Die body for plane CT geometric calibration and plane CT scanning device

Abstract

The utility model provides a die body for plane CT geometric calibration and a plane CT scanning device, the die body comprises a base body and a plurality of pairs of calibration small balls arranged on the base body and used for calibration, and the plurality of pairs of calibration small balls are configured to be of a two-layer structure; the base body is arranged on an object placing surface of a plane CT objective table, and a sphere center connecting line of each pair of calibration small balls is perpendicular to a detector receiving plane of the plane CT. The device is simple in structure, high in precision and convenient to operate, and can be matched with a geometric correction algorithm to quickly realize registration work so as to improve registration efficiency.

Description

Technical Field

[0001] This utility model relates to the field of industrial nondestructive testing, and in particular to a phantom for geometric calibration of planar CT and a planar CT scanning device. Background Technology

[0002] X-ray imaging is widely used in medical diagnostics and industrial inspection. In the field of industrial non-destructive testing, semiconductor packaging testing, as a key step in integrated circuit manufacturing, directly affects product yield and reliability due to its testing accuracy. With the development of semiconductor devices towards higher density and three-dimensional stacking, and the widespread adoption of advanced packaging technologies such as ball grid arrays (BGA) and system-in-package (SiP), traditional two-dimensional X-ray inspection technology (2D AXI) is no longer sufficient to meet the needs of detecting micron-level solder joint defects. Against this backdrop, three-dimensional automated X-ray inspection (3D AXI) technology, with its tomographic imaging advantages, has become a core technology for quality control in the semiconductor packaging and testing field. Traditional circumferential CT scanning equipment is difficult to scan PCBs with large dimensions. Therefore, planar CT scanning is needed to better adapt to the shape and size of PCBs, improving imaging quality and inspection accuracy.

[0003] However, in planar CT systems, the X-ray source and detector move in two separate planes, creating a coordinate registration problem that requires geometric correction. Current technology typically achieves this through mechanically adjusting the planarity, but the horizontal X and Y coordinate positions are difficult to measure precisely because the focal spot position within the X-ray source cannot be accurately measured. Furthermore, the registration accuracy is <30μm, making it difficult to achieve entirely through mechanical assembly and tuning. Therefore, a phantom is needed for auxiliary calibration. Utility Model Content

[0004] In view of the shortcomings of the prior art described above, the technical problem to be solved by this utility model is to provide a phantom and a planar CT scanning device for planar CT geometric calibration, which can effectively improve the accuracy of planar CT geometric calibration and reduce the calibration workload.

[0005] This invention provides a phantom for geometric calibration of planar CT, comprising a base and multiple pairs of calibration spheres disposed on the base, wherein the multiple pairs of calibration spheres are configured as a two-layer structure; the base is placed on the placement surface of the planar CT stage, and the line connecting the centers of each pair of calibration spheres is perpendicular to the detector receiving plane of the planar CT.

[0006] Preferably, the substrate is integrally formed, and the substrate is provided with two layers of calibration holes for placing the calibration ball: a first layer of calibration holes and a second layer of calibration holes.

[0007] Preferably, the substrate includes a first part and a second part, wherein the first part is adjustablely disposed on the second part, or the second part is adjustablely disposed on the first part; the first part is provided with a first layer of calibration holes for placing calibration balls, and the second part is provided with a second layer of calibration holes for placing calibration balls; the relative positions of the first part and the second part are adjusted so that the center lines of the first layer of calibration holes and the second layer of calibration holes coincide.

[0008] Preferably, the first part is provided with a sliding groove, and the second part is provided with a slider that matches the sliding groove; or, the first part is provided with a slider, and the second part is provided with a sliding groove that matches the slider.

[0009] Preferably, the depth and diameter of the calibration hole are the same.

[0010] Preferably, the calibration holes in each layer are arranged in an array, and the adjacent calibration holes are equidistant.

[0011] Preferably, the deviation range of the center distance between adjacent calibration holes is 0 mm to 0.1 mm.

[0012] Preferably, the substrate is made of a transparent material, and the calibration microsphere has a significantly different X-ray absorption capacity from the substrate.

[0013] Another aspect of this utility model provides a planar CT scanning device, including a stage, a movable X-ray source, and a movable detector. The stage is fixed between the X-ray source and the detector. It also includes a phantom for planar CT geometric calibration as described in any of the above embodiments, the phantom being placed on the placement surface of the stage.

[0014] As described above, the phantom and planar CT scanning device for planar CT geometric calibration disclosed in this utility model have the following beneficial effects:

[0015] This invention utilizes multiple pairs of calibration spheres mounted on a substrate, arranged in a two-layer structure. The substrate is placed on the horizontal surface of a planar CT stage, ensuring that the line connecting the centers of each pair of calibration spheres is perpendicular to the detector receiving plane of the planar CT scanner. The phantom is scanned by synchronously moving the planar CT X-ray source and detector, obtaining the projection image of the calibration spheres on the detector receiving plane. Combined with a geometric calibration algorithm, the deviation between the moving planes of the X-ray source and detector is calculated. Based on this deviation, the X-ray source or detector is adjusted so that the focal point of the X-ray source coincides with the center point of the detector receiving plane, thus eliminating the deviation and completing registration. This invention features a simple structure, high precision, and convenient operation, and can quickly achieve registration with the help of a geometric correction algorithm, thereby improving registration efficiency. Attached Figure Description

[0016] Figure 1 This is a three-dimensional schematic diagram of the phantom for planar CT geometric calibration provided in Embodiment 1 of this utility model;

[0017] Figure 2 for Figure 1 Top view;

[0018] Figure 3 This is a three-dimensional schematic diagram of the phantom for planar CT geometric calibration provided in Embodiment 2 of this utility model;

[0019] Figure 4 for Figure 3 Top view;

[0020] Figure 5 This is a three-dimensional schematic diagram of the phantom for planar CT geometric calibration provided in Embodiment 3 of this utility model;

[0021] Figure 6 for Figure 5 Top view;

[0022] Figure 7 This is a three-dimensional schematic diagram of the phantom for planar CT geometric calibration provided in Embodiment 4 of this utility model;

[0023] Figure 8 for Figure 7 Exploded view;

[0024] Figure 9 An exploded view of the phantom for planar CT geometric calibration provided in Embodiment 5 of this utility model;

[0025] Figure 10 A three-dimensional schematic diagram of a novel planar CT scanning device provided in an embodiment of the present invention;

[0026] Figure 11 The phantom projection effect diagram of the planar CT geometric calibration provided in Embodiment 1 of this utility model;

[0027] Figure 12 A schematic diagram illustrating the working principle of the planar CT calibration phantom provided by this utility model.

[0028] Explanation of reference numerals in the attached figures:

[0029] 100, Substrate; 110, First component; 111, Slide groove; 120, Second component; 121, Slider; 200, Calibration ball; 300, Calibration hole; 310, First layer calibration hole; 320, Second layer calibration hole; 400, Stage; 500, X-ray source; 600, Detector; 610, Detector receiving plane. Detailed Implementation

[0030] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification.

[0031] It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation of this utility model. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of this utility model, should still fall within the scope of the technical content disclosed in this utility model. Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity of description and are not intended to limit the scope of implementation of this utility model. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of implementation of this utility model.

[0032] It should be noted that, as Figure 11 As shown, a planar CT includes a stage 400 for placing a phantom, a movable X-ray source 500, and a movable detector 600, wherein the stage 400 is fixed between the X-ray source 500 and the detector 600 so that the X-ray source 500 and the detector 600 can move from the origin (initial position) of the device to scan the phantom placed on the stage 400.

[0033] Example 1

[0034] like Figure 1 , Figure 2 and Figure 10 As shown, a phantom for geometric calibration of planar CT includes a base 100 and multiple pairs of calibration spheres 200 disposed on the base 100, wherein the multiple pairs of calibration spheres 200 are configured as a two-layer structure. The base 100 is placed on the placement surface of the planar CT stage 400, and the line connecting the centers of each pair of calibration spheres 200 is perpendicular to the receiving plane of the planar CT detector to ensure the projection accuracy of each pair of calibration spheres 200, facilitating the analysis and calculation of the projected image formed by the geometric calibration algorithm to obtain the deviation between the horizontal planes where the X-ray source 500 and the detector 600 are located. It should be noted that the shape of the phantom includes, but is not limited to, a cube, a cuboid, a cylinder, a frustum, a truncated cone, etc., which can be determined according to the specific working conditions.

[0035] During use, the X-ray source 500 and detector 600 must be leveled so that the moving plane containing them is horizontal. The X-ray source and detector are leveled and moved to a predetermined position, which is the zero point position of the X-ray source 500 and detector 600, i.e., the initial position. Simultaneously, the stage's placement surface is adjusted to a horizontal state, and the calibration phantom is placed vertically at any position on the placement surface. The flatness of the placement surface is 0.1 μm to reduce tilting errors caused by the phantom being placed on the placement surface. The flatness of the working surface of the base 100 in contact with the placement surface is 0.01 mm, and the parallelism between the working surface and the placement surface is 0.02 mm. Turn on the X-ray source 500. By mechanically tuning the tube voltage and current of the X-ray source 500, adjust its power to a lower level (while ensuring a small focal spot). Simultaneously move the X-ray source 500 and detector 600 to acquire preliminary projection data of the calibration spheres, obtaining projection images (e.g., images of the X-ray source passing through the calibration phantom and each layer of calibration spheres projected onto the detector) on the detector. Figure 11 (As shown). Then, the acquired projection image is processed using a geometric calibration algorithm to obtain the projection coordinates of each calibration ball. Based on the projection coordinates of each calibration ball, the calibration balls are paired to determine the line connecting the projection coordinates of each pair of calibration balls. Based on the obtained line connecting the projection coordinates, the coordinates of the perpendicular point of the X-ray source focus in the planar CT scan within the detector receiving plane are determined. Finally, the position of the X-ray source or detector is adjusted so that the perpendicular point of the X-ray source coincides with the center point of the detector plane, completing the calibration process.

[0036] Furthermore, such as Figure 1 and Figure 2As shown, the phantom is integrally formed, and the base 100 has calibration holes 300 for placing calibration balls. Each calibration hole 300 includes a first layer of calibration holes 310 and a second layer of calibration holes 320. The first layer of calibration holes 310 and the second layer of calibration holes 320 are arranged in layers on the base 100, with each layer corresponding to the other. The line connecting the centers of the calibration balls placed in the first layer of calibration holes 310 and the calibration balls placed in the second layer of calibration holes 320 is perpendicular to the detector receiving plane 610 of the planar CT scanner. In this embodiment, preferably, there are five first layer calibration holes 310 and five second layer calibration holes 320. This ensures sufficient feature points (preventing mismatches) while avoiding excessive points that increase computational complexity, similar to fingerprint recognition which requires enough feature points but not too many. Point P is the focal point of the X-ray source. The first reference plane is the upper surface of the calibration phantom, and the second reference plane is the lower surface of the calibration phantom. The center point of the detector receiving plane 610 is denoted as O. When the X-ray source scans the phantom at point P, the calibration balls on the phantom are projected onto the detector receiving plane to form a projected image. Based on the set grayscale threshold parameters, the centroid coordinates of the 10 balls in the projected image are obtained. Two sets of vertically perpendicular calibration balls, A1 and A2, and B1 and B2, are selected. Their imaging points on the detector receiving plane are A1', A2' and B1', B2', respectively. Since the line connecting A1 and A2 is perpendicular to the detector plane, plane A1A2A1'A2' is perpendicular to the detector receiving plane 610. Similarly, planes B1B2B1'B2' are also perpendicular to the detector receiving plane 610. The intersection line PO' of planes A1A2A1'A2' and B1B2B1'B2' is perpendicular to the detector receiving plane. Therefore, point O' is the perpendicular point of the X-ray source. Consequently, the extension of the line connecting points A1' and A2' intersects the extension of the line connecting points B1' and B2' at point O'. The line connecting the projection points C1'C2' of any third perpendicular sphere C1C2 also intersects at point O'. Line segment OO' represents the horizontal distance between the perpendicular point of the X-ray source and the center of the detector receiving plane. The coordinates (x1, y1) and (x2, y2) of point O' are obtained. The absolute values ​​of (x1-x2) and (y1-y2) are used as compensation values ​​for subsequent movement of the X-ray source or detector. It should be noted that whether the interior of the phantom is solid or hollow in this embodiment is not limited here and can be determined according to the actual working conditions.

[0037] Specifically, such as Figure 12As shown, select the line A1'A2' connecting the projected coordinates of one pair of calibration balls on the detector receiving plane. Select the line B1'B2' connecting the projected coordinates of any pair of calibration balls from the remaining pairs. Extend the lines connecting A1'A2' and B1'B2' to make them intersect, obtaining the first intersection point O'1 on the detector receiving plane. The coordinates of point O'1 are (x1, y1). Select the line C1'C2' connecting the projected coordinates of the remaining pair of calibration balls. Extend the lines connecting A1'A2' and C1'C2' to make them intersect, obtaining the second intersection point O'2. The coordinates of O'2 are (x2, y2). Repeat this step, traversing the line, to obtain the third intersection point O'3 (x3, y3); the fourth intersection point O'4 (x4, y4); and the fifth intersection point O'5 (x5, y5). Calculate the average of the X-axis and Y-axis coordinates of these five intersection points, as follows:

[0038]

[0039] Obtaining the coordinates (x0, y0) of O'0 can effectively reduce the projection error of the calibration ball.

[0040] Furthermore, the substrate 100 is made of a transparent material, which includes, but is not limited to, plexiglass. Optical resin, acrylic sheets, polycarbonate, etc., can also be selected, as long as the light transmittance of the substrate 100 is greater than 90%. As for the material of the calibration ball 200, this embodiment is not limited, as long as the calibration ball 200 and the substrate 100 have a significant difference in their X-ray absorption capabilities, so that the calibration ball 200 can form a clear projection image after being scanned by the X-ray source 500.

[0041] Furthermore, such as Figure 1 and Figure 2 As shown, the depth and diameter of the calibration hole 300 are the same. Since the depth and diameter of the hole are consistent, the calibration ball will not wobble excessively up and down or left and right in the hole, thereby reducing the measurement error caused by position deviation.

[0042] Furthermore, such as Figure 1 and Figure 2 As shown, taking a cube as an example, each layer of calibration spheres 200 is arranged in an array. In this embodiment, a cross arrangement is preferred, with the spheres in the center and at the four corners. Adjacent calibration holes 300 are equidistant, uniformly covering the detection area to improve calibration accuracy and reduce manufacturing difficulty. To reduce calibration error, the deviation range of the center-to-center distance between adjacent calibration holes is 0 mm to 0.01 mm.

[0043] Example 2

[0044] like Figure 3 and Figure 4 As shown, Example 2 is largely the same as Example 1, except that, taking the substrate 100 as preferably a cube, each layer of calibration spheres on the substrate 100 is arranged in an array. In this example, a cross arrangement is preferred, with the center and four sides arranged in the array. This makes the data collected at different positions representative, thereby more accurately reflecting the geometric characteristics of the calibration sphere projection and improving calibration accuracy. The specific calibration process is detailed in Example 1 and will not be repeated here.

[0045] Example 3

[0046] like Figure 5 and Figure 6 As shown, Embodiment 3 is largely the same as Embodiment 1, except that, taking the substrate 100 as preferably a cube, each layer of calibration spheres on the substrate 100 is arranged in an array. In this embodiment, the number of calibration spheres 200 in each layer is preferably 3, and these 3 spheres are arranged in a triangular array, which can reduce data redundancy, simplify the data processing process, and improve calibration efficiency. For details of the calibration process, please refer to Embodiment 1, which will not be repeated here.

[0047] Example 4

[0048] like Figure 7 and Figure 8 As shown, Embodiment 4 is largely the same as Embodiment 1, except that the base 100 includes a first part 110 and a second part 120. The first part 110 is adjustablely disposed on the second part 120, or the second part 120 is adjustablely disposed on the first part 110. The first part 110 has a first layer of calibration holes 310 for placing calibration balls, and the second part 120 has a second layer of calibration holes 320 for placing calibration balls. This adjustable configuration includes, but is not limited to, sliding adjustment, rotational adjustment, and directional adjustment.

[0049] In use, by adjusting the relative positions of the first split 110 and the second split 120, the centerline of the first calibration hole 310 and the centerline of the second calibration hole 320 are made to coincide, ensuring that the centers of the calibration balls in the first calibration hole 310 and the calibration balls in the second calibration hole 320 are connected to the detector receiving plane 610 perpendicular to the plane CT. For details of the calibration process, please refer to Embodiment 1, which will not be repeated here.

[0050] Furthermore, the first split 110 is provided with a groove 111, and the second split 120 is provided with a slider 121 that matches the groove. In use, the second split 120 is placed on the placement surface of the stage. By sliding the first split 110, the relative positions of the first split 110 and the second split 120 are adjusted so that the centers of the calibration balls in the first calibration hole 310 and the calibration balls in the second calibration hole 320 are connected to the detector receiving plane 610 perpendicular to the plane CT, thereby reducing the calibration error of the calibration balls. It should be noted that the overall shape and style of the slider 121 and the groove 111 are not limited in this embodiment, as long as they can be used to adjust the relative positions between the first split 110 and the second split 120.

[0051] Example 5

[0052] like Figure 9 As shown, Embodiment 5 is largely the same as Embodiment 4, except that the first split 110 is provided with a slider 121, and the second split 120 is provided with a groove 111 that matches the slider 121. In use, the second split 120 is placed on the stage surface. By sliding the first split 110, the relative positions of the first split 110 and the second split 120 are adjusted so that the centers of the calibration balls in the first calibration hole 310 and the calibration balls in the second calibration hole 320 are connected to the detector receiving plane 610 perpendicular to the planar CT, thereby reducing the calibration error of the calibration balls. For a detailed calibration process, please refer to Embodiment 1, which will not be repeated here.

[0053] like Figure 10 As shown, this utility model also provides a planar CT scanning device, including a stage 400, a movable X-ray source 500 and a movable detector 600. The stage 400 is fixed between the X-ray source 500 and the detector 600. It also includes a phantom for planar CT geometric calibration as described in any of the above embodiments, and the phantom is placed on the placement surface of the stage 400.

[0054] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A phantom for planar CT geometry calibration, characterized in that, The phantom includes a base (100) and a plurality of pairs of calibration balls (200) arranged on the base, and the plurality of pairs of calibration balls are configured as a two-layer structure; the base (100) is placed on a placement surface of a planar CT loading platform, and a line connecting the centers of each pair of calibration balls (200) is perpendicular to a detector receiving plane (610) of the planar CT.

2. Phantom for planar CT geometry calibration according to claim 1, characterized in that The base (100) is integrally arranged, and the base (100) is provided with first-layer calibration holes (310) and second-layer calibration holes (320) for placing the calibration balls (200).

3. Phantom for planar CT geometry calibration according to claim 1, characterized in that The base (100) includes a first part (110) and a second part (120), and the first part (110) is adjustably arranged on the second part (120). Alternatively, the second part (120) is adjustably arranged on the first part (110). The first part (110) is provided with first-layer calibration holes (310) for placing calibration balls, and the second part is provided with second-layer calibration holes (320) for placing calibration balls; the relative positions of the first part (110) and the second part (120) are adjusted so that the axial center lines of the first-layer calibration holes (310) and the second-layer calibration holes (320) coincide.

4. Phantom for planar CT geometry calibration according to claim 3, characterized in that The first part (110) is provided with a sliding groove (111), and the second part (120) is provided with a sliding block (121) matched with the sliding groove; alternatively, the first part (110) is provided with a sliding block (121), and the second part (120) is provided with a sliding groove (111) matched with the sliding block.

5. Phantom for planar CT geometry calibration according to any of claims 1 to 4, characterized in that The light transmittance of the base (100) is greater than 90%.

6. Phantom for planar CT geometry calibration according to any of claims 2-4, characterized in that, The hole depth of each calibration hole (300) is the same as the hole diameter size.

7. Phantom for planar CT geometry calibration according to any of claims 2-4, characterized in that, Each layer of calibration holes (300) is arranged in an array, and adjacent calibration holes (300) are equidistant.

8. Phantom for planar CT geometry calibration according to claim 7, characterized in that The deviation range of the center distance between adjacent calibration holes (300) is 0mm-0.01mm.

9. Phantom for planar CT geometry calibration according to any of claims 1-4, characterized in that, The base is made of transparent material, and the absorption X-ray capacity of the calibration balls (200) and the base (100) is significantly different.

10. A flat panel CT scanning apparatus comprising a support table (400), a movable radiation source (500) and a movable detector (600), the support table (400) being fixed between the radiation source (500) and the detector (600), characterized in that, The phantom also includes a phantom for planar CT geometric calibration according to any one of claims 1-9, and the phantom is placed on the placement surface of the loading platform (400).

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