A method and system for controlling the speed of a multi-wire saw to prevent excessive wire bow

Abstract

The application discloses a kind of multi-wire cutting prevent saw wire line arch excessive speed control method and system, this method is by establishing the indentation model of single diamond particle, deduces indentation depth and transverse crack length formula, obtains the indentation depth and transverse removal length of single diamond particle, and then calculates out single particle diamond abrasive removal material cross-sectional area;Again, the removal volume formula of macroscopic saw wire unit time is established in combination with abrasive density, thus the line arch stress simulation model is established, the relationship between line arch size and cutting force is clear, and critical line arch value is obtained;Line arch monitoring and speed adjustment are carried out to each speed interval of process in processing, and the control saw wire line arch is realized by the mutual cooperation of feed speed and wire speed.The method of the application can effectively avoid the continuous reduction of feed speed caused by detection, improve the problem of prolonged processing time caused by the reduction of feed speed, and improve the processing production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of diamond multi-wire cutting of silicon wafers, and relates to a speed control method and system for preventing excessive wire bowing during multi-wire cutting. Background Technology

[0002] With the development of the new energy industry, silicon wafer production is trending towards larger diameters and thinner wafers, which brings many technical challenges to silicon wafer cutting. Currently, silicon wafer production mainly uses wire cutting, but due to the high flexibility of diamond saw wires, wire bowing is unavoidable.

[0003] The size of the bow wire is mainly related to the feed rate and wire feed speed. As the feed rate increases, the bow wire also increases. An excessively large bow wire can easily lead to wire breakage, affecting the processing quality and production efficiency of silicon wafers. Currently, the detection equipment used can detect excessive bow wire and reduce the feed rate. However, simply reducing the feed rate cannot effectively solve the problem because it only temporarily alleviates the problem of excessive bow wire. It increases processing time, but bow wire detection is continuous. Every time the bow wire reaches a critical value, the feed rate is reduced. If the bow wire frequently reaches the critical value, the detection and speed reduction will be continuously cycled, resulting in a speed that is too low, affecting processing efficiency and silicon wafer quality. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a speed control method and system for preventing excessive wire bowing in multi-wire cutting. This method can effectively solve the problem of excessive wire bowing while ensuring production efficiency and silicon wafer quality.

[0005] The technical solution adopted in this invention is as follows: A speed control method for preventing excessive wire bowing in multi-wire cutting includes: 1) Establish an indentation model for a single diamond particle, derive the formulas for indentation depth and transverse crack length, obtain the indentation depth and transverse removal length of a single diamond particle, and then calculate the cross-sectional area of ​​material removed by a single diamond abrasive particle, and obtain the material removal volume of a single abrasive particle within time t. 2) Based on the material removal volume formula of a single abrasive grain in step 1), and combined with the abrasive grain density, establish the material removal volume formula of the macroscopic saw wire within time t to clarify the relationship between the removal volume and the cutting force. 3) Establish a simulation model of the force on the line bow to clarify the relationship between the size of the line bow and the cutting force, and obtain the critical line bow value; 4) During processing, the wire bow is monitored and the speed is adjusted for each speed range of the process. The wire bow is controlled by the coordination of the feed speed and the wire feed speed.

[0006] In the above technical solution, further, step 1) specifically includes: Based on the theory of elastoplastic indentation fracture mechanics, the cutting of brittle materials by a single diamond particle is equivalent to a half-angle... The sharp indenter under normal force The pressing process under the action simplifies the single-particle removal area into a rectangular region, the side length of which is determined by the length of the transverse crack. and plastic removal depth The composition, and its theoretical derivation formulas are as follows (1) and (2): (1) (2) In the formula, The coefficient is taken as a constant of 0.226. For abrasive grain half-angle, The elastic modulus of the material. For material hardness, For the fracture toughness of the material, For the material's Poisson's ratio, The normal force of a single abrasive grain; The cross-sectional area S of the groove formed by a single abrasive grain is derived from formulas (1) and (2), and combined with the time of a single abrasive grain... Movement distance within The time of a single abrasive grain was derived. internal removal volume Formula (3): (3) in, The wire feed speed.

[0007] Furthermore, in step 2), the saw wire is in time The total volume of material removed from the interior is: (4) in, This represents the number of abrasive particles within the contact area.

[0008] Furthermore, in step 3), a wire bow force simulation model is established. Based on the force balance under stable cutting conditions and the kinematic trajectory of wire cutting, based on the equivalent conservation relationship between the sum of macroscopic material removal volume and microscopic abrasive grain removal volume under stable cutting conditions, and the contact mechanical geometry characteristics of a single conical abrasive grain indentation, the local cutting resistance experienced by a single abrasive grain is integrated and superimposed in macroscopic space. Simultaneously, the kinematic trajectory characteristics of wire cutting (feed rate) are considered. With wire speed By performing equivalent substitution of variables based on the ratio relationship, the macroscopic feed force of the saw wire can be determined. size.

[0009] Specifically, based on the law of volume conservation under stable cutting conditions, we first establish the equation (5) for the sum of macroscopic and microscopic removal volumes: (5) In the formula The contact length between the saw wire and the material. The radius of the saw wire is 1. For feed rate, This refers to the cross-sectional area of ​​the groove formed by a single abrasive grain cutting. For wire speed, N This refers to the number of abrasive particles within the contact area. Based on the geometric relationship of conical indentation, a single half-angle is established as... The force on the conical diamond abrasive grains Its cutting cross-sectional area Proportional relationship (6): (6) In the formula, For cutting deformation contact stress, The coefficient of friction between the abrasive particles and the material. This represents the average contact stress between the abrasive grains and the material. There are a total of There are individual abrasive grains, but due to their uneven shape, only a portion of them are actually involved in cutting; that is, the proportion of abrasive grains involved in cutting is... A constant of 0.5 is typically used to determine the macroscopic feed force of the saw wire. Expression (7): (7) After transforming and equivalently converting equation (5), we substitute it into equation (7) to perform equivalent substitution of the cross-sectional area variable, and finally derive the macroscopic feed force of the saw wire. The calculation formula (8): (8) Assuming the maximum height of the pantograph is at the midpoint, the critical pantograph value H is derived from the three-point deflection theory. max for (9) In the formula For line tension, The center axis distance between the two guide wheels. For cutting width, This is the elastic modulus of the saw wire.

[0010] Furthermore, within the same process speed range, when the wire bow is first detected to reach the critical value, the wire feed speed is increased to enter the next stage. If the wire bow is detected to reach the critical value again, the feed speed is reduced. The speed reduction process can be repeated multiple times. When the speed needs to be changed according to the process to enter the next speed stage, the speed is restored to the set value and monitoring is performed again.

[0011] This invention also provides a speed control system for multi-wire cutting to prevent excessive wire bowing, comprising: The pantograph critical value determination module determines the pantograph critical value in real time based on the established pantograph stress simulation model; The speed control module adjusts the speed of the wire saw bow for each speed range during processing, based on the bow critical value output by the module. The control of the wire saw bow is achieved through the coordination of the feed speed and the wire feed speed.

[0012] Furthermore, the speed control module controls the wire bow to reach a critical value within the same process speed range. When the wire bow reaches a critical value for the first time, the wire feed speed is increased to enter the next stage. If the wire bow reaches a critical value again, the feed speed is reduced. When the speed needs to be changed according to the process to enter the next speed stage, the speed is restored to the set value, and monitoring and control are performed again.

[0013] The present invention also provides an electronic device, comprising: One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors perform the method as described in any of the preceding methods.

[0014] The present invention also provides a computer-readable storage medium storing computer-executable instructions, which, when executed, are used to implement the method described in any of the preceding claims.

[0015] Based on the establishment and support of the above-mentioned theoretical model, the present invention can establish a pantograph monitoring and speed control program. According to the preset processing parameters, cutting tool parameters and workpiece parameters, the critical pantograph value for pantograph breakage is obtained. By inputting different process parameters, the system can output the corresponding critical pantograph value. The speed is adjusted by the control system to make the pantograph value less than the maximum critical value that the pantograph can withstand, so as to prevent the pantograph from breaking.

[0016] Speed ​​is a major factor affecting the value of the bow wire. In a cutting process, the speed is adjusted at regular intervals to achieve acceleration, constant speed, and deceleration. The method of this invention monitors the bow wire in real time within each speed interval, and transmits the collected data to the data analysis system. The analysis system transmits abnormal signals to the control system, and the control system adjusts the speed according to the set program to reduce the bow wire value and prevent wire breakage.

[0017] Beneficial effects: To address the problems existing in the prior art, this invention proposes a method for effectively preventing excessive saw wire bow speed adjustment during the cutting process. Based on material removal theory and a wire bow numerical simulation model, reasonable process parameters and program settings are established to avoid continuous decreases in feed speed caused by detection, thus mitigating the problem of prolonged processing time due to reduced feed speed and improving processing efficiency. Attached Figure Description

[0018] Figure 1 This is an overall flowchart of one embodiment of the present invention; Figure 2 This is a flowchart of a speed control system according to the present invention; Figure 3 A schematic diagram of the area where a single diamond particle is pressed in; Figure 4 This is a schematic diagram of a wire bow for sawing. Detailed Implementation

[0019] This invention provides a method for controlling the size of the saw wire and adjusting the wire speed in multi-wire cutting. First, a single diamond particle indentation model is established. Based on the depth of the plastic deformation zone and the length of the transverse crack in the workpiece, the removal volume of a single abrasive particle is calculated. Combined with parameters such as abrasive particle density and wire feed speed, the saw wire removal volume per unit time is determined, obtaining the relationship between material removal volume and wire feed speed and feed force. Second, a wire bow stress simulation model is established to determine the maximum wire bow value under different cutting speeds, feed speeds, tension forces, and other parameters. A speed control system avoids excessive wire bow values, solving the problem of wire breakage caused by excessive wire bow. Speed ​​adjustment promotes plastic removal of material, improving surface quality and ensuring production efficiency.

[0020] like Figure 1As shown, this case study provides a method and control system for controlling the bow size in multi-wire EDM. Its features include: ① Determining the relationship between process parameters and bow size through a numerical simulation model, and identifying corresponding critical values. ② Establishing a material removal model to analyze the impact of wire feed speed and feed rate on removal efficiency, allowing for a comparison of their advantages and disadvantages. ③ Monitoring and adjusting the bow size within each speed range, achieving bow control through the coordination of feed rate and wire feed speed. ④ Adjusting each small speed range throughout the entire process ensures process stability and production efficiency.

[0021] like Figure 2 As shown, the speed control method for preventing excessive wire bowing in multi-wire cutting according to the present invention is as follows: when the detection system detects that the wire bowing reaches the critical value for the first time, the speed system first increases the wire feed speed. If the critical value is detected again, the feed speed is reduced. The speed reduction process can be repeated multiple times. When the next speed stage is entered according to the original process, the speed is restored to the set value, and the speed control system restarts.

[0022] The specific steps of the method of the present invention include: Step 1: Based on the theory of elastoplastic indentation fracture mechanics, the cutting of brittle materials such as silicon wafers by a single diamond particle is equivalent to a half-angle... The sharp indenter under normal force The pressing process under pressure. The material undergoes plastic deformation under the indenter, inducing the propagation of transverse cracks upon unloading. The length of the transverse crack propagation. and plastic removal depth It is jointly controlled by the material's hardness, elastic modulus, and fracture toughness, among other mechanical properties. For ease of calculation, such as... Figure 3 The diagram simplifies the single-particle removal area into a rectangular region with transverse crack length. and plastic removal depth The composition, and its theoretical derivation formulas are as follows (1) and (2): (1) (2) In the formula, The coefficient is taken as a constant of 0.226. For abrasive grain half-angle, The elastic modulus of the material. For material hardness, For the fracture toughness of the material, For the material's Poisson's ratio, This represents the normal force of a single abrasive grain.

[0023] The cross-sectional area of ​​the groove formed by a single abrasive grain can be derived from formulas (1) and (2). Because the diamond abrasive grains cut in the wire feeding direction, their time... The distance of movement within is (in (where the wire feed speed is used), from which the time of a single abrasive grain can be derived. The formula for removing volume within (3): (3) Combined with the total number of abrasive particles in the actual contact area By macroscopically summing up the removal volume of individual abrasive grains, the time required to obtain the saw wire's removal volume can be calculated. Formula (4) for the total volume of material removed from the interior: (4) The relationship between feed force, wire speed and removal volume can be analyzed by formula (4). As the feed force decreases, the material penetration depth decreases, so the material removal volume decreases. When the wire speed increases, the number of abrasive grains participating in cutting increases, and the material removal volume increases.

[0024] Step 2: Establish a simulation model of the force on the pantograph, such as... Figure 4 As shown. According to the law of conservation of volume, the volume removed macroscopically is equal to the sum of the volumes removed microscopically, that is: (5) In the formula The contact length between the saw wire and the material. The radius of the saw blade.

[0025] Total force of the saw wire in the feed direction It is formed by the superposition of forces from countless tiny diamond abrasive grains. For a single half-angle... The conical diamond abrasive grains experience resistance including deformation contact force (and...). (related to) and friction (and) (Related). Based on the geometric relationship of conical indentation, the force on a single abrasive grain. Its cutting cross-sectional area There is a proportional relationship between them: (6) There are a total of There are individual abrasive grains, but due to their uneven shape, only a portion of them are actually involved in cutting; that is, the proportion of abrasive grains involved in cutting is... At this point, the macroscopic feed force of the saw wire is obtained. for: (7) At this point, transforming equation (5) yields... Therefore, formula (8) can be derived: (8) Get power Subsequently, the saw wire deflection caused by this force needs further evaluation. Assuming that the maximum height of the wire bow (i.e., the maximum deflection) occurs at the midpoint of the ingot cutting span, the saw wire between the two guide wheels is equivalent to bearing tension at both ends. and central concentrated load The mechanical model is derived. Based on the three-point deflection theory, the critical value for preventing wire breakage is derived. Formula (9): (9) In equation (9) For line tension, The center axis distance between the two guide wheels. For cutting width, This is the elastic modulus of the saw wire.

[0026] Step 3: Based on the theoretical model established above, construct an automatic control program to prevent excessive pantograph size. This program mainly consists of a parameter setting system, a pantograph monitoring system, a data analysis system, and a speed control system.

[0027] Specifically, the parameter setting system calculates and outputs the maximum critical value of the bow wire to the data analysis system based on the input machining process parameters, workpiece material parameters, and wire sawing tool parameters; the bow wire monitoring system is responsible for collecting bow wire deformation data in real time during the cutting process (the detection device can be, but is not limited to, a laser displacement sensor, a vision sensor, or an ultrasonic ranging sensor); and the speed control system dynamically adjusts the feed speed and wire feed speed according to the abnormal instructions issued by the data analysis system, thereby achieving the purpose of reducing the bow wire value and maintaining a stable cutting state.

[0028] In one specific embodiment of the present invention, the overall monitoring and control workflow is as follows: Figure 1 As shown. The pantograph monitoring system transmits the real-time pantograph data to the data analysis system and compares it with the maximum critical value of the pantograph. If the data analysis system determines that the current pantograph value is within the limit (no abnormality), it maintains the current process speed and continues processing until the process is completed; if it determines that the current pantograph value has reached the maximum critical value (abnormality), the system immediately sends a trigger signal to the speed control system, and the speed control system then intervenes by adjusting the speed according to the preset strategy (i.e., increasing the wire feed speed or decreasing the feed speed).

[0029] The specific speed control system's shift intervention process is as follows: Figure 2As shown. Within the same process speed range, when the system first detects that the wire bow has reached a critical value and caused an anomaly, the system prioritizes increasing the wire feed speed. This increases the material removal rate by increasing the number of abrasive grains participating in cutting per unit time, thereby alleviating the wire bowing issue. After increasing the feed speed, if the system detects that the wire bow has reached the critical value again, then the system will execute a program to reduce the feed speed. Within the same speed range, the process of reducing the feed speed can be triggered multiple times in cycles depending on the wire bowing situation. When processing reaches the point where a speed change is required to enter the next process stage according to the original procedure, both the feed speed and the wire feed speed automatically return to the initial values ​​set for the new stage, and a new round of monitoring and speed control is restarted.

[0030] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0031] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0032] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0033] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0034] The embodiments described above are merely some preferred embodiments of the present invention, and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A speed control method for preventing excessive wire bowing in multi-wire cutting, characterized in that, include: 1) Establish an indentation model for a single diamond particle, derive the formulas for indentation depth and transverse crack length, obtain the indentation depth and transverse removal length of a single diamond particle, and then calculate the cross-sectional area of ​​material removed by a single diamond abrasive particle, and obtain the material removal volume of a single abrasive particle within time t. 2) Based on the material removal volume formula of a single abrasive grain in step 1), and combined with the abrasive grain density, establish the material removal volume formula of the macroscopic saw wire within time t to clarify the relationship between the removal volume and the cutting force. 3) Establish a simulation model of the force on the line bow to clarify the relationship between the size of the line bow and the cutting force, and obtain the critical line bow value; 4) During processing, the wire bow is monitored and the speed is adjusted for each speed range of the process. The wire bow is controlled by the coordination of the feed speed and the wire feed speed.

2. The speed control method for preventing excessive wire bowing in multi-wire cutting according to claim 1, characterized in that, Step 1) specifically refers to: Based on the theory of elastoplastic indentation fracture mechanics, the cutting of brittle materials by a single diamond particle is equivalent to a half-angle... The sharp indenter under normal force The pressing process under the action simplifies the single-particle removal area into a rectangular region, the side length of which is determined by the length of the transverse crack. and plastic removal depth The composition, and its theoretical derivation formulas are as follows (1) and (2): （1） （2） In the formula, For the coefficient, take the constant 0.

226. For abrasive grain half-angle, The elastic modulus of the material. For material hardness, For the fracture toughness of the material, For the material's Poisson's ratio, The normal force of a single abrasive grain; The cross-sectional area of ​​the groove formed by a single abrasive grain is derived from formulas (1) and (2). Combining the time of a single abrasive grain Movement distance within The time of a single abrasive grain was derived. internal removal volume Formula (3): （3） in, The wire feed speed.

3. The speed control method for preventing excessive wire bowing in multi-wire cutting according to claim 2, characterized in that, In step 2), the saw wire is in time The total volume of material removed from the interior is: （4） in, This represents the number of abrasive particles within the contact area.

4. The speed control method for preventing excessive wire bowing in multi-wire cutting according to claim 1, characterized in that, Step 3) involves establishing a simulation model of the force on the pantograph, specifically as follows: First, based on the law of volume conservation under stable cutting conditions, establish the equation (5) for the sum of macroscopic removal volume and microscopic removal volume: （5） In the formula The contact length between the saw wire and the material. The radius of the saw wire is 1. For feed rate, This refers to the cross-sectional area of ​​the groove formed by a single abrasive grain cutting. For wire speed, N This refers to the number of abrasive particles within the contact area. Based on the geometric relationship of conical indentation, a single half-angle is established as... The force on the conical diamond abrasive grains Its cutting cross-sectional area Proportional relationship (6): （6） In the formula, For cutting deformation contact stress, The coefficient of friction between the abrasive particles and the material. This represents the average contact stress between the abrasive grains and the material. The macroscopic feed force of the saw wire is obtained. Expression (7): （7） in To determine the proportion of abrasive particles involved in cutting within the contact area, equation (5) is transformed and equivalently converted, then substituted into equation (7) for equivalent substitution of the cross-sectional area variable, ultimately deriving the macroscopic feed force of the saw wire. The calculation formula (8): （8）。 5. The speed control method for preventing excessive wire bowing in multi-wire cutting according to claim 4, characterized in that, Assuming the maximum height of the pantograph is at the midpoint, the critical pantograph value H is derived from the three-point deflection theory. max for: （9） In the formula For line tension, The center axis distance between the two guide wheels. For cutting width, This is the elastic modulus of the saw wire.

6. The speed control method for preventing excessive wire bowing in multi-wire cutting according to claim 1, characterized in that, Within the same process speed range, when the wire bow is first detected to reach the critical value, the wire feed speed is increased to enter the next stage. If the wire bow is detected to reach the critical value again, the feed speed is reduced. The speed reduction process can be repeated multiple times. When the speed needs to be changed according to the process to enter the next speed stage, the speed is restored to the set value and monitoring is performed again.

7. A speed control system for multi-wire cutting to prevent excessive wire bowing, characterized in that, include: The pantograph critical value determination module determines the pantograph critical value in real time based on the established pantograph stress simulation model; The speed control module adjusts the speed of the wire saw bow for each speed range during processing, based on the bow critical value output by the module. The control of the wire saw bow is achieved through the coordination of the feed speed and the wire feed speed.

8. The speed control system for preventing excessive wire bowing in multi-wire cutting according to claim 7, characterized in that, The speed control module controls the wire bow within the same process speed range. When the wire bow reaches the critical value for the first time, the wire feed speed is increased to enter the next stage. If the wire bow reaches the critical value again, the feed speed is reduced. When the speed needs to be changed according to the process to enter the next speed stage, the speed is restored to the set value and monitoring and control are performed again.

9. An electronic device, characterized in that, include: One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in any one of claims 1-6.

10. A computer-readable storage medium storing computer-executable instructions, which, when executed, are used to implement the method of any one of claims 1 to 6.

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