Processing method for surface microstructure of polishing pad

Abstract

A processing method for a surface microstructure of a polishing pad. The polishing pad is made of a soft and tough material. The processing method comprises the following steps: a cutting tool (1) extends into a polishing pad (2), and performs cutting at a first cutting speed and moves; the cutting tool cuts part of the polishing pad until the part of the polishing pad is not completely separated, that is, the part is attached to the polishing pad; along the original cutting trajectory, the cutting tool performs cutting at a second cutting speed and moves in a reverse direction; and the cutting tool cuts off the part attached to the polishing pad, so that the part is separated from the polishing pad, so as to form a target microstructure. According to the method, by adjusting a cutting mode, the cutting volume is increased, so that the material is cut off instead of being left in place, and is completely removed, and the method is particularly suitable for deepening reprocessing of the surface microstructure of the polishing pad.

Description

A method for processing microstructure of polishing pad surface Technical Field

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

[0002] Planarization technology has become an indispensable key technology in semiconductor integrated circuit chip manufacturing. Chemical Mechanical Planarization (CMP) is currently the most effective and mature planarization technology. CMP equipment is fully automated, ensuring wafer safety at every stage of the production process. This is crucial for safe production, reducing losses, and improving production efficiency. CMP equipment primarily uses a polishing head to carry wafers onto a polishing pad for polishing. After polishing, the polishing head then transports the wafers back to the wafer loading rack for unloading.

[0003] Polishing pads typically have grooves on their top surface, and the polishing process relies on filling these grooves with polishing fluid and other media. As the groove depth decreases, the amount of liquid media in the polishing pad grooves decreases, leading to functional failure of the polishing head, reduced process stability, and poor handling stability during polishing. If the initial groove depth is too large, process stability may be compromised, and impurities may become trapped and difficult to remove. Therefore, in actual applications, equipment operators determine the lifespan of polishing pads by determining the processing volume or groove depth, and then replace the polishing pads.

[0004] Polishing pads are made of soft, tough materials like polyurethane. Their top surface features grooves that hold a fluid like polishing slurry. To create these grooves on the polishing pad, the selected processing parameters typically need to meet two key criteria: high cutting rate and low stock removal to facilitate material severing and minimize cutting resistance. For milling, high cutting rate corresponds to sharp tools and high rotational speeds, while low stock removal corresponds to low back engagement and low feed rates, as shown in Figure 1.

[0005] However, in actual processing, the high speed and low feed rate of the milling cutter can well cut and break the polyurethane material. However, due to the soft and tough nature of the material, the material tears when breaking, which easily leaves flash at the chip removal point, as shown in Figure 3. During machining, such flash is usually removed by using a higher speed and lower feed rate (secondary pass - or finishing), as shown in Figure 2. However, this method is not applicable to the flash removal of soft and tough materials, because the flash will be more likely to give up the tool under the friction of the tool (due to the poor rigidity of the material, even if the CNC tool moves exactly according to the designed contour of the part, the soft and tough material is more likely to deform under the squeeze of the tool, resulting in a failure of the secondary pass, resulting in the phenomenon of thicker top and thinner bottom of the part, and out-of-tolerance size) rather than cutting.

[0006] Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, the present invention provides a method for processing the microstructure of a polishing pad surface, which increases the cutting volume by adjusting the cutting method, so that the material is cut off instead of the knife being released, thereby achieving complete removal of the material.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a method for processing the surface microstructure of a polishing pad, wherein the polishing pad is made of a soft and tough material, and the processing method comprises the following steps:

[0009] The cutting blade extends into the polishing pad, cuts at a first cutting speed and moves forward;

[0010] The cutting blade cuts a portion of the polishing pad to an incomplete separation, that is, the portion is attached to the polishing pad;

[0011] The cutting blade cuts along the original cutting path at a second cutting speed and moves in the opposite direction;

[0012] The cutting blade cuts off the portion attached to the polishing pad so that the portion is separated from the polishing pad, thereby forming a target microstructure.

[0013] Furthermore, before forming the target microstructure, the above steps are repeated twice or more.

[0014] Furthermore, 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 polishing pad has an elongation greater than 100%.

[0015] Furthermore, the hardness of the polishing pad is 50-65D; the breaking strength of the polishing pad is 180-220kg / cm 2 ; The elongation of the polishing pad is 120-160%.

[0016] Furthermore, the first cutting speed and the second cutting speed are the same; or, the first cutting speed and the second cutting speed are different.

[0017] Furthermore, the first cutting speed includes a first cutting speed and a first rotational speed of the cutting blade rotating around its own central axis; the second cutting speed includes a second cutting speed and a second rotational speed of the cutting blade rotating around its own central axis.

[0018] Furthermore, the first cutting speed is 400-6000 mm / min, and the first rotation speed is 8000-80000 rpm; the second cutting speed is 400-6500 mm / min, and the second rotation speed is 8000-100000 rpm.

[0019] Further, the following steps are included:

[0020] The cutting blade extends into the polishing pad, moves along a first direction at a first cutting speed, and rotates around its own central axis at a first rotational speed;

[0021] The cutting blade cuts a portion of the polishing pad, the portion being attached to the surface of the polishing pad in a lump, and the lump being connected to the polishing pad;

[0022] The cutting blade moves along the original cutting path at a second cutting speed in a second direction and rotates around its own central axis at a second speed. The second direction is opposite to the first direction, and the rotation direction of the cutting blade around its own central axis remains unchanged.

[0023] The cutting blade continues to cut to separate the lumps attached to the polishing pad from the polishing pad, and all the lumps are connected in a strip shape and separated from the polishing pad at the same time;

[0024] The target microstructure is formed on the surface of the polishing pad.

[0025] Furthermore, the width of the cluster portion is approximately equal to the width of the target microstructure, the thickness of the cluster portion is approximately equal to the depth of the target microstructure, all cluster portions are connected in a strip shape, and the volume of the strip portion is approximately equal to the volume of the removed portion of the polishing pad.

[0026] Furthermore, the diameter of the cutting blade is D, and the width of the target microstructure is L, then L≤D<1.5L.

[0027] Furthermore, 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.

[0028] Furthermore, the cutting blade has two cutting surfaces arranged radially symmetrically; the cutting blade is a double-edged end mill; the cutting blade has a three-edged structure, or a multi-edged structure.

[0029] Furthermore, the surface of the polishing pad has a microstructure, which is used for reprocessing the microstructure of the polishing pad surface to increase the depth of the microstructure.

[0030] The present invention solves the problem of microstructure processing of polishing pads made of soft and tough materials by combining forward and reverse movement and adjusting the cutting speed. It should be emphasized here that for the cutting of soft and tough materials, the key to ensuring the processing accuracy is to control the chip breaking quality of the chips, that is, to be able to cut quickly and not tear the material. When processing large-scale structures, larger-sized tools can be used. Such tools can provide higher cutting forces when rotating, making it easier to cut the material, and therefore are not effective scenarios for the back-knife processing technology. When processing microstructures on soft and tough materials, the reduction in tool size limits the improvement in tool sharpness and cutting force, thereby limiting the processing accuracy of microstructures. The application of the back-knife processing technology can efficiently remove material and improve processing quality, and is particularly suitable for the processing and manufacturing of microstructures on soft and tough materials.

[0031] The beneficial effect of the present invention is that by adjusting and matching the relative size of the cutting blade rotation speed and the cutting speed value, the rotating cutting of the cutting blade during the forward movement of the tool will only lift up part of the material along the processing path instead of cutting it into debris, so that it remains as a continuous mass part, covering the original trajectory, and the material cross-section is shown in Figure 10; at this time, the cutting blade is controlled to move in the opposite direction, the cutting position is changed, and the connection position of the lifted part of the material is cut twice, so that the material of the mass part can be completely cut off, and high-quality groove processing with a smooth contour and no burrs is achieved, as shown in Figure 11. At this time, the cut material is in the form of continuous long or short strips, avoiding the problem of burrs left after the material is chopped and difficult to process. In short, the present invention integrates the chip fragments and flash structure by regulating the rotation speed and cutting speed of the cutting blade, increases the volume of the cut part, and enables it to be completely cut off from the workpiece, thereby achieving high-quality processing of the microstructure of soft and tough materials; due to the soft and tough material properties of the polishing pad, the side wall of the target microstructure is pulled by the cutting blade during processing, and the diameter of the cutting blade needs to be slightly larger than the width of the target microstructure to ensure that the width of the target microstructure remains unchanged after further processing.

[0032] The present invention also discloses a method for reprocessing the surface microstructure of a polishing pad, wherein the polishing pad is made of a soft and tough material, and the processing method comprises the following steps:

[0033] The cutting blade cuts into the polishing pad at a third speed, cuts at a first cutting speed and advances to cut the polishing pad;

[0034] The cutting blade cuts a portion of the polishing pad to an incomplete separation, that is, the portion is attached to the polishing pad;

[0035] The cutting blade moves to a target position and cuts off the portion attached to the polishing pad, so that the portion is separated from the polishing pad, thereby forming a target microstructure.

[0036] Furthermore, the polishing pad is located on a polishing plate, and the polishing plate is movable so that the relatively stationary cutting blade cuts and moves at a first cutting speed.

[0037] Furthermore, the third speed of the cutting blade cutting into the polishing pad is Vz, which is 0.05-0.5 mm / s; the depth of the cutting blade cutting into the polishing pad is d, and the width of the target microstructure is L, then d>1 / 4L, so that the cut part of the polishing pad is continuous.

[0038] Furthermore, the cutting blade includes a front blade face and a back blade face. When the cutting blade moves for cutting, the angle between the front blade face and the plumb bob plane is the front angle, and the angle between the back blade face and the horizontal plane is the back angle. The front angle is 5°-30°, and the back angle is 10°-80°.

[0039] Furthermore, the cut portion of the polishing pad is deposited on the rake surface.

[0040] Furthermore, the cutting blade cuts into the polishing pad, cuts at a first cutting speed, and advances in the step, and the cutting blade itself rotates to adjust the cutting direction.

[0041] Furthermore, 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 polishing pad has an elongation greater than 100%.

[0042] Furthermore, the hardness of the polishing pad is 50-65D; the breaking strength of the polishing pad is 180-220kg / cm 2 ; The elongation of the polishing pad is 120-160%.

[0043] Furthermore, the polishing disc rotates at a speed of 5-200 rpm.

[0044] Furthermore, the width of the cutting blade is D, and the width of the target microstructure is L, then L≤D<1.5L.

[0045] Furthermore, 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.

[0046] Furthermore, the surface of the polishing pad has a microstructure, which is used for reprocessing the microstructure of the polishing pad surface to increase the depth of the microstructure.

[0047] The beneficial effects of the present invention are: the cutting blade is relatively fixed and does not rotate, and the broach structure of the cutting blade is relatively simple; the cutting ability of the cutting blade 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; due to the soft and tough nature of the polishing pad material, the material to be removed needs to have a certain volume. During processing by the cutting blade, under the action of the cutting force of the blade tip, the material on the surface to be processed of the polishing pad is removed and accumulated on the front blade face. Due to the toughness of the material itself, the cutting is continuous and uninterrupted at the blade tip, and the material to be removed is driven by the material that has been removed, thereby achieving complete removal of the material.

[0048] By real-time adjustment of the direction of the tool rake face to align with the groove tangent direction, the types of machinable microstructures are expanded from concentric circular grooves to micro circular hole arrays, micro waist-shaped hole arrays, involute micro grooves, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a schematic diagram of milling processing in traditional milling technology.

[0050] Figure 2 is a schematic diagram of forward and reverse cutting in milling processing in traditional milling technology.

[0051] Figure 3 is a schematic diagram of the milling processing effect in traditional milling technology.

[0052] FIG4 is a schematic diagram of the matching structure of the polishing pad, the polishing disk, and the cutting blade according to the first embodiment of the present invention.

[0053] FIG5 is a schematic diagram of the three-dimensional structure of the cutting blade and the local polishing pad groove according to the first embodiment of the present invention, wherein the cutting is performed at the first cutting speed and moves in the direction of the arrow.

[0054] FIG6 is a schematic diagram of the front view of the structure of the cutting blade and the local polishing pad groove in the first embodiment of the present invention.

[0055] FIG7 is a cross-sectional view taken along line AA in FIG6 .

[0056] FIG8 is a schematic diagram of the three-dimensional structure of the cutting blade and the local polishing pad groove according to the first embodiment of the present invention. At this time, the cutting is performed at the second cutting speed and moves in the direction of the arrow in the opposite direction to the first cutting speed.

[0057] FIG9 is a schematic cross-sectional view of the state shown in FIG8 .

[0058] FIG10 is a schematic diagram showing the connection between the ball-shaped portion and the polishing pad groove in the first embodiment of the present invention.

[0059] FIG11 is a cross-sectional view of the polishing pad after the grooves are processed and the ball-shaped portion is completely separated in Example 1 of the present invention.

[0060] FIG. 12 is a schematic diagram showing the effect of machining the polishing pad grooves using conventional milling technology.

[0061] FIG13 is a schematic diagram of the cutting blade moving along the first direction to form a ball-shaped portion in the first embodiment of the present invention.

[0062] FIG14 is a schematic diagram of the matching structure of the polishing disc, the polishing pad and the cutting blade in the second embodiment of the present invention.

[0063] FIG15 is a first schematic diagram of the matching structure of the cutting blade and the polishing pad in the second embodiment of the present invention.

[0064] FIG16 is a second schematic diagram of the matching structure of the cutting blade and the polishing pad in the second embodiment of the present invention.

[0065] FIG17 is a first schematic diagram of the three-dimensional structure of the cutting blade in the second embodiment of the present invention.

[0066] FIG18 is a second schematic diagram of the three-dimensional structure of the cutting blade in the second embodiment of the present invention.

[0067] FIG19 is a side view of the cutting blade in the second embodiment of the present invention.

[0068] FIG20 is a schematic diagram of the coordination structure of the polishing disc, the polishing pad and the cutting blade in the second embodiment of the present invention, in which the cutting blade rotates by itself.

[0069] FIG21 is a top view of the matching structure of the polishing disc, polishing pad and cutting blade in the second embodiment of the present invention, where the cutting blade itself rotates.

[0070] FIG22 is a top view of the matching structure of the polishing disc, polishing pad and cutting blade in the second embodiment of the present invention. At this time, the cutting blade rotates by itself and the microstructure is a well-shaped groove.

[0071] FIG23 is a top view of the polishing pad in the second embodiment of the present invention, in which the microstructure is concentric circular grooves.

[0072] Among them, 1-cutting blade, 11-cutting surface, 12-front blade surface, 13-flank blade surface, 2-polishing pad, 21-groove, 22-chip, 3-polishing disk, 41-lump part. DETAILED DESCRIPTION

[0073] In order to enable those skilled in the art to better understand the solutions of the present invention, the following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0074] Under the combined effects of the polishing fluid, polishing head, wafer, and pad dresser, the polishing pad continuously wears and thins, and the groove depth gradually becomes shallower. Typically, the polishing pad is bonded to the top surface of the polishing plate. When the polishing pad reaches the replacement point, the polishing head, pad dresser, and pad feed arm move out of the way to make room for removal. The operator then begins removing the polishing pad from the edge and replaces it with a new one.

[0075] The present invention introduces a cutting blade 1. When the polishing pad 2 is placed on a polishing disk 3 or other work platform, the cutting blade 1 moves, or the work platform moves, or both move, so that the cutting blade 1 deepens the cutting of the groove and increases the depth of the groove, thereby achieving reprocessing of the microstructure of the polishing pad surface. The polishing pad 2 can be reused without having to tear the polishing pad 2 off the work platform. After processing, the polishing pad 2 can be put into use again.

[0076] The method of the present invention is not only applicable to the original groove processing of the polishing pad 2, but is also applicable to the reprocessing of the grooves of the polishing pad 2 so as to increase the groove depth.

[0077] Example 1

[0078] A method for reprocessing a microstructure on a polishing pad surface is provided, for forming a microstructure on a polishing pad 2, wherein 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 120kg / cm 2 ; or, the elongation of the polishing pad 2 is greater than 100%; or, the hardness, breaking strength and elongation of the polishing pad 2 meet the above conditions at the same time; or, the hardness, breaking strength and elongation of the polishing pad 2 meet any two of the above conditions, without specific limitation.

[0079] In this embodiment, the hardness of the polishing pad 2 is 50-65D; the breaking strength of the polishing pad is 180-220kg / cm 2 The elongation of the polishing pad is 120-160%. The polishing pad 2 can be a polyurethane (PU) polishing pad, which is made of densely foamed polyurethane material with small cavities distributed inside the material. Preferably, the hardness of the polishing pad 2 is 56D; the breaking strength of the polishing pad is 200kg / cm 2 ; The elongation of the polishing pad is 140%. In other words, the polishing pad 2 is soft and tough and difficult to process.

[0080] A method for reprocessing the surface microstructure of a polishing pad, for the polishing pad 2 made of the soft and tough material, comprises the following steps:

[0081] The cutting blade 1 extends into the polishing pad 2, cuts and moves at a first cutting speed; this can be defined as the first cutting pass;

[0082] The first cutting speed includes a first cutting speed V1 and a first rotational speed N1 of the cutting blade 1 rotating around its own central axis; specifically, the first cutting speed 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;

[0083] The cutting blade 1 cuts a portion of the polishing pad 2 to an incomplete separation, thereby causing the portion to adhere to the polishing pad 2;

[0084] The cutting blade 1 cuts along the original cutting path at a second cutting speed and moves in the reverse direction. The above-mentioned cutting path can be any path. That is, the processing method of the present invention is independent of the path of the cutting blade 1. It only needs to move along the original path twice in the forward and reverse directions. This can be defined as the second reverse direction pass. The combination of the above-mentioned first and second reverse passes is defined as the return process.

[0085] The second cutting speed includes a second cutting speed V2 and a second rotational speed N2 of the cutting blade 1 rotating around its own central axis; the second cutting speed and the first cutting speed may be the same or different; specifically, the second cutting speed 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;

[0086] The cutting blade 1 cuts off the portion attached to the polishing pad 2 so that the portion is separated from the polishing pad 2, thereby forming a target microstructure.

[0087] In the above process, the first pass and the second pass in the opposite direction are performed to achieve the processing of the target microstructure. Of course, in other embodiments, the first pass and the second pass in the opposite direction can be used as one round, and two or more rounds can be performed to achieve the processing of the target microstructure, which is not limited to the specific embodiment.

[0088] Furthermore, a method for reprocessing the surface microstructure of a polishing pad is provided. The method comprises the following steps for processing the polishing pad 2 made of the soft and tough material:

[0089] The cutting blade 1 extends into the polishing pad 2, travels in a first direction at a first cutting speed V1, and rotates about its own central axis at a first rotational speed N1. In this embodiment, the cutting blade 1 extends vertically along the thickness direction of the polishing pad 2. Of course, in other embodiments, the cutting blade 1 may also extend obliquely, without limitation.

[0090] The cutting blade 1 cuts a portion of the polishing pad 2, which is attached to the surface of the polishing pad 2 in a ball shape, and the ball-shaped portion 41 is connected to the polishing pad 2;

[0091] The aforementioned clump portion 41 specifically refers to the portion after being cut by the cutting blade 1. Unlike conventional milling technology, the cut material is not broken up (as shown in FIG8 ). Instead, the material is clumped. That is, the width of the clump portion 41 is substantially equal to the width of the target microstructure, the thickness of the clump portion 41 is substantially equal to the depth of the target microstructure, and all the clump portions 41 are connected in a strip shape. The volume of the strip portion is substantially equal to the volume of the removed portion of the polishing pad 2.

[0092] The cutting blade 1 moves along the original cutting path at a second cutting speed V2 in a second direction and rotates around its own central axis at a second speed N2. The second direction is opposite to the first direction, and the rotation direction of the cutting blade 1 around its own central axis remains unchanged.

[0093] The cutting blade 1 continues cutting to separate the lumps 41 attached to the polishing pad 2 from the polishing pad 2, and all the lumps 41 are connected in a strip shape and separated from the polishing pad 2 at the same time;

[0094] A target microstructure is formed on the surface of the polishing pad 2. In the present embodiment, the target microstructure is a concentric microgroove, or other micro-geometric shapes, such as a micro-circular hole array, a micro-waisted hole array, an involute microgroove, etc. The width of the target microstructure is 0.2-2.0 mm, preferably, the width of the target microstructure is 0.4-0.8 mm, i.e., L=0.4-0.8 mm in FIG. 7 , and the depth of the target microstructure is 0.2-2.0 mm, preferably, the depth of the target microstructure is 0.4-0.8 mm, i.e., d=0.4-0.8 mm in FIG. 7 .

[0095] Define the diameter of the cutting blade 1 as D and the width of the target microstructure as L, then L ≤ D < 1.5L. Because the polishing pad 2 is soft and tough, the sidewalls of the target microstructure are pulled by the cutting blade 1 during cutting. To ensure that the width of the target microstructure remains unchanged after reprocessing, the cutting blade 1 needs to have a diameter D slightly larger than the width L of the target microstructure. The specific ratio can be determined based on the parameters of the polishing pad 2. When the polishing pad 2 has a low hardness and a high fracture strength, this ratio needs to be increased accordingly.

[0096] The cutting blade 1 has two cutting surfaces 11 arranged radially symmetrically. In this embodiment, the cutting blade 1 can be a double-edged end mill, a three-edged structure, or a multi-edged structure. The tip shape of the cutting blade 1 is selected based on the specific application scenario: for example, in the application of processing the groove 21 of the polishing pad 2, due to the small size of the groove 21 (0.4-0.8mm), when selecting the cutting blade 1, it is necessary to comprehensively consider the sharpness of the cutting blade 1, the strength of the cutting blade 1, the cutting efficiency, etc. of the cutting blade 1. Here, a double-edged flat-end milling cutter is selected for processing.

[0097] The displacement of the cutting blade 1 on the workpiece can be achieved by controlling the cutting blade 1 via a numerical control platform such as an XY axis, or preferably, by combining the rotary motion of the polishing pad 2 with the linear motion of the cutting blade 1 along the radial direction. In this way, the linear velocity of the milling cutter tip as the cutting blade 1 on the polishing pad 2 following the rotation of the polishing plate 3 is the blade travel velocity v during milling. c The travel speed can be determined by the rotation speed N of the polishing pad 2. pad Calculate the radius R of the tool tip (v c =2π*N pad *R).

[0098] In this embodiment, several sets of process parameters with better processing quality of the cutting blade 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 chopped).

[0099] Table 1

[0100] As shown in FIG15 , in the machining method of the present invention, when the cutting blade 1 is moving in a first direction at a first cutting speed V1 and rotating about its central axis at a first rotational speed N1, i.e., in a forward cutting direction, the material structure at the cutting edge, i.e., the cutting position, is severed and the material is lifted. As shown in FIG10 , although the majority of the clumped portion 41 is separated from the groove 21, a small portion remains attached to the groove 21 at the chip removal position. It is important to emphasize that the material is not broken up and remains in a connected clumping structure. When the cutting blade 1 is moving in a second direction at a second cutting speed V2 and rotating about its central axis at a second rotational speed N2, the positions of the cutting position and the chip removal position are reversed, and material is cut at the original chip removal position. The attached clumped portion 41 is completely cut off and separated from the groove 21. As shown in FIG11 , the inner wall of the groove 21 is relatively smooth, leaving no burrs. Furthermore, because the clumped portion 41 is connected in a strip shape and simultaneously separated from the polishing pad 2, no finely divided material will adversely affect the polishing pad.

[0101] As shown in Figures 1 and 2, the cutting edge of a conventional milling cutter typically rotates in one direction (forward or counter-rotation). During machining, the electric spindle can only be controlled to rotate at high speed in that direction to provide cutting force. This creates cutting and chip removal areas on the workpiece. Due to the nature of the workpiece material and inadequate cutting, burrs are often left at the chip removal area, forming flash, which is one of the main reasons for poor milling quality.

[0102] To improve machining quality during milling, the motorized spindle speed is typically increased while the cutting speed is reduced. However, when machining soft and tough materials like polyurethane, the high speed during the forward pass can quickly break the material into small pieces, leaving a large amount of flash at the chip removal point. Due to the material's softness, the high-speed rotation of the tool during the reverse pass causes the flash to "give way" and prevent it from being completely removed, as shown in Figure 3.

[0103] By comparison, it can be seen that the traditional cutting method is not suitable for polishing pads made of soft and tough materials, resulting in burrs remaining in the grooves after the cutting is finally completed. In order to effectively remove the burrs, it is necessary to increase the volume of the burrs to increase the rigidity of the material, so that the material can fall off from the original workpiece under the cutting of the blade. The back-cutting processing technology of the present invention (i.e., cutting at a first cutting speed and cutting in the opposite direction of a second cutting speed) realizes effective material removal by moving the tool back and forth. Specifically, by controlling and matching the speed of the electric spindle and the speed of the cutting tool, a partial cutting effect is produced during the first tool pass, that is, the material is partially cut off but not dropped, which is equivalent to enlarging the volume of the burrs; the connecting part is cut off during the second reverse tool pass, and at this time, the burrs with enlarged volume have no space in the groove to "let the tool go", and the connected material is cut off; since the cutting parameters of the two tool passes are similar, only partial cutting occurs, and the chips produced are usually in the form of continuous long strips or short strips, and the edges of the formed grooves are smooth and free of burrs.

[0104] Example 2

[0105] A method for reprocessing a microstructure on a polishing pad surface is provided, for forming a microstructure on a polishing pad 2, wherein 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 120kg / cm 2 ; or, the elongation of the polishing pad 2 is greater than 100%; or, the hardness, breaking strength and elongation of the polishing pad 2 meet the above conditions at the same time; or, the hardness, breaking strength and elongation of the polishing pad 2 meet any two of the above conditions, without specific limitation.

[0106] In this embodiment, the hardness of the polishing pad 2 is 50-65D; the breaking strength of the polishing pad is 180-220kg / cm 2The elongation of the polishing pad is 120-160%. The polishing pad 2 can be a polyurethane (PU) polishing pad, which is made of densely foamed polyurethane material with small cavities distributed inside the material. Preferably, the hardness of the polishing pad 2 is 56D; the breaking strength of the polishing pad is 200kg / cm 2 ; The elongation 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, for the polishing pad 2 made of the soft and tough material, comprises the following steps:

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

[0109] In this embodiment, the cutting blade 1 is relatively stationary, the polishing pad 2 is located on the polishing disk 3, and the polishing disk 3 is movable. Specifically, the polishing disk 3 rotates at a speed of 5-200 rpm, so that the relatively stationary cutting blade 1 cuts and advances at a first cutting speed. At the same time, in order to adjust the cutting direction, the cutting blade 1 itself can be rotated, as shown in FIG20 .

[0110] In this embodiment, the cutting blade 1 is a broach, as shown in Figures 17 to 19 , and includes a rake face 12 and a flank face 13. When the cutting blade 1 is moving and cutting, the angle between the rake face 12 and the plumb bob plane is the rake angle, and the angle between the flank face 13 and the horizontal plane is the clearance angle. The rake angle α is 5°-30°, and the clearance angle β is 10°-80°. In addition, the cut portion 22 of the polishing pad 2, that is, the chips 22, is accumulated on the rake face 12, as shown in Figures 15 and 16 .

[0111] The third speed is Vz, which is 0.05-0.5 mm / s, preferably 0.1-0.2 mm / s;

[0112] The cutting blade 1 cuts a portion of the polishing pad 2 to an incomplete separation, so that the portion of the polishing pad 2 that has been cut but not completely separated remains attached to the polishing pad 2;

[0113] The cutting blade 1 moves to the target position and cuts off the portion attached to the polishing pad 2 so that the portion is separated from the polishing pad 2, thereby forming a target microstructure;

[0114] Define the width of the cutting blade 1 as D and the width of the target microstructure as L, then L ≤ D < 1.5L. Because the polishing pad 2 is soft and tough, the sidewalls of the target microstructure are pulled by the cutting blade 1 during cutting. To ensure that the width of the target microstructure remains unchanged after reprocessing, the cutting blade 1 needs to be slightly wider than the width L of the target microstructure. The specific ratio can be determined based on 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 microstructure is a concentric microgroove, or other micro-geometric shapes: such as a micro-circular hole array, a micro-waisted hole array, an involute microgroove, etc.; the width L of the target microstructure is 0.2-2.0 mm, preferably, the width L of the target microstructure is 0.4-0.8 mm, and the depth d of the target microstructure is 0.2-2.0 mm, preferably, the depth d of the target microstructure is 0.4-0.8 mm, and d>1 / 4L, thereby ensuring that the cut part of the polishing pad 2 is continuous, that is, forming continuous, curly chips 22, as shown in Figures 15 and 16.

[0116] Since the polishing pad 2 is soft and tough in nature, the material to be removed needs to have a certain volume. When the cutting blade 1 is used for broaching, the material on the surface to be processed of the polishing pad 2 is removed under the action of the cutting force at the blade tip, and accumulation occurs on the rake face 12. Due to the toughness of the material itself, the cutting is continuous and uninterrupted at the blade tip, and the material to be removed is driven by the material that has been removed, thereby achieving complete removal of the material.

[0117] The microstructure is a non-concentric groove, as shown in Figure 20. The non-concentric polishing pad groove is processed using a processing device in the prior art. Since the cutting blade 1 has significant directionality, it is necessary to ensure that the front cutting surface 12 is perpendicular to the cutting direction during processing. Therefore, when using the cutting blade 1 to process grooves such as parallel grids, as shown in Figure 21, it is necessary to add a steering device to the cutting blade 1 to adjust the orientation of the cutting blade 1 in real time according to the shape of the groove to ensure the cutting direction of the cutting blade 1 and achieve the best cutting effect.

[0118] As shown in Figure 22, the microstructure is a cross-grid groove, which requires each groove to be fed one by one for processing, and each feed processing forms a continuous, curly chip.

[0119] As shown in Figure 23, the microstructure is a concentric groove. At this time, when the polishing disk 3 is rotating, the cutting blade 1 is relatively stationary. The rotation of the polishing disk 3 causes the cutting blade 1 that cuts into the polishing pad 2 to produce relative movement with the polishing pad 2, thereby achieving cutting of the polishing pad 2.

[0120] The above specific embodiments are used to illustrate the present invention rather than to limit the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for machining 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 and travels 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 a polishing pad according to claim 1, characterized in that: Before forming the target microstructure, repeat the above steps two or more times.

3. The method for processing the surface microstructure of the polishing pad according to claim 1, 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 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 of the polishing pad is 120-160%.

5. The method for processing the surface microstructure of a 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 of the cutting tool rotating around its own central axis; the second cutting speed includes a second cutting rate and a second rotational speed of the cutting tool rotating around its own central axis.

7. The method for processing the surface microstructure of the polishing pad according to claim 6, characterized in that: 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 the polishing pad according to claim 6, wherein 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 cuts 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, the 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 strip shape and detach from the polishing pad simultaneously; A target microstructure is formed on the surface of the polishing pad.

9. The method for processing the surface microstructure of a polishing pad according to claim 8, characterized in that: 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 strip shape, and the volume of this strip-shaped part is approximately equal to the volume of the part cut off from the polishing pad.

10. The method for processing the surface microstructure of the polishing pad according to claim 1, characterized in that: 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, 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.

12. The method for machining the surface microstructure of the polishing pad according to claim 1, wherein: The cutting tool has two cutting surfaces symmetrically arranged radially; 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 processing 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 machining 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 and advances 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 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 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 disk, and the polishing disk is movable so that the relatively stationary cutting tool cuts and advances at a first cutting speed.

16. The method for processing 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 part of the polishing pad is continuous.

17. The method for machining the surface microstructure of a polishing pad according to claim 14, wherein: 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 part 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, characterized in that: 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 processing the surface microstructure of a polishing pad according to claim 14, 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%.

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 disk 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 machining 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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