This paper designs a vacuum packaged Dewar for meteorological satellites. It integrates an 80 × 1 long wavelength photodetector with a wavelength of 13.2 μm to 13.8 μm and a dual band focal plane detector with a wavelength of 10.3um-11.3um / 11.5um-12.5um. The detector uses a mechanical cooler to reach an operating temperature of 60K. The theoretical calculation and simulation analysis are carried out from two aspects: cold load and mechanical vibration of Dewar. The analysis shows that when the ambient temperature is room temperature and the detector operating temperature is 60K, the total heat loads of the cold plate is 1.25W. Where the wires loss accounts for about 36% of the total heat load and the detector Joule heat accounts for about 21%. The mechanical vibration analysis of Dewar shows that the cold plate pillar is the main factor affecting the mechanical properties of the structure. Increasing the pillar support increases the base frequency of the Dewar from 379 Hz to 539 Hz, thereby increasing the mechanical base frequency of the Dewar components.
Experimental setup for evaluating four-stage thermoelectric cooler’s performance was designed. Effects of input power, heat dissipation condition and heat load on the temperature difference (ΔT) of four-stage thermoelectric coolers’ hot and cold faces were obtained experimentally. The result shows that, the ΔT increases as the input power increases. A linear relationship exists between input current and feedback voltage. In different cooling conditions, the ΔT of thermoelectric cooler (TEC) increases with the temperature of hot face. As the temperature increasing on hot face is 1K, the ΔT increasing of TEC can be about 0.5K. Meanwhile, the power consumption of TEC also increases slightly. Water condensation can be prevented in either dry nitrogen environment or vacuum environment, but the vacuum level has great influence to the ΔT, especially in low operation temperature. The better the vacuum level is, the smaller the convection heat loss has. When the operation temperature of focal plane array (FPA) is lower than 220K, it is prior to use vacuum packaging. Considering the Joule-heat of readout circuit and the heat loss of wire conduction, the minimum working temperature of FPA can reach below 200 K when the temperature of the hot face is 285K. And the coefficient of performance (COP) of TEC can increase sharply from 0.8% to 4% when the controlled operation temperature is 220K rather than 200K.
Researchers are engaging on tunable infrared (IR) filters, miniature Fabry-Perot optical devices, to operate IR detector like a spectrometer. This kind of devices was used in astronomical detection field in the 1950s. To meet the miniature, lightweight requirements of the optical detection system, researchers began to make small, lightweight, and cheap tunable IR filters. Nowadays researchers have applied a variety of different structures and the IR filter, and are attempting to integrate them with IR detectors directly. Tunable filter thin film mechanical and thermal properties, and working conditions will affect the tunable filter optical performance. In this article we give two main influencing factors, interface roughness and curvature effect. we also present and discuss the current development of FPF in different groups around the world.
The InGaAs focal plane array (FPA) detectors, covering the near-infrared 1~2.4 μm wavelength range, have been developed for application in space-based spectroscopy of the Earth atmosphere. This paper shows an all-metal vacuum package design for area array InGaAs detector of 1024×64 pixels, and its architecture will be given. Four-stage thermoelectric cooler (TEC) is used to cool down the FPA chip. To acquire high heat dissipation for TEC’s Joule-heat, tungsten copper (CuW80) and kovar (4J29) is used as motherboard and cavity material respectively which joined by brazing. The heat loss including conduction, convection and radiation is analyzed. Finite element model is established to analyze the temperature uniformity of the chip substrate which is made of aluminum nitride (AlN). The performance of The TEC with and without heat load in vacuum condition is tested. The results show that the heat load has little influence to current-voltage relationship of TEC. The temperature difference (ΔT) increases as the input current increases. A linear relationship exists between heat load and ΔT of the TEC. Theoretical analysis and calculation show that the heat loss of radiation and conduction is about 187 mW and 82 mW respectively. Considering the Joule-heat of readout circuit and the heat loss of radiation and conduction, the FPA for a 220 K operation at room temperature can be achieved. As the thickness of AlN chip substrate is thicker than 1 millimeter, the temperature difference can be less than 0.3 K.
In this paper, 256×1 and 512×1 element linear InGaAs detector arrays are hermetic packaged. Some
processes were studied, including the structure design, thermoelectric cooler (TEC) heat load
performance test, TEC vacuum baking, the window sealing, the seam welding of the cover lid and
shell, and so on. The results show that the cooling temperature difference of TEC can reach over 55
K at room temperature, and it decreases by about 0.51 K with each additional 50 mW heat load. TEC
works well after 500 hours of baking at 120 °C. The leakage rate tests show the assembly is better
than 10<sup>-5</sup> Pa.cm3/s.
Uncooled focal plane array (UFPA) has broad application prospects in civilian and space because it's cheaper, more
compact and high reliability. Many research institutes and companies have carried out the research of uncooled focal
plane array. This paper shows a vacuum package design of UFPA, and its architecture will be given. The assembly is an
all-metal vacuum package, which has been proven rugged and reliable. Out-gassing, permeation, evaporator, and air leak
are factors to reduce the component vacuum lifetime. Theoretical analysis shows that material out-gassing is the main
factor of pressure rise inside package. Theoretical analysis and calculation show that designed metallic structure can
meet the need of 10-years life.
In order to prevent Hg running over from the exposing side of HgCdTe LWIR detector with little photosensitive region,
side-passivation detectors are fabricated. Then several experiments are done to characterize the side-passivation effect.
Firstly, a SEM micrograph is shown, and it makes clear that wet etching and side-passivation can remove part of defect
induced by IBE. Secondly, the performance measurement indicates that the performance of side-passivation detector is
superior to the general one, especially for detectors with little photosensitive region. Thirdly, hot dipping is done to say
that the thermal stability of side-passivation detectors is superior to general ones. And with the exception of this, the
less the photosensitive region width is, the stronger the ability of protection is. Last but not the least, the detectivity of
not only general detectors but also side-passivation ones increases obviously. As a whole, the performance of
side-passivation detectors increases more largely than general ones. Above all, side-wall passivating film can
passivate the sensitivity of detector's surface and block Hg out of the surface effectively. The results can provide
experimental reference for IR semiconductor detector.