Silicon drift detector and packaging structure
The airtightness problem in silicon drift detector packaging is solved by using alumina ceramics and coval alloy materials, combined with brazing and laser welding technology, ensuring the stability and long life of the detector.
Patent Information
- Application Number
- CN202510429445.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-08
- Publication Date
- 2025-07-04
AI Technical Summary
Existing silicon drift detectors face airtightness problems during packaging, resulting in performance degradation or short-term failure in vacuum or different gas environments.
Alumina ceramics and cova alloys are used as packaging materials, combined with brazing and laser welding technology to ensure the airtightness and stability of the packaging structure, and use low air effluent materials and high-tensile welding processes to prevent external gas from entering the detector chamber.
It realizes the long-term and stable operation of the detector in a vacuum environment, prevents gas leakage, extends service life, and maintains the stability of the structure.
Smart Images
Figure CN120264882A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of silicon drift detector packaging, and specifically to a silicon drift detector and a packaging structure. Background Art
[0002] A silicon drift detector is a high-performance X-ray detector, and its sensing principle is as follows: When an X-ray photon enters the sensitive area of the silicon drift detector, it generates photoelectrons in the silicon material. The electrons are affected by the electric field in the silicon substrate and start to drift towards the collecting anode. The electric field is formed by the voltage difference between the drift ring and the collecting anode, ensuring that the photoelectrons move along a specific path in the silicon substrate. When the photoelectrons reach the collecting anode, an electrical signal is generated on the anode. This electrical signal is amplified by a preamplifier and then converted into a digital signal by an analog-to-digital converter (ADC), and finally recorded by a data acquisition system. The electric field distribution of the silicon drift detector is the key to its high resolution. By applying different voltages between the drift ring and the collecting anode, an electric field pointing towards the collecting anode is formed. The electric field strength gradually changes in the silicon substrate, ensuring that the photoelectrons are affected by a uniform electric field during the drift process, thereby reducing charge diffusion and improving the resolution of the detector. During the signal processing, the preamplifier amplifies the electrical signal generated by the collecting anode, and then the analog signal is converted into a digital signal by the analog-to-digital converter (ADC). The digital signal is further processed, such as filtering, baseline restoration, and peak detection, and finally the energy information of the X-ray photon is obtained. It has been widely used in high-energy physics, aerospace, industry, medical, and security detection fields due to its high energy resolution and high sensitivity.
[0003] Currently, in terms of the packaging of silicon drift detectors, there is a problem of packaging airtightness. This is mainly because, in the atmospheric environment, solid materials will dissolve or adsorb surrounding gas molecules. When the material is placed in a vacuum environment or transferred to a new gas environment, the original equilibrium state will be disrupted, resulting in outgassing of the material, thereby causing the performance of the detector to decline or even fail within a short period of time.
[0004] In view of the above problems, an improved silicon drift detector and a packaging structure are now designed. Summary of the Invention
[0005] The purpose of the present invention is to provide a silicon drift detector and a packaging structure to solve the problems raised in the above background art.
[0006] To achieve the above purpose, the present invention provides the following technical solutions:
[0007] A silicon drift detector includes a silicon wafer. Multiple cathode ring electrodes and an anode center electrode are provided on the surface of the silicon wafer. The cathode ring electrodes form a gradient electric field through a gradually changing reverse bias voltage, causing photoelectrons to drift towards the anode center electrode. Each cathode ring electrode and the anode center electrode are provided with independent interconnection leads, and the collected electrical signals are transmitted through the interconnection leads.
[0008] A packaging structure of a silicon drift detector includes a ceramic base. A ceramic substrate is provided at the upper end of the ceramic base. The ceramic base and the ceramic substrate are fixed together by a bonding process. Multiple pads are provided on the surface of the ceramic substrate. The silicon wafer, the interconnection leads, and the ceramic substrate are fixed together by a chip mounting and wire bonding process to ensure efficient transmission of electrical signals.
[0009] A housing is sleeved on the ceramic substrate and the silicon wafer. The lower end of the housing is tightly connected to the upper end of the ceramic base by a brazing process. A sealing cover is provided at the upper end of the housing. The side wall of the sealing cover is tightly connected to the top of the housing by a laser welding technique. Laser welding has advantages such as high welding precision and large weld strength, which can ensure the connection tightness between the sealing cover and the housing, prevent external gases from entering the detector chamber, and affect the performance of the detector.
[0010] An X-ray incident window is provided on the sealing cover. The X-ray incident window is a beryllium window with a thickness of 100 μm. The X-ray incident window is tightly combined with the sealing cover by a brazing technique, enabling X-rays to smoothly enter the detector interior, be absorbed by the silicon wafer, and generate photoelectrons. This thickness of the beryllium window can ensure the effective penetration of X-rays while ensuring the tightness of the detector chamber and the mechanical reliability of the structure.
[0011] As a further scheme of the present invention: Both the ceramic base and the ceramic substrate are made of alumina ceramics with low outgassing rate and high density. Alumina ceramics have good mechanical properties and corrosion resistance, can withstand internal pressure changes and various stresses in the external environment, and ensure the stability of the packaging structure.
[0012] As a further scheme of the present invention: Both the housing and the sealing cover are made of kovar alloy materials. Kovar alloy has good thermal matching with materials such as silicon and glass, and is easy to process and weld.
[0013] As a further scheme of the present invention: The installation and connection of the ceramic base, the housing, and the sealing cover need to be carried out in a dust-free and dry clean environment to avoid external impurities and gases from entering the detector interior. After the housing installation is completed, the detector also needs to be subjected to a tightness test to ensure the tight and reliable connection between the housing and the ceramic base and the sealing cover, and effectively prevent gas leakage and the influence of external environmental factors on the detector.
[0014] As a further solution of the present invention: The bonding process between the ceramic base and the ceramic substrate includes the following steps:
[0015] Step 1: Clean the surfaces of the ceramic base and the ceramic substrate to remove impurities and dust on the surfaces, ensuring the reliability of bonding.
[0016] Step 2: Use a high-temperature adhesive or a special adhesive to position and bond the ceramic substrate to the designated position on the ceramic base according to strict process parameter requirements. During the bonding process, parameters such as temperature, pressure, and time need to be precisely controlled to ensure good bonding between the ceramic substrate and the ceramic base, while avoiding damage to the ceramic substrate and the ceramic base.
[0017] Step 3: After bonding, it is also necessary to inspect the bonding effect to ensure that the combination between the two is tight and firm, and can withstand various stresses in subsequent processes.
[0018] As a further solution of the present invention: The chip mounting and wire bonding process between the silicon wafer, the interconnection leads, and the ceramic substrate includes the following steps:
[0019] Step 1: In the chip mounting process, the silicon wafer is accurately mounted on the ceramic substrate through a suitable chip mounting material, such as conductive adhesive or solder, etc., to ensure electrical connection and mechanical fixation between the silicon wafer and the ceramic substrate. During the chip mounting process, parameters such as the amount of chip mounting material, the accuracy of the chip mounting position, and the chip mounting pressure need to be precisely controlled to ensure good contact and stable electrical performance between the silicon wafer and the ceramic substrate.
[0020] Step 2: In the wire bonding process, gold wires are used as the connection material, and through the gold wire bonding process, the electrodes on the silicon wafer are connected to the pads on the ceramic substrate. During the bonding process, parameters such as the length of the lead, the bonding force, and the position of the bonding point need to be precisely controlled to ensure reliable connection of the lead and efficient transmission of electrical signals.
[0021] Step 3: After completing the chip mounting process and the wire bonding process, a stable electrical connection is formed between the silicon wafer and the ceramic substrate, laying a foundation for subsequent packaging processes and the normal operation of the detector.
[0022] Compared with the prior art, the beneficial effects of the present invention are:
[0023] 1. Alumina ceramic and kovar alloy are used as the main packaging materials, and their low outgassing rate and high density ensure the airtightness of the packaging structure, avoiding the influence of material outgassing on the performance of the detector.
[0024] 2. The housing is connected to the ceramic base through the brazing process, and the sealing cover is connected to the housing through the laser welding technology. The combination of these two welding methods ensures the stability and airtightness of the packaging structure, and can effectively prevent gas leakage.
[0025] Compared with existing products, it has the following advantages:
[0026] 1. Good airtightness: The encapsulation structure of the present invention can effectively ensure the airtightness of the detector chamber, prevent gas leakage, and ensure the long-term stable operation of the detector in a vacuum environment by selecting materials with low outgassing rates and advanced welding processes.
[0027] 2. Superior mechanical properties: Alumina ceramics and kovar alloy have good mechanical properties and can withstand internal pressure changes and various stresses in the external environment, enabling the detector to maintain the structural stability in a complex environment.
[0028] 3. Long service life: Since the airtightness problem is solved, the working gas inside the detector can remain pure for a long time, avoiding the influence of gas pollution and material outgassing on the performance of the detector, and greatly extending the service life of the detector. Brief Description of the Drawings
[0029] Figure 1 It is a schematic structural diagram of the present invention after encapsulation.
[0030] Figure 2 It is an exploded view of the present invention.
[0031] Figure 3 It is a schematic structural diagram of the ceramic substrate adhered to the ceramic base in the present invention.
[0032] Figure 4 It is a schematic structural diagram of the silicon wafer, interconnection leads, and ceramic substrate in the present invention.
[0033] Figure 5 It is a schematic structural diagram of the housing after installation in the present invention.
[0034] Wherein: 1. Ceramic base; 2. Ceramic substrate; 3. Interconnection leads; 4. Silicon wafer; 5. Housing; 6. X-ray incident window; 7. Sealing cover. Detailed Embodiments
[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.
[0036] Please refer to Figures 1 - 5, in the embodiment of the present invention, a silicon drift detector includes a silicon wafer 4. A plurality of cathode ring electrodes and an anode center electrode are provided on the surface of the silicon wafer 4. The cathode ring electrodes form a gradient electric field through a gradually changing reverse bias voltage, causing the photoelectrons to drift towards the anode center electrode. Each cathode ring electrode and the anode center electrode are provided with independent interconnection leads 3, and the collected electrical signals are transmitted through the interconnection leads 3.
[0037] When X-ray photons are incident on the silicon wafer 4, photoelectrons will be generated in the silicon wafer 4. The photoelectrons are affected by the electric field in the silicon substrate and start to move towards the anode center electrode. The electric field is formed by the voltage difference between the cathode ring electrodes and the anode center electrode, ensuring that the photoelectrons move along a specific path in the silicon substrate. When the photoelectrons reach the anode center electrode, an electrical signal will be generated on the anode center electrode. This electrical signal is amplified by a preamplifier and then converted into a digital signal by an analog-to-digital converter, and finally recorded by a data acquisition system.
[0038] A packaging structure of a silicon drift detector includes a ceramic base 1. A ceramic substrate 2 is provided at the upper end of the ceramic base 1. The ceramic base 1 and the ceramic substrate 2 are fixed together by a bonding process. A plurality of pads are provided on the surface of the ceramic substrate 2. The silicon wafer 4, the interconnection leads 3, and the ceramic substrate 2 are fixed together by a chip mounting and wire bonding process to ensure the efficient transmission of electrical signals.
[0039] Both the ceramic base 1 and the ceramic substrate 2 are made of alumina ceramics with low outgassing rate and high density. Alumina ceramics have good mechanical properties and corrosion resistance, and can withstand internal pressure changes and various stresses in the external environment, ensuring the stability of the packaging structure.
[0040] An outer shell 5 is sleeved on the ceramic substrate 2 and the silicon wafer 4. The lower end of the outer shell 5 is tightly connected to the upper end of the ceramic base 1 by a brazing process. A sealing cover 7 is provided at the upper end of the outer shell 5. The side wall of the sealing cover 7 is tightly connected to the top of the outer shell 5 by a laser welding technique. Laser welding has the advantages of high welding precision and large weld strength, etc., and can ensure the connection tightness between the sealing cover 7 and the outer shell 5, preventing external gases from entering the detector chamber and affecting the performance of the detector.
[0041] Both the outer shell 5 and the sealing cover 7 are made of kovar alloy materials. Kovar alloy has good thermal matching with materials such as silicon and glass, and is easy to process and weld.
[0042] The sealing cover 7 is provided with an X-ray incident window 6, which is a beryllium window with a thickness of 100 μm. The X-ray incident window 6 is tightly bonded to the sealing cover 7 through brazing technology, enabling X-rays to smoothly enter the interior of the detector, be absorbed by the silicon wafer 4 and generate photoelectrons. The beryllium window of this thickness can ensure the effective penetration of X-rays while ensuring the sealing of the detector chamber and the mechanical reliability of the structure.
[0043] The installation and connection of the ceramic base 1, the housing 5, and the sealing cover 7 need to be carried out in a dust-free and dry clean environment to prevent foreign impurities and gases from entering the interior of the detector. After the housing is completed, the detector also needs to be tested for airtightness to ensure that the connections between the housing 5, the ceramic base 1, and the sealing cover 7 are tight and reliable, effectively preventing gas leakage and the influence of external environmental factors on the detector.
[0044] The bonding process between the ceramic base 1 and the ceramic substrate 2 includes the following steps:
[0045] Step 1: Clean the surfaces of the ceramic base 1 and the ceramic substrate 2 to remove surface impurities and dust, ensuring the reliability of bonding.
[0046] Step 2: Use a high-temperature adhesive or a special adhesive to position and bond the ceramic substrate 2 to the designated position on the ceramic base 1 according to strict process parameter requirements. During the bonding process, parameters such as temperature, pressure, and time need to be precisely controlled to ensure good bonding between the ceramic substrate 2 and the ceramic base 1 while avoiding damage to the ceramic substrate 2 and the ceramic base 1.
[0047] Step 3: After bonding, it is also necessary to inspect the bonding effect to ensure that the combination between the two is tight and firm, capable of withstanding various stresses in subsequent processes.
[0048] The chip mounting and wire bonding process between the silicon wafer 4, the interconnection leads 3, and the ceramic substrate 2 includes the following steps:
[0049] Step 1: In the chip mounting process, the silicon wafer 4 is accurately mounted on the ceramic substrate 2 through a suitable chip mounting material, such as conductive adhesive or solder, etc., to ensure electrical connection and mechanical fixation between the silicon wafer 4 and the ceramic substrate 2. During the chip mounting process, parameters such as the amount of chip mounting material, the accuracy of the chip mounting position, and the chip mounting pressure need to be precisely controlled to ensure good contact and stable electrical performance between the silicon wafer 4 and the ceramic substrate 2.
[0050] Step 2: In the wire bonding process, gold wires are used as the connection material, and through the gold wire bonding process, the electrodes on the silicon wafer 4 are connected to the pads on the ceramic substrate 2. During the bonding process, parameters such as the length of the lead, the bonding force, and the position of the bonding point need to be precisely controlled to ensure reliable connection of the lead and efficient transmission of electrical signals.
[0051] Step 3: After completing the chip mounting process and the wire bonding process, a stable electrical connection is formed between the silicon wafer 4 and the ceramic substrate 2, laying a foundation for the subsequent packaging process and the normal operation of the detector.
[0052] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention.
Claims
1. A silicon drift detector, characterized in that, It includes a silicon wafer (4). Multiple cathode ring electrodes and an anode center electrode are provided on the surface of the silicon wafer (4). The cathode ring electrodes form a gradient electric field through a gradually changing reverse bias voltage, causing the photoelectrons to drift towards the anode center electrode. Each cathode ring electrode and the anode center electrode are provided with independent interconnection leads (3).
2. The packaging structure of the silicon drift detector according to claim 1, characterized in that It includes a ceramic base (1). A ceramic substrate (2) is provided at the upper end of the ceramic base (1). The ceramic base (1) and the ceramic substrate (2) are fixed together by a bonding process. Multiple pads are provided on the surface of the ceramic substrate (2). The silicon wafer (4), the interconnection leads (3), and the ceramic substrate (2) are fixed together by a chip mounting and wire bonding process; A housing (5) is sleeved on the ceramic substrate (2) and the silicon wafer (4). The lower end of the housing (5) is tightly connected to the upper end of the ceramic base (1) by a soldering process. A sealing cover (7) is provided at the upper end of the housing (5). The side wall of the sealing cover (7) is tightly connected to the top of the housing (5) by a laser welding technique; An X-ray incident window (6) is provided on the sealing cover (7). The X-ray incident window (6) is a beryllium window with a thickness of 100 μm. The X-ray incident window (6) is tightly combined with the sealing cover (7) by a soldering technique.
3. The encapsulation structure of a silicon drift detector according to claim 2, characterized in that, Both the ceramic base (1) and the ceramic substrate (2) are made of alumina ceramics with a low outgassing rate and high density.
4. The encapsulation structure of a silicon drift detector according to claim 2, characterized in that Both the housing (5) and the sealing cover (7) are made of kovar alloy materials.
5. The packaging structure of a silicon drift detector according to claim 2, characterized in that The installation and connection of the ceramic base (1), the housing (5), and the sealing cover (7) need to be carried out in a dust-free and dry clean environment to avoid external impurities and gases from entering the detector. After the housing is completed, the detector also needs to be tested for airtightness to ensure the tight and reliable connection between the housing (5) and the ceramic base (1) and the sealing cover (7).
6. The packaging structure of a silicon drift detector according to claim 2, wherein, The bonding process between the ceramic base (1) and the ceramic substrate (2) includes the following steps: Step 1: Clean the surfaces of the ceramic base (1) and the ceramic substrate (2) to remove surface impurities and dust to ensure the reliability of bonding; Step 2: Use a high-temperature adhesive or a special adhesive to position and bond the ceramic substrate (2) to the designated position on the ceramic base (1) according to strict process parameter requirements. During the bonding process, parameters such as temperature, pressure, and time need to be precisely controlled to ensure good bonding between the ceramic substrate (2) and the ceramic base (1), and at the same time avoid damage to the ceramic substrate (2) and the ceramic base (1); Step 3: After the bonding is completed, the bonding effect also needs to be inspected to ensure that the combination between the two is tight and firm and can withstand various stresses in subsequent processes.
7. The encapsulation structure of a silicon drift detector according to claim 2, characterized in that, The chip mounting and wire bonding process between the silicon wafer (4), the interconnection leads (3), and the ceramic substrate (2) includes the following steps: Step 1: In the chip mounting process, the silicon wafer (4) is precisely mounted onto the ceramic substrate (2) through a suitable chip mounting material, ensuring the electrical connection and mechanical fixation between the silicon wafer (4) and the ceramic substrate (2). The chip mounting process requires precise control of parameters such as the amount of chip mounting material, the accuracy of the chip mounting position, and the chip mounting pressure to ensure good contact and stable electrical performance between the silicon wafer (4) and the ceramic substrate (2). Step 2: In the wire bonding process, gold wires are used as the connection material. Through the gold wire bonding process, the electrodes on the silicon wafer (4) are connected to the pads on the ceramic substrate (2). During the bonding process, parameters such as the length of the wire, the bonding force, and the position of the bonding point need to be precisely controlled to ensure reliable connection of the wire and efficient transmission of electrical signals. Step 3: After completing the chip mounting process and the wire bonding process, a stable electrical connection is formed between the silicon wafer (4) and the ceramic substrate (2), laying the foundation for the subsequent packaging process and the normal operation of the detector.