X-ray inspection system, x-ray imaging accessory, sample holder, kit and method of using an x-ray inspection system

Abstract

An x-ray inspection system (100) comprising an x-ray source (10), an x-ray detector (12), a sample holder comprising a pliable material and a sample holder positioning assembly configured to position the sample holder (20) between the x-ray source (10) and the x-ray detector (12). The sample holder (20) is configured to removably hold a sample for inspection in a fixed position relative to the sample holder and is configured such that, in use, at least one surface of the sample is in contact with the pliable material. The sample holder positioning assembly comprises a rotational drive (28) configured to rotate the sample holder about a rotational axis. This allows the sample to be rotated about the rotational axis such that a series of two-dimensional images can be captured by the x-ray detector which can be used to create a three-dimensional reconstruction of the sample.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to UK Patent Application No. 2008738.3, filed on June 9, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to an X-ray inspection system, an X-ray imaging accessory for an X-ray inspection system, a sample holder for an X-ray inspection system, a kit for an X-ray inspection system, and a method of using an X-ray inspection system. Background Technology

[0004] X-ray inspection systems can be used to inspect samples. By placing the sample between an X-ray source (such as an X-ray tube) and an X-ray detector, a two-dimensional image of a cross-section through the sample can be captured. This image provides detailed information about the sample's internal structure. One industry where X-ray inspection is particularly useful is the manufacture of electronic components, including packaged semiconductor devices. It is useful for inspecting voids, cracks, and misalignments in the conductive elements deposited within electronic components.

[0005] Some X-ray examination systems can be used to perform computed tomography (CT) scans. In CT scans, a series of two-dimensional images are captured across a cross-section of the sample, and between these images, the sample is rotated relative to the X-ray source and the X-ray detector, or vice versa. A three-dimensional reconstruction of the sample can then be calculated by combining these two-dimensional images. For example, three-dimensional reconstruction of the sample allows for three-dimensional analysis of the sample's internal structure, virtual microsectioning, and internal dimension measurements. It can also reduce the need for time-consuming microsectioning analysis of the sample, and additionally or alternatively, it helps identify where microsection preparation and investigation should focus.

[0006] In an X-ray inspection system that rotates a sample relative to an X-ray source and an X-ray detector, the system may include a rotating platform with a rotational actuator for rotating the sample about an axis of rotation. To ensure the most accurate three-dimensional visualization possible, it is desirable that the sample moves only about the axis of rotation. For example, when the sample is rotated to different positions, it is desirable that the sample does not move relative to the axis of rotation under the influence of gravity.

[0007] Currently, unwanted sample movement is reduced by securing one end of the sample to a rotary actuator, for example, using a hot glue gun or clamps. However, securing the sample in this way can be laborious and time-consuming. For example, for accurate 3D visualization, it is desirable for the axis of rotation to pass through the center of the sample. Properly positioning the sample in an X-ray inspection system can be difficult.

[0008] Furthermore, especially if the first sample has already been secured with a hot glue gun, replacing the first sample with a second sample for inspection can be slow and laborious. There is also a risk that the sample may be damaged by the glue from the hot glue gun or by the fixture. Additionally, in the current method, samples must be inspected one at a time. If multiple samples are to be inspected, a technician must replace each sample on-site after each inspection.

[0009] Another drawback of fixing one end of the sample to the rotary actuator is that larger and heavier samples may experience some movement of the free end relative to the fixed end during sample rotation, for example, due to bending of the sample. This bending reduces the accuracy of the computer-generated 3D visualization along the sample length.

[0010] When inspecting samples such as electronic components, especially electronic components, it may be desirable to maximize the magnification of the two-dimensional image captured by the X-ray detector. Magnification can be maximized by positioning the sample as close as possible to the X-ray source. However, the size and shape of each sample used for inspection may vary. Samples may have irregular shapes. To avoid collisions between the sample and the X-ray source or other components of the X-ray system while the sample is rotating, the user must ensure that the X-ray inspection system is correctly set up for each sample. This increases the complexity of using the X-ray inspection system.

[0011] The aim is to provide an X-ray inspection system that is simple and quick to use, allows for the creation of high-quality and accurate 3D reconstructions even when the sample is large or heavy, reduces the risk of collision between the sample and the X-ray inspection system while allowing high magnification, and allows multiple samples to be inspected simultaneously or in a single operation. Summary of the Invention

[0012] This invention provides an X-ray examination system, a sample holder assembly for an X-ray examination system, a kit, and a method of using an X-ray examination system, according to the appended independent claims which should be referenced. Preferred or advantageous features of the invention are defined in the dependent claims.

[0013] In a first aspect, an X-ray inspection system is provided, comprising an X-ray source, an X-ray detector, a sample holder, and a sample holder positioning assembly, wherein the sample holder comprises a flexible material. The sample holder positioning assembly is configured to position the sample holder between the X-ray source and the X-ray detector. The sample holder is configured to removably clamp a sample for inspection in a fixed position relative to the sample holder, and the sample holder is configured such that, in use, at least one surface of the sample is in contact with the flexible material.

[0014] In use, the X-ray detector of the X-ray inspection system can capture two-dimensional images of a sample held in a sample holder and in contact with a flexible material. Preferably, a series of two-dimensional images can be captured by the X-ray detector, with the sample in each image rotated at a different angle about an axis. This can be achieved by rotating the sample holder about said axis. In this way, the sample held in the sample holder also rotates about said axis. The axis advantageously extends in a direction orthogonal to a straight line extending between the X-ray source and the X-ray detector. The series of two-dimensional images can be used to create a three-dimensional reconstruction of the sample. When the sample holder is rotated, the held sample can be advantageously held in a fixed position within the sample holder. Therefore, movement of the sample relative to the sample holder can be prevented. This can advantageously allow for the creation of an accurate three-dimensional reconstruction of the sample. The sample being held in a removable manner can advantageously ensure that the sample can be easily removed from the sample holder and replaced.

[0015] The flexible material can be deformable without breaking. Advantageously, the flexible material is significantly more flexible than one or more samples to be examined, and therefore can conform to the shape of at least one surface of the sample in contact with the flexible material. Thus, the sample holder can advantageously accommodate a range of sample sizes and shapes, and in each case, the flexible material can contact at least one surface of the sample. Due to the contact between the flexible material and the sample, the sample can be held in place within the sample holder. In a preferred embodiment, the sample can be surrounded by the flexible material in use, such that all sides of the sample are in contact with and supported by the flexible material. Alternatively, the sample can be in contact with a more rigid material on one side and with the flexible material on the opposite side, thus the sample is held between the flexible and the more rigid material.

[0016] The sample holder can be configured to simultaneously hold multiple samples for examination. Each of the multiple samples can be held such that these samples are spaced apart along the axis of rotation. Advantageously, this allows multiple samples to be examined using an X-ray inspection system without the need to install new samples between imaging operations. This simplifies the operation of the X-ray inspection system and allows for the automation of examining multiple samples.

[0017] The flexible material can be an elastic material. After the sample has been removed from the sample holder, the elastic material will advantageously return to its original shape. The flexible material can be a compressible foam. The compressible foam can be elastic. The compressible foam can have a low density and advantageously a low X-ray attenuation coefficient. Compressible foams with a low X-ray attenuation coefficient can include materials with low atomic numbers or low densities, or materials with both low atomic numbers and low densities.

[0018] The sample holder can be configured to completely surround the sample during use. X-rays transmitted through the sample by the X-ray source can be attenuated by the sample holder, albeit only slightly. By providing a sample holder that completely surrounds the sample during use, the sample holder can attenuate X-rays to a similar degree, regardless of the orientation of the sample holder relative to the X-ray source. This is advantageous for creating high-quality and accurate 3D visualizations of the sample without creating imaging artifacts unrelated to the sample.

[0019] The magnification of an image captured by an X-ray detector can depend on the distance between the X-ray source and the sample. In particular, the closer the sample is to the X-ray source, the greater the magnification. When the sample holder completely surrounds the sample, it can be positioned very close to the X-ray source, at a location where it is known that the sample holder will not collide with features of the X-ray inspection system. Therefore, samples of any shape or size that can be completely surrounded by the sample holder can be reliably positioned at high magnification without calibrating the X-ray inspection system and without the risk of the sample colliding with the X-ray source or any other components of the X-ray inspection system. This can advantageously simplify the user operation of the X-ray inspection system, and particularly simplify the user operation of loading samples into the X-ray inspection system. The ability to capture high-magnification X-ray images can be particularly advantageous when inspecting electronic components, including packaged semiconductor devices.

[0020] The sample holder may include a housing comprising a material more rigid than the flexible material. The housing advantageously provides dimensional stability to the sample holder and reduces bending or deformation of the sample holder's outer surface. The housing also retains the flexible material, thereby providing clamping force to one or more samples held within the sample holder. Both ends of the sample holder may be connected to sample holder positioning components. Providing the housing prevents or reduces bending of the sample holder in the area between the ends. The housing may completely enclose the flexible material. In use, the sample held by the flexible material can be completely contained within the housing.

[0021] The outer shell may comprise at least one fiber selected from carbon fiber or aramid fiber. Alternatively or additionally, the outer shell may comprise polyetheretherketone (PEEK). Alternatively, the outer shell may comprise a low-density metal, such as aluminum. An outer shell comprising carbon fiber, aramid fiber, PEEK, or a low-density metal can advantageously possess high rigidity while also exhibiting low density and low X-ray radiation attenuation. Such a material can advantageously resist degradation caused by X-ray beams passing through the outer shell.

[0022] The sample holder may have a longitudinal axis, and the housing may be defined with a cross-section extending along the longitudinal axis. Preferably, the cross-section of the housing is substantially circular, such that X-rays passing through the sample holder penetrate substantially the same depth through the same material of the sample holder, regardless of the rotation angle of the sample holder. A sample holder with a circular cross-section may have a cylindrical shape. The diameter of the sample holder may be between 15 mm and 130 mm.

[0023] When the outer shell is not substantially circular, the cross-section can preferably have a sufficiently high order of rotational symmetry such that each two-dimensional image used to form the three-dimensional reconstruction can be intercepted through the line of symmetry of the sample holder. The cross-section can have a rotational symmetry order of at least 16, 32, 64, 128, 256, 512, or 720.

[0024] The outer shell can define an internal space. This internal space can be filled with a flexible material. In this case, "filling" means that the flexible material within the outer shell must be compressed to accommodate one or more samples, the volumes of which are within the expected sample volume range. Advantageously, when the sample holder is rotated about its axis, as the flexible material is compressed between the sample and the outer shell, the flexible material applies sufficient clamping force on the sample to hold the sample in a fixed position relative to the outer shell.

[0025] The sample holder may include a first portion and a second portion. The first portion is movable relative to the second portion between an open position and a closed position. In the open position, the sample holder is capable of accommodating a sample. In the closed position, the sample holder can clamp the sample contained within the sample holder between the first and second portions of the sample holder.

[0026] The first portion may include a first portion of a flexible material. The second portion may include a second portion of a flexible material. Advantageously, the flexible material in the second portion is the same as, or at least has substantially the same, X-ray attenuation coefficient as, the flexible material in the first portion. When the sample is contained in a closed sample holder, the first and second portions of the flexible material can each contact at least one surface of the sample and conform to the shape of said at least one surface, such that the sample is supported by the flexible material and fixed in place relative to the sample holder.

[0027] The first portion of the sample holder is separable from the second portion of the sample holder. Alternatively, the first portion of the sample holder can be hinged to the second portion of the sample holder. The first portion of the sample holder is movable relative to the second portion of the sample holder via the hinge. The hinge may comprise flexible resin or flexible tape fixed to the first and second portions of the sample holder. Alternatively, the hinge may comprise one or more Mylar strips, each Mylar strip being fixed to the first and second portions of the sample holder, for example, using tape. Alternatively, the first portion of the sample holder is slidable relative to the second portion of the sample holder.

[0028] The sample holder may include means for holding the first and second portions in a closed position. This advantageously ensures that the sample holder remains in the closed position in any orientation.

[0029] The means for holding the first and second portions of the sample holder in a closed position may include tape configured to removably attach to both the first and second portions of the sample holder. Alternatively, in the closed position, the first portion of the sample holder may engage with the second portion of the sample holder. Alternatively, the means for holding the first and second portions of the sample holder in a closed position may include clips configured to engage both the first and second portions of the sample holder when the sample holder is in the closed position. The sample holder may include more than one clip configured to engage both the first and second portions of the sample holder. The clips may be releasably engaged or clamped to the sample holder. The clips may be removed from the sample holder to allow the sample holder to be moved from a closed position to an open position. The clips are capable of sliding along the sample holder. The clips are capable of sliding from a first position where the clips engage both the first and second portions of the sample holder to a second position where the clips engage only the first or second portion of the sample holder. When the sample holder is in the closed position, the clips may be in the first position. The user may slide the clips to the second position to allow the sample holder to be moved from the closed position to the open position.

[0030] When the first part of the sample holder is not connected to the second part of the sample holder, it may be particularly suitable that the means for holding the first and second parts in the closed position includes one or more clamps.

[0031] The sample holder can be removably attached to the sample holder positioning assembly. This advantageously allows the original sample holder to be replaced with another sample holder having different cross-sectional dimensions, preferably different cross-sectional diameters. The user can select a sample holder of an appropriate size based on the dimensions of the sample to be examined. A smaller sample holder allows the sample to be positioned closer to the X-ray source, and thus a higher magnification can be achieved. However, it is preferable to select a sample holder that is large enough to completely surround the sample to be examined.

[0032] A retaining mechanism can be used to removably attach the sample holder to the sample holder positioning assembly. For example, a C-clamp can be used to removably attach the sample holder to the sample holder positioning assembly. The C-clamp is advantageously easy to use and reliably secures the sample holder to the sample holder positioning assembly.

[0033] The sample holder positioning assembly may include a base. The base can be mounted to an X-ray inspection system. Specifically, the base can be mounted to the platform of the X-ray inspection system. The base may be in the form of a tray. The sample holder positioning assembly may include a frame attached to the base, to which the sample holder is connected. An X-ray source may be positioned on the side of the base opposite to the sample holder, such that the X-rays generated by the X-ray source pass through the base before reaching the X-ray detector. Therefore, the smaller the gap between the sample holder and the base, the greater the magnification of the image captured by the X-ray detector. The gap between the sample holder and the base may be 1 mm or less, preferably 0.5 mm or less.

[0034] The base may include a window configured such that X-rays pass through the window when the sample holder is positioned between the X-ray source and the X-ray detector. The window may be formed of a low-attenuation material. Such a material may have a low atomic number or low density, or may include materials that have both a low atomic number and low density. The window may be formed of carbon fiber. Alternatively, the window may be an opening in the base.

[0035] An X-ray inspection system may include one or more X-ray filters located between an X-ray source and an X-ray detector, configured to absorb parasitic low-energy X-rays. The X-ray filters may contain copper or zinc. Copper-containing X-ray filters may have a thickness of approximately 100 micrometers. Zinc-containing X-ray filters may have a thickness of approximately 150 micrometers.

[0036] A first X-ray filter may be positioned between the X-ray source and the sample. The first X-ray filter provides beam hardening of the X-rays emitted by the X-ray source. The first X-ray filter may be supported by a base and may extend through a window in the base. The first X-ray filter may take the form of a coating on the window in the base. The X-ray inspection system may include a second X-ray filter positioned between the sample and the X-ray detector. The second X-ray filter may be configured to absorb parasitic low-energy scattered X-rays to prevent them from reaching the detector.

[0037] Alternatively or additionally, the sample holder may include an X-ray filter. The sample holder X-ray filter may be in the form of a coating on the sample holder housing. X-rays passing through the sample holder may pass through the sample holder X-ray filter twice. Therefore, X-rays passing through the sample holder may undergo beam hardening, and parasitic low-energy scattered X-rays may be absorbed.

[0038] The frame is movable about a pivot fixed relative to the base. This advantageously allows for adjustment of the frame's position relative to the base. In some embodiments, this advantageously allows the sample holder to be moved closer to or further away from the base, making it possible to adjust the magnification of the image of the sample captured by the X-ray detector. The frame can also be positioned relative to the base in other ways, such as by translating the frame linearly along a track toward and away from the base.

[0039] A movable frame can be particularly advantageous for allowing sample holders of different sizes to be removably attached to the sample holder positioning assembly. The position of the frame can be adjustable to allow sample holders of different diameters to be attached to the sample holder positioning assembly. Thus, it is advantageous to maintain a gap of 1 mm or less, preferably 0.5 mm or less, between the sample holder and the base, regardless of the size of the sample holder.

[0040] The sample positioning assembly may include a support for holding the frame in a predetermined position relative to the base.

[0041] When connecting sample holders of different sizes to the sample holder positioning assembly, support columns of different sizes can be used.

[0042] Alternatively, the sample positioning assembly may include a support post for holding the frame relative to the base in one of a plurality of predetermined positions. In each predetermined position, the frame can be held at a different distance from the base. This advantageously allows the user to select a predetermined position of the frame without altering the support post, the predetermined position being suitable for a specific size of the sample holder coupled to the sample holder positioning assembly. The support post may include a plurality of slots or holes. Each of the plurality of slots or holes may be configured to removably receive an engagement element of the frame to hold the frame in one of the predetermined positions. The engagement element may include a spring-loaded bolt configured to be removably received in each of the plurality of slots or holes. Alternatively, the support post may include a plurality of engagement elements, each configured to be removably received in a slot or hole in the frame at one of the predetermined positions.

[0043] The first end of the support column can be fixed to the base. The support column can extend upward from the first end. The plurality of slots can be distributed along the length of the support column. The sample positioning assembly can preferably include a second support column, which includes a slot or engagement element corresponding to the first support column. The first and second support columns can be located on opposite sides of the frame, respectively. The first and second support columns can be fixed to the base at their respective first ends. The first and second support columns can support the frame from opposite sides. This can advantageously provide improved mechanical stability compared to an arrangement including a single support column.

[0044] The sample positioning assembly may also include a screw-shaped device for adjusting the pitch of the frame relative to the base. Fine adjustments can be made by turning the screw.

[0045] The sample holder positioning assembly may include an encoder configured to measure the position of the frame relative to the base. This allows for determining the distance between the sample holder and the base, and thus advantageously allows for the calibration of images captured by an X-ray detector or for magnification calculations.

[0046] An X-ray examination system may include a controller that includes an image processor. The image processor may be connected to an X-ray detector to receive data from the detector. The image processor may be configured to perform computed tomography calculations to generate a three-dimensional reconstruction of the sample based on a series of two-dimensional images captured by the X-ray detector.

[0047] The sample holder positioning assembly also includes a rotary actuator configured to rotate the sample holder about a rotation axis. The rotary actuator can be fixed to the frame of the sample holder positioning assembly.

[0048] The rotary actuator may include a motor. The motor can be connected to an image processor and can output positional information to the image processor. Positional changes between images, and particularly rotational changes of the sample relative to the X-ray source and detector, can be used in computed tomography calculations. Accurate positional information is required when generating a 3D reconstruction of the sample. The more accurate the sample's positional information, the better the image resolution.

[0049] The motor can be offset from the axis of rotation. The rotary actuator may include a linkage located between the motor and the sample holder. In use, the offset motor can advantageously be positioned on the side of the axis of rotation opposite to the X-ray source. For example, if the X-ray source is located below the axis of rotation in use, the motor can be located above the axis of rotation. This can advantageously allow for a motor or linkage larger than the sample holder in a direction perpendicular to the axis of rotation without increasing the minimum distance between the sample and the X-ray source and thus without limiting the maximum magnification of the X-ray inspection system. By offsetting the motor from the axis of rotation, a more powerful motor can be used without limiting the magnification. Alternatively or additionally, a larger transmission can be used in the linkage. This can advantageously allow for precise control of the rotation of the sample holder.

[0050] The linkage may include a drive gear connected to a motor. The drive gear may be coupled to a gear directly or indirectly coupled to the sample holder. The drive gear may be coupled to the sample holder via one or more backlash-eliminating gears. These one or more backlash-eliminating gears can advantageously reduce or eliminate backlash to ensure stable rotation of the sample holder and thus ensure good image quality captured at the X-ray detector. This can be particularly advantageous when the center of mass of the sample housed in the sample holder is off-axis of rotation. Without backlash-eliminating gears, the mass of the sample may result in backlash in certain orientations that are detrimental to the direction of rotation. Alternatively, the drive gear may be coupled to the sample holder via a toothed belt.

[0051] The sample holder can hold the sample for inspection such that the sample is positioned on the axis of rotation. Therefore, when capturing a series of images of a sample with different orientations relative to the x-ray source, each image can be superimposed along the axis. This can advantageously reduce the computational complexity of generating a 3D reconstruction of the sample from this series of 2D images.

[0052] An X-ray inspection system may include a vertical positioning mechanism for moving a sample holder positioning assembly and thus the sample holder vertically toward or away from the X-ray source. As mentioned above, the magnification of the image captured by the X-ray detector depends on the distance between the X-ray source and the sample. Therefore, moving the sample holder toward or away from the X-ray source advantageously allows for magnification control. The vertical positioning mechanism moves the sample holder by moving the sample holder positioning assembly. When the sample holder positioning assembly includes a base, the vertical positioning mechanism can be configured to move the base.

[0053] An X-ray inspection system may include: a first horizontal positioning mechanism for moving a sample holder positioning assembly and thus the sample holder along a first horizontal direction; and a second positioning mechanism for moving the sample holder along a second horizontal direction. The first and second horizontal directions may be orthogonal to a vertical direction and define a horizontal plane. The first and second horizontal positioning mechanisms can move the sample holder by moving the sample holder positioning assembly. When the sample holder positioning assembly includes a base, the first and second horizontal positioning mechanisms may be configured to move the base.

[0054] The X-ray inspection system may include a sample holder position detection component, which includes a non-contact position measuring device positioned adjacent to a sample holder positioning component and configured to detect the position or positional change of the sample holder positioning component. The non-contact position measuring device can measure the position of the sample holder positioning component in the vertical direction. For example, the non-contact position measuring device may include a laser interferometer, an optical linear encoder, a magnetic encoder, or a capacitive sensor.

[0055] The X-ray inspection system may include another non-contact position measurement device for measuring the position of the sample holder positioning assembly in each of the first and second horizontal directions. Any non-contact position measurement device can output sample-related position information to the image processor.

[0056] In computed tomography (CT) calculations, the positional variations of a sample relative to the x-ray source and detector in the vertical direction and in the first and second horizontal directions can be used between images.

[0057] The sample holder is suitable for removably clamping electronic components. Sample lengths can range from 12 mm to 250 mm. Sample widths can range from 15 mm to 130 mm.

[0058] In a second aspect of the invention, an x-ray imaging accessory for an x-ray examination system is provided. The x-ray imaging accessory includes a sample holder and a sample holder positioning assembly, the sample holder positioning assembly including a rotary actuator configured to rotate the sample holder about a rotation axis. The sample holder comprises a flexible material and is configured to removably clamp a sample for examination in a fixed position relative to the sample holder, and the sample holder is configured such that, in use, at least one surface of the sample is in contact with the flexible material.

[0059] The sample holder can be coupled to a sample holder positioning assembly. Specifically, the sample holder can be coupled to a rotary driver. The sample holder can be removably coupled to the rotary driver.

[0060] X-ray imaging accessories can be configured to fit into an X-ray examination system comprising an X-ray source and an X-ray detector, such that a sample holder is positioned between the X-ray source and the X-ray detector. In use, a rotary actuator advantageously allows the sample holder to rotate about a rotation axis, such that the X-ray detector captures a series of two-dimensional images of the sample, each image showing the sample rotated about the axis at a different angle. The axis advantageously extends in a direction orthogonal to a straight line extending between the X-ray source and the X-ray detector. This series of two-dimensional images can be used to create a three-dimensional reconstruction of the sample in computed tomography applications.

[0061] The rotary actuator may include a motor. The motor may be offset from the axis of rotation. The rotary actuator may include a linkage located between the motor and the sample holder. The linkage may include a drive gear connected to the motor. The drive gear may be coupled to a gear coupled to the sample holder. The drive gear may be coupled via one or more backlash-free gears.

[0062] The flexible material can be easily bent without breaking, and therefore can conform to the shape of at least one surface of the sample it contacts. In a preferred embodiment, the sample can be surrounded by the flexible material during use, so that all sides of the sample are in contact with and supported by the flexible material. Alternatively, the sample can be in contact with a more rigid material on one side and with the flexible material on the opposite side, thus the sample is held between the flexible and the more rigid material.

[0063] Flexible materials can be elastic materials. Flexible materials can be compressible foams. Compressible foams can be elastic. Compressible foams can have low density and advantageously have a low X-ray attenuation coefficient. Compressible foams with a low X-ray attenuation coefficient can include materials with low atomic number or low density, or materials with both low atomic number and low density.

[0064] The sample holder can be configured to completely surround the sample during use.

[0065] The sample holder may include a housing comprising a material with greater rigidity than the flexible material. The housing can advantageously provide dimensional stability to the sample holder and reduce bending or deformation of the outer surface of the sample holder. The housing can also retain the flexible material, thereby providing clamping force to one or more samples held within the sample holder. The housing can completely surround the flexible material. In use, the sample held by the flexible material can be completely contained within the housing. The housing may comprise at least one fiber selected from carbon fibers or aramid fibers. Alternatively or additionally, the housing may comprise polyetheretherketone (PEEK). Alternatively, the housing may comprise a low-density metal, such as aluminum. Housings comprising carbon fibers, aramid fibers, PEEK, or low-density metals can advantageously possess high rigidity while also having low density and low X-ray radiation attenuation. Such materials can also advantageously resist degradation caused by X-ray beams passing through the housing.

[0066] The sample holder may have a longitudinal axis, and the housing may be defined with a cross-section extending along the longitudinal axis. Preferably, the cross-section of the housing is substantially circular, such that X-rays passing through the sample holder penetrate substantially the same depth through the same material of the sample holder, regardless of the rotation angle of the sample holder. A sample holder with a circular cross-section may have a cylindrical shape. The diameter of the sample holder may be between 15 mm and 130 mm.

[0067] When the outer shell is not substantially circular, the cross-section can preferably have a sufficiently high order of rotational symmetry such that each two-dimensional image used to form the three-dimensional reconstruction can be truncated at the line of symmetry. The cross-section can have a rotational symmetry order of at least 16, 32, 64, 128, 256, 512, or 720.

[0068] The outer shell can define an internal space. This internal space can be filled with a flexible material.

[0069] The sample holder may include a first portion and a second portion. The first portion is movable relative to the second portion between an open position and a closed position. In the open position, the sample holder is capable of accommodating a sample. In the closed position, the sample holder can clamp the sample contained within the sample holder between the first and second portions of the sample holder.

[0070] The first portion may include a first portion of a flexible material. The second portion may include a second portion of a flexible material. Advantageously, the flexible material in the second portion is the same as, or at least has substantially the same, X-ray attenuation coefficient as, the flexible material in the first portion. When the sample is contained in a closed sample holder, the first and second portions of the flexible material can each contact at least one surface of the sample and conform to the shape of said at least one surface, such that the sample is supported by the flexible material and fixed in place relative to the sample holder.

[0071] A first portion of the sample holder can be hinged to a second portion of the sample holder. The first portion of the sample holder is movable relative to the second portion of the sample holder via the hinge. The hinge may comprise flexible resin or flexible tape fixed to the first and second portions of the sample holder. Alternatively, the hinge may comprise one or more Mylar strips, each Mylar strip being fixed to the first and second portions of the sample holder, for example, using tape. Alternatively, the first portion of the sample holder is slidable relative to the second portion of the sample holder.

[0072] The sample holder may include means for holding the first and second portions in a closed position.

[0073] The means for holding the first and second portions in the closed position may include adhesive tape configured to removably attach to the first and second portions of the sample holder. Alternatively, in the closed position, the first portion of the sample holder may engage with the second portion of the sample holder.

[0074] The sample holder can be removably attached to the sample holder positioning assembly. This advantageously allows the original sample holder to be replaced with another sample holder having different cross-sectional dimensions, preferably different cross-sectional diameters. The user can select a sample holder of an appropriate size based on the dimensions of the sample to be examined. A smaller sample holder allows the sample to be positioned closer to the X-ray source, and thus a higher magnification can be achieved. However, it is preferable to select a sample holder that is large enough to completely surround the sample to be examined.

[0075] A retaining mechanism can be used to removably attach a sample holder to the sample holder assembly. For example, a C-clamp can be used to removably attach the sample holder to the sample holder positioning assembly. The C-clamp is advantageously easy to use and reliably secures the sample holder to the sample holder positioning assembly. Alternatively, the retaining element may include a quick-release mechanism. The quick-release mechanism may include a spring-loaded element, such as a spring-loaded bolt. The spring-loaded element may be part of the sample holder and configured to releasably engage the sample holder positioning assembly to secure the sample holder to the sample holder positioning assembly. Alternatively, the spring-loaded element may be part of the sample holder positioning assembly and configured to releasably engage the sample holder to secure the sample holder to the sample holder positioning assembly.

[0076] The quick-release mechanism may include a claw clutch. The sample holder may include a first portion of the claw clutch. The sample holder positioning assembly may include a second portion of the claw clutch. In this way, the sample holder can be engaged to the sample holder positioning assembly via the two portions of the claw clutch. The use of the claw clutch advantageously reduces slippage between the sample holder and the sample holder positioning assembly. A spring-loaded element may include a portion of either the first or second portion of the claw clutch, such that these portions of the claw clutch are pressed together. The first and second portions of the claw clutch may each include corresponding teeth configured to engage each other. The teeth may be conical.

[0077] The sample holder positioning assembly may include a base. The base may be adapted for mounting into an X-ray inspection system. In particular, the base may be mounted onto the platform of the X-ray inspection system. The base may be in the form of a tray. The sample positioning assembly may include a frame attached to the base, with the sample holder connected to the frame. The gap between the sample holder and the base may be 1 mm or less, preferably 0.5 mm or less. The frame may include a rotary actuator. The frame is capable of moving about a pivot fixed relative to the base. This advantageously allows adjustment of the frame's position relative to the base. The sample positioning assembly may include a detector configured to measure the position of the frame relative to the base.

[0078] The base may include a window configured such that X-rays pass through the window when the sample holder is positioned between the X-ray source and the X-ray detector. The window may be formed of a low-attenuation material. This material may have a low atomic number or low density, or include materials that have both a low atomic number and low density. The window may be formed of carbon fiber. Alternatively, the window may be an opening in the base.

[0079] The sample holder positioning assembly may include one or more X-ray filters configured to absorb parasitic low-energy X-rays. The X-ray filters may contain copper or zinc. Copper-containing X-ray filters may have a thickness of approximately 100 micrometers. Zinc-containing X-ray filters may have a thickness of approximately 150 micrometers.

[0080] A first X-ray filter may be positioned between the X-ray source and the sample. The first X-ray filter provides beam hardening of the X-rays emitted by the X-ray source. The first X-ray filter may be supported by a base and may extend through a window in the base. The first X-ray filter may take the form of a coating on the window in the base. The X-ray inspection system may include a second X-ray filter positioned between the sample and the X-ray detector. The second X-ray filter may be configured to absorb parasitic low-energy scattered X-rays to prevent them from reaching the detector.

[0081] Alternatively or additionally, the sample holder may include an X-ray filter. The sample holder X-ray filter may be in the form of a coating on the sample holder housing. X-rays passing through the sample holder may pass through the sample holder X-ray filter twice. Therefore, X-rays passing through the sample holder may undergo beam hardening, and parasitic low-energy scattered X-rays may be absorbed.

[0082] The sample holder may include an X-ray filter. The X-ray filter may be in the form of a coating on the sample holder housing. The X-ray filter may be configured to absorb parasitic low-energy scattered X-rays, preventing them from passing through the sample. The X-ray filter layer may contain copper.

[0083] Alternatively or additionally, when the X-ray examination system includes a base, the base may include an X-ray filter. When the base includes a window, the window may be a window that includes an X-ray filter.

[0084] In a third aspect of the invention, a sample holder for an X-ray examination system is provided, the sample holder comprising a flexible material and a mechanical interface for connection with a rotary actuator. The sample holder is configured to removably clamp a sample for examination in a fixed position relative to the sample holder, and is configured such that, in use, at least one surface of the sample is in contact with the flexible material.

[0085] A mechanical interface is provided that allows the sample holder to be connected to a rotary drive of a sample holder assembly that can be part of an X-ray examination system. The mechanical interface advantageously allows the sample holder to be removably coupled to the rotary drive, enabling easy attachment or removal of the sample holder from the rotary drive. The mechanical interface may include a protrusion or shaft. This protrusion or shaft can be connected to the rotary drive, for example, to the shaft of a motor. This connection can be achieved via a clamping mechanism (e.g., a C-clamp).

[0086] In use, the sample holder connected to the rotary driver can rotate about the rotation axis. The sample holder can hold the sample for inspection so that the sample is located on the rotation axis of the sample holder.

[0087] The sample holder may include a second mechanical interface on the side of the sample holder opposite to the first mechanical interface. The second mechanical interface may be used to connect to a second shaft or protrusion of the sample holder positioning assembly.

[0088] The flexible material of the sample holder can be a material that is easily bent without breaking, and therefore can conform to the shape of at least one surface of the sample it contacts. In a preferred embodiment, the sample can be surrounded by the flexible material during use, so that all sides of the sample are in contact with and supported by the flexible material.

[0089] Flexible materials can be elastic materials. Flexible materials can be compressible foams. Compressible foams can be elastic. Compressible foams can have low density and advantageously have a low X-ray attenuation coefficient. Compressible foams with a low X-ray attenuation coefficient can include materials with low atomic number or low density, or materials with both low atomic number and low density.

[0090] The sample holder can be configured to completely surround the sample during use.

[0091] The sample holder may include a housing comprising a material more rigid than the flexible material. The housing can advantageously provide dimensional stability to the sample holder and reduce bending or deformation of the outer surface of the sample holder. The housing can also hold the flexible material, thereby providing clamping force to one or more samples held within the sample holder. The housing can completely enclose the flexible material. In use, the sample held by the flexible material can be completely contained within the housing.

[0092] The housing may comprise at least one fiber selected from carbon fiber or aramid fiber. Alternatively or additionally, the housing may comprise polyetheretherketone (PEEK). Alternatively, the housing may comprise a low-density metal, such as aluminum. Housings comprising carbon fiber, aramid fiber, PEEK, or low-density metal can advantageously possess high rigidity while also having low density and low X-ray radiation attenuation. Such materials can also advantageously resist degradation caused by X-ray beams passing through the housing. The sample holder may have a longitudinal axis, and the housing may define a shape having a cross-section extending along the longitudinal axis. Preferably, the cross-section of the housing is substantially circular, such that X-rays passing through the sample holder penetrate substantially the same depth through the same material of the sample holder, regardless of the rotation angle of the sample holder. A sample holder with a circular cross-section may have a cylindrical shape. The diameter of the sample holder may be between 15 mm and 130 mm.

[0093] When the outer shell is not substantially circular, the cross-section can preferably have a sufficiently high order of rotational symmetry such that each two-dimensional image used to form the three-dimensional reconstruction can be truncated at the line of symmetry. The cross-section can have a rotational symmetry order of at least 16, 32, 64, 128, 256, 512, or 720.

[0094] The sample holder may include an X-ray filter configured to absorb parasitic low-energy X-rays. The X-ray filter may be in the form of a coating on the sample holder housing. The X-ray filter may be configured to absorb parasitic low-energy scattered X-rays to prevent them from penetrating the sample. The X-ray filter layer may contain copper.

[0095] The sample holder may include a first portion and a second portion. The first portion is movable relative to the second portion between an open position and a closed position. In the open position, the sample holder is capable of accommodating a sample. In the closed position, the sample holder can clamp the sample contained within the sample holder between the first and second portions of the sample holder.

[0096] The first portion may include a first portion of a flexible material. The second portion may include a second portion of a flexible material. Advantageously, the flexible material in the second portion is the same as, or at least has substantially the same, X-ray attenuation coefficient as, the flexible material in the first portion. When the sample is contained in a closed sample holder, the first and second portions of the flexible material can each contact at least one surface of the sample and conform to the shape of said at least one surface, such that the sample is supported by the flexible material and fixed in place relative to the sample holder.

[0097] A first portion of the sample holder can be hinged to a second portion of the sample holder. The first portion of the sample holder is movable relative to the second portion of the sample holder via the hinge. The hinge may comprise flexible resin or flexible tape fixed to the first and second portions of the sample holder. Alternatively, the hinge may comprise one or more Mylar strips, each Mylar strip being fixed to the first and second portions of the sample holder, for example, using tape. Alternatively, the first portion of the sample holder is slidable relative to the second portion of the sample holder.

[0098] The sample holder may include means for holding the first and second portions in a closed position. This advantageously ensures that the sample holder remains in the closed position in any orientation.

[0099] The means for holding the first and second portions in the closed position may include adhesive tape configured to be removably secured to either the first or second portion of the sample holder. Alternatively, in the closed position, the first portion of the sample holder may engage with the second portion of the sample holder.

[0100] The outer shell can define an internal space. This internal space can be filled with a flexible material.

[0101] The sample holder is suitable for removably clamping electronic components. Sample lengths can range from 12 mm to 250 mm. Sample widths can range from 15 mm to 130 mm.

[0102] The sample holder can be configured to simultaneously hold multiple samples for inspection. The sample holder can hold each of the multiple samples such that these samples are spaced apart along the axis of rotation.

[0103] In a fourth aspect of the invention, a kit is provided for an X-ray examination system comprising a plurality of sample holders as defined in a third aspect of the invention, wherein each of the plurality of sample holders has a different diameter.

[0104] Each of the plurality of sample holders can define a shape in which a cross-section extends along the longitudinal axis of the sample holder. Each sample holder can be cylindrical. The diameter of each sample holder can be between 15 mm and 130 mm. Exemplary diameters of the sample holders include 15 mm, 20 mm, 50 mm, or 127 mm. For example, a kit can include three sample holders. The first sample holder can have a diameter of 20 mm, the second sample holder can have a diameter of 50 mm, and the third sample holder can have a diameter of 127 mm.

[0105] The kit may also include a sample holder positioning assembly comprising a rotary actuator. Each of the plurality of sample holders is removably coupled to the rotary actuator. The sample holder positioning assembly can be configured to fit into an X-ray inspection system including an X-ray source and an X-ray detector, such that the sample holder coupled to the sample holder positioning assembly can be positioned between the X-ray source and the X-ray detector. In use, the rotary actuator can advantageously allow the coupled sample holder to rotate about a rotation axis, so that a series of two-dimensional images of the sample are captured by the X-ray detector. The series of two-dimensional images can be used to create a three-dimensional reconstruction of the sample in computed tomography applications.

[0106] Because each sample holder can be removably attached to the sample holder positioning assembly, the user can choose which of the multiple sample holders to attach. Therefore, the user can select a sample holder of an appropriate size for the size of the sample to be examined.

[0107] In a fifth aspect of the invention, a method is provided using an X-ray inspection system comprising an X-ray source, an X-ray detector, and a sample holder comprising a flexible material. The method comprises: clamping a sample to be inspected in the sample holder such that the sample is in a fixed position relative to the sample holder and at least one surface of the sample is in contact with the flexible material; positioning the sample holder between the X-ray source and the X-ray detector; recording an X-ray image of the sample; rotating the sample holder relative to the X-ray source; and recording a second X-ray image of the sample.

[0108] The method may further include repeating steps c) and d) multiple times. The method may include repeating steps c) and d) until at least 32 X-ray images of the sample corresponding to at least 32 different rotational positions of the sample have been recorded. The method may further include performing computed tomography calculations using the recorded X-ray images to generate a three-dimensional reconstruction of the sample.

[0109] The sample holder may include a first portion and a second portion, the first portion being movable relative to the second portion. In this case, the step of clamping the sample to be inspected may include: moving the first portion of the sample holder relative to the second portion of the sample holder to an open position; placing the sample in the sample holder; and moving the first portion of the sample holder relative to the second portion of the sample holder to a closed position, in which the sample is clamped by the sample holder.

[0110] It should be understood that the features described with respect to one aspect can be applied to other aspects of the invention. Attached Figure Description

[0111] Embodiments of the invention will now be described in detail by way of example only with reference to the accompanying drawings, in which:

[0112] . Figure 1 This is a schematic diagram of an X-ray inspection system including a sample positioning assembly and a sample holder according to the present invention;

[0113] . Figure 2 This is a perspective view of a part of an X-ray inspection system that includes a sample holder positioning assembly;

[0114] . Figure 3 This is a perspective view of the sample holder connected to the sample holder positioning assembly according to the present invention;

[0115] . Figure 4a and Figure 4b yes Figure 1 A perspective view of the sample holder separate from the X-ray inspection system, in which... Figure 4a The sample holder is shown in the closed position, while Figure 4b The sample holder is shown in the open position with the sample placed in the sample holder.

[0116] . Figure 5 yes Figure 4a A cross-sectional view of the sample holder, in which the sample is contained;

[0117] . Figure 6 This is a perspective view of the sample holder in the open position, with three samples placed inside.

[0118] . Figure 7 yes Figure 3 A cross-sectional view of the rotary drive shown;

[0119] . Figure 8 yes Figure 3 A close-up perspective view of the connection between the rotary actuator of the sample holder positioning assembly and the sample holder;

[0120] . Figure 9 Different sample holders are connected to Figure 3 A perspective view of the sample holder positioning assembly shown;

[0121] . Figure 10 A kit is shown, comprising a sample holder positioning assembly and multiple sample holders, each of which is connectable to the sample positioning assembly and has a different diameter; and

[0122] . Figure 11 This is a flowchart of a method using the X-ray examination system according to the present invention. Detailed Implementation

[0123] . Figure 1A schematic diagram of an X-ray inspection system 100 is shown. The operation of such an X-ray inspection system 100 is described in more detail in European Patent EP1766381B1.

[0124] The X-ray inspection system 100 includes an X-ray source in the form of an X-ray tube 10 and an X-ray detector 12. Between the X-ray tube 10 and the X-ray detector 12 is a platform 14, which can move along the X, Y, and Z directions via suitable slides and under the control of a motor. The platform 14 consists of an open frame (…). Figure 1 (not shown) is formed and adapted to support the sample holder positioning assembly 18.

[0125] The sample holder 20 is attached to the frame 22 of the sample holder positioning assembly 18. The sample to be examined can be accommodated in the sample holder 20. The sample contained in the sample holder 20 can be moved relative to the x-ray tube 10 and the x-ray detector in the XY plane and along the Z-axis via the moving platform 14. The sample holder positioning assembly 18 also includes a rotary actuator 28, which is coupled to the mechanical interface of the sample holder. The rotary actuator 28 can be used to rotate the sample holder 20 about a rotation axis perpendicular to the Z-axis.

[0126] The X-ray inspection system 100 also includes a controller containing an image processor. The controller is not shown in the figure. The image processor is connected to the X-ray detector 12 to receive data. The image processor is configured to perform computed tomography calculations to generate a three-dimensional reconstruction of the sample based on a series of two-dimensional images captured by the X-ray detector at different rotational positions of the sample holder. The controller is also used to control the movement of the platform 14 along the X, Y, and Z directions and the rotation of the rotary actuator 28.

[0127] In this example, the sample holder positioning assembly 18 is a sub-assembly that can be retrofitted to an existing X-ray inspection system 100. The sample holder positioning assembly 18 and the sample holder 20 form part of a kit that can be fitted into and removed from the X-ray inspection system. This kit may include multiple different sample holders. In use, the sample holder assembly 18 is secured to the platform 14 of the X-ray inspection system. Alternatively, the sample holder assembly 18 may be provided as an integral part of the X-ray inspection system.

[0128] . Figure 2 A perspective view of the sample holder positioning assembly 18 assembled into an X-ray inspection system 100 is shown. Not all X-ray inspection systems 100 are equipped with this assembly. Figure 2 As can be seen in the text. Figure 2 The platform 14 and the base 19 mounted on the platform 14 are shown more clearly.

[0129] . Figure 3A sample holder positioning assembly 18, separate from the rest of the X-ray examination system, is shown. The sample holder positioning assembly 18 includes a coupled sample holder 20. As described above, the sample holder positioning assembly 18 includes a base 19 and a frame 22. The sample holder 20 is coupled to the frame 22, which is movable about a pivot 32 fixed relative to the base 19. This allows adjustment of the position of the frame 22 relative to the base 19. The frame is held in place using a strut 30, which is configured to hold the sample holder 20 in a position such that the gap between the base 19 and the sample holder 20 is 1 mm or less. In this position, the magnification of the X-ray examination system can be maximized because the sample holder is positioned as close as possible to the X-ray source (located directly below the base 19) while avoiding collisions between the sample holder 20 and the base 19.

[0130] . Figure 3 The support column 30 shown is adapted to hold the frame relative to the base in a single predetermined position. Alternatively, the sample holder positioning assembly 18 may include a support column adapted to hold the frame relative to the base in one of a plurality of predetermined positions. In such an arrangement, a first end of the support column is secured to the base 19. The support column extends upward and has a plurality of slots or holes formed therein along its length. The frame includes spring-loaded bolts configured to removably engage each of the plurality of slots or holes. By engaging the spring-loaded bolts with specific slots or holes, a user can select one of a plurality of predetermined positions of the frame relative to the base. The sample holder positioning assembly 18 may include two support columns, each including a corresponding slot or hole. The two support columns are secured to the base 19 at opposite sides of the frame, respectively. The frame includes two spring-loaded bolts configured to engage the two support columns.

[0131] The sample holder positioning assembly 18 also includes a screw 36 that connects to the frame 22 and to the base 19. Turning the screw 36, if necessary, allows for fine adjustments to the pitch of the frame. This allows for adjustment of the gap between the base and the sample holder 20.

[0132] The base 19 includes a window 34 located in the base region, positioned between the X-ray tube 10 of the X-ray inspection system and the sample holder 20. This window is formed of carbon fiber and therefore has a low X-ray radiation attenuation coefficient. The window 34 also includes a coating comprising copper and having a thickness of 100 micrometers, which acts as an X-ray filter configured to absorb parasitic low-energy scattered X-rays to prevent them from penetrating the sample. In some embodiments, additionally or alternatively, the sample holder 20 may include a copper-containing coating.

[0133] The rotary drive 28 is connected to the frame 22, and therefore the rotary drive 28 moves with the frame as the frame moves about the pivot 32.

[0134] . Figure 4a and Figure 4b A sample holder 20, separate from the rest of the X-ray examination system, is shown. The sample holder 20 includes a first portion 20a and a second portion 20b, the first portion being movable relative to the second portion about a hinge formed of flexible resin. The hinge is not shown in the figure. Alternatively, the first portion 20a is separate from the second portion 20b without a hinge. In use, the separate first and second portions can be held in place relative to each other by retaining clips extending around the outer sides of the first and second portions. The sample holder includes a cylindrical housing 42 formed of carbon fiber, which is also divided into two portions 42a and 42b.

[0135] . Figure 4a The sample holder is shown in the closed position, while Figure 4b The sample holder is shown in the open position with sample 46 contained in sample holder 20.

[0136] The sample holder 20 comprises a flexible material 44 in the form of compressible foam with elastic properties. For example... Figure 4b As shown, the first portion of the flexible material 44 is associated with the first portion of the sample holder, while the second portion 44b of the flexible material is associated with the second portion of the sample holder.

[0137] The flexible material 44 fills the internal space defined by the housing 42 and is held by the housing 42. In the closed position, the surface of the sample 46 housed in the sample holder 20 contacts the first and second portions of the flexible material, causing the flexible material to be compressed to conform to the shape of the sample. Thus, the flexible material applies sufficient clamping force to the sample to hold it in a fixed position relative to the housing. The sample is secured in the appropriate position within the sample holder 20.

[0138] . Figure 5 This is a schematic cross-sectional view of the sample holder 20 in the closed position with the sample 46 housed between the first portion 44a and the second portion 44b of the flexible material. When the sample holder 20 is in the closed position, the sample 46 is surrounded by the flexible material 44 and completely contained within the housing 42. The sample 46 is clamped in a position such that when the rotary actuator 28 rotates the sample carrier 20, the sample 46 is located on the axis of rotation of the sample carrier 20.

[0139] .like Figure 4a , Figure 4b and Figure 5As shown, the sample holder also includes two mechanical interfaces 48 and 49. These mechanical interfaces are in the form of protrusions. The first mechanical interface 48 allows the sample holder to be coupled to the rotary driver 28. The second mechanical interface 49 allows the sample holder 20 to be coupled to another axis or protrusion of the frame 22 of the sample holder positioning assembly. The connection between the first mechanical interface 48 and the rotary driver 28 will be described in more detail below.

[0140] One or more samples 46 can be accommodated in the sample holder 20 and held by a flexible material. Figure 6 One embodiment is shown in which three samples 46 are housed in a sample holder 20 in the open position. The samples 46 are spaced apart along the axis of rotation. By providing multiple samples in the sample holder 20, inspection operations can be performed on each sample without requiring technicians to change samples and restart the inspection system between samples. In other words, the inspection of multiple samples can be automated.

[0141] . Figure 7 A close-up of the rotary actuator 28 with the housing removed is shown. The rotary actuator 28 includes a motor 47 coupled to a drive gear 50. The drive gear 50 is connected to a first backlash-free gear 51, which is coupled to a second backlash-free gear 52. The second backlash-free gear 52 drives another gear 54 coupled to a sample holder. Therefore, rotation of the drive gear 50 causes rotation of gear 52, and thus causes rotation of the sample holder 20. The backlash-free gears 51 and 52 reduce or eliminate backlash to ensure stable rotation of the sample holder 20.

[0142] . Figure 7 The arrangement of the rotary actuator 28 shown allows the motor 47 to deviate from the rotation axis of the sample holder 20. This deviation allows the rotary actuator 28 to extend above the horizontal plane of the frame 22 (e.g., Figure 6 (As shown), and thus allows for the use of a larger motor 47 or a larger transmission without increasing the minimum clearance between the sample holder 20 and the base 19. Without deviation, the rotary drive 28 will also extend below the horizontal plane of the frame, and will therefore increase the minimum distance between the x-ray source and the base 19. This will reduce the maximum magnification achievable using an x-ray inspection system.

[0143] . Figure 8 The connection between the sample holder 20 and the rotary actuator 28 is shown. The first mechanical interface 48 of the sample holder 20 is connected to the protrusion 56 of the rotary actuator 28 using a C-clamp 51. The C-clamp 58 secures the sample holder to the protrusion 56. In use, the protrusion 56 is positioned relative to the protrusion as described above. Figure 7The described electric motor 47 drives the sample holder 20 to rotate. The sample holder 20 is secured to the protrusion in such a way that rotation of the protrusion causes the sample holder 20 to rotate about an axis of rotation passing through the center of the cylindrical sample holder 20. This ensures that the sample holder 20 does not "wobble" during rotation, keeping the distance between the housing 42 and the base 19 constant. A similar C-clamp arrangement is used to clamp the second mechanical interface 49 to a rotatable second protrusion on the frame. This is not shown in the figure.

[0144] The C-clamp arrangement advantageously allows the user to remove the sample holder and replace it with a different sample holder. A quick-release mechanism, including a spring-loaded bolt, can be used instead of the C-clamp to releasably secure the sample holder to the frame. This similarly allows the user to remove the sample holder and replace it with a different sample holder. This is not shown in the figures.

[0145] . Figure 9 One embodiment is shown in which sample holder 20 has been replaced with a different sample holder 52. The diameter of sample holder 52 is larger than that of sample holder 20. Sample holder 20 has a diameter of 50 mm, while sample holder 52 has a diameter of 127 mm. These dimensions are exemplary. Sample holders of various diameters can be used. In particular, the user can select a sample holder of an appropriate size for the size of the sample to be examined. Generally, it is advantageous to use a sample holder with the smallest possible diameter while ensuring that the sample is completely contained within and surrounded by the sample holder. This is because the smaller the sample holder, the closer the sample can be positioned to the X-ray source, and therefore a higher magnification can be obtained.

[0146] . Figure 10 A kit is shown comprising three sample holders of different sizes 60, 62, and 64, and a sample holder positioning assembly 18 as already described. As mentioned above, each sample holder can be removably coupled to the sample holder positioning assembly.

[0147] . Figure 11 It outlines the use Figure 1 The flowchart shows the method of the X-ray examination system.

[0148] In step 100, the sample is clamped in the sample holder 20, and the sample holder 20 is connected to the sample holder positioning assembly 18, which is in turn supported by the platform 14 of the X-ray inspection system.

[0149] Clamping the sample 46 involves moving the first portion 20a of the sample holder relative to the second portion 20b about a hinge, such that the sample holder is in the open position as shown. The sample 46 is then placed on the first portion 44a of the flexible material within the sample holder. This... Figure 4b As shown in the figure. Of course, any number of samples can be placed in the sample holder, spaced apart along the length of the sample holder 20. Figure 5 An example is shown in which three samples are placed on the first part 44a of the flexible material.

[0150] Once the sample has been placed in the sample holder, the first portion 20a of the sample holder is moved to the closed position relative to the second portion 20b. This is as follows: Figure 4a and Figure 5 As shown. In the closed position, the surface of the sample 46 housed in the sample holder 20 contacts the first and second portions of the flexible material, causing the flexible material to be compressed to conform to the shape of the sample. Therefore, the flexible material applies sufficient clamping force to the sample to hold it in a fixed position relative to the housing 42. The sample is secured in the proper position within the sample holder 20. The sample is clamped in the sample holder.

[0151] In step 102, the sample holder is positioned between the X-ray source and the X-ray detector. This step may include using a controller to move platform 14 along the X, Y, and Z axes under the control of appropriate motors, such that if the sample holder positioning assembly 18 is not yet positioned between the X-ray source and the X-ray detector, it is typically positioned between them. In this step, the sample holder in the sample holder positioning assembly 18 may also be adjusted. For example, the position of frame 22 relative to base 19 may be adjusted. Supports 30 may be used to hold frame 22 relative to base 19 in a predetermined position. For example, other fine adjustments may be made by turning screw 36.

[0152] In step 104, a (first) image of the sample is recorded. The image of the sample is recorded by the X-ray detector 12 and received by the controller. This image is a two-dimensional image of a cross-section through the sample 46. The magnification of the sample image depends on the distance between the sample and the X-ray source 10. Therefore, if a high magnification image is required, this distance should be minimized. This can be achieved in step 100 by moving the platform 14 as close as possible to the X-ray source 10 along the Z direction and by reducing the gap between the sample holder 20 and the base 19 of the sample holder positioning assembly 18 to the smallest possible size, preferably less than 1 mm, or even more preferably less than 0.5 mm.

[0153] In step 106, the sample holder 20 is rotated relative to the x-light source 10. This rotation is achieved using a rotary driver 28. The motor 47 of the rotary driver is controlled by a controller.

[0154] In step 108, a second image of the sample is recorded. This image is also recorded by the X-ray detector 12 and received by the controller.

[0155] Repeat steps 106 and 108 until the sample has been rotated 360 degrees. In other words, repeat steps 106 and 108 until the sample holder returns to the position where the first image was recorded. Thus, the controller receives a series of two-dimensional images captured by the X-ray detector throughout the X-ray examination.

[0156] In step 110, computed tomography calculations are performed using the recorded X-ray images to generate a three-dimensional reconstruction of the sample. The controller's image processor is used to perform the computed tomography calculations.

[0157] The more images of the sample in the sample holder, and therefore the more imaging locations, the better the 3D reconstruction. Typically, at least 16 sample images are required, and therefore steps 106 and 108 are repeated at least 14 times. For example, the method may include repeating steps 106 and 108 14, 30, 62, 126, 254, 510, or 718 times. Preferably, the rotation angle between each image is equal.

[0158] As the sample holder is rotated to each imaging position, the sample 46, clamped within the sample holder, is held in a fixed position within the sample holder. In other words, movement of the sample relative to the sample holder is prevented. This results in the creation of an accurate 3D reconstruction of the sample.

[0159] When multiple samples are held in a sample holder, only one sample can be imaged at a time. In this case, after generating a 3D reconstruction of the first sample, the method is repeated for the second sample, which involves positioning the second sample between the X-ray source and the X-ray detector using the moving platform 14. This process can be automated, allowing for the automatic examination of multiple samples without the need to change samples between imaging operations.

[0160] Because the flexible material holds the sample in a removable manner, the sample can be easily removed from the sample holder after imaging is complete. The method can then be repeated using different samples from the sample holder.

[0161] As previously described, the sample holder 20 is removably coupled to the sample holder positioning assembly 18, which allows different sample holders to be coupled to the sample holder positioning assembly 18. In particular, this allows sample holders with different diameters to be coupled to the sample holder positioning assembly 18. Therefore, step 100 may include selecting a sample holder of an appropriate size for the sample to be examined. The smaller the sample holder, the closer the sample can be positioned to the X-ray source, and thus a higher magnification can be obtained. However, a sufficiently large sample holder should be selected to completely surround the sample to be examined.

Claims

1. An x-ray inspection system comprising: an x-ray source; an x-ray detector; a sample holder comprising a pliable section; and a sample holder positioning assembly configured to position the sample holder between the x-ray source and the x-ray detector; wherein the sample holder is configured to removably hold a sample for inspection in a fixed position relative to the sample holder, and the sample holder is configured such that, in use, at least one surface of the sample is in contact with the pliable section; and wherein the sample holder comprises an outer shell such that, when in use, i) the outer shell completely encloses the pliable section, and ii) the sample is completely contained within the outer shell. The pliable section is a resilient material.

2. The x-ray inspection system of claim 1, wherein, The pliable section is a compressible foam.

3. The x-ray examination system of any one of claims 1 or 2, wherein, In use, the pliable section completely encloses the sample such that all sides of the sample are in contact with and supported by the pliable section.

4. The x-ray examination system of any one of claims 1 or 2, wherein, The outer shell comprises a material that is more rigid than the pliable section.

5. The x-ray inspection system of either of claims 1 or 2, wherein, The outer shell comprises carbon fiber or aramid fiber.

6. The x-ray inspection system of either of claims 1 or 2, wherein, The sample holder comprises a first portion and a second portion, the first portion being movable relative to the second portion between an open position in which the sample holder is able to contain the sample, and a closed position in which the sample holder holds the sample between the first and second portions of the sample holder.

7. The x-ray inspection system of either of claims 1 or 2, wherein, The sample holder positioning assembly comprises a base and a frame attached to the base, the sample holder being connected to the frame.

8. The x-ray inspection system of any one of claims 1 or 2, wherein, The frame is movable about a pivot axis that is fixed relative to the base.

9. The x-ray inspection system of claim 8, wherein, 10. The x-ray inspection system of any one of claims 1 or 2, further comprising an x-ray filter between the x-ray source and x-ray detector. The sample holder positioning assembly comprises a rotational drive configured to rotate the sample holder about a rotational axis.

11. The x-ray inspection system of either of claims 1 or 2, wherein, 12. The x-ray inspection system of any one of claims 1 or 2, further comprising a vertical positioning mechanism for moving the sample holder in a vertical direction towards or away from the x-ray source.

13. The x-ray inspection system of any one of claims 1 or 2, further comprising: a first horizontal positioning mechanism for moving the sample holder in a first horizontal direction; and a second positioning mechanism for moving the sample holder in a second horizontal direction. The pliable section is configured such that, when in use, the pliable section completely encloses and clamps the sample such that every side of the sample is in contact with the pliable section.

15. An x-ray imaging accessory for an x-ray inspection system comprising:

14. The x-ray inspection system of claim 1, wherein, a sample holder comprising a pliable section; and a sample holder positioning assembly comprising a rotational drive configured to rotate the sample holder about a rotational axis; ​ ​ ​ wherein the sample holder is configured to removably hold a sample for examination in a fixed position relative to the sample holder, and the sample holder is configured such that, in use, at least one surface of the sample is in contact with the pliable section; and wherein the sample holder comprises an outer shell such that, when in use, i) the outer shell completely encloses the pliable section, and ii) the sample is completely contained within the outer shell.

16. The x-ray imaging accessory of claim 15, wherein, The pliable section is of an elastic material.

17. The x-ray imaging accessory of either one of claims 15 or 16, wherein, The outer shell comprises a material that is more rigid than the pliable section.

18. The x-ray imaging accessory of either one of claims 15 or 16, wherein, The sample holder positioning assembly comprises a base and a frame attached to the base, the sample holder being connected to the frame.

19. The x-ray imaging accessory of claim 18, wherein, The frame is moveable about a pivot that is fixed relative to the base.

20. The x-ray imaging accessory of claim 15, wherein, The pliable section is configured such that, when in use, the pliable section completely encloses and clamps the sample such that every side of the sample is in contact with the pliable section.

21. The x-ray imaging accessory of claim 16, wherein, The pliable section is a compressible foam.

22. The x-ray imaging accessory of claim 17, wherein, The outer shell comprises carbon fibre, aramid fibre, PEEK or metal.

23. A sample holder for an x-ray examination system, the sample holder comprising: a pliable section; and a mechanical interface for connection with a rotary drive; wherein the sample holder is configured to removably hold a sample for examination in a fixed position relative to the sample holder, and the sample holder is configured such that, in use, at least one surface of the sample is in contact with the pliable section; and wherein the sample holder comprises an outer shell such that, when in use, i) the outer shell completely encloses the pliable section, and ii) the sample is completely contained within the outer shell.

24. The sample holder of claim 23, wherein, The mechanical interface comprises a protrusion or shaft that is connectable to the rotary drive.

25. The sample holder of claim 23, wherein, The pliable section is configured such that, when in use, the pliable section completely encloses and clamps the sample such that every side of the sample is in contact with the pliable section.

26. A kit for an x-ray examination system, the kit comprising a plurality of sample holders, each sample holder being a sample holder according to any one of claims 23 or 24; wherein each of the plurality of sample holders has a different diameter.

27. The kit of claim 26, further comprising a sample holder positioning assembly, the sample holder positioning assembly comprising a rotary drive, and wherein each of the plurality of sample holders is removably couplable to the rotary drive.

28. A method of using an x-ray examination system, the x-ray examination system comprising an x-ray source, an x-ray detector and a sample holder, the sample holder comprising a pliable section and an outer shell, the method comprising: holding a sample to be examined in the sample holder such that the sample is in a fixed position relative to the sample holder and at least one surface of the sample is in contact with the pliable section, wherein i) the outer shell completely encloses the pliable section, and ii) the sample is completely contained within the outer shell; positioning the sample holder between the x-ray source and the x-ray detector; recording an x-ray image of the sample; rotating the sample holder relative to the x-ray source; and recording a second x-ray image of the sample.

29. The method of claim 28, wherein, The sample holder comprises a first part and a second part, the first part being movable relative to the second part, and wherein the step of clamping the sample to be inspected comprises: moving the first part of the sample holder relative to the second part of the sample holder and into an open position; placing the sample in the sample holder; and moving the first part of the sample holder relative to the second part of the sample holder and into a closed position in which the sample is clamped by the sample holder.

30. The method of claim 28, wherein, When the sample is clamped, the pliable section completely surrounds the sample such that each side of the sample is in contact with the pliable section. When the sample is clamped, the pliable section completely surrounds the sample such that each side of the sample is in contact with the pliable section.

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