Circularly polarised aperture antenna fed by CPW and built in MCM-Dtechnology

A new design for a circularly polarised aperture type antenna fed by a coplanar waveguide, is introduced. The antenna has been built in MCM-D technology which offers an easy way to reduce the leakage to the slotline mode of the CPW. The proposed antenna has been studied both theoretically and experimentally. The results show that the antenna has both a high impedance and high circular polarisation bandwidths. It is designed to operate around 25.5 GHz. Return loss, axial ratio, and radiation patterns are presented and briefly discussed     

Simultaneous thermal and electrical analysis of nonlinear microwavecircuits

A software tool for the simultaneous determination of the thermal and electrical steady-state regimes of nonlinear microwave circuits containing temperature-dependent active devices is introduced. The analysis technique is an extension of the classic piecewise harmonic-balance method, and is quite general-purpose. It can be applied to networks operating under multiple-tone excitation, including pulsed-RF regimes. The simulation problem is reduced to a nonlinear algebraic system whose unknowns are electrical and thermal state-variable harmonics. Advanced numerical techniques are used to overcome the difficulties arising from the high degree of nonlinearity and from the very large number of unknowns of the numerical problem. The program incorporates a facility for the evaluation of the thermal constants of multiple finger planar devices starting from geometrical data     

Photoreflectance and electrical characterization of Si-implanted GaAs

Si-implanted semi-insulating GaAs was studied by the photoreflectance (PR) technique and electrical analysis. Different energies and doses were used for Si implantation in two groups of samples. Subsequently, different rapid thermal annealing (RTA) conditions were utilized for one group of samples to optimize the damage removal and impurity activation. A significant annealing temperature dependence of the electrical activation and damage removal was observed. The 120 keV Si implantation introduced two impurity-like transitions in the PR spectra at photon energies about 40 meV and 100 meV from the band-edge. The 180 keV implantation introduced two impurity-like signals with energies about 50 meV and 65 meV from the band-edge which could be removed by RTA. Particularly, the 950‡ C, 10s RTA can totally remove the 65 meV signal caused by the 180 keV implantation. Samples exhibiting good PR signal also produced diodes from which electrical data was superior to the other cases.     

Integral 3-D thermal, electrical and mechanical design of an automotive DC/DC converter

Power electronics is finding increasingly more applications in high temperature environments where power density is also a driving factor. The engine compartment of a passenger vehicle is one such example. In this paper, an integral thermal, electrical, and mechanical design of a high power density dc/dc converter operating in the thermally harsh automotive environment is discussed. The interactions and interdependencies between the three design disciplines are considered. It is illustrated how these interactions can be manipulated and used to an advantage in meeting the harsh temperature and high power density requirements of the automotive converter. Packaging and circuit techniques are identified that can be used to this end. Two case studies of a 2-kW 14-V/42-V dc/dc converter for application in the automotive environment are considered. The first prototype achieved a power density of 170 W/in/sup 3/ while the second prototype, operating with a higher environmental temperature achieved a power density of 120 W/in/sup 3/. The experimental structures and practical results are presented. Technology issues concerning the three-dimensional construction of the prototypes that need research attention are also identified.     

Modeling and characterization of the polymer stud grid array (PSGA) package: electrical, thermal and thermo-mechanical qualification

We characterize the polymer stud grid array (PSGA) package electrically, thermally and thermo-mechanically for successful commercial application. For the electrical characterization, we extract lumped parameter resistance-inductance-capacitance (RLC) models for the interconnects from simulations. We also measure the RF performance of the package on printed circuit board (PCB) test structures. The average self-inductance from the wirebond pad to the bottom of the stud is 0.53 nH and the total capacitance to the ground is 0.26 pF for an interconnection of the periphery of the over the edge (OTE) type PSGA. The lumped RLC model is verified by full three-dimensional (3-D) EM simulations. Simulation models also indicate that the "Micro-via" (/spl mu/-via) type of interconnection on the PSGA package improves performance by decreasing the inductance on an average by 60%. Thermal characterization involves the development of a steady-state thermal compact model with six nodes for the 72-pin PSGA. We also perform transient thermal measurements on test packages to fine-tune the detailed model. For the thermo-mechanical case we test the first level and second level reliability by experiments and optimize them using simulations. The board level reliability for the 72-pin PSGA mounted on a PCB is very high (N50%>10000 cycles). Simulations also show a higher reliability for the PSGA than the plastic ball grid array (PBGA).     

陶瓷金属工艺改善热特性和电气特性

衬底制造商LaminaCeramics公司开发的一个多层技术能使未经烧制的陶瓷结合在科伐(Kovar)合金或铜钼铜(CuMoCu)金属上。这个多层印刷电路板制造工艺叫作低温共烧陶瓷金属(LTCC-M),它能够降低收缩率,改善导热性,有望缩小RF和微波组件、高速电路底板和光组件等元件的封装尺寸并降低成本。这项技术为设计人员提供了把元件嵌入金属层的能力。新技术把x-y平面的共烧收缩率缩小到了大约0.1%,远远低于标准LTCC和HTCC工艺的12.7%～15%。大到16×16平方英寸的多层印刷电路板可以有多达24层0.004英寸厚的层。元件可以直接小片装配到金属板层,…     

Simulation of electrical overstress thermal failures in integratedcircuits

Electrical overstress (EOS) and electrostatic discharge (ESD) pose the most dominant threats to integrated circuits (ICs) reliability. As a measure for EOS/ESD reliability, the power-to-failure versus time-to-failure relationship (power profile) has been recently proposed to determine the EOS failure thresholds of integrated circuits. This paper presents a nonlinear mixed 2D-1D thermal simulator, iTSIM, for ESD/EOS failure studies in ICs. iTSIM's computational efficiency to handle large-scale EOS thermal problems in ICs derives from the special set of boundary conditions introduced in this paper. Simulated power profiles for various combinations of major thermal parameters of the IC die-package structure are shown to agree with experimental data     

Noninvasive electrical characterization of materials at microwavefrequencies using an open-ended coaxial line: test of an improvedcalibration technique

Dielectric measurements using a probe consisting of a coaxial transmission line with an open-circuit end placed against the sample are discussed. For the 2.99- or 3.6-mm (OD) probes considered, a simple lumped parameter model shows errors above 1 GHz that increase greatly with frequency. An approximate model based on measured probe impedances from 1 to 18 GHz with samples consisting of water, methanol, and dioxane-water mixtures is evaluated. This model is more accurate than the lumped-parameter model and is better suited for calibration of the automatic network analyzer (ANA). The errors introduced in dielectric measurements by the use of approximate models for the probe are discussed. The technique succeeds because of partial cancellation of errors in modeling the probe in ANA-based measurements     

Optical and electrical characterization ofn- andp-type Fe-doped InP

N-andp-type Fe doped InP crystals were grown by the LEC technique by co-doping with Zn and Te, respectively. The incorporation of these dopants is examined by chemical, electrical and optical analysis. The electronic transport properties of the InP: Fe, Zn crystal are investigated by a comparison of Hall effect measurements and theoretical calculations indicating a partial compensation of the Zn atoms by a deep donor.     

Integration and electrical characterization of carbon nanotube via interconnects

Carbon nanotubes (CNTs) are considered a promising material for interconnects in the future generations of microchips because of their low electrical resistance and excellent mechanical stability. In particular, CNT-based contacts appear advantageous when compared with current tungsten or copper technologies and could therefore find an application as metal contacts interconnecting the transistors with the back end of line of the microchip. In this work, the integration of vertical CNT bundles in sub-micron contact holes is evaluated at wafer scale and the major integration challenges encountered in the practical realization of the process are discussed. Nickel PVD films were used to selectively grow CNT into the contact holes at temperatures as low as 400 °C, which is the thermal budget available for contacts. The height of the contacts and the length of the CNT are controlled by a chemical mechanical polishing step (CMP) after embedding the CNT into SiO₂. Ti/Au metal pads are then formed onto the CNT bundles by PVD and lift-off. The integrated CNT are electrically characterized and an annealing treatment was found to improve the CNT-via resistance. As the electrical properties of the CNT can be evaluated, the structure and the process presented constitute a test vehicle for the development of high-quality CNT-contacts.     

Fabrication and electrical characterization of p-NiPc/n-Si heterojunction

Nickel-phthalocyanine (NiPc) thin film was prepared by thermal evaporation method on n-Si single-crystal substrate to fabricate p-NiPc/n-Si heterojunction. The electrical transport properties of the p-NiPc/n-Si heterojunctions were investigated by temperature-dependent current-voltage (I-V) measurements and room temperature capacitance-voltage (C-V) measurements. The temperature-dependent I-V characteristics revealed that the forward conduction was determined by thermionic-emission and space-charge-limited current (SCLC) mechanisms at low and high voltage, respectively⋅ On the other hand, the reverse current is limited by the carrier generation process. The 1/C²-V plot indicated the junction was abrupt and the junction built-in potential was 0.61 V at room temperature.     

Optical and electrical properties of thermal Tantalum oxide films on silicon

Tantalum pentoxide is of interest as an alternative dielectric to SiO2for MOS devices. In the present work, RF-sputtered tantalum films on silicon substrates were thermally oxidized at 500°C. Ellipso-metric measurements showed that films made in this way were uniform in refractive index except for a narrow region of tapered index at the silicon interface. Capacitance measurements gave a relative permittivity of about 26, in the range shown by anodic Ta2O5films. The conduction currents depended on the oxidation period but were comparable to or slightly better than reported for CVD Ta2O5.     

Mechanical, thermal, and electrical analysis of a compliant interconnect

Ball grid array (BGA) package styles use solder balls as electrical interconnects between packages and application boards. Solder balls are rigid and tend to fracture under thermal fatigue and/or shock loading. Metalized polymer spheres (MPS) offer a more compliant interconnect, compared to solder balls, thereby increasing the thermal cycling fatigue life. A reduction in thermal and electrical performance may be expected for MPS interconnects as a result of its higher thermal and electrical resistances. A 5% and an 8% increase in MPS thermal resistance was measured for a carrier array ball grid array (CABGA) package and a plastic ball grid array (PBGA) package, respectively, compared to eutectic solder balls. However, this small reduction was offset by large gains in the solder joint life. A 1.6 times increase in the mean thermal fatigue life was measured for a CABGA using MPS interconnects compared to eutectic solder balls. A first-order model showed that eutectic solder balls provide greater process margins, compared to MPS interconnects, due to the ball collapse during reflow.     

Conversion of thermal to electrical energy with ferroelectric materials

The subject is reviewed and recent experimental and theoretical results are presented. It is shown that materials with high polarization and high dielectric strength can yield good conversion efficiencies. Very high specific outputs are calculated for the conversion of uncollected solar radiation by a spinning space vehicle. Such high specific outputs require suitable thin ferroelectric films of high thermal shock resistance. These requirements can not be met in present experimental converters. Approaches for the improvement of insulation resistance and polarization are given.     

Analytical approach for thermal and electrical design of multilayerstructure integrated devices

An analytical method for the electrothermal design of multilayer structure integrated devices is presented. It can be easily applied to a large variety of devices and is independent of the specific physical properties of the layers, also accounting for the temperature dependence of the thermal conductivity     

Experimental and theoretical characterization of electrical contactin anisotropically conductive adhesive

Electrical conduction through anisotropically conductive adhesive (ACA) is caused by deformation of metal fillers under pressure and heat. In this work, the hardness of the electrical particles under various deformation degrees was determined by nano-indentor measurements and the electrical resistance of the electrical contacts was measured under various deformation degrees. Theoretical model and simulation have been developed for the microscopic mechanism of the electrical conduction through metal fillers in the anisotropically conductive adhesive. By comparing with experimental data it is concluded that the deformation of the metal filler in our ACA is plastic even at rather low external load. Further theoretical simulation reveals two important aspects of the conductance characteristics. The conductance is improved by increasing the external load but the dependence of the conductance on the spatial position of the metal filler becomes stronger. Design and optimization of the ACA with respect to the absolute value of the electric conductance and its dependence on the spatial position of the metal filler are of essential importance for the electronics packaging application of the anisotropically conductive adhesives     

Optical and electrical characterization of hafnium oxide deposited by MOCVD

The paper reports on electrical and optical investigations performed on HfO₂ high-k films deposited by Metal-organic chemical vapor deposition (MOCVD). Spectroellipsometry investigations show the presence of a transition layer between HfO₂ and the silicon substrate, which can be optically modelled as a mixture of Si and SiO₂; this information is further used in the assessment of the electrical measurements. Hysteresis effects have been observed in the Capacitance–Voltage (C–V) measurements for the as-deposited sample as well as the annealed samples. For the samples with large hysteresis, Poole–Frenkel (PF) conduction is the most likely dominant conduction mechanism. The energy of dominant trap level was found to be 0.7 eV.