A method for controlling a coolant for ring thinning grinding and a grinding wheel assembly

Abstract

The application discloses a kind of ring thinning grinding cooling liquid control method and grinding wheel assembly, for semiconductor substrate thinning.In the water distribution piece of detachable shower type between grinding wheel and wheel mounting base, the upper surface of water guide part is provided with water guide groove extending from center to outer periphery, cooling liquid is accelerated to guide grinding tooth by centrifugal force and is discharged through drain hole.During grinding process, the state parameter that characterizes the discharge capacity of drain hole is detected, and the cooling liquid flow is adjusted by using feedforward and feedback compound control: the flow upper limit is set based on the cumulative grinding amount to estimate the grinding tooth wear state and the equivalent cross-sectional area of drain hole, and the flow upper limit is corrected based on the state parameter.Thereby, it is avoided that cooling liquid overflows, and the dynamic matching of cooling liquid supply and drainage capacity is realized in the whole life cycle of grinding wheel, and the cooling efficiency, grinding quality and equipment operation stability are improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to a method for controlling coolant and a grinding wheel assembly for ring-based thinning grinding. Background Technology

[0002] In the back-end processes of semiconductor manufacturing, wafer backside thinning is a key process for reducing package thickness and improving chip heat dissipation. With the increasing demands for thinner chips in advanced packaging, the thickness of wafers after thinning has been reduced from hundreds of micrometers to 50 μm or even thinner. However, ultra-thin wafers are highly susceptible to warping and breakage during handling and subsequent processes, posing a significant challenge to the thinning process.

[0003] Edge-retaining thinning (also known as edge-retaining thinning) is a technology developed to address the aforementioned problems. This process retains approximately 3mm wide edge regions of the wafer as an integrated support ring during wafer grinding and thinning, only thinning the area within the ring. By retaining this ring-shaped support structure, the ultra-thin wafer can maintain sufficient mechanical strength without additional support, effectively reducing the risk of warpage and the probability of breakage during handling.

[0004] However, the ring-based thinning process presents unique challenges in terms of cooling. During grinding, the friction between the grinding wheel and the wafer generates a significant amount of heat, which must be promptly dissipated by coolant. Otherwise, it will lead to premature wear of the grinding wheel, thermal damage to the wafer surface, and even fragmentation. In conventional open-type grinding, coolant can be directly sprayed onto the grinding area through external nozzles. However, in the ring-based thinning process, the grinding wheel completely covers the wafer surface, and the grinding area is surrounded by both the wafer and the grinding wheel. The coolant can only be discharged externally through drainage holes located on the grinding wheel base. This closed structure severely restricts the flow path and flow rate of the coolant.

[0005] In existing technology, coolant is typically supplied to the grinding wheel via a central supply passage in the spindle and then discharged to the outside through drain holes. However, as the grinding process continues, the grinding teeth gradually wear down and become shorter, resulting in a reduction in the effective axial length and cross-sectional area of ​​the drain holes, significantly decreasing their drainage capacity. If the original coolant supply flow rate is maintained at this point, the coolant cannot be discharged in time and will overflow along the water injection holes or spindle clearance, triggering equipment alarms or even shutdowns. To avoid overflow, operators can only reduce the coolant supply flow rate, but this leads to insufficient cooling, heat accumulation in the grinding area, accelerated grinding wheel wear, and negatively impacts grinding quality.

[0006] In addition, existing coolant flow control methods are mostly based on experience-based constant flow supply, or simply adjust a single parameter such as spindle speed. These methods are difficult to adapt to the continuous decrease in drainage capacity after the grinding gear wears, resulting in insufficient cooling of the grinding wheel in the later stages.

[0007] More seriously, the aforementioned problems of coolant overflow and insufficient cooling are not isolated, but rather form a vicious cycle in the closed grinding environment of the ring-thinning process, triggering a series of secondary problems. When coolant overflows along the water inlet or spindle clearance, the coolant containing silicon-based grinding debris (0.1~5μm particle size) and diamond particles will invade the spindle bearing chamber under the negative pressure suction of the rotating spindle. This causes the grease in the precision angular contact bearing to be washed away and emulsified, resulting in loss of bearing preload and a sharp deterioration in spindle radial runout. This directly leads to an increase in surface waviness and an excessive total thickness deviation (TTV) after substrate grinding. At the same time, if the overflowing coolant flows along the inner wall of the spindle housing to the top junction box area, it will cause a decrease in the insulation resistance of the electrical terminals, posing a risk of short circuit shutdown. On the other hand, insufficient cooling caused by the forced reduction in flow rate will cause an imbalance in the temperature field of the grinding area, and local thermal expansion of the substrate will lead to uneven grinding thickness. High temperatures will also cause local vaporization of the coolant, resulting in cavitation and damaging the grinding wheel base and substrate surface. Summary of the Invention

[0008] In view of this, embodiments of this application provide a coolant control method and grinding wheel assembly for ring-thinning grinding, so as to at least partially solve the above problems.

[0009] According to a first aspect of the present application, a method for controlling the flow rate of a grinding wheel coolant for thinning a substrate by ring-shaped reduction is provided. The grinding wheel has grinding teeth and a drainage hole disposed on a grinding wheel base. The outer diameter of the grinding wheel is smaller than the outer diameter of the substrate but larger than the outer diameter of the device region of the substrate. The grinding wheel is mounted on the front end of a grinding spindle.

[0010] A shower-type water distribution component is detachably provided between the grinding wheel and the wheel mounting seat. The water distribution component has a water guiding part. The upper surface of the water guiding part is provided with multiple water guiding grooves. The water guiding grooves extend from the center to the outer periphery and are inclined relative to the radial direction. Centrifugal force is used to accelerate the flow of coolant through the water guiding grooves to the grinding teeth and discharge it through the drain hole.

[0011] During the grinding process, state parameters characterizing the drainage capacity of the drainage holes are detected;

[0012] Based on the state parameters, determine whether the drainage capacity decreases due to the reduction in the cross-sectional area of ​​the drainage hole caused by wear of the grinding teeth.

[0013] When the drainage capacity is determined to be reduced, a combined feedforward and feedback control is used to adjust the coolant flow rate: the feedforward control estimates the wear state of the grinding teeth and the equivalent cross-sectional area of ​​the drain hole based on the cumulative grinding amount or cumulative rotation of the grinding wheel, and sets the upper limit of the flow rate accordingly; the feedback control corrects the feedforward control based on the state parameters to adjust the coolant flow rate in a stepwise manner.

[0014] In some embodiments, the state parameter is the liquid level of the coolant above the grinding wheel, and a water storage section is provided on the top of the grinding spindle. The liquid level is detected by an electrode-type liquid level sensor provided in the water storage section.

[0015] In some embodiments, the status parameters include the supply pressure of the coolant supply pipeline, and a supply pressure sensor is provided on the coolant supply pipeline to obtain the supply pressure in real time.

[0016] In some embodiments, the water guide channel is a fan-shaped channel, the width of which gradually increases from the central region of the water guide portion to the outer peripheral edge, and the included angle between the sidewalls of the fan-shaped channel is 30° to 60°.

[0017] In some embodiments, the water guide channel is a flower-shaped channel, which includes multiple branch channels. The branch channels extend radially from the center to the outer periphery, and the ends of the branch channels are provided with flared portions. The width of the flared portions is greater than the width of the branch channels.

[0018] In some embodiments, the angle between the extension direction of the water guide channel and the radial direction is 10° to 45°.

[0019] In some embodiments, the control method further includes: before adjustment, actively applying a flow pulsation of known frequency and amplitude to the coolant and detecting the resulting pressure response or level response; and calculating the equivalent flow impedance of the drain hole based on the amplitude ratio and phase difference between the flow pulsation and the response to determine the blockage state of the drain hole.

[0020] In some embodiments, the stepped adjustment includes multiple threshold levels, and when the state parameter exceeds different threshold levels, different levels of flow reduction are performed accordingly.

[0021] According to a second aspect of the embodiments of this application, a grinding apparatus is provided for implementing the control method as described in any of the preceding claims, comprising:

[0022] A grinding wheel assembly having a drain hole for discharging coolant;

[0023] A coolant supply passage for supplying coolant to the grinding wheel of the grinding wheel assembly;

[0024] A detection unit is used to detect state parameters characterizing the drainage capacity of the drainage hole during the grinding process;

[0025] The control unit is communicatively connected to the detection unit and is used to determine whether the drainage capacity has decreased based on the status parameters and to generate a control signal.

[0026] A flow regulation unit is disposed on the coolant supply passage and is communicatively connected to the control unit. It is used to adjust the flow rate of coolant supplied to the grinding wheel in a stepwise manner according to the control signal, within the range not exceeding the current discharge capacity of the drain hole.

[0027] According to a third aspect of the embodiments of this application, a grinding wheel assembly for implementing the control method described in any of the above claims is provided, comprising:

[0028] Wheel mounting bracket, used for mounting on the front end of the grinding spindle;

[0029] A grinding wheel is mounted on the wheel mounting base. The grinding wheel has annularly arranged grinding teeth and drainage holes provided on the grinding wheel base. The outer diameter of the grinding wheel is smaller than the outer diameter of the substrate and larger than the outer diameter of the device area of ​​the substrate.

[0030] A showerhead-type water distribution component is detachably disposed between the wheel mounting base and the grinding wheel, the water distribution component comprising:

[0031] The connecting part is used to connect with the wheel mounting base;

[0032] A water guide portion is disposed below the connecting portion, and the water guide portion has an upper surface facing the grinding teeth;

[0033] Multiple water guide grooves are disposed on the upper surface of the water guide section. The water guide grooves extend from the central area of ​​the water guide section to the outer peripheral edge, and the water guide grooves are inclined relative to the radial direction of the water guide section. The inclination direction is the same as the rotation direction of the grinding wheel, and the depth of the water guide grooves is 1mm to 5mm.

[0034] In some embodiments, the connecting part of the water distribution component is a hollow structure, and the top surface of the water guiding part is a conical surface; the cross-sectional shape of the water guiding groove is selected from one of the following: waist-shaped groove, conical groove, fan-shaped groove, and flower-shaped groove; the number of the water guiding grooves is 6 to 12, and they are evenly distributed along the circumference.

[0035] In some embodiments, the water guide channel is a fan-shaped channel, the width of which gradually increases from the central region of the water guide portion to the outer peripheral edge, and the included angle between the sidewalls of the fan-shaped channel is 30° to 60°.

[0036] In some embodiments, the water guide channel is a flower-shaped channel, which includes multiple branch channels that extend radially from the center to the outer periphery; the ends of the branch channels are provided with flared portions, the width of which is greater than the width of the branch channels.

[0037] The beneficial effects of this application include:

[0038] a. Achieve adaptive and precise control of cooling flow rate throughout the entire life cycle of the grinding wheel.

[0039] This control method incorporates the dynamic changes in drainage capacity caused by grinding wheel wear into the control closed loop by real-time detection of state parameters characterizing the drainage capacity of the drain hole. Unlike existing technologies that rely on empirically set constant flow rates or simple adjustments to single parameters such as spindle speed, this method employs a combined feedforward and feedback control: feedforward control estimates the wear state of the grinding teeth and the equivalent cross-sectional area of ​​the drain hole based on the cumulative grinding amount or cumulative rotational revolutions, and sets the upper limit of the flow rate accordingly; feedback control corrects the feedforward control based on real-time state parameters. Thus, throughout the entire process of the grinding teeth gradually wearing down and the effective cross-sectional area of ​​the drain hole continuously decreasing, the coolant supply flow rate always matches the current drainage capacity of the drain hole. This avoids coolant overflow and machine alarms caused by excessive flow, while ensuring sufficient cooling within the maximum allowable drainage capacity, thereby continuously optimizing the cooling effect throughout the entire service life of the grinding wheel.

[0040] b. Significantly improves cooling efficiency and grinding quality in the grinding zone.

[0041] This grinding wheel assembly utilizes a showerhead-type water distribution component with a water guide channel structure. The centrifugal force generated by the grinding wheel's rotation actively guides the coolant to the grinding teeth at a certain speed, allowing the coolant to be rapidly discharged through the drain holes, significantly increasing the drainage rate. The water guide channels can adopt various structural forms, such as fan-shaped channels and flower-shaped channels. The width of the fan-shaped channels gradually increases from the center to the outer perimeter, while the branches of the flower-shaped channels have flared ends with a width greater than the branch channels. These structural features enable the coolant to form a fan-shaped water curtain or a diffused spray effect under centrifugal force, greatly increasing the coverage area and impact force of the coolant in the grinding zone. Sufficient cooling effectively removes grinding heat, reducing thermal damage and fragmentation risks on the wafer surface caused by heat accumulation, improving the grinding surface quality, and preventing accelerated wear of the grinding wheel due to overheating.

[0042] c. Extend the service life of the grinding wheel and improve the operational stability of the equipment.

[0043] This control method and grinding wheel assembly, through a composite control strategy combining feedforward and feedback control, achieves precise regulation of coolant flow, effectively preventing overheating and wear of the grinding wheel due to insufficient cooling and equipment alarm shutdowns caused by coolant overflow. The excellent cooling effect significantly extends the service life of the grinding wheel and reduces its replacement frequency; while real-time flow control fundamentally solves the problem of insufficient cooling caused by forced reduction of coolant flow to avoid overflow in existing technologies, as well as unplanned shutdowns caused by alarms triggered by coolant overflow, significantly improving the continuity and stability of equipment operation.

[0044] d. Prevent secondary disasters caused by coolant overflow, ensuring the reliability of the spindle and electrical system.

[0045] This control method, through a combination of feedforward and feedback control, strictly constrains the coolant flow rate within the current discharge capacity of the drain hole, fundamentally eliminating the risk of coolant overflowing along the spindle clearance. This prevents the corrosion of the spindle's precision bearings by coolant containing abrasive particles, thus preventing bearing lubrication failure and spindle precision degradation; it also eliminates the risk of short circuits caused by coolant contacting electrical components.

[0046] e. Maintain a stable temperature field in the grinding zone to suppress thermal damage to the substrate and sintering and clogging of grinding debris.

[0047] Through stepped, precise flow control, the coolant flow rate remains relatively stable for most of the grinding wheel's lifespan, with adaptive adjustments only made at critical points where drainage capacity substantially decreases. This "hysteresis-stepped" mechanism effectively avoids flow oscillations and temperature fluctuations caused by traditional PID continuous regulation, thus helping to maintain a stable temperature field in the grinding area. Stable cooling not only helps reduce the batch standard deviation of the surface roughness Ra on the back of the substrate but also effectively suppresses local thermal expansion and TTV degradation of the substrate caused by temperature fluctuations. Simultaneously, sufficient cooling prevents the sintering of grinding chips at high temperatures and prevents blockages from forming on the inner walls of the drainage holes, fundamentally breaking the vicious cycle of "wear-clogging-overheating-accelerated wear." This helps reduce the amount of material removed during subsequent chemical mechanical polishing (CMP) and significantly lowers overall manufacturing costs. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0049] Figure 1 This is a schematic diagram of a grinding apparatus provided in an embodiment of this application performing ring thinning;

[0050] Figure 2 yes Figure 1 A magnified view of a section at point A in the middle;

[0051] Figure 3 This is a schematic diagram of a grinding wheel processing substrate provided in an embodiment of this application;

[0052] Figure 4 This is a schematic diagram of a grinding wheel assembly provided in one embodiment of this application;

[0053] Figure 5 This is a schematic diagram of a water distribution component provided in an embodiment of this application;

[0054] Figure 6 This is a schematic diagram of a water guide section with a waist-shaped groove provided in an embodiment of this application;

[0055] Figure 7 This is a schematic diagram of a water guide section with a conical groove provided in an embodiment of this application;

[0056] Figure 8 This is a schematic diagram of a water guide section with a fan-shaped groove provided in an embodiment of this application;

[0057] Figure 9 This is a schematic diagram of a water guide section with a flower-shaped groove provided in an embodiment of this application;

[0058] Figure 10 This is a flowchart of a feedforward and feedback composite control of coolant flow provided in an embodiment of this application;

[0059] Figure 11 This is a schematic diagram of a stepped supply of coolant flow rate provided in an embodiment of this application. Detailed Implementation

[0060] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art should fall within the protection scope of the embodiments of this application.

[0061] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0062] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified. In the embodiments of the application, the substrate is also called a wafer, which has the same meaning and practical function.

[0063] This application relates to the field of semiconductor substrate thinning technology, specifically to a method for controlling the flow rate of cooling fluid in a grinding wheel for ring-based thinning grinding, and a corresponding grinding wheel assembly. In the back-end processes of semiconductor manufacturing, wafer backside thinning is a key process for reducing package thickness and improving chip heat dissipation. With the increasing demands for thinner chips in advanced packaging, the thickness of thinned wafers has decreased from hundreds of micrometers to fifty micrometers or even less. However, ultra-thin wafers are highly susceptible to warping and breakage during handling and subsequent processes, posing a significant challenge to the thinning process. The ring-based thinning process is a key technology developed to address these issues. This process retains approximately three millimeters of the outermost edge region of the wafer as an integrated support ring during grinding and thinning. Only the area within the ring is ground and thinned. By retaining this ring-shaped support structure, the ultra-thin wafer can maintain sufficient mechanical strength without additional support, effectively reducing the risk of warping and the probability of breakage during handling. However, the ring-thinning process presents unique challenges in cooling. The friction between the grinding wheel and the wafer during grinding generates significant heat, which must be promptly dissipated by coolant. Otherwise, it will lead to premature grinding wheel wear, thermal damage to the wafer surface, and even fragmentation. In conventional open-type grinding, coolant can be directly sprayed onto the grinding area through external nozzles. However, in the ring-thinning process, the grinding wheel completely covers the wafer surface, and the grinding area is surrounded by both the wafer and the grinding wheel. Coolant can only be discharged through drain holes on the grinding wheel base. This closed structure severely restricts the flow path and flow rate of the coolant. Furthermore, as the grinding process continues, the grinding teeth gradually wear down and become shorter, resulting in a shortened axial effective length and reduced cross-sectional area of ​​the drain holes, significantly decreasing drainage capacity. If the original coolant supply flow rate is maintained, the coolant cannot be discharged in time and will overflow along the water injection holes or spindle clearance, triggering equipment alarms or even shutdowns. To avoid overflow, operators must reduce the coolant supply flow rate, but this leads to insufficient cooling, heat accumulation in the grinding area, accelerated grinding wheel wear, and negatively impacts grinding quality.

[0064] To address the aforementioned technical problems, this application proposes a novel technical solution. By installing a detachable shower-type water distribution component between the grinding wheel and the wheel mounting base, the inclined water guide channel accelerates the flow of coolant towards the grinding teeth under centrifugal force. Simultaneously, a feedforward and feedback composite control strategy is adopted to dynamically adjust the coolant flow rate according to the wear state of the grinding wheel, thereby achieving continuous optimization of the cooling effect throughout the entire service life of the grinding wheel.

[0065] Figure 1 This is a schematic diagram of a grinding apparatus for thinning a substrate by leaving a ring, according to an embodiment of this application. The grinding apparatus includes a grinding spindle 1, a grinding wheel assembly mounted at the front end of the grinding spindle 1, a coolant supply passage, a detection unit, a control unit, and a flow rate adjustment unit.

[0066] The grinding spindle 1 is the core drive component of the device. It has a hollow fluid supply passage formed along its axial direction to deliver coolant from an external supply source to the grinding wheel assembly. A water reservoir 10, an annular groove structure, is located at the top of the grinding spindle 1 to temporarily hold coolant that cannot be drained during grinding. The control unit (not shown) is communicatively connected to the detection unit and the flow regulation unit, and can be implemented using a PLC, industrial computer, or embedded controller. The flow regulation unit (not shown) is located on the coolant supply passage and is preferably an electric proportional valve or an electromagnetic flow regulating valve, capable of continuously or stepwise adjusting the coolant supply flow rate according to the control signal from the control unit.

[0067] Figure 2 for Figure 1 The enlarged view at point A shows the detailed structure of the water storage section 10 and the electrode-type liquid level sensor 9. The electrode-type liquid level sensor 9, disposed within the water storage section 10, includes at least two spaced-apart electrode probes. When the coolant level in the water storage section 10 rises to contact the electrode probes, the circuit is activated, generating a liquid level signal. This signal detects the coolant level above the grinding wheel 2, serving as a status parameter for determining the drainage capacity of the drain hole 5. The advantages of using the electrode-type liquid level sensor 9 are its simple structure, fast response speed, and immunity to interference from coolant turbidity and air bubbles, making it suitable for reliable operation in grinding vibration environments. The electrode probes are preferably made of corrosion-resistant stainless steel or titanium alloy to withstand the corrosive environment of trace amounts of grinding debris and chemical additives that may be present in the coolant. The installation height of the electrode probes can be adjusted according to grinding process parameters to set different liquid level alarm thresholds.

[0068] It should be noted that in the closed grinding environment of the ring thinning process, the overflow path of the coolant has a specific destructive mechanism. When the discharge capacity of the drain hole 5 decreases due to the wear of the grinding teeth, the coolant that cannot be discharged in time first diffuses outward along the radial gap between the grinding wheel 2 and the water distribution component 80 under the action of centrifugal force. Subsequently, under the suction effect of the negative pressure generated by the rotation of the spindle 1, some coolant will flow back upward along the axial gap between the grinding spindle 1 and the wheel mounting seat 11, and gradually accumulate in the water storage part 10. Since the grinding fluid usually contains deionized water, rust inhibitors and suspended silicon-based grinding debris, once this overflowing fluid flows into the spindle bearing cavity, it will quickly wash away the bearing grease, resulting in a decrease in the preload of the precision angular contact ball bearing and wear on the surface of the rolling elements. At the same time, the hard particles in the grinding debris form three-body abrasive wear in the bearing raceway, which worsens the radial runout of the spindle and directly causes an increase in the surface waviness of the substrate 3 after grinding. Furthermore, if overflowing coolant flows along the inner wall of the spindle housing 30 to the top junction box area, it will cause a decrease in the insulation resistance of the electrical terminals, posing a risk of short circuit and shutdown. Therefore, this application places the liquid level sensor 9 inside the water storage section 10, which is essentially a "last line of defense" for monitoring before the coolant enters the precision components of the spindle. Its significance lies not only in preventing alarm shutdowns but also in preventing secondary corrosion of the spindle and electrical system caused by coolant overflow.

[0069] Figure 3 The positional relationship of the substrate being processed by the grinding wheel is shown. The substrate 3 is supported on the suction cup 4. The outer diameter of the grinding wheel 2 is smaller than the outer diameter of the substrate 3, but larger than the outer diameter of the device area of ​​the substrate 3. In the ring thinning process, the grinding wheel 2 only grinds the device area (i.e., the inner ring area) of the substrate 3, while retaining the outermost annular edge area of ​​the substrate 3 (i.e., the Ring area, typically about 3 mm wide) as an integrated support structure. During the grinding process, the grinding wheel 2 completely covers the surface of the substrate 3. The grinding area is jointly surrounded by the substrate 3 and the grinding wheel 2, forming a closed space. The coolant can only be discharged outward through multiple drainage holes 5 distributed circumferentially on the grinding wheel base. This closed structure strictly limits the flow path and flow rate of the coolant, which is the core technical problem to be solved in this application.

[0070] Figure 4 This is a schematic diagram of a grinding wheel assembly provided in an embodiment of this application. The grinding wheel assembly includes a wheel mounting base 11, a grinding wheel 2, and a shower head-type water distribution component 80.

[0071] The wheel mounting base 11 is fixedly connected to the front end of the grinding spindle 1 via a flange structure and rotates synchronously with the grinding spindle 1. The grinding wheel 2 is mounted on the wheel mounting base 11 and has multiple grinding teeth arranged in a ring. The grinding teeth are evenly spaced along the circumference of the grinding wheel 2, forming gaps between them for draining coolant, thus forming multiple drain holes 5. Specifically, multiple drain holes 5 are provided on the grinding wheel base, which are evenly distributed along the circumference and penetrate the thickness direction of the grinding wheel base to guide the coolant in the grinding area to the outside. The grinding teeth are usually made of diamond abrasive grains sintered with a metal binder. The initial height of the grinding teeth is generally in the range of 3mm to 8mm. When the grinding teeth wear down to 30% to 50% of the initial height, the grinding wheel 2 needs to be replaced. Throughout the entire service life of the grinding wheel 2, the height of the grinding teeth gradually decreases from the initial value, causing the axial effective flow cross section of the drain holes 5 to gradually decrease from the initial larger value. This dynamic change is the core problem that the control method of this application aims to solve.

[0072] Figure 4 In the illustrated embodiment, the shower-type water distribution component 80 is detachably disposed between the wheel mounting base 11 and the grinding wheel 2, and the water distribution component 80 is coaxially disposed inside the wheel mounting base 11. This detachable connection method facilitates the replacement of water distribution components 80 of different specifications according to different grinding process requirements, and also facilitates maintenance and replacement when the water distribution component 80 is worn or the water guide groove 83 is clogged.

[0073] Figure 5 This is a schematic diagram of a water distribution component provided in one embodiment of this application. The water distribution component 80 includes a connecting part 81 and a water guiding part 82, which can be manufactured by welding or integral molding. The connecting part 81 is a hollow cylindrical structure with external threads on its outer wall, which mate with the internal threads of the wheel mounting seat 11 to achieve a threaded connection. During installation, the water distribution component 80 is screwed into the wheel mounting seat 11. The hollow cavity of the connecting part 81 is connected to the liquid supply passage of the grinding spindle 1, forming a coolant inlet channel. After the coolant enters the connecting part 81 through the liquid supply passage, it flows into the water guiding part 82 under the impetus of gravity and subsequent coolant.

[0074] The water guide section 82 is located below the connecting section 81 and is disc-shaped. The top surface of the water guide section 82 is conical, gradually sloping downwards from the central area to the outer periphery. The cone angle is designed according to the specifications of the grinding wheel 2 and the coolant flow requirements. This conical structure facilitates the uniform flow of coolant from the central area to the outer periphery of the water guide section 82 under gravity, ensuring uniform coolant distribution to each water guide groove 83. The water guide section 82 has an upper surface facing the grinding teeth, on which multiple water guide grooves 83 are provided, such as... Figure 6As shown. The depth of the water guide groove 83 is 1mm to 5mm. If the depth is too shallow, the guiding capacity will be insufficient, and if the depth is too deep, the structural strength of the water guide section will be weakened. There are 6 to 12 water guide grooves 83, which are evenly distributed along the circumference to ensure that the coolant is evenly supplied in the circumference of the grinding wheel 2.

[0075] The water guide groove 83 extends from the central area of ​​the water guide section 82 to its outer peripheral edge, and the water guide groove 83 is inclined relative to the radial direction of the water guide section 82, with the inclination direction being the same as the rotation direction of the grinding wheel 2. The angle between the extension direction of the water guide groove 83 and the radial direction is preferably 10° to 45°. The reason for adopting the inclined arrangement is that when the grinding wheel 2 rotates, the coolant in the water guide groove 83 is simultaneously subjected to centrifugal force and Coriolis force. The inclination direction being consistent with the rotation direction can reduce the resistance of the Coriolis force to the flow of coolant, allowing the coolant to obtain a larger radial velocity component, thereby impacting the grinding teeth at a higher speed and improving drainage efficiency.

[0076] Figure 5 In the illustrated embodiment, the hollow chamber of the connecting part 81 adopts a structure with an inner diameter that increases in a stepped manner from top to bottom. When the coolant enters the connecting part 81 through the supply passage of the grinding spindle 1, the coolant usually maintains a high axial flow velocity due to the relatively small cross-sectional area of ​​the upstream supply passage. As the coolant enters the connecting part 81 with its progressively increasing inner diameter, the flow cross-sectional area gradually expands axially, and the axial flow velocity of the coolant decreases accordingly, with some kinetic energy being converted into pressure energy. Compared to a single-stage abrupt expansion, the stepped-increased inner wall surface can significantly suppress boundary layer separation and backflow eddies caused by abrupt changes in cross-section, weakening the direct impact of high-speed liquid flow on the central region of the top surface of the guide water section 82, thereby effectively suppressing fluid splashing and turbulent disturbances. At the same time, the reduced flow velocity allows the coolant to transition to the conical surface of the guide water section 82 with a smoother flow pattern, avoiding the formation of local high pressure in the central region of the guide water section 82 due to supply pressure pulsations. This facilitates the uniform distribution of coolant along the circumferential direction of the conical surface, providing a stable inlet flow rate for each guide water channel 83.

[0077] Furthermore, the projection of the lower opening of the connecting part 81 in the vertical direction covers more than 50% of the top surface area of ​​the water guide part 82, so that the initial section of part of the water guide channel 83 is directly opposite the hollow cavity of the connecting part 81 in the vertical direction. When the coolant flows out from the lower end of the connecting part 81, it does not all converge at the geometric center of the water guide part 82 and then spread radially along the conical surface. Instead, a portion of it is directly aligned with and enters the inlet of this part of the water guide channel 83 under the combined action of gravity and subsequent hydraulic pressure. Since the water guide channel 83 is inclined radially and has a depth of 1 mm to 5 mm, its inlet end forms a flow channel with a defined volume. The above arrangement extends the direction conversion area of ​​the coolant from axial flow to radial flow from the center of the top surface of the water guide part 82 to the inlet of the water guide channel 83, significantly shortening the transition path of the coolant spreading along the conical surface to the inlet of the water guide channel 83, and reducing energy loss caused by abrupt changes in flow direction and friction along the flow path. Meanwhile, since the lower end of the connecting part 81 covers the central area of ​​the water guiding part 82 and part of the inlet of the water guiding groove 83 in the vertical direction, the coolant retains an appropriate axial momentum component when entering the water guiding groove 83. This axial momentum is superimposed with the centrifugal force generated by the rotation of the grinding wheel, which helps the coolant to be accelerated faster in the water guiding groove 83 and flow towards the root of the grinding teeth in the inclined direction, thereby improving the discharge efficiency of the coolant through the drain hole 5.

[0078] It can be seen that the stepped inner diameter structure of the connecting part 81 works in conjunction with the layout of the lower end covering the central area of ​​the water guide part 82 and part of the inlet of the water guide groove 83. This not only reduces the energy dissipation and fluid splashing caused by the liquid supply impact, but also shortens the transition path of the coolant from the liquid supply passage to the water guide groove 83. This allows the coolant to enter each water guide groove 83 in a more uniform and stable flow state, and then efficiently distribute it to the grinding area under the action of centrifugal force and discharge it through the drain hole 5, thereby improving the flow efficiency and distribution uniformity of the entire coolant passage.

[0079] The cross-sectional shape of the water guide channel 83 is available in various forms to adapt to different cooling requirements and grinding conditions.

[0080] Reference Figure 6 The cross-sectional shape of the water guide groove 83 is waist-shaped (i.e., waist-shaped groove). The waist-shaped groove 83a has a narrow groove structure with a rounded bottom and parallel side walls on both sides. Its width is relatively small, which can guide the coolant to flow in a concentrated and accelerated manner along the groove direction, forming a directional jet with a certain speed. It is suitable for grinding conditions that require concentrated cooling.

[0081] Reference Figure 7The cross-sectional shape of the water guide channel 83 is conical (i.e., conical channel). The width of the conical channel 83b gradually increases from the bottom to the opening, and the cross-section is V-shaped or trapezoidal. The structure of the conical channel 83b is conducive to the diffusion of coolant along the channel wall towards the opening under the action of centrifugal force, so that the coolant forms a diffused jet at a certain angle when flowing out of the water guide channel, thereby expanding the coverage area of ​​the coolant in the grinding area.

[0082] Reference Figure 8 The water guide channel 83 is a fan-shaped channel 83c. The width of the fan-shaped channel 83c gradually increases from the central area of ​​the water guide section 82 to the outer periphery, and the included angle between its sidewalls is 30° to 60°. Utilizing its gradually expanding width, the fan-shaped channel 83c allows the coolant to naturally form a fan-shaped water curtain under the propulsion of centrifugal force, achieving a larger coverage area and more uniform coolant distribution in the grinding area. When the included angle of the sidewalls of the fan-shaped channel 83c is within the above-mentioned range, it ensures that the coolant has a sufficient diffusion angle without excessively reducing the flow rate due to excessive diffusion, thus balancing coverage area and coolant impact force.

[0083] Reference Figure 9 The water guide groove 83 is a flower-shaped groove 83d. The flower-shaped groove 83d includes multiple branch grooves, which extend radially from the central area of ​​the water guide section 82 to the outer periphery. Each branch groove has a flared end, the width of which is greater than the width of the branch groove. The structure of the flower-shaped groove 83d, through multi-branch diffusion and end flaring, allows the coolant to form multiple diffused jets before reaching the grinding teeth. These jets overlap, significantly increasing the contact area and impact force between the coolant and the grinding teeth. The flower-shaped groove 83d is particularly suitable for grinding wheels with a large number of grinding teeth that require large-area uniform cooling.

[0084] The following combination Figures 1 to 4 The coolant flow control method provided in the embodiments of this application will be described in detail.

[0085] During the grinding process, coolant is supplied from an external source through the coolant supply passage to the internal channel of the grinding spindle 1, and then enters the water distribution component 80 through the central hole of the wheel mounting seat 11. The coolant flows sequentially through the hollow cavity of the connecting part 81 and the top surface of the conical surface of the water guiding part 82, and is evenly distributed to the inlet end of each water guiding groove 83 under the guidance of the conical surface. Under the action of centrifugal force generated by the rotation of the grinding spindle 1, the coolant accelerates along the inclined direction of the water guiding groove 83, and impacts the root area of ​​the grinding teeth of the grinding wheel 2 at a certain speed from the outlet end of the water guiding groove 83. After fully cooling the grinding area, the coolant, carrying grinding heat and debris, is discharged to the outside through the drain hole 5 between the grinding teeth. Since the centrifugal force provides additional kinetic energy to the coolant, the coolant gains a significant velocity increment in the water guiding groove 83, the throughput capacity of the drain hole 5 is effectively utilized, and the drainage rate is greatly improved compared with the traditional natural flow method.

[0086] During the grinding process, the detection unit monitors the status parameters characterizing the drainage capacity of the drain hole 5 in real time. Preferably, the status parameter is the coolant level above the grinding wheel 2. Specifically, as the grinding process continues, the grinding teeth gradually wear down due to continuous friction with the substrate 3, shortening the effective axial length of the drain hole 5, reducing its equivalent cross-sectional area, and decreasing its drainage capacity. At this time, coolant that cannot be discharged through the drain hole 5 in time flows upwards along the gap between the grinding wheel 2 and the water distribution member 80, and the gap between the grinding spindle 1 and the wheel mounting seat 11, gradually accumulating in the water storage section 10 at the top of the grinding spindle 1. The electrode-type liquid level sensor 9 monitors the liquid level in the water storage section 10 in real time and transmits the liquid level signal to the control unit. When the liquid level exceeds a preset reference value, it indicates that the drainage capacity of the drain hole 5 is insufficient to match the current coolant supply flow rate, requiring flow rate adjustment.

[0087] Alternatively, the supply pressure of the coolant supply line can be used as the status parameter. A supply pressure sensor is installed on the coolant supply line to obtain the supply pressure in real time. When the drainage capacity of drain hole 5 is normal, the supply pressure remains within the normal range. When the drainage capacity of drain hole 5 decreases due to wear of the grinding gears, the flow resistance of the coolant in the grinding area increases, and the supply pressure rises. By detecting the trend and magnitude of this supply pressure change, the pressure sensor does not need to be in direct contact with the coolant, making installation and maintenance more convenient.

[0088] After receiving the status parameters, the control unit first determines whether the drainage capacity has decreased due to the reduced cross-sectional area of ​​the drainage holes caused by wear of the grinding teeth. If the control unit determines that the drainage capacity has decreased, it employs a combined feedforward and feedback control strategy to generate a control signal and send it to the flow regulation unit. Figure 10 This is a flowchart of a feedforward and feedback combined control of coolant flow provided in an embodiment of this application.

[0089] Feedforward control section: The control unit establishes an estimation model of the wear state of the grinding teeth based on the cumulative grinding amount or cumulative number of rotations of the grinding wheel. Specifically, the wear amount of the grinding teeth is positively correlated with the cumulative grinding amount (i.e., the total area or thickness of the ground substrate) or the cumulative number of rotations, and this correlation can be obtained through pre-calibration experiments. Based on the pre-calibrated wear curve, the control unit calculates the remaining height of the current grinding teeth from the cumulative grinding amount, and then calculates the equivalent cross-sectional area of ​​the drainage hole 5.

[0090] To establish the wear curve required for the aforementioned feedforward control, offline calibration experiments were conducted before the grinding wheel 2 was put into use, or using samples from the same batch. The calibration experiments were performed under standard grinding conditions: the spindle speed was fixed at 3000 rpm, the substrate 3 used silicon wafers consistent with those used in production, and the grinding depth was set to 50 μm. The calibration was performed after each predetermined cumulative grinding amount ΔM (e.g., after grinding 50 substrates or after each cumulative rotation of 1 × 10⁻⁶) was completed.6 The machine was stopped, and the remaining height hᵢ of the ground teeth was measured using a high-precision profilometer. Simultaneously, the equivalent flow cross-sectional area Aᵢ of the drain hole 5 was measured using the flow-pressure differential method. Multiple sets of (Mᵢ, hᵢ, Aᵢ) data were recorded, and the following mathematical model was obtained by fitting using the least squares method:

[0091] h=h0−k1·M

[0092] A=A0·(h / h0)=A0·(1−k1·M / h0)

[0093] Where h0 is the initial height of the grinding teeth, A0 is the initial equivalent cross-sectional area of ​​the drainage hole 5, and k1 is the wear coefficient of the unit cumulative grinding amount of the grinding teeth, which is determined by fitting the calibration experimental data. For the grinding wheel 2 that uses annular grinding teeth and whose drainage hole 5 is formed by the gap between adjacent grinding teeth, the equivalent cross-sectional area A is approximately linearly proportional to the grinding tooth height h, so the above model has good prediction accuracy.

[0094] The calibrated h0, A0, and k1 are pre-stored in the control unit.

[0095] It is important to emphasize that the reduction in the cross-sectional area of ​​the drain hole caused by grinding wear not only leads to flow overflow but also triggers secondary problems such as grinding debris sintering and blockage in the high-temperature environment of the grinding zone. During silicon wafer grinding, the generated silicon grinding debris typically ranges in size from 0.1 to 5 μm. When the temperature in the grinding zone exceeds 60°C and the coolant flow is insufficient, these silicon debris react with alkaline additives in the coolant, easily forming SiO2·nH2O gel-like deposits on the inner wall of the drain hole 5. As grinding continues, these deposits gradually sinter and harden under high temperature and pressure, further reducing the effective cross-sectional area of ​​the drain hole 5 by 20% to 30% on top of the grinding wear, forming the aforementioned vicious cycle of "wear-blockage-drainage deterioration-overheating-accelerated wear." The feedforward control in this application uses a pre-calibrated wear model to preventatively constrain the flow rate in the early stages of grinding wear, avoiding coolant stagnation and backflow at the drain hole 5, thereby controlling the temperature in the grinding zone below a safe threshold and effectively suppressing grinding debris sintering and blockage.

[0096] During the actual grinding process, the control unit continuously monitors the current grinding amount M, substitutes it into the above model to estimate the equivalent cross-sectional area A of the current drain hole 5, and calculates the maximum coolant flow rate allowed by the current drainage capacity. :

[0097] ;

[0098] Where C is the comprehensive flow coefficient related to the structure of drain hole 5 and the viscosity of coolant, ΔP is the maximum allowable pressure difference before and after drain hole 5, ρ is the coolant density, n is the current rotational speed of grinding spindle 1, and f(n) is the centrifugal pressurization correction function related to rotational speed. Thus, feedforward control achieves dynamic and quantitative setting of the upper limit of coolant flow, enabling preventative flow constraints in the early stages before significant wear of the grinding teeth occurs, avoiding the risk of hysteretic overflow caused by relying on a single feedback signal.

[0099] Based on the equivalent cross-sectional area of ​​drain hole 5 and the current rotational speed of grinding spindle 1, the control unit calculates the maximum coolant flow rate allowed by the current drainage capacity and sets this value as the upper limit of the flow rate. The role of feedforward control is to predict the changing trend of drainage capacity in advance and to preventively constrain the flow rate before the state parameters show obvious abnormalities, so as to avoid large-scale coolant overflow.

[0100] Feedback Control Section: The control unit corrects the upper limit of the flow rate set by the feedforward control based on the real-time liquid level height detected by the liquid level sensor 9. When the liquid level height exceeds the first preset threshold, it indicates that the actual drainage capacity is lower than the drainage capacity estimated by the feedforward model (possibly due to factors such as partial blockage of the drain hole or uneven wear of the grinding teeth). The control unit further reduces the target flow rate based on the upper limit. When the liquid level height falls back below the safe range, the control unit can appropriately adjust the flow rate to provide sufficient cooling as much as possible without overflowing.

[0101] The flow regulation unit is located in the coolant supply passage and can be an electric proportional valve, an electromagnetic flow regulating valve, or other controllable flow regulation devices. Based on the control signal from the control unit, the flow regulation unit adjusts the coolant flow supplied to the grinding wheel 2 in a stepwise manner, within the range not exceeding the current discharge capacity of the drain hole 5.

[0102] Figure 11 This is a schematic diagram of a stepped coolant flow rate according to an embodiment of this application. The stepped adjustment includes multiple thresholds. When the state parameter exceeds different thresholds, different levels of flow rate adjustment are executed accordingly: for example, when the liquid level reaches the first threshold H1, the coolant flow rate is reduced by the first level (e.g., reduced to 80% of the rated flow rate); when the liquid level reaches the second threshold H2, it is reduced by the second level (e.g., reduced to 60% of the rated flow rate); when the liquid level reaches the third threshold H3, it is reduced by the third level (e.g., reduced to 40% of the rated flow rate). When the liquid level falls back below the corresponding threshold, the flow rate can be gradually restored. This graded control method avoids frequent fluctuations in flow rate, ensures the stability of the grinding process, and simultaneously achieves refined management of the coolant flow rate.

[0103] It should be further explained that if continuous proportional control is used, for example, by continuously changing the opening of the electric proportional valve based on the liquid level deviation using a PID algorithm, the liquid level signal is prone to high-frequency, small-amplitude fluctuations due to the vibration of the grinding wheel 2 during grinding, the random bursting of air bubbles in the coolant, and the detection noise of the electrode-type liquid level sensor 9. This fluctuation, amplified by the PID, will cause frequent changes in the valve opening, resulting in continuous fluctuations in the coolant flow rate. These flow fluctuations not only cause unstable cooling intensity in the grinding area, directly affecting the consistency of the surface roughness of the substrate 3, but also significantly exacerbate the mechanical wear and electrical fatigue of the flow control unit.

[0104] This application employs a stepped adjustment strategy, triggering a step-by-step switch in flow rate only when the liquid level crosses preset thresholds H1, H2, and H3, while maintaining a constant flow rate within the same threshold range, forming a graded control with hysteresis characteristics. This "hysteresis-step" mechanism effectively filters out frequent adjustments caused by detection noise and short-term liquid level fluctuations, ensuring that the coolant flow rate remains relatively stable for most of the grinding wheel 2's service life, with adaptive adjustments only made at critical points where drainage capacity substantially decreases. Experimental comparisons show that, under the same grinding conditions and the same liquid level detection accuracy, stepped control, compared to continuous proportional adjustment, helps reduce the number of flow rate adjustment executions and lowers the batch standard deviation of the substrate grinding surface roughness Ra, significantly improving batch consistency of grinding quality and extending the service life of the flow rate adjustment unit.

[0105] As a further optimization control measure, active diagnosis of drain hole blockage can be performed before adjusting the coolant flow rate. Specifically, the control unit controls the flow regulation unit to periodically modulate the coolant supply flow rate at a predetermined frequency (e.g., 1Hz to 5Hz) and amplitude (e.g., ±5% to ±10% of the rated flow rate), while simultaneously detecting the resulting pressure or level response using a pressure sensor or level sensor. Based on the amplitude ratio and phase difference between the flow pulsation and the response, the control unit calculates the equivalent flow impedance of drain hole 5 using frequency domain analysis.

[0106] Specifically, the equivalent flow impedance Z can be expressed as Z = ΔP / ΔQ, where ΔP is the amplitude of the pressure response and ΔQ is the amplitude of the flow pulsation; the phase difference reflects the relative strength of the inertial and damping effects of the flow within the drain hole 5. When the equivalent flow impedance exceeds the preset normal range, it indicates that there may be abnormal conditions such as wear debris blockage or scaling in the drain hole 5. The control unit can issue a warning signal to prompt the operator to check the status of the drain hole, or automatically adjust the parameters of the feedforward model to compensate for the blockage effect. This active diagnostic method can detect problems in the early stages of abnormal blockage in the drain hole, and can complete the diagnosis online without interrupting the grinding process, further improving the accuracy and reliability of coolant flow control and avoiding insufficient cooling or coolant overflow due to undetected blockages.

[0107] To verify the technical effectiveness of the coolant control method and grinding wheel assembly described in this application, a comparative experiment was conducted on a grinding device of the same model. The experimental group adopted the feedforward and feedback composite control method of this application and was equipped with a grinding wheel assembly with a shower-type water distribution component 80; the control group used a conventional constant flow supply (flow rate fixed at the rated flow rate of 4L / min) and a conventional grinding wheel without a water distribution component. Both groups of experiments used the same specifications of grinding wheel 2 (initial grinding tooth height 5mm, 14 drainage holes 5 evenly distributed along the circumference), the same substrate 3 (silicon wafer, diameter 300mm), and the same grinding process parameters (spindle speed 3000rpm, feed rate 1μm / s, target thinning thickness 50μm). The experiment continued until the grinding teeth of grinding wheel 2 were worn down to 30% of the initial height (i.e., the remaining grinding tooth height was about 1.5mm), and the following key indicators were recorded during the process:

[0108] (1) Number of coolant overflows: In the control group, due to the significant reduction in the cross-sectional area of ​​the drain hole 5 in the later stage of grinding wear (after the cumulative grinding amount exceeded 60% of the whole life cycle), the coolant could not be discharged in time and frequently overflowed upward along the spindle clearance, triggering the equipment liquid level alarm and causing unplanned shutdowns a total of 12 times; The experimental group predicted the downward trend of drainage capacity in advance through the feedforward model and dynamically reduced the flow rate in combination with feedback control. No coolant overflow events occurred during the whole life cycle of the grinding wheel 2, and the continuous operation rate of the equipment remained at 100%.

[0109] (2) Service life of grinding wheel: The end of service life was determined by the wear of the grinding teeth to 30% of the initial height. Due to the deterioration of cooling and the aggravation of thermal damage in the later stage, the average effective service life of the control group was only 75% of the standard service life; the experimental group achieved an average effective service life of more than 95% of the standard service life by dynamically matching the coolant supply and drainage capacity throughout the entire life cycle, and the service life of grinding wheel 2 was extended by about 27%.

[0110] (3) Coolant consumption: The experimental group maintained the rated flow rate to ensure sufficient cooling when the grinding wheel 2 was first put into use through step-by-step precise control, and reduced the flow rate as needed in the later stage of wear. The total coolant consumption throughout the entire life cycle was reduced by about 22% compared with the constant flow supply of the control group, which significantly reduced the waste liquid treatment cost and environmental burden.

[0111] The above experimental results show that, through the synergistic effect of the flow guiding structure of the shower-type water distribution component 80 and the feedforward-feedback composite control strategy, this application can achieve dynamic matching of coolant supply and drainage capacity throughout the entire life cycle of the grinding wheel 2, effectively preventing coolant overflow, improving the grinding surface quality of the substrate 3, extending the service life of the grinding wheel 2, and reducing coolant consumption, thus achieving significant technological progress.

[0112] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this application should be included within the protection scope of this application. For example, the shape of the water guide groove 83 of the water distribution component 80 is not limited to the above four types and can be combined or designed into other shapes according to the actual grinding conditions; the liquid level detection method of the water storage part 10 can also use a non-contact ultrasonic or capacitive liquid level sensor instead of an electrode liquid level sensor; the estimation of the wear state of the grinding teeth in the feedforward control can also be combined with parameters such as spindle torque and grinding current for multi-information fusion to improve the estimation accuracy. These changes do not depart from the protection scope of this application.

[0113] Those skilled in the art will recognize that the units and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the embodiments of this application.

[0114] The above embodiments are only used to illustrate the embodiments of this application, and are not intended to limit the embodiments of this application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the embodiments of this application. Therefore, all equivalent technical solutions also fall within the scope of the embodiments of this application, and the patent protection scope of the embodiments of this application should be defined by the claims.

Claims

1. A method for controlling the flow rate of a grinding wheel coolant for thinning a substrate by ring-shaped retraction, wherein the grinding wheel has grinding teeth and a drain hole disposed on a grinding wheel base, the outer diameter of the grinding wheel is smaller than the outer diameter of the substrate but larger than the outer diameter of the device region of the substrate, and the grinding wheel is mounted on the front end of a grinding spindle; characterized in that, A shower-type water distribution component is detachably provided between the grinding wheel and the wheel mounting seat. The water distribution component has a water guiding part. The upper surface of the water guiding part is provided with multiple water guiding grooves. The water guiding grooves extend from the center to the outer periphery and are inclined relative to the radial direction. Centrifugal force is used to accelerate the flow of coolant through the water guiding grooves to the grinding teeth and discharge it through the drain hole. During the grinding process, state parameters characterizing the drainage capacity of the drainage holes are detected; Based on the state parameters, determine whether the drainage capacity decreases due to the reduction in the cross-sectional area of ​​the drainage hole caused by wear of the grinding teeth. When it is determined that the drainage capacity has decreased, a combined feedforward and feedback control is used to adjust the coolant flow rate: the feedforward control estimates the wear state of the grinding teeth and the equivalent cross-sectional area of ​​the drain hole based on the cumulative grinding amount or cumulative number of rotations of the grinding wheel, and sets the upper limit of the flow rate accordingly. The feedback control modifies the feedforward control based on the state parameters to adjust the coolant flow rate in a stepwise manner.

2. The control method according to claim 1, characterized in that, The state parameter is the liquid level of the coolant above the grinding wheel. A water storage section is provided on the top of the grinding spindle, and the liquid level is detected by an electrode-type liquid level sensor provided in the water storage section.

3. The control method according to claim 1, characterized in that, The status parameters include the supply pressure of the coolant supply pipeline, and a supply pressure sensor is installed on the coolant supply pipeline to obtain the supply pressure in real time.

4. The control method according to claim 1, characterized in that, The water guide channel is a fan-shaped channel, and the width of the fan-shaped channel gradually increases from the central area of ​​the water guide section to the outer peripheral edge. The included angle between the side walls of the fan-shaped channel is 30° to 60°.

5. The control method according to claim 1, characterized in that, The water guide channel is a flower-shaped channel, which includes multiple branch channels. The branch channels extend radially from the center to the outer periphery. The ends of the branch channels are provided with flared portions, and the width of the flared portions is greater than the width of the branch channels.

6. The control method according to claim 1, characterized in that, The angle between the extension direction and the radial direction of the water guide channel is 10° to 45°.

7. The control method according to claim 1, characterized in that, Also includes: Before adjustment, a flow pulsation of known frequency and amplitude is actively applied to the coolant, and the resulting pressure response or liquid level response is detected. Based on the amplitude ratio and phase difference between the flow pulsation and the response, the equivalent flow impedance of the drain hole is calculated to determine the blockage status of the drain hole.

8. The control method according to claim 1, characterized in that, The stepped adjustment includes multiple threshold levels. When the state parameter exceeds different threshold levels, different levels of flow reduction are executed accordingly.

9. A grinding apparatus for implementing the control method as described in any one of claims 1 to 8, characterized in that, include: A grinding wheel assembly having a drain hole for discharging coolant; A coolant supply passage for supplying coolant to the grinding wheel of the grinding wheel assembly; A detection unit is used to detect state parameters characterizing the drainage capacity of the drainage hole during the grinding process; The control unit is communicatively connected to the detection unit and is used to determine whether the drainage capacity has decreased based on the status parameters and to generate a control signal. A flow regulation unit is disposed on the coolant supply passage and is communicatively connected to the control unit. It is used to adjust the flow rate of coolant supplied to the grinding wheel in a stepwise manner according to the control signal, within the range not exceeding the current discharge capacity of the drain hole.

10. A grinding wheel assembly for implementing the control method according to any one of claims 1 to 8, characterized in that, include: Wheel mounting bracket, used for mounting on the front end of the grinding spindle; A grinding wheel is mounted on the wheel mounting base. The grinding wheel has annularly arranged grinding teeth and drainage holes provided on the grinding wheel base. The outer diameter of the grinding wheel is smaller than the outer diameter of the substrate and larger than the outer diameter of the device area of ​​the substrate. A showerhead-type water distribution component is detachably disposed between the wheel mounting base and the grinding wheel, the water distribution component comprising: The connecting part is used to connect with the wheel mounting base; A water guide portion is disposed below the connecting portion, and the water guide portion has an upper surface facing the grinding teeth; Multiple water guide grooves are disposed on the upper surface of the water guide section. The water guide grooves extend from the central area of ​​the water guide section to the outer peripheral edge, and the water guide grooves are inclined relative to the radial direction of the water guide section. The inclination direction is the same as the rotation direction of the grinding wheel, and the depth of the water guide grooves is 1mm to 5mm.

11. The grinding wheel assembly according to claim 10, characterized in that, The connecting part of the water distribution component is a hollow structure, and the top surface of the water guiding part is a conical surface; the cross-sectional shape of the water guiding groove is selected from one of the following: waist-shaped groove, conical groove, fan-shaped groove, and flower-shaped groove; the number of the water guiding grooves is 6 to 12, and they are evenly distributed along the circumference.

12. The grinding wheel assembly according to claim 11, characterized in that, The water guide channel is a fan-shaped channel, and the width of the fan-shaped channel gradually increases from the central area of ​​the water guide section to the outer peripheral edge. The included angle between the side walls of the fan-shaped channel is 30° to 60°.

13. The grinding wheel assembly according to claim 11, characterized in that, The water guide channel is a flower-shaped channel, which includes multiple branch channels. The branch channels extend radially from the center to the outer periphery. The ends of the branch channels are provided with flared portions, and the width of the flared portions is greater than the width of the branch channels.

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