Interface features of ultrasonic flip chip bonding and reflow soldering in microelectronic packaging

Ultrasonic features in the bonding area are of interest for researchers in the field of microelectronic packaging. In this study, the interface characteristics of bonding were examined using an XD7100 X‐ray instrument and a transmission electron microscope (TEM). It was seen that bubbles were usually detected at the interfaces of the reflow‐soldered flip chip (FC), but they were not found at the interfaces of ultrasonically formed FC, and so ultrasonic FC bonding is more reliable than reflow soldering. The strong mechanical effect of ultrasonic vibration activates the dislocations in the crystalline metal lattice. Dislocation diffusion is more prominent than crystal diffusion when the temperature is relatively low during ultrasonic bonding, and therefore the processes of ultrasonic bonding enhance by several orders of magnitude. This indicates that the mechanism of ultrasonic bonding is different from the melting mechanism of reflow soldering. Copyright © 2007 John Wiley & Sons, Ltd.     

Theoretical description of the interactions between a mixture of vapors and a set of chemical sensors by variable temperature

A sensor system is expected to detect gas concentrations of interest within low-ranges. The interactions between a sensor array and mixture of vapors hang not only on mixture composition and temperature but also on the partial sensitivities of the array elements. The aim of this paper is to find a useful equation in differential form that relates the change of sensors partial sensitivities to mixture component concentrations and temperature. This kind of equations is known in the thermodynamic of miscellaneous as equations of Gibbs–Duhéme.     

大功率准连续Nd:YAG陶瓷激光器研究

采用侧面环绕均匀排布的紧凑型抽运结构,实现了激光二极管阵列侧向抽运Nd∶YAG陶瓷激光器高效率激光输出。理论计算得到谐振腔输出镜的最佳输出耦合透射率为22.2%,并在输出耦合镜透射率为22%的条件下,用掺杂原子数分数为1%,尺寸为5mm×75mm的Nd∶YAG陶瓷棒,获得了平均功率大于230W的准连续1064nm激光输出,其光光效率和斜率效率分别高达52.4%和61%。并测得输出激光脉冲宽度为160μs,光谱线宽略小于0.8nm,光束发散角为16mrad。实验结果显示,Nd∶YAG陶瓷激光器输出功率Nd∶YAG单晶激光器相当。     

High-performance IR detectors at SCD present and future

For over 27 years, SCD has been manufacturing and developing a wide range of high performance infrared detectors, designed to operate in either the mid-wave (MWIR) or the long-wave (LWIR) atmospheric windows. These detectors have been integrated successfully into many different types of system including missile seekers, time delay integration scanning systems, hand-held cameras, missile warning systems and many others. SCD’s technology for the MWIR wavelength range is based on its well established 2D arrays of InSb photodiodes. The arrays are flip-chip bonded to SCD’s analogue or digital signal processors, all of which have been designed in-house. The 2D focal plane array (FPA) detectors have a format of 320×256 elements for a 30-μm pitch and 480×384 or 640×512 elements for a 20-μm pitch. Typical operating temperatures are around 77–85 K. Five years ago SCD began to develop a new generation of MWIR detectors based on the epitaxial growth of antimonide based compound semiconductors (ABCS). This ABCS technology allows band-gap engineering of the detection material which enables higher operating temperatures and multi-spectral detection. This year SCD presented its first prototype FPA from this program, an InAlSb based detector operating at a temperature of 100 K. By the end of this year SCD will introduce the first prototype MWIR detector with a 640×512 element format and a pitch of 15 μm. For the LWIR wavelength range SCD manufactures both linear Hg_1−xCd_xTe (MCT) detectors with a line of 250 elements and time delay and integration (TDI) detectors with formats of 288×4 and 480×6. Recently, SCD has demonstrated its first prototype uncooled detector which is based on VO_x technology and which has a format of 384×288 elements, a pitch of 25 μm, and a typical NETD of 50 mK at F/1. In this paper, we describe the present technologies and products of SCD and the future evolution of our detectors for the MWIR and LWIR detection. The paper presented there appears in Infrared Photoelectronics, edited by Antoni Rogalski, Eustace L. Dereniak, Fiodor F. Sizov, Proc. SPIE Vol. 5957, 59570S (2005).     

The effect of the nature of the dopant on the sensor response of poly(3-methylthiophene) films

The effect of the nature of the dopant on the response of a sensor array based on films of poly(3-methylthiophene) under the influence of various organic solvents was studied. It was established that the electroconductivity of the polymer can both increase and decrease under the influence of the analytes. It was suggested that the main factors determining the magnitude of the response of poly(3-methylthiophene) are the ratio of the number of radical-cationic and dicationic states in the polymer, which depends on the nature of the dopant-anion, and also the polarity of the analyte. It was shown that the polymer has high sensitivity to chloroform vapor, which makes sensor arrays based on poly(3-methylthiophene) selective with respect to this analyte. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 6, pp. 331–338, November–December, 2006.     

Quadrupolar susceptibility and magnetic phase diagram of PrNi2Cd20 with non-Kramers doublet ground state

ABSTRACT

In this study, ultrasonic measurements were performed on a single crystal of cubic PrNi₂Cd₂₀, down to a temperature of 0.02?K, to investigate the crystalline electric field ground state and search for possible phase transitions at low temperatures. The elastic constant (C₁₁?C₁₂)/2, which is related to the Γ₃-symmetry quadrupolar response, exhibits the Curie-type softening at temperatures below ～30?K, which indicates that the present system has a Γ₃ non-Kramers doublet ground state. A leveling-off of the elastic response appears below ～0.1?K toward the lowest temperatures, which implies the presence of level splitting owing to a long-range order in a finite-volume fraction associated with Γ₃-symmetry multipoles. A magnetic field–temperature phase diagram of the present compound is constructed up to 28?T for H || [110]. A clear acoustic de Haas–van Alphen signal and a possible magnetic-field-induced phase transition at H ～26?T are also detected by high-magnetic-field measurements.     

交替投影盲反卷积的阵不变量被动定位*

本文针对低信噪比下传统盲反卷积技术提取格林函数过程中存在的图像模糊问题,提出了一种基于交替投影法的阵不变量浅海被动定位方法。该种方法利用交替投影的方法对波束信号进行分离,并利用分离出的波束分别提取格林函数。最后通过补偿时延的方式将多组波束提取的结果相干组合起来,实现格林函数的多波束联合估计。通过仿真实验证明了该方法有效增强了提取格林函数的强度,使得在低信噪比下利用阵不变量的连续声源定位方法更加稳健。     

Interfacial deformation of confined photocurable fluid for fabrication of shape-imprinted microspheres

This study presents a simple route to fabricate shape imprinted microspheres and their application toward multiplex immunoassay. Specifically, a photocurable fluid (polyethylene glycol diacrylate, [PEGDA]) confined in a micromold results in drop formation due to mold swelling and capillarity upon addition of immiscible wetting fluid; during this formation, part of the photocurable fluid is entrapped at the swollen open end, thereby producing polymeric microspheres with controlled imprinted shapes on their surface upon photopolymerization. This approach is able to produce highly uniform microspheres with different imprinted shapes depending on mold geometry in a consistent manner; their size can also be tuned by varying mold dimensions. Furthermore, we impart amine-reactive functional groups to the microsphere, which allows them to be functionalized efficiently. Lastly, we conjugate different capture antibodies on microspheres with different imprinted shapes, and these microspheres were demonstrated to be shape-encoded suspension arrays for multiplex immunoassays. This technique provides high selectivity and a simple decoding method for biosensing applications.     

On the Performance of Free Radicals Combined Electrocoagulation Treatment Processes

The electrocoagulation (EC) combined treatment processes have shown promising performances in which the removal of pollutants from industrial wastewater was greatly enhanced. The integration of a free radical producing step with EC has been considered as one of these new combinations that show synergy and improvements in the overall cleaning process performance. This review is devoted to discuss and analyze references on free radicals-assisted EC processes. Different combinations of free radical mechanisms were cited in the literature during the last two decades. They included ozone, advanced oxidation and ultrasound energy-assisted EC. It was noted that most of those studies were lab-scale processes that used synthetic wastewaters rather than real wastewaters. In addition the performances of those combined processes were improved compared to the EC process alone. This review considers the main parameters of free radical EC processes such as mechanisms, kinetic models, scale-up and cost estimation. Many concluding remarks were stated to give insights for possible future investigations. It seems from the results that the ozone-assisted EC is the most efficient combination since its removal efficiency is high in most applications. On the other hand, the combination of ultrasonic energy with EC was reported to reduce electrode passivation.