve the best cutting effect.

[0118] such as Figure 22As shown, the microstructure is a cross-grid groove, and each groove needs to be machined by successive feeding. Each feeding process forms a continuous and curly chip.

[0119] As Figure 23 shown, the microstructure is a concentric circle groove. At this time, when the polishing disc 3 rotates, the cutting tool 1 is relatively stationary. The rotation of the polishing disc 3 causes the cutting tool 1 cutting into the polishing pad 2 to generate relative movement with the polishing pad 2, realizing the cutting of the polishing pad 2.

[0120] The above specific implementation manners are used to explain the present invention, rather than limit the present invention. Any modification and change made to the present invention within the spirit and scope of the claims of the present invention fall within the protection scope of the present invention.

Claims

1. A method for processing the surface microstructure of a polishing pad, the polishing pad being made of a soft and tough material, characterized in that, The processing method includes the following steps: The cutting tool extends into the polishing pad and cuts while advancing at a first cutting speed; The cutting tool cuts a part of the polishing pad to an incomplete separation, that is, this part adheres to the polishing pad; The cutting tool cuts along the original cutting trajectory, cuts while advancing in the reverse direction at a second cutting speed; The cutting tool cuts off the part adhering to the polishing pad so that this part detaches from the polishing pad to form a target microstructure.

2. The method for machining the surface microstructure of the polishing pad according to claim 1, wherein: Before forming the target microstructure, the above steps are repeated two or more times.

3. The method for machining the surface microstructure of the polishing pad according to claim 1, characterized in that: The hardness of the polishing pad is less than 70D, and / or, the breaking strength of the polishing pad is greater than 120 kg / cm 2 , and / or, the elongation rate of the polishing pad is greater than 100%.

4. The method for machining the surface microstructure of the polishing pad according to claim 1 or 3, characterized in that: The hardness of the polishing pad is 50-65D; the breaking strength of the polishing pad is 180-220 kg / cm 2 ; the elongation rate of the polishing pad is 120-160%.

5. The method for processing the surface microstructure of the polishing pad according to claim 1, wherein: The first cutting speed and the second cutting speed are the same; or, the first cutting speed and the second cutting speed are different.

6. The method for processing the surface microstructure of a polishing pad according to claim 1 or 5, characterized in that: The first cutting speed includes a first cutting rate and a first rotational speed at which the cutting tool rotates around its own central axis; the second cutting speed includes a second cutting rate and a second rotational speed at which the cutting tool rotates around its own central axis.

7. The method for processing the surface microstructure of a polishing pad according to claim 6, wherein: The first cutting rate is 400 - 6000 mm / min, the first rotational speed is 8000 - 80000 rpm; the second cutting rate is 400 - 6500 mm / min, the second rotational speed is 8000 - 100000 rpm.

8. The method for machining the surface microstructure of a polishing pad according to claim 6, wherein It includes the following steps: The cutting tool extends into the polishing pad, advances along a first direction at a first cutting rate, and rotates around its own central axis at a first rotational speed; The cutting tool cuts a part of the polishing pad, and this part adheres to the surface of the polishing pad in a mass shape, and this mass-shaped part is connected to the polishing pad; The cutting tool advances along the original cutting trajectory, advances along a second direction at a second cutting rate, and rotates around its own central axis at a second rotational speed, this second direction is opposite to the first direction, and the rotational direction of the cutting tool around its own central axis remains unchanged; The cutting tool continues to cut to detach the mass-shaped part adhering to the polishing pad, and all the mass-shaped parts are connected in a band shape and detach from the polishing pad simultaneously; A target microstructure is formed on the surface of the polishing pad.

9. The method for machining the surface microstructure of a polishing pad according to claim 8, wherein: The width of the mass-shaped part is approximately equal to the width of the target microstructure, the thickness of the mass-shaped part is approximately equal to the depth of the target microstructure, all the mass-shaped parts are connected in a band shape, and the volume of this band-shaped part is approximately equal to the volume of the part cut off from the polishing pad.

10. The method for machining the surface microstructure of a polishing pad according to claim 1, wherein: The diameter of the cutting tool is D, and the width of the target microstructure is L, then L ≤ D < 1.5L.

11. The method for processing the surface microstructure of a polishing pad according to claim 1, characterized in that: The microstructure is a microgroove, or a micro geometric shape; the width of the target microstructure is 0.2 - 2.0 mm, and the depth of the target microstructure is 0.2 - 2.0 mm.

12. The method for machining the surface microstructure of a polishing pad according to claim 1, wherein: The cutting tool has two cutting surfaces symmetrically arranged in the radial direction; the cutting tool is a double-edge end mill; the cutting tool is a three-edge structure, or a multi-edge structure.

13. The method for machining the surface microstructure of the polishing pad according to claim 1, wherein: The surface of the polishing pad has a microstructure, which is used for reprocessing the microstructure on the surface of the polishing pad to increase the depth of the microstructure.

14. A method for processing the surface microstructure of a polishing pad, the polishing pad being made of a soft and tough material, characterized in that, The processing method includes the following steps: The cutting tool cuts into the polishing pad at a third speed, cuts while advancing at a first cutting speed to perform polishing pad cutting; The cutting tool cuts a part of the polishing pad to an incomplete separation, that is, this part adheres to the polishing pad; The cutting tool advances to the target position and cuts off the part adhering to the polishing pad so that this part detaches from the polishing pad to form a target microstructure.

15. The method for machining the surface microstructure of a polishing pad according to claim 14, characterized in that: The polishing pad is located on the polishing disc, and the polishing disc is movable so that the relatively stationary cutting tool cuts and advances at a first cutting speed.

16. The method for machining the surface microstructure of a polishing pad according to claim 14, wherein: The third speed at which the cutting tool cuts into the polishing pad is Vz, and Vz is 0.05 - 0.5 mm / s; the depth at which the cutting tool cuts into the polishing pad is d, and the width of the target microstructure is L, then d > 1 / 4L so that the cut portion of the polishing pad is continuous.

17. The method for machining the surface microstructure of a polishing pad according to claim 14, characterized in that: The cutting tool includes a rake face and a flank face. When the cutting tool advances and cuts, the angle between the rake face and the plumb plane is the rake angle, and the angle between the flank face and the horizontal plane is the flank angle. The rake angle is 5° - 30°, and the flank angle is 10° - 80°.

18. The method for machining the surface microstructure of a polishing pad according to claim 17, wherein: The cut portion of the polishing pad accumulates on the rake face.

19. The method for machining the surface microstructure of a polishing pad according to claim 14, wherein: When the cutting tool cuts into the polishing pad and cuts and advances at a first cutting speed, the cutting tool rotates itself to adjust the cutting direction.

20. The method for machining the surface microstructure of a polishing pad according to claim 14, wherein: The hardness of the polishing pad is less than 70D, and / or the breaking strength of the polishing pad is greater than 120 kg / cm 2 , and / or the elongation rate of the polishing pad is greater than 100%.

21. The method for machining the surface microstructure of a polishing pad according to claim 14 or 20, characterized in that: The hardness of the polishing pad is 50-65D; the breaking strength of the polishing pad is 180-220 kg / cm 2 ; the elongation rate of the polishing pad is 120-160%.

22. The method for processing the surface microstructure of a polishing pad according to claim 15, characterized in that: The polishing disc rotates at a speed of 5 - 200 rpm.

23. The method for machining the surface microstructure of a polishing pad according to claim 14, wherein: The width of the cutting tool is D, and the width of the target microstructure is L, then L ≤ D < 1.5L.

24. The method for processing the surface microstructure of a polishing pad according to claim 14, wherein: The microstructure is a microgroove or a micro geometric shape; the width of the target microstructure is 0.2 - 2.0 mm, and the depth of the target microstructure is 0.2 - 2.0 mm.

25. The method for machining the surface microstructure of a polishing pad according to claim 14, characterized in that: The surface of the polishing pad has a microstructure, which is used for reprocessing the surface microstructure of the polishing pad to increase the depth of the microstructure.

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