An automatic focusing mechanism for following the height of a curved surface for ultrasonic testing

Abstract

This application belongs to the field of ultrasonic testing equipment, specifically disclosing an automatic focusing mechanism for ultrasonic testing that follows the curvature of a curved surface. The mechanism includes a linear module, a frameless motor, and an automatic focusing module. The automatic focusing module is connected to the lead screw structure of the linear module, and the frameless motor is also connected to the linear module. The automatic focusing module drives the lead screw structure of the linear module to reciprocate along the Z-axis to move closer to or further away from the sample to be tested. The automatic focusing module includes a voice coil motor and an ultrasonic probe. The voice coil motor is fixedly connected to the lead screw structure, and the ultrasonic probe is fixedly connected to the voice coil motor. The voice coil motor drives the ultrasonic probe to reciprocate along the Z-axis according to the curvature of the sample to be tested. This application enables the dynamic maintenance of a constant focal length for the ultrasonic probe, ensuring that both the center and edge areas of the product under test can be detected completely and clearly, thereby obtaining a clear acoustic image and achieving consistent imaging across the entire field of view.

Description

Technical Field

[0001] This application belongs to the field of ultrasonic testing equipment, and more specifically, relates to an automatic focusing mechanism for ultrasonic testing that follows the height of a curved surface. Background Technology

[0002] A scanning acoustic microscope (SAM) is a non-destructive testing device that uses ultrasonic pulse echoes to visualize the internal structure of materials. Traditional SAMs typically employ mechanical scanning, where a precision linear motion mechanism drives an ultrasonic transducer (probe) to move back and forth across a horizontal plane in a Cartesian coordinate system above the sample, acquiring echo signals at various points on the sample and combining them to form a complete acoustic image. Currently, SAMs suffer from the following problems: 1) Fixed Z-axis scanning: The probe height is constant, suitable for flat samples, but cannot accommodate wafer warping, resulting in blurred images; 2) Mechanical servo focusing: Servo motors or piezoelectric ceramics are used to adjust the Z-axis movement, but the response speed is slow (>10ms), affecting scanning efficiency; 3) Multi-probe parallel scanning: Increases speed but is costly, and defocusing issues still exist. Furthermore, in traditional scanning acoustic microscopy, if the wafer under test has a large warp (e.g., >100μm), the probe with a fixed Z-axis height will cause the following problems: 1) Defocusing: the distance between the probe and the sample surface fluctuates, the focus of the ultrasonic beam deviates from the ideal position, and the imaging of the edge area is blurred; 2) Echo signal attenuation: the difference in sound path causes inconsistent signal intensity, affecting the sensitivity of defect detection; 3) Uneven coupling fluid thickness: the change in water layer thickness leads to acoustic impedance mismatch and produces artifacts.

[0003] In summary, existing scanning acoustic microscopes have the following technical defects: 1) Uneven imaging clarity: warping causes the ultrasonic focus to deviate, resulting in decreased resolution in the edge areas; 2) Low scanning efficiency: traditional focusing mechanisms have high inertia and cannot meet the requirements of high-speed scanning; 3) High system complexity: multi-probe solutions require complex calibration and have high maintenance costs. Utility Model Content

[0004] To address the shortcomings of existing technologies, the purpose of this application is to provide an automatic focusing mechanism for ultrasonic testing that follows the height of curved surfaces, aiming to solve the problems of uneven imaging clarity, low imaging efficiency, and high maintenance costs of existing ultrasonic scanning microscopes for samples with large warpage.

[0005] To achieve the above objectives, this application provides an automatic focusing mechanism for ultrasonic testing that follows the curvature of a curved surface, comprising: a linear module, a frameless motor, and an automatic focusing module. The automatic focusing module is connected to the lead screw structure of the linear module, and the frameless motor is connected to the linear module, driving the lead screw structure of the linear module to reciprocate along the Z-axis to move closer to or further away from the sample to be tested. The automatic focusing module includes a voice coil motor and an ultrasonic probe. The voice coil motor is fixedly connected to the lead screw structure, and the ultrasonic probe is fixedly connected to the voice coil motor. The voice coil motor is used to drive the ultrasonic probe to reciprocate along the Z-axis according to the curvature of the sample to be tested.

[0006] Furthermore, the linear module is a lead screw driven linear module.

[0007] Furthermore, the focusing accuracy of the voice coil motor is ±0.5μm.

[0008] Furthermore, a first connecting plate is fixed to the lead screw structure of the linear module, and the voice coil motor is fixed to the first connecting plate; a second connecting plate is provided on the voice coil motor, and the first connecting plate and the second connecting plate are fixedly connected.

[0009] Furthermore, the second connecting plate is a pair of L-shaped connecting plates, one side of which is connected to both ends of the voice coil motor along the Z-axis, and the other side of which is connected to both ends of the first connecting plate along the Z-axis.

[0010] Furthermore, it also includes a linear guide rail, which is fixed to the first connecting plate; the ultrasonic probe is connected to the linear guide rail via a third connecting plate, and the third connecting plate is also fixedly connected to the mover of the voice coil motor; the mover of the voice coil motor can reciprocate along the Z-axis direction to drive the ultrasonic probe to reciprocate on the linear guide rail.

[0011] Furthermore, the first connecting plate, the second connecting plate, and the third connecting plate are all made of aluminum alloy.

[0012] Furthermore, the motion response time of the voice coil motor is no greater than 1ms.

[0013] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: (1) This application provides an ultrasonic testing robot structure for adaptive adjustment in the Z-axis direction of a curved surface. It consists of a linear module, a frameless motor, and an autofocus module. The autofocus module includes a voice coil motor and an ultrasonic probe. Specifically, the detection height in the Z-axis direction is adjusted slightly by the coordinated movement and operation of the voice coil motor and the ultrasonic probe. The high-precision ultrasonic probe is used to measure distance by direct drive of the voice coil motor, thereby achieving ultra-high focusing accuracy. Furthermore, the constant focal length of the ultrasonic probe is dynamically maintained by the dual reciprocating motion of the linear module and the voice coil motor in the Z-axis direction, ensuring that the center and edge areas of the product under test can be detected completely and clearly to obtain a clear acoustic image and achieve full-field imaging consistency.

[0014] (2) This application has a large adaptive adjustment range, which can be compatible with products with planar deformation or irregular surface height. It has a fast response speed and high positioning accuracy. The voice coil motor of this application has electromagnetic direct drive characteristics, which greatly shortens the motion response time and can effectively compensate for the defocusing problem caused by wafer warping, avoiding the time increase introduced by frequent mechanical focusing actions. It can handle wafers with warping up to 200μm and can adapt to the detection needs of curved samples, such as flexible displays, optical lenses, etc.

[0015] (3) This application uses a small-sized and lightweight screw drive linear module, voice coil motor and frameless motor. The first and second connecting plates for connecting and fixing the voice coil motor and ultrasonic probe are made of aluminum alloy, which realizes the lightweight and low cost of the overall automatic focusing mechanism that follows the height of the curved surface. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of an automatic focusing mechanism for ultrasonic testing that follows the height of a curved surface. Figure 2 This is an exploded structural diagram of an automatic focusing mechanism for ultrasonic testing that follows the height of a curved surface.

[0017] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-Linear module; 11-First connecting plate; 2-Frameless motor; 3-Voice coil motor; 31-Second connecting plate; 4-Linear guide rail; 5-Ultrasonic probe; 51-Third connecting plate. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0019] In this article, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The symbol " / " in this article indicates that the related objects are in an "or" relationship; for example, A / B means A or B.

[0020] The terms "first" and "second," etc., used in the specification and claims herein are used to distinguish different objects, not to describe a specific order of objects. For example, "first response message" and "second response message," etc., are used to distinguish different response messages, not to describe a specific order of response messages.

[0021] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0022] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0023] The embodiments of this application are described below with reference to the accompanying drawings.

[0024] This embodiment provides an automatic focusing mechanism for ultrasonic testing that follows the curvature of a curved surface. The mechanism includes a linear module 1, a frameless motor 2, and an automatic focusing module. The automatic focusing module is connected to the lead screw structure of the linear module 1. The frameless motor 2 is connected to the linear module 1 and drives the lead screw structure of the linear module 1 to reciprocate along the Z-axis to move closer to or further away from the sample to be tested. The automatic focusing module includes a voice coil motor 3 and an ultrasonic probe 5. The voice coil motor 3 is fixedly connected to the lead screw structure, and the ultrasonic probe 5 is fixedly connected to the voice coil motor 3. The voice coil motor 3 drives the ultrasonic probe 5 to reciprocate along the Z-axis according to the curvature of the sample to achieve automatic focusing of the sample.

[0025] Specifically, in this embodiment, the linear module 1 is a lead screw driven linear module, which is vertically installed above the workpiece inspection platform. A first connecting plate 11 is fixed on the lead screw structure of the lead screw driven linear module, and the first connecting plate 11 can reciprocate up and down with the lead screw structure; a second connecting plate 31 is provided on the voice coil motor 3, and the first connecting plate 11 and the second connecting plate 31 are fixedly connected by bolts.

[0026] In this embodiment, the second connecting plate 31 is a pair of L-shaped connecting plates. One side of the pair of L-shaped connecting plates is aligned and connected to both ends of the voice coil motor 3 along the Z-axis direction, and the other side of each L-shaped connecting plate is aligned and connected to both ends of the first connecting plate 11 along the Z-axis direction.

[0027] In this embodiment, the first connecting plate 11, the second connecting plate 31, and the third connecting plate 51 are all made of aluminum alloy.

[0028] In this embodiment, the automatic focusing mechanism following the height of the curved surface also includes a linear guide rail 4, which is fixed in the middle of the first connecting plate 11; the ultrasonic probe 5 is located directly above the sample to be tested and is fixedly connected to the linear guide rail 4 and the mover of the voice coil motor 3 respectively. The mover of the voice coil motor 3 can reciprocate along the Z-axis direction to drive the ultrasonic probe 5 to reciprocate on the linear guide rail 4.

[0029] Specifically, the linear guide 4 is a cross roller guide with the following specifications: guide length 74mm, positioning accuracy ±0.5μm. During installation, the base of the linear guide 4 is connected to the external support frame of the lead screw drive linear module via M4 screws. The slider of the linear guide 4 is rigidly connected to the mover of the voice coil motor 3. The ultrasonic probe 5 is connected to the slider of the linear guide 4 via the third connecting plate 51, and the preload level of the linear guide 4 is PN (medium preload).

[0030] In this embodiment, the technical parameters of the aforementioned voice coil motor 3 are: peak thrust of 20N, continuous thrust of 5N, stroke of ±10mm, and resolution of 0.1μm. Specifically, the stator of the voice coil motor is connected to the support frame of the lead screw drive linear module through a special mounting plate, and its focusing accuracy is ±0.5μm.

[0031] In this embodiment, the motion response time of the aforementioned voice coil motor 3 is no more than 1ms, which is sufficient to maintain a constant focal length of the ultrasonic probe 5 while driving the ultrasonic probe 5 to move.

[0032] In this embodiment, the ultrasonic probe 5 has an ultrasonic frequency of 100MHz, a resolution of 5μm, a VCM adjustment bandwidth of 500Hz, and a thrust of 10N.

[0033] The frameless motor in this embodiment is an adaptive improvement on the component motor with a reduced size for the specific application scenario of this application. Its structural form is diverse and variable, and will not be described in detail here.

[0034] The automatic focusing mechanism for following the height of the curved surface in this embodiment is connected to an external controller. The external controller can adopt a DSP+FPGA architecture; the drive module is a PWM servo driver with a sampling frequency of 100kHz; the analog output is ±10V, which can be used to control the voice coil motor 3.

[0035] The working principle of the automatic focusing mechanism for following the height of a curved surface provided in this embodiment is as follows: The DSP (Digital Signal Processing) controller moves the ultrasonic probe 5 to a preset origin in the Z-axis direction. The ultrasonic probe 5 emits detection pulses to the sample and receives echo signals to calculate the time of flight. The actual distance from the probe to the sample is calculated using the echo signals. During the position adjustment phase of the ultrasonic probe 5, the DSP controller calculates the position deviation of the ultrasonic probe based on the actual distance using existing calculation methods and outputs a PWM control signal to drive the voice coil motor 3 to complete the position adjustment within 1ms, ensuring stable probe focal length. When the voice coil motor 3 reciprocates along the Z-axis, it drives the ultrasonic probe 5 to reciprocate synchronously to adjust its probe height to compensate for the position deviation. During the compensation process, the ultrasonic probe 5 can automatically focus and achieve a constant focal length, thereby obtaining a high-definition detection image.

[0036] In summary, compared to traditional non-destructive testing equipment with a focusing accuracy of only ±20μm, a response speed of 10~20ms, blurry imaging edges, and applicability only to flat samples, the automatic focusing mechanism for following the surface height of this application achieves a focusing accuracy of ±0.5μm, a response speed of 1ms, clear imaging across the entire field of view, and is applicable to the testing of warped wafers or other curved surfaces.

[0037] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0038] Furthermore, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0039] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixed connection" refers to a connection where the relative positional relationship remains unchanged after connection. "Rotary connection" refers to a connection where the components can rotate relative to each other after connection. "Sliding connection" refers to a connection where the components can slide relative to each other after connection. The directional terms mentioned in the embodiments of this application, such as "top," "bottom," "inner," "outer," "left," and "right," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of this application, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0040] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are limitations specific to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are permissible; approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. "A and B are perpendicular" means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0041] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A height-following automatic focusing mechanism for ultrasonic testing, characterized in that, include: The system comprises a linear module (1), a frameless motor (2), and an autofocus module. The autofocus module is connected to the lead screw structure of the linear module (1). The frameless motor (2) is connected to the linear module (1) and is used to drive the lead screw structure of the linear module (1) to move the autofocus module back and forth along the Z-axis to approach or move away from the sample to be tested. The autofocus module includes a voice coil motor (3) and an ultrasonic probe (5). The voice coil motor (3) is fixedly connected to the lead screw structure, and the ultrasonic probe (5) is fixedly connected to the voice coil motor (3). The voice coil motor (3) is used to drive the ultrasonic probe (5) to move back and forth along the Z-axis according to the curvature of the sample to be tested.

2. The automatic focusing mechanism for following the height of a curved surface as described in claim 1, characterized in that, The linear module (1) is a lead screw driven linear module.

3. The automatic focusing mechanism for following the height of a curved surface as described in claim 1, characterized in that, The focusing accuracy of the voice coil motor (3) is ±0.5μm.

4. The automatic focusing mechanism for following the height of a curved surface as described in claim 1, characterized in that, The linear module (1) has a first connecting plate (11) fixed on its lead screw structure, and the voice coil motor (3) has a second connecting plate (31) fixedly connected to it.

5. The automatic focusing mechanism for following the height of a curved surface as described in claim 4, characterized in that, The second connecting plate (31) is a pair of L-shaped connecting plates. One side of the pair of L-shaped connecting plates is connected to both ends of the voice coil motor (3) along the Z-axis direction, and the other side is connected to both ends of the first connecting plate (11) along the Z-axis direction.

6. The automatic focusing mechanism for following the height of a curved surface as described in claim 4, characterized in that, It also includes a linear guide rail (4), which is fixed on the first connecting plate (11); the ultrasonic probe (5) is connected to the linear guide rail (4) through a third connecting plate (51), and the third connecting plate (51) is also fixedly connected to the mover of the voice coil motor (3). The mover of the voice coil motor (3) can reciprocate along the Z-axis direction to drive the ultrasonic probe (5) to reciprocate on the linear guide rail (4).

7. The automatic focusing mechanism for following the height of a curved surface as described in claim 6, characterized in that, The first connecting plate (11), the second connecting plate (31) and the third connecting plate (51) are all made of aluminum alloy.

8. The automatic focusing mechanism for following the height of a curved surface as described in claim 1, characterized in that, The motion response time of the voice coil motor is no more than 1ms.

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