A vibration filtering control structure and method for a wafer chamfering machine

Abstract

The present invention belongs to the field of semiconductors, and particularly relates to a vibration filtering control structure and method for a wafer chamfering machine, including: a base and a machine base which are cast, both the base and the machine base are hollow structures, and the machine base is fixed on the base; a "rice" - shaped rib plate is arranged in the space where the base is hollow; the machine base includes an independent main machine base and a suspension machine base, a "cross" - shaped rib plate is arranged in the hollow part of the main machine base, and an "X" - shaped rib plate is arranged in the hollow part of the suspension machine base. Through CAE simulation and experimental data verification, this system can effectively solve the problem of large amplitude during semiconductor processing and meet the requirements of high - precision semiconductor processing.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor manufacturing equipment, and particularly relates to a vibration filtering control structure and method for a wafer chamfering machine. Background Art

[0002] In the process of semiconductor manufacturing, wafer chamfering is an important process used to remove the sharp corners at the edges of the wafer, prevent cracks or other defects from occurring in subsequent processes, and thus improve the yield rate in the subsequent processing. The wafer chamfering machine belongs to the electronic core industry in the new generation of information technology industry and is one of the key equipment in the semiconductor manufacturing process. Its independent research and development helps to enhance the independent controllability of the national semiconductor industry chain.

[0003] The wafer chamfering process usually requires the use of multiple ultra-high-speed motors to drive the precision grinding wheel to work. The rotational speed of the motors is generally between 100,000 r / min and 200,000 r / min. Due to the high cost of semiconductor wafer processing, in any process, the work efficiency is improved as much as possible. Therefore, usually, a wafer chamfering machine is provided with 2 sets of precision grinding stations, and each set of precision grinding stations is provided with 4 ultra-high-speed motors. And a total of 8 ultra-high-speed motors in 2 sets of precision grinding stations are always in a high-speed rotating state, and the rotational speed will be changed in real time according to the situation of the wafer edge during the precision grinding process. Each ultra-high-speed motor will generate obvious vibrations when rotating, and the vibrations generated by 8 motors when the rotational speed changes at any time are more complex and changeable, which has a great impact on the precision processing of wafer chamfering.

[0004] Since the wafer processing has extremely high requirements for precision, any tiny vibration may affect the quality of the final product. Especially during the wafer chamfering process, when multiple ultra-high-speed grinding tools work simultaneously, resonance is likely to occur, which will cause an increase in the amplitude value during the processing, thereby affecting the processing precision of the wafer. According to industry standards, during the wafer chamfering process, the amplitude value received by the wafer shall not exceed 0.003 mm, otherwise the finished product ground by precision grinding cannot meet the requirements of subsequent processing.

[0005] In order to ensure the quality of wafer chamfering, the existing wafer chamfering machines usually set vibration filtering devices on the machine frame to reduce the influence of vibrations. However, traditional vibration filtering devices are often only effective at specific frequencies, have limited vibration filtering effects within a wide frequency band, and cannot dynamically adjust the vibration filtering parameters according to the actual working conditions. Therefore, developing a vibration filtering device that can effectively filter vibrations within a wide frequency band and can adjust the vibration filtering parameters in real time according to the processing state is of great significance for improving the quality and production efficiency of wafer chamfering. Summary of the Invention

[0006] The present invention aims to provide a vibration filtering control structure and method for a wafer chamfering machine, aiming to solve the problem that it is difficult to effectively filter vibrations in a multi-axis and variable rotational speed environment in the prior art wafer chamfering machine, so as to ensure that the amplitude value during the wafer chamfering process does not exceed 0.003 mm, thereby improving the processing accuracy and product quality.

[0007] To achieve the above object, the solution of the present invention is: a vibration filtering control structure for a wafer chamfering machine, including: a cast base and a machine base, both the base and the machine base are hollow structures, and the machine base is fixed on the base; in the space where the base is hollow, there is a rib plate with a "rice" - shaped cross - section. The "rice" - shaped cross - section rib plate first reduces the weight of the base, enables vibrations to be transmitted along with the rib plate, and facilitates the concentrated weakening of vibrations. The machine base includes an independent main machine base and a suspension machine base. The hollow part of the main machine base is provided with a "cross" - shaped rib plate, and the hollow part of the suspension machine base is provided with an "X" - shaped rib plate.

[0008] Further, the "rice" - shaped rib plate is provided with square through - holes.

[0009] Further, the axis of the "cross" - shaped rib plate is parallel to the axis of the main machine head, the cross - section of the rib plate is "cross" - shaped, and the cross - section is perpendicular to the axis of the main machine head.

[0010] Further, the height of the hollow part of the machine base is 1 / 5 - 1 / 4 of the height of the entire machine base. The vibration of the suspended part of the "cross" - shaped rib plate can be superimposed and weakened with the vibration generated by the rotation of the machine head. The main machine base is a "∏" structure, the connecting plates on both sides are connected to the base, and the cross - plate is provided with the machine head. The "cross" - shaped rib plate is arranged between the two connecting plates on both sides. There is a hollow between the top of the "cross" - shaped rib plate in the axial direction and the cross - plate of the main machine base, and the distance is one - fifth to one - quarter of the height of the entire machine base. With the above settings, the vibration generated when the main machine head rotates at ultra - high speed can be transmitted to the base and the "cross" - shaped rib plate through the connecting plates on both sides of the main machine base. The rib plates of the "cross" - shaped rib plate that are not connected to the connecting plates can vibrate freely, generating vibrations with a frequency opposite to that of the main machine head, thereby offsetting the vibration generated by the main machine head and making the amplitude value of the entire base within the effective working amplitude value range.

[0011] Vibration path: When the main machine head rotates at ultra - high speed, the generated vibration is transmitted to the connecting plates on both sides of the main machine base through the cross - plate. Part of these vibrations is transmitted to the base through the connecting plates, and the other part is transmitted to the "cross" - shaped rib plate.

[0012] Since the axial top of the "cross-shaped" rib plate is not directly connected to the transverse plate, the rib plate part not connected to the connecting plate can vibrate freely. After these freely vibrating parts are subjected to the transmitted vibration excitation, vibrations opposite to the vibration frequency of the main engine head will be generated. The core of this design lies in using the free vibration of the "cross-shaped" rib plate to cancel out the vibration of the main engine head. Since the freely vibrating rib plate part is not directly connected to the connecting plate, its own vibration characteristics can be adjusted so that its vibration frequency and phase are opposite to those of the main engine head, thereby physically achieving partial or complete cancellation of the vibration. By dispersing the vibration to each part of the "cross-shaped" rib plate, the overall vibration energy of the system is effectively dispersed and absorbed, thereby reducing the amplitude finally transmitted to the base. Further, there are at least 2 main engine bases, and the rib plates in the X direction of the "cross-shaped" rib plates of each main engine base are not parallel, while the rib plates in the Y direction are parallel. The above setting means that the rib plates of the "cross-shaped" rib plates of each main engine base that are not connected to the connecting plate have an included angle with each other. This setting is to cancel out the vibration generated by the rotation of the machine head by the vibration of the rib plates in the suspended part, thereby achieving further vibration filtering.

[0013] When the main engine head is running at ultra-high speed, the generated vibration has multi-directional characteristics. By setting rib plates at different angles, each rib plate can cancel out the vibration in different directions, thereby achieving comprehensive suppression of vibrations in all directions. If all the rib plates are arranged in the same direction, resonance may occur at certain frequencies, resulting in enhanced vibration. By setting rib plates at different angles in the X direction, the vibration energy can be effectively dispersed and absorbed, avoiding the occurrence of resonance. In the Y direction, keeping the rib plates parallel can ensure that the vibration characteristics of each main engine base are consistent in this direction, facilitating the control and management of the overall vibration. The design of parallel rib plates can enhance the overall stability of the system and provide a consistent support and cancellation effect when dealing with longitudinal vibrations. The included angle between the rib plates can introduce a vibration phase difference. Due to different vibration phases, the rib plates can achieve a vibration cancellation effect in multiple directions when interacting with each other. By precisely controlling these included angles, the design can maximize the vibration cancellation effect. Due to the existence of the included angle, the rib plates of different main engine bases can provide shock absorption at different positions and in different directions. This multi-point and multi-direction shock absorption method enables the overall system to maintain a low amplitude in a complex vibration environment. The rib plate design of multiple main engine bases makes the vibration path more complex, and the vibration energy is dispersed into rib plates in different directions and at different angles. The vibration cancellation effect of each rib plate will be superimposed together to form a comprehensive vibration weakening effect. Since there is an included angle between each rib plate, these included angles make the vibrations between the rib plates not completely synchronous, and can more effectively cancel out the vibration through different phases and directions. Through the above design, the overall amplitude of the system can be significantly reduced, ensuring that the vibration of the system remains within the effective working range under various complex working conditions.

[0014] Furthermore, amplitude sensors are provided on the base and the machine base.

[0015] Furthermore, circular through-holes are evenly provided on the "rice"-shaped rib plates, and vibration filtering blocks are matched with the through-holes.

[0016] Through the settings of the hollowing and rib plates, the above structure effectively achieves the purpose of controlling the amplitude of the entire machine tool within 0.003 mm during the wafer chamfering process.

[0017] A vibration filtering control method for a wafer chamfering machine includes the following steps:

[0018] a: The amplitude sensor collects the real-time amplitude value;

[0019] b: When the real-time amplitude value is greater than 0.003 mm, the control system performs vibration filtering control calculation to calculate the number and position of the vibration filtering blocks that need to be increased or decreased;

[0020] c: According to the vibration filtering block arrangement information given by the control system, the vibration filtering blocks at the corresponding positions are increased or decreased;

[0021] The calculation formula of the control system is as follows:

[0022]

[0023] A: The amplitude of the overall chamfering machine;

[0024] F0: The amplitude generated by the machine head;

[0025] k: The stiffness of the chamfering machine base;

[0026] m: The mass of the chamfering machine;

[0027] ω: The angular velocity of the machine head, ω = 2πf, where f is the working frequency of the machine head; c: The damping coefficient.

[0028] The position arrangements of the amplitude sensors are as follows:

[0029] 1. Near the main machine head: The main machine head is the direct generating part of the vibration source. Installing an amplitude sensor near the main machine head (such as at the junction of the cross plate and the connecting plate) can most directly and quickly detect the vibration caused by high-speed rotation and provide real-time vibration amplitude data.

[0030] 2. The suspended ends of the "cross"-shaped rib plates: Arranging sensors at the suspended parts of the "cross"-shaped rib plates that are not connected to the connecting plate, especially at the ends of each rib plate, can monitor the actual effect of free vibration and ensure that its vibration effectively cancels out the vibration of the main machine head.

[0031] 3. Base "rice"-shaped ribs: The central intersection point is the stress concentration point of the entire "rice"-shaped rib plate and also the key node of the vibration mode. Arranging an amplitude sensor at the central position can capture the main vibration responses of the entire rib plate structure, especially the vibration situation when the vertical vibration generated by the main machine head is transmitted here. Sensors are respectively arranged at the end positions of the four rib plates of the "rice"-shaped structure. These positions are usually the endpoints of the free vibration of the rib plates and can reflect the vibration amplitude and frequency changes of the rib plates. By monitoring the vibration at the ends, the transmission and attenuation of vibration energy can be understood. Sensors are arranged at several key support points on the base, and these points are the parts where the vibration finally transmits to. By monitoring the amplitude at these positions, the vibration control effect of the entire system can be effectively evaluated.

[0032] Based on the above settings and methods, the vibration of the entire chamfering machine can be effectively controlled, and the vibration generated during the wafer chamfering process can be effectively filtered out, ensuring that the amplitude value during the wafer chamfering process does not exceed 0.003 mm, thereby improving the quality and production efficiency of wafer chamfering. Brief Description of the Drawings

[0033] Figure 1 Isometric view of the embodiment of the present invention.

[0034] Figure 2 Schematic diagram of the bottom structure of the embodiment of the present invention.

[0035] Figure 3 Is the vibration distribution of the wafer chamfering machine simulated by CAE software in the embodiment of the present invention at different frequencies.

[0036] Figure 4 Is the total deformation curve diagram of the embodiment of the present invention and the wafer chamfering machine without adopting this solution under the combined force in the X, Y, and Z axes at a frequency of 3000 - 3500 Hz.

[0037] Figure 5 Is the deformation curve diagram of the X axis of the embodiment of the present invention and the wafer chamfering machine without adopting this solution at a frequency of 3000 - 3500 Hz.

[0038] Figure 6 Is the deformation curve diagram of the Y axis of the embodiment of the present invention and the wafer chamfering machine without adopting this solution at a frequency of 3000 - 3500 Hz.

[0039] Figure 7 Is the deformation curve diagram of the Z axis of the embodiment of the present invention and the wafer chamfering machine without adopting this solution at a frequency of 3000 - 3500 Hz. Detailed Description of the Invention

[0040] The following is a further detailed description through specific embodiments:

[0041] The markings in the attached drawings of the specification include: 1 - base; 11 - "rice"-shaped rib plate; 12 - square through-hole; 2 - main base; 21 - "cross"-shaped rib plate; 22 - suspension base; 23 - "X"-shaped rib plate.

[0042] A vibration filtering control structure for a wafer chamfering machine, comprising: a base 1 and a base casting, both the base 1 and the base are hollow structures, and the base is fixed on the base 1; a "rice"-shaped rib plate 11 is provided in the space where the base 1 is hollow; the base includes an independent main base 2 and a suspension base 22, a "cross"-shaped rib plate 21 is provided in the hollow part of the main base 2, and an "X"-shaped rib plate 23 is provided in the hollow part of the suspension base 22. The "rice"-shaped rib plate 11 is provided with a square through-hole 12. The axis of the "cross"-shaped rib plate 21 is parallel to the axis of the main head, the cross-section of the "cross"-shaped rib plate 21 is "cross"-shaped, and the cross-section is perpendicular to the axis of the main head. The height of the hollow part of the base is 1 / 5 - 1 / 4 of the height of the entire base. The main base 2 is a "∏" structure, the connecting plates on both sides are connected to the base, and the main head is arranged on the cross plate. The "cross"-shaped rib plate 21 is arranged between the connecting plates on both sides, and there is a hollow between the top of the "cross"-shaped rib plate 21 in the axial direction and the cross plate of the main base, and the distance is one-fifth to one-fourth of the height of the entire base. With the above settings, the vibration generated when the main head rotates at ultra-high speed can be transmitted from the connecting plates on both sides of the main base to the base and the "cross"-shaped rib plate 21. The rib plates of the "cross"-shaped rib plate 21 that are not connected to the connecting plates can vibrate freely, generating vibrations with a frequency opposite to that of the main head, thereby canceling out the vibrations generated by the main head, so that the amplitude value of the entire base is within the effective working amplitude value range.

[0043] Vibration path: When the main head rotates at ultra-high speed, the generated vibration is transmitted to the connecting plates on both sides of the main base through the cross plate. Part of these vibrations is transmitted to the base through the connecting plates, and the other part is transmitted to the "cross"-shaped rib plate 21.

[0044] Since the axial top of the "cross"-shaped rib plate 21 is not directly connected to the cross plate, the rib plate part that is not connected to the connecting plate can vibrate freely. After being excited by the transmitted vibration, these freely vibrating parts will generate vibrations with a frequency opposite to that of the main head. The core of this design is to use the free vibration of the "cross"-shaped rib plate 21 to cancel out the vibration of the main head. Since the freely vibrating rib plate part is not directly connected to the connecting plate, its own vibration characteristics can be adjusted so that its vibration frequency and phase are opposite to those of the main head, thereby physically achieving partial or complete cancellation of the vibration. By dispersing the vibration to each part of the "cross"-shaped rib plate, the overall vibration energy of the system is effectively dispersed and absorbed, thereby reducing the amplitude transmitted to the base finally.

[0045] There are at least two main pedestals 2. The X-direction ribs of the "cross"-shaped ribs 21 of each main pedestal 2 are not parallel, while the Y-direction ribs are parallel. The above setting refers to the ribs of the "cross"-shaped ribs 21 of each main pedestal that are not connected to the connecting plate and have an angle between them. When the main head runs at ultra-high speed, the generated vibration has multi-directional characteristics. By setting ribs at different angles, each rib can cancel the vibration in different directions, thereby achieving comprehensive suppression of vibrations in all directions. If all the ribs are arranged in the same direction, resonance may occur at certain frequencies, resulting in enhanced vibration. By setting ribs at different angles in the X direction, the vibration energy can be effectively dispersed and absorbed, avoiding the occurrence of resonance. In the Y direction, keeping the ribs parallel can ensure that the vibration characteristics of each main pedestal are consistent in this direction, facilitating the control and management of the overall vibration. The design of parallel ribs can enhance the overall stability of the system and provide consistent support and cancellation effects when dealing with longitudinal vibrations. The angle between the ribs can introduce a vibration phase difference. Due to different vibration phases, the ribs can achieve vibration cancellation effects in multiple directions when interacting with each other. By precisely controlling these angles, the design can maximize the vibration cancellation effect. Due to the existence of the angle, the ribs of different main pedestals can provide shock absorption at different positions and in different directions. This multi-point and multi-direction shock absorption method enables the overall system to maintain a low amplitude in a complex vibration environment. The rib design of multiple main pedestals makes the vibration path more complex, and the vibration energy is dispersed into ribs in different directions and at different angles. The vibration cancellation effects of each rib will be superimposed together to form a comprehensive vibration weakening effect. Due to the angle between each rib, these angles make the vibrations between the ribs not completely synchronous, and can more effectively cancel the vibration through different phases and directions. Through the above design, the overall amplitude of the system can be significantly reduced, ensuring that the vibration of the system remains within the effective working range under various complex working conditions. Amplitude sensors are provided on the base 1 and the machine base. The "rice"-shaped ribs 11 are evenly provided with circular through holes, and vibration filtering blocks are matched with the through holes.

[0046] Through simulation with CAE software for the above structure, the Figure 3 comparative data are obtained, where 3000 Hz refers to the vibration frequency when the head speed is 180,000 r / min; 3250 Hz is the vibration frequency at 190,000 r / min; 3500 Hz is the vibration frequency at 200,000 r / min.

[0047] Figures 4 - 7 Among them, Frequency represents the frequency value, and Displancement(Grids) represents the deformation value. The green curve represents the force condition using this solution, and the red curve represents the force condition without using this solution. Figure 4It is the total deformation curve graph detected under the combined force acting on the three axes of X, Y, and Z at a frequency of 3000 - 3500 Hz. It can be seen from the curve graph that the force-bearing situation of adopting this solution is better than that of not adopting this solution.

[0048] Figure 5 It is the force-bearing situation of the X-axis at a frequency of 3000 - 3500 Hz. The force-bearing situation of adopting this solution is better than that of not adopting this solution.

[0049] Figure 6 It is the force-bearing situation of the Y-axis at a frequency of 3080 - 3230 Hz. The force-bearing situation of adopting this solution is better than that of not adopting this solution.

[0050] Figure 7 It is the force-bearing situation of the Z-axis in the frequency bands of 3000 Hz - 3120 Hz and 3290 Hz - 3500 Hz. The force-bearing situation of adopting this solution is better than that of not adopting this solution.

[0051] A vibration filtering control method for a wafer chamfering machine includes the following steps:

[0052] a: The amplitude sensor collects real-time amplitude values;

[0053] b: When the real-time amplitude value is greater than 0.003 mm, the control system performs vibration filtering control calculation to calculate the number and position of vibration filtering blocks that need to be increased or decreased;

[0054] c: According to the vibration filtering block arrangement information given by the control system, increase or decrease the vibration filtering blocks at the corresponding positions;

[0055] The calculation formula of the control system is as follows:

[0056]

[0057] The main function of the vibration filtering block is to change the vibration characteristics of the system by increasing the local mass and adjusting the local stiffness. Based on the vibration theory, we can model the influence of the vibration filtering block on the system as a change in the local mass m i and the local stiffness k i of the system.

[0058] Amplitude adjustment formula: The total amplitude A can be calculated by the following formula:

[0059]

[0060] k is the total stiffness of the system, including the stiffness of all rib plates and vibration filtering blocks.

[0061] m is the total mass of the system, including the mass of rib plates and vibration filtering blocks.

[0062] Assume there are n vibration filtering blocks on the rib plate, and the position of each vibration filtering block is x i and stiffness k i as well as mass m i all contribute to the total amplitude of the system.

[0063] Mass of the vibration filtering block:

[0064] Stiffness of the vibration filtering block:

[0065] where m current and k current are the total mass and total stiffness of the current rib plate respectively.

[0066] Adjustment formula for the position and number of vibration filtering blocks

[0067] To determine the position and number of vibration filtering blocks to achieve the target amplitude A target , we need to reverse-derive:

[0068] Adjust the vibration filtering blocks by quantity

[0069] We assume that the mass and stiffness of all vibration filtering blocks are the same, that is, the mass of each vibration filtering block is m b , and the stiffness is k b . When adding n vibration filtering blocks on the rib plate, the changes in total mass and stiffness are:

[0070] m total = m current + n * m b

[0071] k total = k current + n * k b

[0072] Substitute into the total amplitude formula:

[0073]

[0074] Solve the equation to determine the number n of required vibration filtering blocks:

[0075]

[0076] Adjust the vibration filtering blocks by position

[0077] The position of the vibration filtering block affects the action of the vibration filtering block on the local stiffness and mass of the rib plate. Assume the influence functions of the position x i on the system stiffness and mass are f k (x i ) and f m (x i ), then the stiffness and mass of the system can be written as:

[0078]

[0079]

[0080] Substitute into the total amplitude formula for adjustment:

[0081]

[0082] Position selection: By adjusting the functions f x (x i ) and d m (x i ), the best position of the vibration filtering block can be selected to optimize the amplitude control. Generally, the vibration filtering block should be placed at a position with stronger vibration response (such as the vibration peak position) to achieve better vibration filtering effect.

[0083] Quantity control: Use the above formula to calculate the required number of vibration filtering blocks and adjust according to the actual design objectives and physical space limitations.

[0084] Example calculation

[0085] Assume that the amplitude of the current system is 0.004 mm and the target amplitude is 0.003 mm. Assume that the mass m b and stiffness k b of each vibration filtering block are known, and the position functions f x (x i ) = 1 and f m (x i ) = 1. We can determine the number n of vibration filtering blocks and their possible positions x i .

[0086] The above are only the embodiments of the present invention. Common knowledge such as specific structures and characteristics known in the solution is not described in detail here. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can still be made, and these should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the present invention. The specific implementation manners and the like recorded in the specification can be used to explain the content of the claims.

Claims

1. A vibration filtering control structure for a wafer chamfering machine, comprising: The base and the machine base are cast, and both the base and the machine base are hollow structures. The machine base is fixed on the base; a "rice"-shaped rib plate is provided in the space where the base is hollow; the machine base includes an independent main machine base and a suspension machine base. The hollow part of the main machine base is provided with a "cross"-shaped rib plate, and the hollow part of the suspension machine base is provided with an "X"-shaped rib plate; amplitude sensors are provided on the base and the machine base; the "rice"-shaped rib plate is evenly provided with circular through holes, and vibration filtering blocks are matched with the through holes; when the control structure works, the amplitude sensors collect real-time amplitude values; when the real-time amplitude value is greater than 0.003 mm, vibration filtering control calculation is carried out according to the following formula to calculate the number and position of the vibration filtering blocks that need to be increased or decreased. The calculation formula is as follows: Wherein, A: the amplitude of the whole chamfering machine; F0: the amplitude generated by the machine head; k: the stiffness of the chamfering machine base; m: the mass of the chamfering machine; ω: the angular velocity of the machine head, ω = 2πf, where f is the working frequency of the machine head; c: the damping coefficient. According to the vibration filtering block arrangement information given by the control system, the vibration filtering blocks at the corresponding positions are increased or decreased.

2. The vibration filtering control structure of the wafer chamfering machine according to claim 1, wherein: The "rice"-shaped rib plate is provided with square through holes.

3. The vibration filtering control structure of the wafer chamfering machine according to claim 2, characterized in that: The axial direction of the "cross"-shaped rib plate is parallel to the axial direction of the main machine head.

4. The vibration filtering control structure of the wafer chamfering machine according to claim 3, wherein: The height of the hollow part of the machine base is 1 / 5 - 1 / 4 of the height of the whole machine base.

5. The vibration filtering control structure of the wafer chamfering machine according to claim 4, characterized in that: At least two main machine bases are provided, and the rib plates in the X direction of the "cross"-shaped rib plates of each main machine base are not parallel, and the rib plates in the Y direction are parallel.

6. Wafer chamfering machine, characterized by: It includes the vibration filtering control structure of the wafer chamfering machine according to any one of claims 1 - 5.

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