Infrared detector chip low-temperature strain stress testing device and method

Abstract

The invention discloses a low-temperature strain stress testing device and method for an infrared detector chip, and relates to the infrared detector technology, and the device comprises a Dewar (1) which is filled with liquid nitrogen; the Dewar cooling table (2) is connected with the Dewar (1); the electrical leading-out frame (3) is arranged on the Dewar cooling table (2); the low-temperature strain gauge (4) is arranged on the infrared detector chip (5) and is used for measuring the strain of the infrared detector chip at low temperature; the temperature measuring diode (6) is arranged adjacent to the infrared detector chip (5) and is used for measuring the temperature of the infrared detector chip (5); and the signal collector (8) is respectively connected to the low-temperature strain gauge (4) and the temperature measuring diode (6) through wires, and sends collected signals to a computer (9). According to the testing device provided by the embodiment of the invention, direct strain and stress measurement and characterization of the infrared detector chip in the cooling process can be realized.

Description

Technical Field

[0001] This application relates to the technical field of infrared detectors, and particularly to a low-temperature strain and stress testing device and method for an infrared detector chip. Background Art

[0002] Infrared detection technology is widely used in various fields such as astronomical science, medical and health, military, and industrial equipment testing in today's society. Cooling is a necessary working condition for high-performance infrared photon detectors. A low working temperature can suppress the background noise of the detector, improve the signal-to-noise ratio and sensitivity of the detector, and greatly enhance the detection performance of the detector. Currently, conventional infrared focal plane detectors made of indium antimonide (InSb) and mercury cadmium telluride (HgCdTe) materials usually operate in the temperature range of 77K to 90K. A general structural schematic diagram of a mercury cadmium telluride infrared focal plane detector is as Figure 1 shown. It can be clearly observed from the figure that the component consists of at least three layers of structures. Due to the relatively large differences in the thermal expansion coefficients of each layer of materials, when the working environment of the detector decreases from room temperature (encapsulated at room temperature) to low temperature (about 77K), thermal stress will be generated due to the thermal mismatch between the materials, which will in turn cause low-temperature deformation of the entire component module. When the low-temperature deformation exceeds the critical deformation threshold that the detector component can withstand, catastrophic fracture failure will occur. Its failure phenomena are mainly manifested in the fracture of the focal plane detector chip, fatigue damage of the solder joints, and the decline of the overall performance of the device. Therefore, the thermal mismatch problem between materials is the most critical and important factor affecting the reliability of the device. In addition, before the infrared focal plane device is put into normal use, its component module usually needs to undergo multiple high-low temperature shock experiments. During the high-low temperature cyclic shock process, the device is always under the influence of relatively large thermal stress and deformation, so it is more likely to cause fatigue failure. Especially with the continuous expansion of the device scale, the phenomenon of detector failure due to excessive stress caused by this type of thermal mismatch becomes more obvious, which is also an inevitable problem in the development of large-area focal plane arrays. Summary of the Invention

[0003] The embodiments of this application provide a low-temperature strain and stress testing device and method for an infrared detector chip, which can directly measure and characterize the strain and stress during the cooling process of the infrared detector chip, and provide an important data basis and support for optimizing the thermal stress environment and improving the reliability of the infrared detector.

[0004] The embodiments of this application provide a low-temperature strain and stress testing device for an infrared detector chip, including:

[0005] A Dewar 1 filled with liquid nitrogen;

[0006] A Dewar cold stage 2 connected to the Dewar 1;

[0007] The electrical lead-out frame 3 is arranged on the Dewar cold stage 2;

[0008] The cryogenic strain gauge 4 is arranged on the infrared detector chip 5 and is used for measuring the strain of the infrared detector chip at low temperature;

[0009] The temperature-measuring diode 6 is arranged adjacent to the infrared detector chip 5 and is used for measuring the temperature of the infrared detector chip 5;

[0010] The signal collector 8 is respectively connected to the cryogenic strain gauge 4 and the temperature-measuring diode 6 through wires and sends the collected signals to the computer 9.

[0011] Optionally, the cryogenic strain gauge 4 and the temperature-measuring diode 6 are respectively connected to different channels of the signal collector 8.

[0012] The embodiment of the present application also provides a method for testing the low-temperature strain and stress of an infrared detector chip, which is realized based on the aforementioned device for testing the low-temperature strain and stress of an infrared detector chip, and includes:

[0013] Orient and bond the infrared detector chip 5 and the electrical lead-out frame 3 to the end face of the liquid nitrogen Dewar cold stage;

[0014] Bond the cryogenic strain gauge 4 to the middle position of the detector chip;

[0015] Bond the temperature-measuring diode 6 to a position adjacent to the detector chip 5;

[0016] Perform internal lead bonding between the cryogenic strain gauge 4, the temperature-measuring diode 6 and the electrical lead-out frame 3 on a gold wire bonder, and bond the external leads of the electrical lead-out frame 3;

[0017] After bonding, fasten, couple and seal with the infrared detector Dewar structure window seat, and perform vacuum exhaust so that the vacuum degree inside the Dewar meets the requirements;

[0018] Connect the electrical lead-out wires of the temperature-measuring diode 6 and the cryogenic strain gauge 4 to the signal collector 8. After the signal collector is stable, pour liquid nitrogen into the liquid nitrogen Dewar for refrigeration, and process the collected data through the computer 9 to obtain the strain and stress results.

[0019] Optionally, it further includes completely curing after bonding.

[0020] Optionally, after bonding, it further includes measuring and judging whether the resistance values of the electrical lead-out wires of the cryogenic strain gauge and the temperature-measuring diode are normal.

[0021] Optionally, connecting the electrical lead-out wires of the temperature-measuring diode 6 and the cryogenic strain gauge 4 to the signal collector 8 includes: connecting the electrical lead-out wires of the temperature-measuring diode 6 and the cryogenic strain gauge 4 to different channels of the signal collector 8 respectively.

[0022] Optionally, vacuum evacuation is performed so that the internal vacuum degree of the Dewar is below 10 -3 Pa.

[0023] The stress test device of the embodiment of the present application realizes the direct strain and stress measurement and characterization of the infrared detector chip during the cooling process, providing an important data basis and support for the optimization of the thermal stress environment and the improvement of the reliability of the infrared detector.

[0024] The above description is only an overview of the technical solution of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present application more obvious and understandable, the specific embodiments of the present application are specifically exemplified below. Description of the Drawings

[0025] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. And throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0026] Figure 1 is a schematic diagram of the general structure of a mercury cadmium telluride detector;

[0027] Figure 2 is a schematic structure of the low-temperature strain and stress test device for the infrared detector chip of the embodiment of the present application. Detailed Embodiments

[0028] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art.

[0029] With the continuous improvement of system application requirements for large field of view, high spatial resolution, high temporal resolution, etc., the scale of detectors is gradually developing towards large area arrays. When large area array detectors work at low temperature, large thermal mismatch generates significant stress and deformation, leading to an increasingly prominent problem of chip cracking. Therefore, developing direct measurement and characterization techniques for the thermal stress of detector chips under low temperature operation is of great significance for the development of next-generation infrared focal plane technology. For infrared detector chips operating at low temperature, this application designs a strain and stress measurement scheme suitable for infrared detector chips at low temperature, which has the characteristics of high sensitivity and high reliability, and is used to directly measure and characterize the strain and stress values of the chip during the cooling process. Specifically, the embodiments of this application provide a low-temperature strain and stress test device for infrared detector chips, as Figure 2 shown, including:

[0030] A Dewar 1 filled with liquid nitrogen;

[0031] A Dewar cold stage 2 connected to the Dewar 1;

[0032] An electrical lead-out frame 3 disposed on the Dewar cold stage 2;

[0033] A low-temperature strain gauge 4 disposed on the infrared detector chip 5 for measuring the strain of the infrared detector chip at low temperature;

[0034] A temperature-measuring diode 6 disposed adjacent to the infrared detector chip 5 for measuring the temperature of the infrared detector chip 5;

[0035] A signal collector 8 is respectively connected to the low-temperature strain gauge 4 and the temperature-measuring diode 6 through wires and sends the collected signals to a computer 9.

[0036] In some embodiments, the low-temperature strain gauge 4 and the temperature-measuring diode 6 are respectively connected to different channels of the signal collector 8.

[0037] The test device of the embodiments of this application can directly characterize and measure the real-time strain and stress of the infrared detector chip during the cooling process from room temperature to low temperature. It can simultaneously measure the chip strain, stress, and temperature changes, with a resolution accuracy as high as 1 με.

[0038] The strain and stress obtained through experimental measurement can verify, guide, and correct the numerical simulation parameters of the detector assembly, and further support the accuracy of the numerical simulation of complex structure components.

[0039] The test device of the embodiments of this application can realize multi-point strain and stress measurement, and obtain the low-temperature strain and stress distributions at different positions and across the entire chip.

[0040] The embodiment of the present application also provides a method for testing the low-temperature strain and stress of an infrared detector chip, which is implemented based on the aforementioned device for testing the low-temperature strain and stress of an infrared detector chip, and includes the following steps:

[0041] In step S301, the infrared detector chip 5 and the electrical lead frame 3 are directionally bonded to the end face of the liquid nitrogen dewar cold stage. Specifically, the infrared detector chip 5 and the electrical lead frame 3 can be directionally bonded to the end face of the liquid nitrogen dewar cold stage through low-temperature glue under a tool microscope and baked at a high temperature until completely cured.

[0042] In step S302, the low-temperature strain gauge 4 is bonded to the middle position of the detector chip. Specifically, it can be pasted to the center of the detector chip through low-temperature glue and baked at a high temperature until completely cured.

[0043] In step S303, the temperature-measuring diode 6 is bonded to a position adjacent to the detector chip 5. Still, the temperature-measuring diode 6 can be pasted to the detector chip through low-temperature glue and baked at a high temperature until completely cured.

[0044] In step S304, internal lead bonding is performed between the low-temperature strain gauge 4, the temperature-measuring diode 6, and the electrical lead frame 3 on a gold wire bonder, and external lead bonding is performed on the electrical lead frame 3. In some embodiments, after bonding, it further includes measuring and determining whether the resistance values of the electrical leads of the low-temperature strain gauge and the temperature-measuring diode are normal. For example, the resistance value can be measured with a multimeter.

[0045] In step S305, after bonding, it is fastened, coupled, and sealed with the infrared detector dewar structure window seat, and vacuum exhaust is performed to make the internal vacuum degree of the dewar meet the requirements. For example, vacuum exhaust is performed to make the internal vacuum degree of the dewar below 10 -3 Pa.

[0046] In step S306, the electrical leads of the temperature-measuring diode 6 and the low-temperature strain gauge 4 are connected to the signal collector 8. After the signal collector is stable, liquid nitrogen is poured into the liquid nitrogen dewar for refrigeration, and the collected data is processed by a computer 9 to obtain the strain and stress results.

[0047] In some embodiments, connecting the electrical leads of the temperature-measuring diode 6 and the low-temperature strain gauge 4 to the signal collector 8 includes: connecting the electrical leads of the temperature-measuring diode 6 and the low-temperature strain gauge 4 to different channels of the signal collector 8 respectively. After the signal collector is stable, liquid nitrogen is poured into the liquid nitrogen dewar to achieve chip refrigeration. The data is collected by the collector in real time at a frequency of 10 Hz, and the strain and stress results are obtained by inputting the data into a computer.

[0048] The embodiment of the present application also provides an implementation case of a method for testing the low-temperature strain and stress of an infrared detector chip, including the following steps:

[0049] 1) Surface inspection. Re-inspect the surface condition of the components required for low-temperature testing, and test the relevant indicators (resistance value) of the low-temperature strain gauges and temperature-measuring diodes.

[0050] 2) Intermediate testing and screening. Conduct intermediate testing and screening on 640×512 mercury cadmium telluride chips. Qualified chips are prepared for encapsulation process and bonding of strain gauges and diodes, and a low-temperature adhesive is selected as the bonding agent.

[0051] 3) Frame and chip bonding. Under a tool microscope, sequentially bond and assemble the electrical lead frame and 640×512 mercury cadmium telluride chips onto the cold table end face of the cold finger component of the liquid nitrogen dewar. After each bonding process, it needs to be baked until the bonding agent is completely cured before proceeding to the next operation.

[0052] 4) Chip surface cleaning. Use chemical solvents such as anhydrous ethanol and acetone to clean the chip surface and remove dirt such as grease. When cleaning, wipe the absorbent cotton dipped in anhydrous ethanol in one direction until there are no stains on the absorbent cotton.

[0053] 5) Paste strain gauges and temperature-measuring diodes. Apply low-temperature adhesive at the paste position of the strain gauge. Use tweezers to hold the lead of the strain gauge and place it steadily on the low-temperature adhesive. Press it with a cotton swab, and wipe off the overflowing low-temperature adhesive on both sides of the strain gauge with dust-free paper. Place a small piece of polytetrafluoroethylene film on the surface of the strain gauge, press it with a small weight, and then put it into an oven for heating and curing. The same method is used for pasting the temperature-measuring diode.

[0054] 6) Resistance value inspection. After the strain gauges and temperature-measuring diodes are cured, check whether they are firmly pasted. Check whether the resistance of the strain gauges and temperature-measuring diodes is normal.

[0055] 7) Inner lead welding. After the above components are mutually matched with the special tooling, they are installed on the platform of the gold wire bonder for inner lead bonding between the strain gauges, temperature-measuring diodes and the frame pads.

[0056] 8) Outer lead welding. Fix the above components on the gold wire bonder through special tooling for outer lead bonding. The two ends of the bonding are the pads of the frame and the bonding wires of the electrical lead flexible tape respectively. After the bonding is completed, measure the resistance value of the outer lead bonding wires of the low-temperature strain gauges and temperature-measuring diodes again to ensure that the resistance is normal.

[0057] 9) Sealing and vacuum evacuation. Fasten and couple-seal the infrared detector dewar structural window seat and the above components using connectors such as screws; the finished product is evacuated under a vacuum evacuation table to ensure that the internal vacuum degree of the dewar is below 10 -3 Pa to reduce heat conduction and maintain a vacuum environment.

[0058] 10) Liquid nitrogen cooling and data acquisition. Connect the electrical leads of the cryogenic strain gauges and temperature-measuring diodes to different channels of the signal collector. After the signal collector stabilizes, pour liquid nitrogen into the liquid nitrogen dewar to cool the chip. The data is collected in real time by the collector at a frequency of 10 Hz, and the data is input into a computer to obtain the strain, stress, and temperature results.

[0059] The low-temperature strain and stress test device and test method for the infrared detector chip of the present application can directly characterize and measure the strain and stress of the chip during the cooling process from room temperature to low temperature; the test device of the present application is not limited to the measurement of chips with a size of 640×512, and can also measure large-area array focal plane infrared detectors with various pixel specifications such as 320×256, 1280×1024, 2K×2K, 4K×4K, 8K×8K large-area mosaic focal plane infrared detectors, ultra-large-scale linear array focal plane infrared detectors, etc., with pixel pitches of 7.5μm, 10μm, 25μm, 50μm, etc., and infrared chips of various models with detection spectral bands such as short wave and medium wave; in addition, it can simultaneously measure the changes in chip strain, stress, and temperature.

[0060] The stress test device of the embodiment of the present application realizes the direct strain and stress measurement and characterization of the infrared detector chip during the cooling process, providing an important data basis and support for optimizing the thermal stress environment and improving the reliability of the infrared detector.

[0061] It should be noted that in each embodiment of the present application, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the element.

[0062] The serial numbers of the above embodiments of the present application are only for description and do not represent the advantages and disadvantages of the embodiments.

[0063] The embodiments of the present application have been described above in conjunction with the accompanying drawings, but the present application is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present application, those of ordinary skill in the art can also make many forms without departing from the purpose of the present application and the scope protected by the claims, and these all belong to the protection scope of the present application.

Claims

1. A low temperature strain stress testing device for an infrared detector chip, characterized in that: include: Dewar (1), which contains liquid nitrogen; A Dewar cooling stage (2), connected to the Dewar (1); An electrical lead frame (3) is arranged on the Dewar cooling platform (2); A low temperature strain gauge (4), arranged on the infrared detector chip (5), and used for measuring the strain of the infrared detector chip at low temperature; A temperature measuring diode (6) is arranged adjacent to the infrared detector chip (5) and is used to measure the temperature of the infrared detector chip (5); The signal collector (8) is connected to the low-temperature strain gauge (4) and the temperature measuring diode (6) respectively through wires, and sends the collected signals to a computer (9).

2. The infrared detector chip low temperature strain stress testing device according to claim 1, characterized in that: The low-temperature strain gauge (4) and the temperature measuring diode (6) are respectively connected to different channels of the signal collector (8).

3. A method for testing low temperature strain and stress of an infrared detector chip, implemented based on the low temperature strain and stress testing device of an infrared detector chip as claimed in claim 1 or 2, characterized in that: include: Directly bonding the infrared detector chip (5) and the electrical lead frame (3) to the end surface of the liquid nitrogen Dewar cooling table; Bonding the low temperature strain gauge (4) to the middle position of the detector chip; Bonding the temperature measuring diode (6) to a position adjacent to the detector chip (5); Performing inner lead bonding between the low-temperature strain gauge (4), the temperature measuring diode (6) and the electrical lead frame (3) on a gold wire bonding machine, and performing outer lead bonding on the electrical lead frame (3); After bonding, it is fastened and coupled with the infrared detector Dewar structure window seat, sealed, and vacuum exhausted to make the vacuum degree inside the Dewar meet the requirements; The electrical lead wires of the temperature measuring diode (6) and the low temperature strain gauge (4) are connected to a signal collector (8). After the signal collector is stable, liquid nitrogen is poured into the liquid nitrogen dewar for cooling. The collected data is processed by a computer (9) to obtain strain and stress results.

4. The low temperature strain stress testing method for an infrared detector chip according to claim 3, characterized in that: It also includes full curing after bonding.

5. The low temperature strain stress testing method for an infrared detector chip according to claim 3, characterized in that: After bonding, it also includes measuring and judging whether the resistance value of the electrical lead wires of the low-temperature strain gauge and the temperature measuring diode is normal.

6. The low temperature strain stress testing method for an infrared detector chip according to claim 3, characterized in that: Connecting the electrical lead wires of the temperature measuring diode (6) and the low temperature strain gauge (4) to the signal collector (8) comprises: connecting the electrical lead wires of the temperature measuring diode (6) and the low temperature strain gauge (4) to different channels of the signal collector (8) respectively.

7. The low temperature strain stress testing method for an infrared detector chip according to claim 3, characterized in that: Perform vacuum exhaust to make the vacuum degree inside the Dewar at 10 -3 Below Pa.

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