冷光学用多波段长波红外探测器杜瓦封装技术

Dewar Packaging Technology of Multiband Long-Wave Infrared Focal Plane Array Detectors for Cryogenic Optics

针对拼接型多波段长波红外探测器组件在冷光学系统中的应用要求,本文分析了低温光学用多波段长波红外探测器封装的难点。本团队通过研究4个512×12模块呈品字形拼接后与4个三波段集成滤光片的低温配准、组件在200 K低温光窗的支撑与隔热、探测器与制冷机耦合应力等封装技术,提出了可以实现三波段集成滤光片与探测器背套对中误差在10μm以下的配准方法以及红外探测器杜瓦组件柔性波纹外壳实现101 mW隔热的方案,同时在杜瓦冷平台上设计了物理隔离耦合应力的多层热层结构,解决了多波段长波红外探测器组件的低光串、低背景辐射、低功耗、冷平台高温度均匀性和探测器高可靠性等关键技术,成功研制了低温光学用12.5μm三波段长波2000×12元红外探测器制冷组件。一系列空间环境适应性试验验证结果表明,试验前后组件的性能未发生明显变化,能够满足工程化应用要求。

Objective Most current advanced optical systems employ low-temperature optical technology to cool the optical lens to a lower temperature level to reduce optomechanical radiation and enhance the detection sensitivity and dynamic range of remote sensing instruments, which helps to enhance the detection performance of optical remote sensing instruments. This research focuses on the packaging technologies that are required for the engineering application of multiband longwave infrared detectors for cryogenic optics, including multimodule splicing and multiband integrated filter lowtemperature registration, support and heat insulation of low-temperature optical windows of modules, and coupling stress between detectors and refrigerators. Through systematic investigation, the multiband long-wave infrared detector’s Dewar for low-temperature optics has been successfully developed, and it has been confirmed by a series of space environment adaptability tests. Methods 1. Low-temperature module splicing registration and four three-band integrated filters. The filter was designed based on the imaging optical path. The closer the filter was to the chip, the smaller the non-uniformity, stray radiation energy, and the detector image surface’s stray ratio. To enhance the detector image plane’s uniformity, the filter in the Dewar package should be as close to the chip as possible(Fig. 5). Detectors and filters were packaged as follows: 1) four three-band detectors were spliced and cemented on the ceramic substrate, and the flatness of the cemented surface of the ceramic substrate detector’s gemstone was controlled to be less than 5 μm;2) the four integrated filters were preliminarily bonded to the filter holder, and the splicing accuracy was controlled in the range from-3 μm to +3 μm;3) the filter holder was aligned with the detector’s center, ensuring the alignment accuracy was in the range from-5 μm to +5 μm.2. The design of the flexible bellows shell’s thermal insulation structure. We proposed a Dewar flexible bellows shell structure for the infrared detector assembly employed in the low-temperature optical system. By increasing the heat transfer path, reducing heat leakage, and increasing thermal insulation, the heat transfer area of the transfer link can be reduced.3. The design of a cold platform for physical isolation of coupled stress. In this research, based on the detector’s coupling characteristics and the refrigerator’s cold finger, an arc-shaped isolation groove of a specific shape was designed and processed on the cold platform. The groove width is H1(Fig. 8). On the heat transfer capacity’s premise needed by a certain heat load, the heat conduction link’s physical isolation and the coupling stress transfer channel were achieved.Results and Discussions Through the positioning and integration design of four three-band integrated filters, the alignment error between three-band integrated filter and detector back cover is less than 10 μm. By implementing the Dewar flexible bellows shell structure, the thermal isolation between the infrared detector Dewar refrigeration assembly’s low-temperature shell and the refrigerator expander or pulse tube is achieved, as well as the infrared detector Dewar assembly flexible corrugated shell’s 101 m Wthermal insulation(Table 1). During the thermal vacuum test, at the operating temperature of 55 K, the temperatures of the compressor’s cooling surface and the pulse tube’s cooling surface increased immediately, and there was no visible response to the Dewar temperature(Fig. 7). We measured the cold platform’s surface deformation after slotting and compared it with the cold platform’s surface deformation without slotting(Fig. 9). During the implementation of the Dewar’s full coupling and the refrigerator, the unslotted cold platform’s surface deformation increases sharply and stabilizes at around 40 μm/m, while the cold platform’s surface deformation after grooving does not change, and stabilizes at about 8 μm/m, and the deformation decreases by about 80%. From this, it can be deduced that the cold platform’s surface stress is reduced by 80% after grooving. Conclusions The challenges of packaging multiband long-wave infrared detectors are examined to meet the requirements of spliced multiband long-wave IRFPA in cryogenic optics. It is proposed that the three-band integrated filter and the detector’s back cover can be aligned with a misalignment of fewer than 10 μm, and the Dewar flexible corrugated housing 101 m Wheat insulation is realized. Simultaneously, measures including a multilayer thermal layer structure that physically isolates the coupled stress are designed on the Dewar cold platform. It addresses essential technologies like low light string, low background radiation, low power consumption, high-temperature uniformity of cold platform, and high reliability of multiband long-wave infrared detector components. A 12.5 μm three-band 2000×12 element detector component for cryogenic optics was successfully developed and a series of space environment adaptation tests were implemented, and the test results indicate that the Dewar assembly meets the criteria of engineering application.