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1.
双波长干涉检测技术可以实现高动态范围与高测试精度的兼顾,是一种极具潜力的检测技术,用于干涉检测的压电位移机械移相技术存在着一些问题,使用全视场外差移相技术,低频差的外差光源与面阵探测器采集帧率相配合,相较于传统的压电位移机械移相技术,可以同时保证不同波长的移相精度,简化移相的复杂度,且可以方便实现多步移相。提出了全视场外差移相双波长干涉测量技术,并搭建了全视场外差移相双波长干涉测量系统,测试了在边缘最高偏离顶点球13 μm的非球面以及高度为(1.3±0.1) μm的台阶,经过实验验证其非球面面形PV测试精度为λ/3.53 (λ=633 nm),面形PV测试重复精度为λ/77.38,面形RMS测试精度为λ/14.16,面形RMS测试重复精度为λ/919.10,台阶高度测试精度为λ/16.19,测试重复精度为λ/311.85。 相似文献
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The addition of Cu nanoparticles into the solder pastes by mechanical mixing method creates a positive effect on the microstructure refinement of the LED solder joints. The grain size of β-Sn and Cu6Sn5 decrease obviously due to the increasing concentration of the nanoparticles in the solder pastes. However, the addition of nanoparticles facilitates the formation of voids in the solder joints, especially when the concentration of nanoparticles is higher than 0.5 wt% in the solder pastes. Both the microstructure refinement and void percentage affect the shear strength of the solder joints. Since the increase of the void percentage is limited when the concentration of nanoparticles increases from 0 to 0.5 wt%, the microstructure refinement shows a dominant effect on the shear performance and thus improves the shear strength of the solder joints from 49.8 to 55 MPa. Further addition of nanoparticles in the solder pastes leads to a sharp increase of the void percentage. Consequently, the shear strength of the solder joints decreases from 55 to 48.8 MPa when the concentration of doped particles increases from 0.5 to 1 wt% in the solder pastes. 相似文献
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A new approach to the three-dimensional (3-D) measurement of position and velocity of moving particles is introduced. A single TV camera with an apparatus to add circular shift to the image enables us to record the 3-D movement of particles as spiral streaks on a single image. Every shape of the spiral streak on the image plane is related to the position and the velocity of the individual particle. The information about 3-D movement of particles is extracted from the image using an image processing technique. We applied the technique to the measurement of the 3-D water-flow field seeded with tracer particles in a test tank and obtained satisfactory results 相似文献
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Romano Lapasin Sabrina Pricl Vittorio Sirtori Donato Casati 《Journal of Electronic Materials》1998,27(3):138-148
Two solder pastes, used in an electronic card assembly process, were investigated under both oscillating and continuous shear
fields, in order to characterize their viscoelastic and plastic properties. A further study on the vehicle used for the formulation
of a paste was carried out in order to isolate the contribution of the disperse phase to the rheological properties of the
corresponding system. The stress conditions for the departure from linear viscoelasticity and the transition from the solid-
to liquid-like behavior, respectively, were defined on the basis of creep and oscillatory data. Appreciable elastic components
were exhibited by the pastes examined, particularly at low stress conditions and, hence, can affect their screening performance.
The contribution of the disperse phase is almost negligible at low shear or frequency, despite the high content of the disperse
phase, and increases with increasing strain rate or frequency, essentially concerning only the viscous properties of the paste.
This means that the rheological properties of the paste can be properly modulated by adjusting the formulation of the vehicle. 相似文献
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Solder paste is the strategic material for the electronic card assembly process, based on the surface mounting technology.
The paste is a concentrated suspension (50% of volume) of metallic powder in an organic continuous phase and its screening
on the printed circuit board is the first operation of the assembly. The result of the screening depends strongly on the rheological
characteristics of the solder paste but, nevertheless the research activity on this material is so far very poor. In this
paper, an analytical procedure for the rheological characterization is given and the most important rheological parameters,
affecting the screening performance, are shown. 相似文献
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Minna Arra Dongkai Shangguan Erro Ristolainen Toivo Lepistö 《Journal of Electronic Materials》2002,31(11):1130-1138
Solder balling in Sn/Ag/Cu solder pastes was studied in this work. Three different solder pastes, several different reflow
profiles and conditions, and two stencil thicknesses were used in the investigation. During the first phase, called the verification
phase, the solder pastes were checked to ensure they met the minimum requirements. In the process-screening phase, the reflow
profile was varied. Results show that besides flux chemistry, reflow atmosphere plays the major role in solder balling. The
average number of solder balls with the best paste was one fifth of that with the worst paste. Furthermore, with all the pastes,
the number of solder balls dropped close to zero when nitrogen atmosphere was used. Another finding during the reflow process
screening was the influence of the stencil thickness on the solder-balling result. With a thinner stencil, two of the pastes
exhibited significant solder balling. This is assumed to be caused by the different ability of fluxes to withstand oxidation
during the preheating in the reflow process. In the last phase, the effect of the solder-paste particle size on solder balling
was studied more closely. The flux chemistry was kept unchanged, and the solder particle size was varied between type 3 and
type 4. The results show that, with type 4 paste, significantly more solder balls are formed compared to type 3 paste. It
was also confirmed that, regarding the reflow profile, the ramp-up rate from 150°C to 217°C and the reflow atmosphere were
the most significant factors that determine the solder-ball formation for both types of paste. 相似文献
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3-D radar imaging using range migration techniques 总被引:8,自引:0,他引:8
Lopez-Sanchez J.M. Fortuny-Guasch J. 《Antennas and Propagation, IEEE Transactions on》2000,48(5):728-737
An imaging system with three-dimensional (3-D) capability can be implemented by using a stepped frequency radar which synthesizes a two-dimensional (2-D) planar aperture. A 3-D image can be formed by coherently integrating the backscatter data over the measured frequency band and the two spatial coordinates of the 2-D synthetic aperture. This paper presents a near-field 3-D synthetic aperture radar (SAR) imaging algorithm. This algorithm is an extension of the 2-D range migration algorithm (RMA). The presented formulation is justified by using the method of the stationary phase (MSP). Implementation aspects including the sampling criteria, resolutions, and computational complexity are assessed. The high computational efficiency and accurate image reconstruction of the algorithm are demonstrated both with numerical simulations and measurements using an outdoor linear SAR system 相似文献
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This study investigates the effects of employing different two-dimensional (2-D) and three-dimensional (3-D) finite element analysis (FEA) models for analyzing the solder joint reliability performance of a flip chip on board assembly. The FEA models investigated were the 2-D-plane strain, 2-D-plane stress, 3-D-1/8th symmetry and 3-D-strip models. The different stress and strain responses generated by the four different FEA models were applied to various solder joint low cycle fatigue life prediction relationships. The investigation shows that the 2-D-plane strain and 2-D-plane stress models gave the highest and lowest solder joint strains, respectively. The 3-D-strip and 3-D-1/8th symmetry model results fall in between the 2-D-plane strain and 2-D-plane stress model results. The 3-D-1/8th symmetry model agrees better with the 2-D-plane strain model, while the 3-D-strip model agrees better with the 2-D-plane stress model results. The results for the fatigue life prediction analyses also show similar trends 相似文献
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为了提高条纹投影动态3-D形貌测量精度, 采用加窗傅里叶分析辅助相移的方法来减小运动导致的相移误差。首先采用加窗傅里叶分析法估计变形条纹间的实际相移量, 然后采用最小二乘法估计出变形条纹的高精度相位分布, 最后由估计的相位计算得到场景3维形貌。理论分析了物体运动对相移量的影响, 通过仿真研究了所提方法的相移量估计精度, 并搭建了实验系统进行验证。结果表明, 实验中采用所提方法的相位恢复精度达到0.1673rad, 比现有方法有明显提高。该方法用来提高条纹投影动态3-D形貌测量中相位精度是有效的。 相似文献
12.
S. F. Corbin 《Journal of Electronic Materials》2005,34(7):1016-1025
During this investigation, a high-temperature, variable melting point (VMP) Sn-Sb solder paste was developed. The solder was
created by mixing pure Sn and Sb powders together with a flux to form a paste. The proper choice of flux composition and Sn
powder size resulted in a Sn-10wt.%Sb solder paste that had an initial melting point of 232°C and solder ball formation at
peak temperatures as low as 241°C. This represents a significant reduction in the process temperature that would normally
be required for a prealloyed solder with a melting point of 250°C. When this solder paste is reheated, significant remelting
does not take place until a temperature above 241°C is reached. In this way, the solder exhibits a VMP. Experiments indicate
that this VMP behavior is due to isothermal solidification (or freezing) at the solder temperature owing to the partial transient
liquid-phase (TLP) behavior of the solder powder paste. 相似文献
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《Microelectronics Reliability》2014,54(9-10):1753-1757
Thermo Mechanical Cycle Lifetime (TMCL) test is a widely used test methodology for evaluating the reliability of solder joints in the microelectronics industry. The commonly used measurement techniques to monitor solder joint failures during the TMCL test are either event detector or data logger. In this study, TMCL test has been carried out on the same devices in parallel with both measurement techniques. The pros and cons of both techniques are compared. It is observed that the solder joint reliability results on the investigated samples by both techniques are comparable. The event detector can catch short intermittent events, while the data logger is able to capture the details of the solder joint degradation process. In applications for which performance is dependent on the transmission of signals with a frequency of several hundred megahertz or more, the event detector technique shall be used. In such cases the data logger technique may overestimate product lifetime. On the other hand, for some applications where the performance is less susceptible to intermittent solder joint interconnect interruption but more to the increase of the solder joint resistance, the data logger shall be used. In such cases the event detector technique may underestimate product lifetime. In conclusion depending on the end application of the device, the most suitable technique can be selected. 相似文献
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The use of an IMPATT reflection amplifier to produce phase modulation at microwave frequencies has been demonstrated. By operating the IMPATT diode near to avalanche resonance frequency, phase-switching through 180° can be obtained, and the drive current can be set to give equal gain in the two phase states so that no amplitude modulation is produced. Possible application to high-frequency data-transmission systems is envisaged. 相似文献
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A full-duplex dual-frequency self-steering array using phase detection and phase shifting is presented. By RF decoupling the transmitter and receiver arrays, the proposed system promises greater system efficiency by ensuring a constant transmit power. This also allows for a separate low-frequency interrogating signal capable of various modulation schemes. A two-element prototype is demonstrated with interrogating and retrodirective frequencies of 1.425 and 2.85 GHz, respectively. Retrodirectivity is reported for angles of 0/spl deg/, -15/spl deg/, and +25/spl deg/. The power of the received signal is improved by up to 12 dB for -60/spl deg//spl les//spl theta//spl les/60/spl deg/ when compared to a conventional two-element array. 相似文献
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提出了利用数字图像相关技术测量印刷电路板全场微应变的方法,用于评估电路板由应力所导致的失效风险,克服传统实验测试方法不能有效测量全场应变以及难以给出应变集中区域的不足。设计了基于三维数字图像相关技术和应力加载策略的实验方法,通过所获得的全场主应变分布及局部区域内应变历史曲线来评估电路板的失效风险。实验结果表明,所提出的电路板微应变测量方法的重复性优于100 ,能够有效地获得电路板全场的微应变分布,尤其是能够直观地显示电路板应变超过额定值的区域分布,为改进电路板设计、降低电路板失效风险和保护电子元器件的安全提供了重要的实测数据。 相似文献
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