Filament heating voltage governs thermionic electron emission in electron-beam guns, but its influence on weld formation under fixed electron-beam welding settings has received limited quantitative investigation. In this study, Ti-6Al-4V thin sheets were welded at filament heating voltages of 2.8–3.4 V, while the accelerating voltage, beam current, focusing current, and welding speed were kept constant. Weld cross-sections were characterized experimentally, and the resulting thermal process was analyzed using a simplified cathode-emission calculation and finite element thermal analysis. A clear change in weld penetration behavior was observed within approximately 3.2–3.3 V. The weld aspect ratio increased from approximately 0.4 below this region to approximately 0.6 at 3.3 V and further to approximately 0.63 at 3.4 V. Concurrent changes in the required bias voltage, calculated equivalent cathode area, and weld geometry were consistent with a change toward a more stable cathode operating condition. The weld-geometry changes were also consistent with a change in the effective beam-energy distribution, although the beam profile was not measured directly. These results show that filament heating voltage should be treated as an independent equipment-side control variable even when the main electron-beam welding settings remain unchanged. Although the specific transition range depends on the electron gun, beam-current setting, and cathode condition, the electrical-response-based identification approach may provide a practical method for identifying the filament operating range when direct beam diagnostics are unavailable.

Flash joining (FJ) typically requires applying a threshold electric field at high temperatures to generate oxygen vacancies, a process that often imparts damage to the base material. Existing improvement approaches, such as pretreatment, can introduce oxygen vacancies in advance but involve complex processes. To address this, we propose a novel two‐step FJ technique. Unlike ordinary FJ, this method implements dual electric field: initial application at a lower temperature followed by reheating to target temperature with field reapplication. The key strategy of applying electric fields in stages is to generate vacancies prior to the joining process, which effectively lowers the onset FJ conditions. Additionally, this approach significantly enhances bonding of yttrium oxide/titanium, achieving a 65.8% increase in shear strength compared with ordinary FJ. The two‐step FJ plays a role in two ways: (i) Promoting oxygen vacancy generation to reduce current excitation time, thereby reducing damage to the base material; (ii) Vacancy aggregation at the interface to accelerate filling reactions and atomic diffusion. By applying an electric field in stages to control defects, these findings provide a new approach to improving FJ strength.

In this study,the simulation analysis and optimization of stray radiation in deep cryogenic Dewar components were conducted using a multiwave common optical path Dewar infrared system.The thermal radiation effects on the detector from key surfaces at different temperatures were analyzed using temperature field and dichroic surface simulations.Suitable cold transmission materials were selected,and Kovar was used for the cold platform,cold screen,and dichroic holder of the Dewar system.The effects of different blade levels and surface treatments of the cold screen on the point source transmittance were also evaluated.Based on these findings,the following optimization scheme was proposed:an elevated cold screen to block most of the radiation emitted or reflected by the window cap,adopting two levels of blades for the cold screen,and spraying graphene on the inner surface of the cold screen to improve the suppression of stray radiation.This scheme provides both theoretical and practical value for the design and application of low-temperature Dewar modules.

The reliability of lead zirconate titanate (PZT) ceramics/4J29 Kovar alloy joints is essential for the performance of piezoelectric transducers during drilling operations. This study investigates the use of Sn-Ag-Cu solder as a substitute for organic adhesives to improve joint performance. A (Ti + Ni + Cu) metallization layer was applied to PZT ceramics to enhance solder wettability and facilitate the formation of a reliable joint. Stable joints are formed as Sn diffuses into the 4J29 Kovar alloy, creating a diffusion layer. Simultaneously, Sn, Cu, and Ni combine to form a homogeneous intermetallic compounds (IMCs) layer that effectively bonds the solder to the metallization. Optimal layer thicknesses of Ni (2000 nm) and Cu (150 nm) yield a maximum joint strength of 33.0 +/- 3.2 MPa. The aging time significantly impacts IMCs thickness and joint strength; longer aging periods increase IMCs thickness while reducing joint strength. This research highlights the potential of Sn-Ag-Cu solder for joining metallized PZT ceramics and the 4J29 Kovar alloy, providing valuable insights for future developments in solder systems.

Objective The miniaturization and integration of multispectral detectors have become one of the development directions for infrared detectors.This paper proposes a component structure that integrates a lens and window with airtight packaging,focusing on the characteristics of integrating low-temperature optical lenses for multispectral detectors.Various aspects are investigated,including high-precision optical alignment for different focal planes of the same component multispectral detector,low deformation filter support structure,and suppression of optical crosstalk and stray light.These studies address a series of issues related to high-precision alignment,low deformation filter support,prevention of optical crosstalk,and suppression of stray light in the miniaturization and integration packaging of multispectral detectors.The developed component has been successfully applied in a spectral imaging instrument for a specific project. Methods A component structure for a multispectral infrared detector with an integrated lens has been designed(Fig.3).The airtight packaging component structure of the multispectral infrared detector with an integrated lens includes a component housing,coverplate,lens,primary aperture,filter holder,filter,chip module,electrode plate,and filter holder support.Before packaging,the entire component is evacuated,followed by filling with inert gas,and finally sealed using parallel seam welding.The airtightness meets the long-term requirements of the payload. By designing a three-layer laminated low-deformation multispectral filter holder assembly,multiple small filter pieces are adhered to the low-stress filter holder structure.This structure can also be used for the assembly of multiple mid-wave and long-wave filter pieces with the detector.It overcomes the problems of size interference and complex integration process with low yield associated with traditional bonding methods.It achieves the coupling of low-deformation multispectral filters with the detector(Fig.4). This study employs the micro-adjustment technique for different focal planes of the multispectral infrared detector and the coaxial lens adjustment technique.It achieves a precision deviation of less than±5 μm between different focal planes and the filter assembly for a three-band detector within the same component.The lens-to-detector alignment precision within±15 μm is achieved(Table 1).Spectral tests are performed using the infrared detector component with an integrated lens,and the results indicate no significant optical crosstalk among channels(Fig.6). Results and Discussions Through the design of a three-layer laminated structure with low deformation,multiple small filters have been successfully bonded to the low deformation stress filter frame.The maximum low-temperature deformation of the 1.64 μm filter at 130 K is 0.9278 μm,while the maximum low-temperature deformation of the 2.13 μm and 1.38 μm filters at 130 K is 0.2292μm(Fig.5).By using micro-adjustment techniques for different focal planes of the multi-band infrared detectors and coaxial lens adjustment techniques,the deviation in the alignment between different focal planes of the three-band detectors and the filters within the same component is better than±5 μm,and the alignment precision between the lens and the detectors is better than±15 μm.Spectral testing is conducted using the integrated lens infrared detector component.The results of the spectral testing indicate that there is no significant optical crosstalk among channels.A series of low-stress design and process improvements are applied to the low-temperature lens,and the results show that the band detection rate is greater than 1.5×1011 cm·Hz1/2·W-1(130 K).The maximum absolute variation in band response rate before and after rigorous environmental testing is 8.5％(Fig.9).The high-performance multi-spectral integrated infrared detector component is obtained,and the experimental results confirm that the detector functions properly and the component performs well(Table 2). Conclusions This article focuses on solving the packaging technology of multi-channel integrated infrared detector components,proposes a multi-band infrared detector airtightness packaging component with integrated lenses,and emphasizes the key technologies such as jointing of different focal planes for different bands and coaxial lens adjustment technology for the same component,high reliability support structure for multi-filter narrow seam splicing,and stray light suppression,solving the high-precision alignment of multi-channel integrated infrared detector components,low stress control,low optical crosstalk,low power consumption,and high reliability of the detector.A high-performance multi-band infrared detector component with integrated lenses has been obtained.

Reliable material parameters, correct boundary condition settings, and a reasonably simplified numerical model are key to obtain reliable and reasonable analysis results. A new finite element analysis model for the HgCdTe infrared focal plane array detector is presented, which includes the core column. The thermal stress and strain of the new model and current model are analyzed, and their distribution laws are obtained. The results are compared, and the reasons are analyzed, which can provide some references for the simulation of infrared detector package structure.

The integrated application of microlens and detector chip can improve the efficiency of light en-ergy utilization of the detector and thus increase the sensitivity of the detector.For two kinds of InP-based InGaAs single-photon infrared detectors,two kinds of square aperture microlens arrays with materials of GaP and Si are designed respectively.The design process of the structural parameters of the microlens ar-rays is introduced and the design points of each step are analyzed.The structural parameters of the de-signed microlens arrays are simulated and calibrated by ray tracing software,which determines that the two microlens arrays meet the design requirements.The morphology of the two fabricated microlens ar-rays was examined using a step meter and a confocal microscope.The curvature deviations of the two mi-crolens arrays were calculated to be 1.38%and 3.44%,respectively.The focal lengths of two microlens arrays in air at 1.064 μm wavelength were tested experimentally,and the focal deviations of 5.69%and 2.76%were obtained in comparison with the simulated results.By analyzing the manufacturing process of microlenses,the two deviations meet the application requirements.

Electron beam welding of TZM and Ti-6Al-4V was performed with different beam offsets. A comprehensive analysis was undertaken to evaluate the effects of beam offsets on the joint's microstructure, element distribution, phase composition, and mechanical properties. The microstructure of welded joints underwent a transformation from sporadic dendrite to uninterrupted dendrite structure. With the 0.3 mm beam offset, the fusion zone predominantly comprised martensite. Interestingly, as the beam offset increased, the Mo concentration in the fusion zone decreased from 20 to 1.55 at.

Electron beam welding of pure molybdenum (Mo) and titanium alloy (Ti-6Al-4V) was performed with beam oscillation. The effects of beam oscillation with offset on the welded joints were analyzed in terms of microstructure, element distribution, chemical composition, microhardness, and tensile strength. The results showed that the fusion zone expanded with beam oscillation. Reaction layers were generated in both joints welded with and without beam oscillation. The thickness of the reaction layers decreased along the perpendicular direction. The reaction layers were (Mo, Ti) solid solutions. Both welded joints consisted of single-phase Mo, the beta-Ti phase, and Mo-Ti solid solutions. The microhardness distribution of the joint welded with beam oscillation was more consistent than that of the joint welded without beam oscillation, and the maximum hardness was reduced from 340 HV to 270 HV. The tensile strength increased from 124 MPa to 204 MPa.

InGaAs single-photon detectors are extensively used in laser 3D imaging,long-distance high-speed digital communication,free-space optical communication,and quantum communication.Different packaging formats,including coaxial packaging,butterfly packaging,and pin grid array packaging,have been designed for unit,line array,and small panel array devices.The impact of the temperature on the efficacy of InGaAs single-photon devices and the methodologies for controlling component temperature are discussed.Detailed comparisons and analyses of high-precision coupling methods for optical components such as microlenses,lenses,optical fibers,etc.to the semiconductor are provided.For high-frequency signal output,the lead type,wiring method,packaging structure design,and other issues are reviewed,and the development trend of the InGaAs single-photon detectors is forecasted.

Si3N4 and Invar alloy brazed joints were achieved using two types of Ag-based interlayers: a Ag-Cu-In-Ti foil and a Ag-Cu-In-Ti/Cu/Ag-Cu multi-interlayer. The results showed that when only using a single Ag-Cu-In-Ti filler, the wave-shaped Fe2Ti + Ni3Ti intermetallic compounds are concentrated in the middle of the brazing seam. When adding Cu as the interlayer, the dissolution of the Cu interlayer formed a large number of Cu(s,s) blocks of different sizes in the brazing seam, which hindered the concentrated distribution of Fe2Ti + Ni3Ti intermetallic compounds in the brazing seam. As a result, Fe2Ti and Ni3Ti were dispersedly distributed in the brazing seam, increasing the shear strength of the brazed joint. The shear strength of brazed joints was increased by 82 % compared to joints brazed with a single Ag-Cu-In-Ti filler when the Cu interlayer was added.

Electron beam welding of pure molybdenum (Mo) and titanium alloy (Ti-6Al-4V) was performed with beam oscillation. The effects of beam oscillation with offset on the welded joints were analyzed in terms of microstructure, element distribution, chemical composition, microhardness, and tensile strength. The results showed that the fusion zone expanded with beam oscillation. Reaction layers were generated in both joints welded with and without beam oscillation. The thickness of the reaction layers decreased along the perpendicular direction. The reaction layers were (Mo, Ti) solid solutions. Both welded joints consisted of single-phase Mo, the β-Ti phase, and Mo-Ti solid solutions. The microhardness distribution of the joint welded with beam oscillation was more consistent than that of the joint welded without beam oscillation, and the maximum hardness was reduced from 340 HV to 270 HV. The tensile strength increased from 124 MPa to 204 MPa.

Electron beam welding of 4J36 invar alloy and TC4 titanium alloy was carried out with Cu-Nb composite diffused metal interlayer. The results showed that the depth to width ratio and the tensile strength of welded joints increased with the increase of electron beam current. Under the designed process parameters, two melting zones (MZ) in welded joints formed solid solutions (ss), the welded joint tensile strength reached maximum value of 244.1 MPa, and the fracture location was mainly located at 4J36/Cu interface.

为满足拼接式超大面阵型红外探测器的空间应用需求,超大规模冷平台组件需要在低温下工作,冷平台支撑结构需要较高的刚度以满足组件的抗振动性能,又需要较高的结构热阻以降低其传导漏热.提出了对称式八杆结构作为冷平台支撑,该支撑结构采用新型的高强度、低热导率的氧化锆陶瓷材料.基于有限元软件分析了支撑结构的高度、安装倾斜角度、宽厚比和材料对于组件的模态基频、支撑结构热阻以及组件在 30g静力学载荷下的最大应力的影响,通过对比选取了其中一组参数设计了实际的测试组件,支撑的结构热阻达到了 220 K/W,对组件进行了 5～2 000 Hz的正弦扫频试验、总均方根为 9g RMS的XYZ三个方向的随机振动等力学环境试验,最终组件通过了空间环境适应性试验验证,组件的基频达到了 560 Hz,并且测试结果与仿真结果趋势符合较好.结果表明:对称式八杆氧化锆支撑结构解决了超大面阵型红外探测器冷平台组件既需要高力学性能又需要低漏热的难题,满足工程化应用需求.

The main factor affecting the vacuum life of the infrared detector Dewar is the internal material outgassing. The Langmuir adsorption model outgassing equation is used to calculate the vacuum lifetime due to the outgassing mechanism and the long-term degassing procedure of the Dewar. An innovative method of changing the temperature at the end of the degassing procedure was proposed to obtain the outgassing activation energy. The outgassing rate was measured at different temperatures while simultaneously removing the influence of coverage on the outgassing rate. The out gassing rates at storage temperature and the rule of outgassing rate changing over time were deduced. The difference among the three Dewar outgassing activation energies obtained in different conditions was 8. 8%. The heat load of the Dewar was tracked for two years to verify the method. The estimated error of Dewar's vacuum lifetime was 7. 2%. It is a non-destructive testing estimation method for the vacuum life of small and diverse Dewar.

The joining of Si 3 N 4 and Mo using Ag–Cu–In–Ti active filler alloy with the brazing temperature ranging from 720 to 860 °C for 10 min is investigated in this article. The correlation between the joint strength and the microstructures of the brazed joints is discussed. In the results, it is shown that the activity of Ti is different at different temperatures, and thus the degree of diffusion of Ti to the interface is different. The activity of Ti gradually increases as the brazing temperature increases, and more Ti atoms diffuse into both sides of the base materials, resulting in a progressively thicker TiN + Ti 5 Si 3 reaction layer on the Si 3 N 4 ceramic side. Between 720 and 860 °C, the shear strength of the joint first increases and then decreases with brazing temperature. The maximum shear strength (223 MPa) is obtained at 830 °C.

Graphene nanoplatelets (GNPs) and diamond are considered as reinforcements due to their high strength and thermal conductivity. The key problem is the interfacial bonding between the reinforcement and the matrix and the construction of the laminated structure in this study. The interfacial bonding between the reinforcement and the matrix is improved by coating copper on the surfaces of the reinforcement. Lamellar composites were successfully prepared by the combination of flake powder metallurgy and vacuum hot pressing. The results show that the mechanical and thermal properties of lamellar composites are better than the non-lamellar composites. With the increase of GNPs content, the laminated structure becomes more and more obvious, and the strength and thermal conductivity increase. When the content of GNPs reaches 1.5 wt%, the tensile strength, compressive strength and thermal conductivity of X-Y direction is 267 MPa, 663.33 MPa, 402 W/mK, respectively. In summary, copper-coated diamond and copper-coated GNPs improve the bonding with the matrix, and the lamellar structure extends the crack path and provides more heat conduction channels, thus increasing the mechanical and thermal properties of the composites. This work provides an effective method for the development of new thermal management structures and functional materials.

Tungsten-copper alloy, as an electronic packaging material with excellent comprehensive performance, is widely used in the cooled packaging dewar structure of HgCdTe infrared focal plane detector. Thermodynamic properties (Coefficient of Thermal Expansion (CET), Thermal Conductivity (TC), Specific Heat Capacity (SHC)), mechanical properties and microstructure of W-20 wt% Cu(W-20Cu) are investigated in the range of 300 K similar to 4.2 K, respectively. The quasi-static tensile tests are carried out on an electronic universal testing machine to obtain the typical stress-strain curves and mechanical properties of W-20Cu. The yield strength (YS), ultimate tensile strength (UTS), elongation and shrinkage of the specimens are measured. Besides, the Scanning Electronic Microscopy (SEM) are applied to observe the microstructure of W-20Cu alloy. The results demonstrate that W-20Cu alloy has outstanding thermal properties of high strength and hardness, high specific heat and low heat capacity and expansion coefficient. Tensile properties of the alloy significantly improve at extremely low temperature, and compared with 300 K, the YS and UTS of W-20Cu increase by 30.68 % and 11.27 % at 77 K. At 4.2 K, the YS increase by 44.49 %, and the UTS increase by 17.20 %, while the plasticity and fracture toughness have a sharp reduction from 300 K to 4.2 K. All specimens exhibit brittle fracture characteristics. With the increase of W crystals cleavage ratio and W-W continuity, the microstructure continuity and uniformity are improved. The number of plastic dimples of Cu phase decreases and the dimples become shallow slightly.

A novel composite filler was prepared by introducing CoCrNi medium-entropy alloy (MEA) into the AgCuTi filler and it was then used to enhance the Sapphire/4 J33-Kovar alloy brazed joints. The effects of CoCrNi MEA on the interfacial microstructure and mechanical properties of brazed joints were discussed by comparatively studying the brazed joints with single AgCuTi and composite filler. The results demonstrated that the porous CoCr2 phase surrounded by the Ni3Ti layer was in-situ synthesized in the brazing seam with the addition of CoCrNi MEA, which relieved the local residual stress during the cooling process. Moreover, the effect of porous structure on retarding the diffusion of metal atoms limited the reaction of Ti with Fe, which promoted the sufficient interfacial reaction between brazing filler and sapphire. The maximum shear strength of 95 MPa was achieved when 3 wt% CoCrNi MEA was added into the AgCuTi filler, which was similar to 57.5% higher than that of the joint brazed with the single AgCuTi filler. The reaction mechanism at the brazing seam with different CoCrNi MEA amounts was also illustrated.

Electron beam welding of TC4 titanium alloy and 4J29 Kovar alloy was performed by using different thicknesses of silver interlayers. The microstructure and the composition of welded joints were characterized by scanning electron microscopy, X-ray diffraction, and energy-dipersive spectrometry. The mechanical properties of welded joints were evaluated by tensile strength tests. The results indicated that Ag thickness has great effects on the weld appearance, microstructure, and mechanical properties of electron beam-welded joints. In case of 0.3 and 0.4 mm thickness of Ag interlayers, a considerable part of 4J29 and TC4 melts and a large amount of Fe, Ti, and Ni elements diffuse into the molten pool forming intermetallic compounds (IMCs) such as TiFe2, NiTi, and FeTi. In case of 0.6 mm thickness of Ag interlayer, the welded joint exhibits brazing characteristics with little IMCs near the fusion line of 4J29 Kovar alloy side. When the thickness of the Ag interlayer increases to 0.8 mm, the diffusion of Ti and Fe elements is completely inhibited by Ag. As the thickness of the Ag interlayer increases from 0.3 to 0.8 mm, the tensile strength of the welded sample shows a phenomenon that first rises and then falls, and the largest tensile strength is 243 MPa.