Sparse SiPM array reflecting material filling method

Abstract

The invention relates to a sparse SiPM array reflecting material filling method. The method comprises the steps that the number of layers of reflecting materials and the thickness of each layer of reflecting material are determined according to the height of a chip in a SiPM array; determining the hole site size of each layer of reflecting material according to the length and width of the chip; determining hole site center coordinates according to the chip center coordinates; cutting according to the size of each layer of reflecting material and the center coordinate of the hole site; and sequentially superposing a plurality of layers of reflecting materials among the sparse SiPM arrays so as to complete filling of the reflecting materials of the sparse SiPM arrays. The beneficial effects are that the filling efficiency of the SiPM array reflection material can be improved, the dead zone area can be reduced, the photon collection efficiency can be improved, the performance of the SIPM array detector can be further improved, the repair is easy, and the manufacturing cost can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of medical device nuclear medicine, and in particular to a method for filling a sparse SiPM array with a reflective material. Background Art

[0002] Silicon photomultiplier (SiPM) is a revolutionary photodetector device. It has become a hot topic in the research of positron emission tomography (PET) detectors due to its outstanding performance in high quantum efficiency, fast time response, compact package size and insensitivity to magnetic fields. In order to improve the performance of PET systems, SiPM arrays usually reduce the gap between chips as much as possible. However, under the premise of ensuring system performance, increasing the gap can reduce the number of chips used, thereby reducing the price of PET systems and improving cost performance. The gap between SiPM arrays is a detection dead zone, which will cause light loss. The reflective film filling the gap between SiPM arrays can reflect the originally lost light back to the scintillation crystal array, and then be detected by SiPM after multiple reflections, thereby increasing the amount of light collection, and then improving the energy resolution and position resolution of the PET system.

[0003] Traditional methods of filling sparse SiPM reflective materials, such as barium sulfate paste filling, have complex filling processes and are difficult to repair. In addition, there are many potential risks in filling the gaps between chips with barium sulfate paste. Filling with other reflective materials has the risk of large detection dead zones and easy light loss between chips, which seriously affects the performance of SiPM array detectors. Summary of the invention

[0004] Technical issues to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for filling a sparse SiPM array reflective material, which solves the technical problems that the traditional method for filling sparse SiPM reflective materials has a complex filling process, is difficult to repair, and the performance of the SiPM array detector needs to be further improved.

[0006] Technical Solution

[0007] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0008] The present invention provides a method for filling a sparse SiPM array with a reflective material, comprising:

[0009] Determine the number of reflective material layers and the thickness of each reflective material layer according to the chip height in the SiPM array;

[0010] Determine the hole size of each layer of reflective material according to the chip length and width;

[0011] Determine the center coordinates of the hole according to the center coordinates of the chip;

[0012] Cutting is performed according to the size of each layer of reflective material and the coordinates of the center of the hole;

[0013] The reflective material is sequentially stacked in multiple layers between the sparse SiPM arrays to complete the filling of the sparse SiPM array with the reflective material.

[0014] Optionally, the reflective material includes a PET reflective film.

[0015] Optionally, the total thickness of the multi-layer reflective material is equal to the chip height.

[0016] Optionally, the reflective material is divided into a forward offset layer, a reverse offset layer and a non-offset layer, and the sum of the number of layers of the forward offset layer and the reverse offset layer is n≥2.

[0017] Optionally, the thickness of the forward offset layer and the reverse offset layer is greater than that of the non-offset layer, and the thickness of the non-offset layer is less than 0.2 mm.

[0018] Optionally, the hole size of each layer of reflective material is determined according to the chip length and width, including:

[0019] According to the chip length L1 and width L2, the hole length of each layer of reflective material is determined to be (L1+0.1) and the hole width is determined to be (L2+0.1).

[0020] Optionally, the reflective material is sequentially stacked in multiple layers and attached between the sparse SiPM arrays, including:

[0021] The center coordinates of the holes in the forward offset layer are offset by 0.02 mm in any direction and pasted between the sparse SiPM arrays;

[0022] The hole center coordinates of the reverse offset layer are offset 0.02 mm in the opposite direction of the offset direction of the forward offset layer and pasted between the sparse SiPM arrays;

[0023] The hole center coordinates of the non-offset layer are pasted between the sparse SiPM arrays without offset.

[0024] Optionally, the forward offset layer and the reverse offset layer are cut by a laser cutting machine, and the non-offset layer is cut by a carving machine.

[0025] Beneficial Effects

[0026] The beneficial effects of the present invention are as follows: a sparse SiPM array reflective material filling method of the present invention adopts a new reflective material size design, cutting method and filling process method, which can reduce the SiPM array reflection dead zone area, increase the photon collection energy of the SiPM array, and reduce the SiPM light loss risk. At the same time, the filling process method is simple and does not have potential risks, and rework is easy. The present invention greatly reduces production costs, avoids potential risks in the filling process, and improves the detector performance of sparse SiPM. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the design dimensions of the reflective material provided in an embodiment of the present invention;

[0028] Figure 2 A schematic side view of a SiPM array filled with reflective material provided in an embodiment of the present invention;

[0029] Figure 3 This is a front schematic diagram of a SiPM array filled with reflective material provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0031] The gap between sparse SiPMs is a detection dead zone, which will cause light loss. Reflective materials are filled between traditional sparse SiPM arrays to reduce the dead zone area and increase the photon collection of the SiPM array. Traditional methods of filling reflective materials: such as the filling process of barium sulfate paste is complicated, time-consuming, and difficult to repair. The biggest problem is that there is a potential risk of barium sulfate paste filling between the gaps of SiPM array chips; if an enhanced specular reflector (ESR) is used as a reflective material for filling, in order to achieve the filling process, there will still be a certain dead zone between the ESR reflective film and the sparse SiPM array; and because the thickness of the ESR reflective film is relatively thin, the thickness of the reflective film after filling is much lower than the height of the SiPM chip, resulting in the phenomenon of light loss between the SiPM array chips, which will affect the performance of the SiPM array detector. Based on the above problems, a method for filling a sparse SiPM array reflective material is proposed in an embodiment of the present invention. Through this filling process method, the dead zone area of ​​the sparse SiPM array can be reduced, the possibility of light loss of the sparse SiPM array can be reduced, and the photon collection amount and imaging quality of the sparse SiPM array detector can be further improved. The present invention can solve the problem that the filling process of barium sulfate paste is complicated and has potential risks; it also solves the problem that the dead area of ​​the ESR film filling process is large and light loss between chips is easy to affect the performance of the detector.

[0032] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0033] This embodiment provides a method for filling a sparse SiPM array with a reflective material, comprising:

[0034] Determine the number of reflective material layers and the thickness of each layer of reflective material according to the chip height in the SiPM array; determine the hole size of each layer of reflective material according to the chip length and width; determine the hole center coordinates according to the chip center coordinates; cut each layer of reflective material according to the size and hole center coordinates; stack the reflective material in multiple layers in sequence between the sparse SiPM array to complete the filling of the sparse SiPM array reflective material.

[0035] The reflective material in this embodiment can be fixed by any method.

[0036] Such as mechanical fixation: use screws, nails or clamps, add frames, etc., select reflective materials with adhesive backing to fit together, bond with glue, press with pressure, etc.

[0037] The present embodiment provides a method for filling a sparse SiPM array with a reflective material, which can reduce the dead zone area of ​​the sparse SiPM array, avoid the problem of light loss between SIPM array chips, and improve the photon collection rate and imaging quality of the SiPM array. At the same time, this process method is simple and easy to operate, has no potential risks, and is easy to repair, thereby improving production efficiency and reducing the production cost of sparse SiPM array detectors.

[0038] When choosing reflective materials, choose those with adhesive backing, so that the reflective material can be directly attached to the sparse SiPM array, which simplifies the mounting process and is easy to repair.

[0039] Optionally, the reflective material includes a PET reflective film.

[0040] Optionally, the total thickness of the multi-layer reflective material is equal to the chip height.

[0041] Optionally, the reflective material is divided into a forward offset layer, a reverse offset layer and a non-offset layer, and the sum of the number of layers of the forward offset layer and the reverse offset layer is n≥2.

[0042] The filling of the sparse SiPM array reflective material adopts a multi-layer filling method. The multi-layer filling can make the height of the reflective film consistent with the height of the SiPM array chip, so as to solve the problem of light loss between chips due to the thin reflective material between chips; at the same time, the SiPM array is filled with reflective material and the SiPM array chip to form a plane, which will reduce the generation of bubbles during the bonding process of the scintillation crystal array and the SiPM array, and also reduce the thickness of the bonding layer, thereby improving the performance of the SIPM array detector. Multi-layer filling reflective material, through multi-layer superposition, plus the slight deviation of the bottom material and the top material, makes the reflective materials slightly misaligned with each other, filling the reflective dead zone, so that the reflective dead zone can be greatly reduced, thereby improving the photon collection ability and image quality of the sparse SiPM detector.

[0043] Optionally, the thickness of the forward offset layer and the reverse offset layer is greater than that of the non-offset layer, and the thickness of the non-offset layer is less than 0.2 mm.

[0044] Optionally, the hole size of each layer of reflective material is determined according to the chip length and width, including:

[0045] According to the chip length L1 and width L2, the hole length of each layer of reflective material is determined to be (L1+0.1) and the hole width is determined to be (L2+0.1).

[0046] Optionally, the reflective material is sequentially stacked in multiple layers and attached between the sparse SiPM arrays, including:

[0047] The center coordinates of the holes in the forward offset layer are offset by 0.02 mm in any direction and pasted between the sparse SiPM arrays;

[0048] The hole center coordinates of the reverse offset layer are offset 0.02 mm in the opposite direction of the offset direction of the forward offset layer and pasted between the sparse SiPM arrays;

[0049] The hole center coordinates of the non-offset layer are pasted between the sparse SiPM arrays without offset.

[0050] The reflective material is designed to be a pattern that maps to the position of the SiPM array chip. However, in order to reduce the difficulty of operation and make it easier to attach the reflective material between the SiPM arrays, the hole position of the reflective material needs to be designed to be slightly larger than the chip size, which will result in a reflective dead zone area. However, if the hole position of the reflective material is as close to the chip size as possible in order to reduce the reflective dead zone area, the difficulty of process operation will increase (because the number of chips in the SiPM array is large, there will be errors in the mounting accuracy, and it is difficult to completely align all chip positions for mounting), and it is easy to cause the filled reflective material to be uneven, which affects the thickness of the SiPM array detector bonding layer. In order to solve the above problems, the bottom reflective material size and the top layer size are designed to be different specifications. The bottom reflective material design hole position is larger and has a small coordinate offset; while the top reflective material design adopts a hole position coordinate centering design to reduce the problem of filling the reflective dead zone.

[0051] Optionally, the forward offset layer and the reverse offset layer are cut by a laser cutting machine, and the non-offset layer is cut by a carving machine.

[0052] There are two cutting methods for cutting reflective materials: for cutting the bottom material, you can choose a laser cutting machine, which has high cutting efficiency but has certain losses on the edges; for cutting the top material, you can choose a cutting machine with no damage to the edges, but its cutting efficiency is relatively low.

[0053] A method for filling a sparse SiPM array reflective material of the present invention is further described below in conjunction with a specific embodiment. The method includes three parts: selection and size design of reflective material, processing method of reflective material and filling process method of reflective material.

[0054] First, the reflective material should be adhesive-backed, such as the PET reflective film widely used in the field of light box lighting. The material has been tested to show excellent reflectivity similar to that of barium sulfate paste, and its performance is slightly better than that of traditional ESR film. PET reflective film has a variety of thickness specifications to choose from. PET reflective film with different thickness specifications can be selected according to the height of the SiPM array chip. For example, in this example, Figure 2 and Figure 3 , specification A + specification B + specification C = chip height H.

[0055] In the size design of the PET reflective film, the PET reflective film needs to be completely embedded in the gaps between the SiPM array chips. Since the chip mounting of the SiPM array has a certain tolerance, the tolerance needs to be considered in the design of the reflective film size. At the same time, due to the large number of chips, the PET reflective film needs to be completely flattened, so the design size needs to be increased to facilitate mounting the reflective film in the gaps of the SiPM array. The design of the PET reflective film of the present invention is divided into three specifications or is not limited to three specifications, such as Figure 1 As shown, the chip coordinate position of the SiPM array can be seen. The size of the chip is L1×L2, and the coordinate system is (X i , Y i ); Specification A is the bottom reflective film, and the hole size corresponding to the chip is designed to be (L1+0.1)×(L2+0.1). This 0.1mm tolerance is an empirical parameter obtained based on the mounting accuracy of the SiPM array and the number of chips. This tolerance can ensure that the PET reflective film is easy to attach to the SIPM array, the operation process is simple, the mounting is flat, and the unqualified rate is reduced. The design of the reflective film of specification A is designed with a coordinate system misalignment, and the X coordinate system and the Y coordinate system are all increased by 0.02mm, that is, (X+0.02, Y+0.02). Specification B is also the bottom reflective film, and its hole size is (L1+0.1)×(L2+0.1), and its coordinate system is that the X coordinate system and the Y coordinate system are all reduced by 0.02mm, that is, (X-0.02, Y-0.02). Specification C is the top reflective film, and its size is (L1+0.1)×(L2+0.1), and its coordinates are (X, Y). By alternately pasting specification A and specification C, the dead zone area can be greatly reduced.

[0056] The processing of reflective materials can be carried out simultaneously by laser cutting and engraving machines. The thickness of specifications A and B is slightly thicker because of the bottom reflective film. A laser cutting machine with relatively high cutting efficiency is selected, but the laser cutting edge is damaged. The thickness of the top reflective film specification C is selected to be less than 0.2mm, so a engraving machine with slightly lower cutting efficiency is selected, but the engraving machine has almost no edge damage, which is used to be mounted on the top surface of the SiPM array.

[0057] The mounting process of the SiPM array reflective film is to first tear off the adhesive paper on the thinner specification A reflective surface, align it with the SiPM array and stick it between the gaps of the SiPM array; then use a hard sheet to gradually flatten the PET reflective film in the gap of the SiPM array. Then use the same method to stick the slightly larger specification B reflective film between the gaps of the SiPM array. Finally, stick the top specification C reflective layer between the SiPM array. After all three layers are pasted, the thickness of the reflective layer is consistent with the height of the SiPM array chip, forming a plane, which can directly bond the SiPM array and the scintillation crystal. No bubbles will be generated during the bonding process, and the bonding glue layer will be reduced to the thinnest, so that there will be no light loss between the SiPM arrays. At the same time, the three layers of PET reflective film alternate with each other, greatly reducing the dead area of ​​the SiPM array, which will greatly increase the photon collection energy of the SiPM array and improve the performance of the SiPM array detector. At the same time, the filling process of this PET reflective film is simple, and rework only needs to tear off the PET reflective film directly, which will not cause damage to the SiPM chip and reduce the rework cost.

[0058] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention should also include these modifications and variations.

[0059] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for filling a sparse SiPM array with a reflective material, characterized in that: include: Determine the number of reflective material layers and the thickness of each reflective material layer according to the chip height in the SiPM array; Determine the hole size of each layer of reflective material according to the chip length and width; Determine the center coordinates of the hole according to the center coordinates of the chip; Cutting is performed according to the size of each layer of reflective material and the coordinates of the center of the hole; The reflective material is sequentially stacked in multiple layers between the sparse SiPM arrays to complete the filling of the sparse SiPM array with the reflective material.

2. A method for filling a sparse SiPM array with a reflective material according to claim 1, characterized in that: The reflective material includes a PET reflective film.

3. A method for filling a sparse SiPM array with a reflective material according to claim 2, characterized in that: The total thickness of the multiple layers of reflective material is equal to the chip height.

4. A method for filling a sparse SiPM array with a reflective material according to claim 3, characterized in that: The reflective material is divided into a forward offset layer, a reverse offset layer and a non-offset layer, and the number of layers of the forward offset layer and the reverse offset layer is n≥2.

5. A method for filling a sparse SiPM array with a reflective material according to claim 4, characterized in that: The thickness of the forward offset layer and the reverse offset layer is greater than that of the non-offset layer, and the thickness of the non-offset layer is less than 0.2 mm.

6. A method for filling a sparse SiPM array with a reflective material according to claim 5, characterized in that: The hole size of each layer of reflective material is determined according to the chip length and width, including: According to the chip length L1 and width L2, the hole length of each layer of reflective material is determined to be (L1+0.1) and the hole width is determined to be (L2+0.1).

7. A method for filling a sparse SiPM array with a reflective material according to claim 6, characterized in that: The reflective materials are sequentially stacked in multiple layers between the sparse SiPM arrays, including: The center coordinates of the holes in the forward offset layer are offset by 0.02 mm in any direction and pasted between the sparse SiPM arrays; The hole center coordinates of the reverse offset layer are offset 0.02 mm in the opposite direction of the offset direction of the forward offset layer and pasted between the sparse SiPM arrays; The hole center coordinates of the non-offset layer are pasted between the sparse SiPM arrays without offset.

8. The method for filling a sparse SiPM array with a reflective material according to claim 7, characterized in that: The positive offset layer and the reverse offset layer are cut by a laser cutting machine, and the non-offset layer is cut by a carving machine.

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