Novel microcontacts in microwave chip carriers developed by UV-liga process part II

This paper presents the design and development of novel type microcontacts in monolithic microwave integrated circuit (MMIC) chip-carriers to printed circuit board (PCB) assembly. Several new concepts of microcontacts for packaging solutions of microwave and millimeter-wave MMIC are depicted. Simulation and vector network analyzer (VNA) measurement results for these microcontact transitions are discussed. The results show that the electrical parameters are highly dependent on the transition dimensions and substrate features. These contacts are based on male stud (bump) and female (ring) concept. When mating each other, there are clips effect and self-alignment features. Special attention is paid to the shape of the microcontacts in order to facilitate assembly and strengthen the connection. Equivalent electrical circuit is proposed for PSPICE simulation of the dc contact resistance. Finally, the article discusses the technological implementation of the proposed new microcontact stud-ring through low-cost ultraviolet electroplating, lithography, and molding (UV-LIGA) process and the regime influence on the shape, geometry, and mating capabilities. Results from mechanical pull and adhesion tests are also discussed.     

Novel microwave GaAs field-effect transistors

A technology is described for the fabrication of Schottky-barrier f.e.t.s with electrodes on either or both sides of a submicrometre thick single-crystal layer of GaAs. Preliminary d.c. and microwave results are given together with possible advantages of these novel f.e.t. structures.     

新的芯片设计改进了SSL加密技术

网络安全处理器制造商NetOctave（位于北卡州的Morrisville）,提出了一　种新的芯片设计,预期可以提高SSL（secure-sockets-layer）性能;并且可以保持工业界现行的PCI结构不变。这一项技术,被命名为‘加密处理’（CipherSuite Processins）,可以使该公司的NSP2000安全保密处理器,从控制处理器中只用一次总线传输,就可以下载整个SSL协议,这样可以显著地缩短了等待时间和传输时间,并且解放了系统的TCP/IP资源。 SSL协议包括一个握手过程（通常是进行RSA解密功能）,和进行加密/确认功能的过程。加密/确认功能或者使用ARC4/MD5,或者使用3DES/SHA-1     

Al/SiC carriers for microwave integrated circuits by a new technique of pressureless infiltration

Materials with high thermal conductivity and thermal expansion coefficient matching with that of Si or GaAs are being used for packaging high density microcircuits due to their ability of faster heat dissipation. Al/SiC is gaining wide acceptance as electronic packaging material due to the fact that its thermal expansion coefficient can be tailored to match with that of Si or GaAs by varying the Al:SiC ratio while maintaining the thermal conductivity more or less the same. In the present work, Al/SiC microwave integrated circuit (MIC) carriers have been fabricated by pressureless infiltration of Al-alloy into porous SiC preforms in air. This new technique provides a cheaper alternative to pressure infiltration or pressureless infiltration in nitrogen in producing Al/SiC composites for electronic packaging applications. Al-alloy/65vol% SiC composite exhibited a coefficient of thermal expansion of 7/spl times/10/sup -6/ K/sup -1/ (25/spl deg/C-100/spl deg/C) and a thermal conductivity of 147 Wm/sup -1/K/sup -1/ at 30/spl deg/C. The hysteresis observed in thermal expansion coefficient of the composite in the temperature range 100/spl deg/C-400/spl deg/C has been attributed to the presence of thermal residual stresses in the composite. Thermal diffusivity of the composite measured over the temperature range from 30/spl deg/C to 400/spl deg/C showed a 55% decrease in thermal diffusivity with temperature. Such a large decrease in thermal diffusivity with temperature could be due to the presence of micropores, microcracks, and decohesion of the Al/SiC interfaces in the microstructure (all formed during cooling from the processing temperature). The carrier showed satisfactory performance after integrating it into a MIC.     

Scheme to process arbitrary microwave devices in FDTD

An improved finite-difference time-domain (FDTD) formulation is applied to determine a microwave device's port voltage and current without solving the state equations of the equivalent circuits at each time step. This new approach has been validated by comparison with the equivalent current-source method. The results based on the proposed approach show good accuracy and computation efficiency     

芯片设计中的IP技术

从IP开发和集成两个方面入手,重点阐述了IP的基本特征,IP的设计流程及设计中的关键技术,IP集成的一般考虑及集成的关键技术,IP模块的评估与选择等,并探讨了国内IP技术发展的一些思路。     

A new method developed in measuring the dielectric constants of metallic nanoparticles by a microwave double-cavity dielectric resonator

A microwave double dielectric resonator is implemented to measure the dielectric constants of nano-metallic powders. The metallic nanoparticles prepared by vacuum evaporation in inert gas are collected and mixed with alumina powder to fill the inner hole of a sapphire disc by which the resonant frequency and Q factor are measured at the TE/sub 011/ mode to derive the complex dielectric constant.     

Encapsulation process development for flexible-circuit based chip scale packages

The ultimate driving forces for the development of small form-factor chip scale packages (CSPs) are the market demands for small, light and high performance products. The flex-based /spl mu/BGA technology has been a very successful package format, and tremendous efforts have been implemented in the process development for the technology. In this article, three flex-based chip scale packages (based on patented /spl mu/BGA technology) will be discussed. The focus will be on the encapsulation process development. Because of the unique package structures and material sets used in the flex-based CSPs, various encapsulation challenges were raised. The encapsulation solutions are compared and discussed for each type of flex-based /spl mu/BGA technologies, including the dispensing pump technologies, material characterization, process characterization and optimization. Based on the evaluation results, type C /spl mu/BGA technology is recommended for its simple assemble process flow, balanced protection on beam leads and solder ball joints and shorter manufacturing cycle time as well.     

微波电路用共面电极TaNx薄膜片式电阻器

采用反应溅射方法制作TaNx电阻薄膜,并通过溅射Ni、Au形成双层共面电极。研究了溅射条件对电阻薄膜组分的影响以及此类电阻器的微波特性。结果显示,溅射工作真空度小于0.5Pa,氮气体积分数大于5%时,可以得到阻值稳定的六方晶体结构TaNx电阻薄膜,其共面电极的电阻器使用频率上限大于20GHz。     

Minimum test chip sample size selection for characterizing process parameters

A method for determining a test chip sample size to estimate effectively the electrical parameter distributions on an integrated circuit wafer is presented. This method gives relations among sample size and the figure of merit for four statistical techniques (trimmed mean, biweighted mean, median, and arithmetic mean) by which estimates are calculated. To demonstrate its use, the method has been applied to the evaluation of a CMOS fabrication process. Measurements on wafers completely patterned with identical test chips were used to determine actual parameter distributions for an entire wafer (true parameter values). Estimates of true parameters were determined using a site selection plan which is representative of sampling plans employed in industry. The above four statistical techniques were used to compute estimates for electrical parameters and their respective figures of merit. These estimates were compared with the true parameter values determined from testing all test chips on the wafer. This method may be used in conjunction with other criteria for determining test chip sample size and enables one to make judgments on the effectiveness of sampling strategies for various processes and process technologies. The results, reported in this paper for CMOS processes, are interpreted using graphs of the figure of merit versus the sample size.     

Novel microwave projection imaging for determination of internal structure

A novel microwave imaging technique based on the generalised weighted backprojection operator is introduced and tested using experimental data. Images of the internal structure of penetrable objects using this technique are compared and contrasted with images found from the classical back-projection method. It is demonstrated that the new method provides high-quality images of both discrete and continuous internal structure without the distortions characteristic of traditional methods.     

Novel means of detecting microwave power using optical fibres

A single-mode optical fibre positioned in a waveguide structure (2.45 GHz) is shown to sense microwave power. The effect is studied quantatively by monitoring the output of an all-fibre Mach-Zehnder interferometer, one limb of which incorporates the test fibre.     

Effect of microwave preheating on the bonding performance of flip chip on flex joint

A microwave (MW) preheating mechanism of anisotropic conductive adhesive film (ACF) has been introduced in order to reduce the bonding temperature for flip chip technology. Thermal curing of epoxy shows a very sluggish and non-uniform curing kinetics at the beginning of the curing reaction, but the rate increases with time and hence requires higher temperature. On the other hand MW radiation has the advantage of uniform heating rate during the cycle. In view of this, MW preheating (for 2/3 s) of ACF prior to final bonding has been applied to examine the electrical and mechanical performance of the bond. Low MW power has been used (80 and 240 W) to study the effect of the MW preheating. It has been found that 170 °C can be used for flip chip bonding instead of 180 °C (standard temperature for flip chip bonding) for MW preheating time and power used in this study. The contact resistance (0.015–0.025 Ω) is low in these samples where the standard resistance is 0.017 Ω (bonded at 180 °C without prior MW preheating). The shear forces at breakage were satisfactory (152–176 N) for the samples bonded at 170 °C with MW preheating, which is very close and even higher than the standard sample (173.3 N). For MW preheating time of 2 s, final bonding at 160 °C can also be used because of its low contact resistance (0.022–0.032 Ω), but the bond strength (137.3–145 N) is somewhat inferior to the standard one.     

Novel technique for investigating high-power microwave pulses using Kerr effect

A novel method for the measurement of peak power of microwave pulses up to the few hundred kilowatts level based on the microwave-induced electro-optical Kerr effect in nonlossy dielectric liquids is described. This method provides additional information about the shape of the pulse, which is not usually given by the conventional methods.<>     

DC field response of hot carriers under circular polarized intense microwave fields in semiconductors limited to two-dimension

Hot carrier dynamics under intense microwave fields is investigated theoretically for the case that the dominant scattering process is optical phonon emission, and the carrier motion limited to two-dimension is intrinsic. When the microwave amplitude is appropriately large, an accumulated distribution of carriers in momentum space appears. The system of this motion is found to cause various peculiar DC fields response, e.g. strong non-linearity, negative differential conductivity, and negative response, under realistic physical conditions [J. Phys. Soc. Jpn 68 (1995) 2994]. In the proper strength of microwave and DC electric fields, especially in the case of circular polarized microwave fields, the carrier motions are converged to some trajectories in momentum space [Proceeding of 25th International Conference on the Physics of Semiconductors, 2001]. Resultantly a new type of accumulated distribution of carriers in momentum space appears. This situation is a sort of population inversion of carriers and causes various phenomena including a negative differential conductivity and/or a negative response appeared in the drift velocity vs. DC field relation not found in the case of linear polarized microwave fields. The carrier motion restricted in two-dimensional band may be essential and effective for these properties.     

Novel method of diameter control in optical-fibre drawing process

A novel method for controlling fibre diameter is devised, utilising the phenomenon that slight changes of gas flow in the fibre-drawing-machine furnace cause rapid variations in optical-fibre diameter. Resultant diameter fluctuations are reduced to ±05% for fibre lengths of over 1 km.     

Low-power chip interconnection by dynamic termination

A low-power dynamic termination scheme is proposed and demonstrated as a way to reduce power dissipation for high-speed data transport. In this scheme, the transmission lines are terminated only if the signals change. The gate of a switching MOS transistor connected to a termination resistor is driven by differentiating the transmission signal with a resistor and a capacitor. The power dissipation of the terminating resistor can be reduced to 1/5 in the conventional determination scheme, and overshoot can be reduced to 1/5 that in the open scheme. This scheme is promising for use with palm-top equipment, facilitating high-speed low power operation     

Novel microwave reflectometer for accurate characterisation of high-speed photodiode optoelectronic response

A reflectometer technique which corrects source-mismatch errors using scalar optoelectronic measurements alone is demonstrated. Results corrected using voltage-reflection-coefficient (VRC) measurements of both the photodiode and measurement system are compared with those determined by the new technique for a GaInAs photodiode measured to 40 GHz by a 1.5 mu m DFB laser heterodyne system. The optoelectronic response determined by the new technique falls within the scatter of the VRC corrected measurements.<>