Objective Infrared detection technology finds applications in various fields such as medical detection, meteorological detection, space remote sensing, national defense, and military. It converts infrared radiation signals into electrical signals and offers advantages like strong anti-interference capabilities and a wide detector range. In comparison to traditional detection technology, infrared detection technology is better equipped to handle complex and ever-changing environments. The advancement of space infrared detection technology has led to increased demands for infrared detection performance. As a result, large-area array and long-line array infrared detectors have emerged as the future direction of infrared detector development. This article focuses on the research of 2 k×2 k detectors, analyzing the characteristics and challenges associated with packaging technology for large-area array detectors. It also proposes corresponding solutions and methods.
Methods The suppression of the infrared system's own radiation is crucial for ensuring the imaging quality of the optical system. This study analyzes the impact of the self-radiation of key surfaces in the Dewar component on the stray light of the detector. To reduce the stray light of the large-area array detector, low-temperature optics are employed in the design of the Dewar window (Fig.2). The study also examines the effect of Dewar window deformation on the imaging quality of the optical system under three different working conditions (Fig.4). Additionally, the research investigates the impact of the cold platform's structural design on noise suppression in detection, and evaluates the influence of the transition substrate thickness on the fluctuation of the detector's operating temperature (Fig.5, Tab.3). In contrast to commonly used wires like gold wire, silicon-aluminum wire, and platinum wire, this study introduces the use of platinum-iridium wire with high strength and low thermal conductivity in aerospace-grade packaging design for the first time (Fig.8). The components were evaluated for aerospace mechanics.
Results and Discussions Among the various components of the Dewar, the radiation from the Dewar window has a significant impact on the stray light of the 2 k×2 k detector. The stray light emitted by the 300 K Dewar window accounts for approximately 29.9% of the detector signal illumination (Fig.2). However, by implementing a low-temperature optical design with a 200 K Dewar window, the stray light emitted by the window is reduced to only 5.9% of the detector signal illumination. To minimize window deformation, the window cap is appropriately thickened. Fortunately, the impact of window cap deformation on the imaging quality of the optical system can be disregarded under all three working conditions (Tab.2-3). In order to mitigate the noise caused by mechanical disturbances from the refrigerator, a 5 cm thick layer of SiC substrate is added between the detector and the cold head. This effectively eliminates noticeable noise disturbances in the central area of the detector (Fig.5), resulting in a detector operating temperature fluctuation of less than 0.1 K (Tab.4). Furthermore, the use of platinum-iridium wire as component bonding wire improves both the conduction heat leakage and lead strength of the Dewar. The maximum conduction heat leakage is reduced from 576 mW to 49 mW, leading to a corresponding decrease in refrigerator power consumption from 72 W to 39 W. Additionally, the lead pull force experiment shows a value greater than 0.245 N, indicating satisfactory lead strength. The encapsulated components have successfully passed aerospace-grade mechanical tests (Fig.9).
Conclusions This article aims to address challenges in the packaging technology of large-area array 2 k×2 k infrared detector components. The study focuses on various aspects including the low-deformation window support structure, low-noise cold platform structure, low heat leakage, and high-reliability wire bonding process. The research successfully resolves issues related to stray light, deformation of large-diameter windows, and detection in large area array detector packaging. By tackling problems such as detector noise, lead heat leakage, and strength, the study achieves an outstanding performance in the assembly of a large area array 2 k×2 k infrared detector.
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