As an important way to simulate the dynamic infrared scene, the technology of resistive arrays, especially large format resistive arrays are developing very fast. Principle of resistive arrays is introduced. The unit cell is composed by two MOS transistors, a capacitor and a resistor. The resistor is the main element to make infrared radiation by heating. Key parameters, such as temperature, frame rate, uniformity and cross-talk are used to standard to evaluate the performance of the arrays. Several methods to improve the parameters is put forward. In addition, development and current situation of the packaging technology is discussed and analyzed in this paper. At last, the technology developments of resistive arrays and packaging are summed up and an outlook of the future is provided.
For the long wavelength infrared detection, HgCdTe (MCT) photoconductive devices are selected as the core of
next-generation meteorological because of its mature fabrication technique and stable performance. During the assembly
process, an innovative multilayer ceramic board providing mechanical support is designed as the electrical
interconnection between MCT chips and external circuits for cryogenic application. Furthermore, due to its brittleness,
long linear MCT device is normally glued to sapphire substrates on the multilayer ceramic board with cryogenic glue.
Thus, it can be seen clearly that the assembly structure is a multilayer configuration which comprises various kinds of
materials, including ceramic broad, sapphire, MCT and glues. As a result, the difference in Thermal Expansion
Coefficient (TEC) between the layers could create the potential to introduce thermal stress at working environmental
temperature (approximately 70K), which could result in device performance degradation, even die crack.
This article analyzes the thermal stress between long linear MCT devices and a multilayer ceramic board by using Finite
Element Method (FEM). According to analysis results, two factors are revealed as the most significant causes for
introducing thermal stress: one is the sapphire substrate thickness; the other is the parameters of various materials, for
instance Yong's modulus and TEC. Since the structure of MCT detector is determined by system requirements and is
under the limitation of manufacture technology, this article reveals two effective approaches to reduce the unavoidable
thermal stress: first, choosing the appropriate thickness of ceramic board which is made by Al2O3; second, adding another
metal cushion Invar. With the above considerations, the distribution of thermal stress is simulated using FEM under
different parameter conditions. Based on the results of simulations, an optimal design of package structure which could
improve the reliability of linear MCT with minimum thermal stress is demonstrated.
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 10-5 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.
The influence of larger constant current burning was studied and analyses on the failed detectors were given. "1/f" noise is observed in the reign of g-r noise, and the exponential factor had a trend of increasing with burning time. Peak wavelength and cutoff wavelength of the detectors had no apparent change during electrical burning, but there were decreases on the short wavelength side in spectral response. After a long time burning, minority carrier lifetime of the detectors decreased as well as black-body signals. Analyses showed that defects increased at the surface of detectors after burning, which was responsible for decreasing the detector performance, even detector failure.
For the limit of its lifetime, the Stirling cooler is operated on the intermittent mode in satellite in some cases. Thus such cryogenic semiconductor components as HgCdTe mid or long wavelength infrared (IR) detectors are subjected to thousands of repeated thermal cycles from below -173°C to room temperature. Therefore, a series of experiments focused on quality, performance and reliability are essential in order to satisfy the reasonable requirements. Accordingly, a feasible thermal cycle screening system is put forward. And a vast experimental data show that thermal cycle tests play the most effective role in the environment stress screen (ESS).
In this paper, we introduce the system to help to study the main failure mechanisms and improve the performance of the semiconductor components. Such main failure mechanisms as solder-ball invalidation encountered commonly in the detector modules, which is due to the large thermal expansion coefficient mismatch among different materials.
The thermal cycle system is based on the principle of heat exchange. We expect HgCdTe IR detectors be cooled to lower than -173°C and heated to room temperature in a few minutes. Above all, we simulate the heating and cooling system through finite element method (FEM). As a result, the computations reveal that the IR detectors can be heated and cooled at a higher rate than expected. A consequent design of the entire system is founded on the simulation. At last, we adjust the mechanical structure of heat exchange system to the adaptive state to accomplish the ESS.
The thermal cycle screening system includes an autocontrol part and a test part. The autocontrol part is adopted to realize the heat exchange between IR detectors and the environment, and the test one to inspect the temperature and electrical parameters of these detectors. And at least four IR detector samples can be screened at one time.
This study is concerned with electrical shock effect on performance of the n-type HgCdTe photoconductive detector with a composition of x≈0.225 in order to improve the reliability under this certain situation. Ideally, responsivity of HgCdTe photoconductive detector is proportional to its bias current. Since there are a number of thermal interfaces between the detector and the cooling reservoir, the temperature of HgCdTe chip will rise and the response will decrease with the increase of bias current.
The detectors we used in the experiment were divided into two groups, one for room temperature experiment and the other for liquid nitrogen temperature experiment. A large pulse bias current was used to give the detector "an electrical shock". After the shock the resistance, responsivity and detectivity of detectors were measured at normal conditions. For the group of room temperature, the experiment results show that the detector responsivity will decrease under a 200mW pulse electric-power and the resistance will change under 400mW. When the pulse electric-power reaches 2000mW the detector will be burned out. But for the group of liquid nitrogen temperature experiment the detector responsivity will change under a 90mW pulse electric-power and the resistance will change under 290mW. A 550mW pulse electric-power will burn the detector out. Analysis with one-dimension approximation model was given, which showed that epoxy used between the interfaces was essential for increasing the reliability of HgCdTe detector.
In this paper, low frequency noise has been investigated in SWIR HgCdTe photodiodes from 4Hz to 3.2 KHz at different reverse bias. At low frequency the noise mainly consists of flicker noise and generation recombination (g-r) noise while at high frequency thermal noise is the dominant component. The flicker noise current is proportional to the detector current at small reverse bias, and the Hooge parameter αH of the device is evaluated. In addition, the low frequency noise at 100mV reverse bias measured from 250-300K are reported. The fluctuation time constant of g-r noise is extracted by fitting the curve of the low frequency noise, and the trap thermal activation energy of the deep level is obtained from the relation of τ and temperature.