Vibration lifetime modelling of PCB assemblies using steinberg model

Automotive requirements are nowadays not only limited to high temperatures but more and more demands are driven towards vibration and higher acceleration values due to the direct mounting of the Electronic Control Units on the Engine.Temperature cycle testing and combined testing methods have been under study for a long time but literature concerning Vibration Modelling is very poor in comparison with thermal models like Arrhenius or thermo-mechanical based models like Coffin-Manson.In this article, a revisit of the Steinberg Model is presented with a direct application on tantalum capacitors populated boards. Experimental results with various sinusoidal excitation g-level are presented; whereas on the other side FEM simulations are performed and results are implemented in the Steinberg Model, in order to identify model parameters.     

A hybrid finite element method for 3-D scattering using nodal andedge elements

A hybrid finite element method for three-dimensional scattering is presented and numerical examples shown. This approach, which couples finite element discretization with the method of moments, is particularly well suited for monostatic radar cross section calculations. The method is based on a scalar and vector potential formulation of Maxwell's equations, the use of nodal elements, and a highly efficient body of revolution implementation of the method of moments. Combined nodal and edge elements are employed to accurately model fields around corners and edges. A curvature-based sampling criterion is derived and shown to ensure accurate answers for highly curved scatterers. Numerical results and Cray computer timings are compared with published results for an edge element code using radiation boundary conditions     

A Bayes approach to simultaneous evaluation of similar assemblies

Simultaneous qualification testing of similar electronic-assembly designs that have the same reliability objectives lends itself to a Bayes approach. The author presents a method for obtaining the number of units to be put on test (test units) and the number of survivors required for this problem. The Bayes approach can reduce the total number of test units. The similarity of any two assemblies can be qualified using projected failure rates of components common to each design and components that differ between them. Under binomial sampling, survival probabilities follow the conjugate beta distribution. Two systems of linear equations are developed. Their solutions are vectors that describe, for each design: (1) the number of test units, and (2) the minimum number of survivors to demonstrate the reliability objective     

An advanced quality and reliability assessment approach applied to thermal stress issues in electronic components and assemblies

A new failure analysis and reliability assessment approach has been developed, based on surface topography analysis of ICs and assemblies under thermal stress conditions. An important application concerns the assessment of the ability of ICs to withstand typical JEDEC type solder cycles without too strong stress accumulation in the components. An important advantage of this new technology is the predictive power, i.e. the delamination risk may be visualized before physical failure occurs.     

A simple unsupervised MRF model based image segmentation approach

A simple technique has been suggested to obtain optimal segmentation based on tonal and textural characteristics of an image using the Markov random field (MRF) model. The technique takes an initially over segmented image as well as the original image as its inputs and defines an MRF over the region adjacency graph (RAG) of the initially segmented regions. A tonal-region based segmentation technique due to Kartikeyan and Sarkar (1989) has been used for initial segmentation. The energy function has been defined over the first order cliques of the MRF. The essence of this approach is primarily based on quantitative values of the second order statistics, on region characteristics and consequently deciding upon the action of merging neighboring regions using the F-statistic. The effectiveness of our approach is demonstrated with wide variety of real life examples viz., indoor, outdoor and satellite and a comparison of its output with that of a previous work in the literature has been provided.     

Analysis of waveguide discontinuities using edge elements in ahybrid mode matching/finite elements approach

A mode matching (MM)/finite element method (FEM) for the analysis of waveguide discontinuities is presented. The hybrid approach described combines the computational efficiency of the modal analysis with the versatility and flexibility of FEM and enables us to accurately model arbitrary cross section waveguides, where modal expansions cannot be derived analytically. The proposed procedure is based on the edge element expansion of the transverse field components for the direct calculation of the coupling integrals involved in the MM formulation. Numerical and experimental results are presented to show the validity and the accuracy of the method     

A finite difference approach to the wire junction problem

An approach to treating the thin-wire junction geometry, which arises in the computer modeling of a great many electromagnetic radiation and scattering problems, is presented. The method is based upon a finite-difference type interpretation of the differential operator in the Pocklington form of the integro-differential equation representing the junction problem. An important advantage of the method is that it is capable of producing accurate results even with relatively simple basis and testing functions, e.g., pulse anddelta-functions. Furthermore, the method does not require the imposition of additional constraints, such as the Kirchhoff current law or the conservation of charge, at the junction points. The method is versatile in that it applies to L-shaped structures as well as to junctions of thin wires of dissimilar radii. Numerical results based on the present finite difference approach have been computed and good agreement with results derived by other independent methods has been observed. An important conclusion of this work is that the conventional interpretation of the differential operator leads to erroneous results since the sampling interval in the conventional finite difference scheme is different from the correct value of the sampling interval found in this paper.     

A discrete approach to the modeling of power electronic switchingnetworks

An approach to time-domain analysis and modeling of power electronic circuits is described. All circuit components (including active and passive elements) are modeled in a discrete manner by transmission-line sections using the transmission-line modeling (TLM) method. This method requires a fixed system matrix which depends only upon the circuit configuration and time step and not on the switching states of the circuit. Since this method adopts a discrete approach, it provides an exact solution to the discrete model and is stable even for stiff networks. Errors are due to the modeling process only and not to the approximate solution of an approximate calculus model. A simulation on a switched-mode power supply is used to illustrate the modeling method, and the simulated results are compared with measurements     

A simple method to test the existence of 2-D partial fraction decomposition

In this paper we give a simple method to test the existence of the decomposition of the form

$\text{A(Z}{}_1\text{, Z}{}_2\text{) A(Z}{}_1{}^{\mathrm{?1}}\text{, Z}{}_2{}^{\mathrm{?1}}\text{B(Z}{}_1\text{, Z}{}_2\text{B(Z}{}_1{}^{\mathrm{?1}}\text{, Z}{}_2{}^{\mathrm{?1}}\text{=}\text{(Z}{}_1\text{, Z}{}_2\text{)}\text{B(Z}{}_1\text{, Z}{}_2\text{+}\text{P(Z}{}_1{}^{\mathrm{?1}}\text{, Z}{}_2{}^{\mathrm{?1}}\text{)}\text{B(Z}{}_1{}^{\mathrm{?1}}\text{, Z}{}_1{}^{\mathrm{?1}}\text{)}$

for a stable two-dimensional transfer function of a recursive filter H(Z₁, Z₂) = A(Z₁, Z₂)/B(Z₁, Z₂).     

A simple approach to the problem of in-circuit resistance measurement

This letter proposes a simplification to the circuit presented by M. Rehman et al. in "A Self-Balancing Bridge for In-Circuit Resistance Measurement" published in the November 1985 issue of the PROCEEDINGS.     

A simple approach to modeling cross-talk in integrated circuits

A simple engineering approach for rapid simulation of cross-talk in mixed-mode IC's using SPICE is presented. A side-by-side comparison of several cross-talk reduction schemes has shown that while an SOI-based process provides high isolation from cross-talk at low operating frequencies, its benefit is lost at high frequencies. Simple guard ring substrate contacts appear to be the technique best suited for preventing cross-talk at high operating frequencies. Lumped parameter equivalent circuits have also been developed to represent different isolation schemes in SPICE. The isolation characteristics of test structures employing the above techniques are computed using SPICE and the results compared with two-dimensional device simulation. The results are also compared with experimental measurements on actual silicon to validate the models     

A 2-D systems approach to river pollution modelling

The paper presents some applications of 2-D systems theory to the problem of modeling the river pollution processes and the associated selfpurification phenomena. The dynamical evolution of the biological oxygen demand (BOD) and the dissolved oxygen (DO) in a one-dimensional river model is discussed under various physical assumptions.     

A new approach for subset 2-D AR model identification fordescribing textures

This paper addresses the problem of identification of appropriate autoregressive (AR) components to describe textural regions of digital images by a general class of two-dimensional (2-D) AR models. In analogy with univariate time series, the proposed technique first selects a neighborhood set of 2-D lag variables corresponding to the significant multiple partial auto-correlation coefficients. A matrix is then suitably formed from these 2-D lag variables. Using singular value decomposition (SVD) and orthonormal with column pivoting factorization (QRcp) techniques, the prime information of this matrix corresponding to different pseudoranks is obtained. Schwarz's (1978) information criterion (SIG) is then used to obtain the optimum set of 2-D lag variables, which are the appropriate autoregressive components of the model for a given textural image. A four-class texture classification scheme is illustrated with such models and a comparison of the technique with the work of Chellappa and Chatterjee (1985) is provided.     

A simple approach to obtaining network state equations

A simple approach to obtaining the state equations for electric networks is introduced. This approach can easily accommodate any type of network element. It requires a relatively small number of simultaneous equations. An illustrative example is included.     

A simple variational approach to optical rib waveguides

A simple method for the calculation of the mode properties of optical rib waveguides is presented. The method is based on a scalar variational principle combined with a vector perturbation analysis for the polarization correction. It is demonstrated that, with the proper trial functions, the approach can predict very accurately the dispersion characteristics with much less effort (in terms of formulation and computation) than the existing numerical techniques. The field patterns of the modes can be computed from the scalar analysis. The vector property of the mode can be taken into account by a perturbation formula. The computation is carried out on an IBM PC. The user-friendly computer program is written in Fortran     

A simple analogue approach to fast Walsh transform

A version of a fast Walsh transform algorithm is derived by setting an analogy with a programme chart of a sports tournament.     

A SIMPLE APPROACH TO THE CALCULATION OF THE MECHANICAL STRESS IN SILICON DEVICES

The residual mechanical stress in SiO_2 films results in the degradation of mobilitiesin MOSFETs. Based on the edge force approximation in SiO_2 films, the stress field in MOS devicesis calculated. The results here are in agreement with those measured by the Raman spectrummethod.     

A novel approach to the 2-D blind deconvolution problem in medical ultrasound

The finite frequency bandwidth of ultrasound transducers and the nonnegligible width of transmitted acoustic beams are the most significant factors that limit the resolution of medical ultrasound imaging. Consequently, in order to recover diagnostically important image details, obscured due to the resolution limitations, an image restoration procedure should be applied. The present study addresses the problem of ultrasound image restoration by means of the blind-deconvolution techniques. Given an acquired ultrasound image, algorithms of this kind perform either concurrent or successive estimation of the point-spread function (PSF) of the imaging system and the original image. In this paper, a blind-deconvolution algorithm is proposed, in which the PSF is recovered as a preliminary stage of the restoration problem. As the accuracy of this estimation affects all the following stages of the image restoration, it is considered as the most fundamental and important problem. The contribution of the present study is twofold. First, it introduces a novel approach to the problem of estimating the PSF, which is based on a generalization of several fundamental concepts of the homomorphic deconvolution. It is shown that a useful estimate of the spectrum of the PSF can be obtained by applying a proper smoothing operator to both log-magnitude and phase of the spectra of acquired radio-frequency (RF) images. It is demonstrated that the proposed approach performs considerably better than the existing homomorphic (cepstrum-based) deconvolution methods. Second, the study shows that given a reliable estimate of the PSF, it is possible to deconvolve it out of the RF-image and obtain an estimate of the true tissue reflectivity function, which is relatively independent of the properties of the imaging system. The deconvolution was performed using the maximum a-posteriori (MAP) estimation framework for a number of statistical priors assumed for the reflectivity function. It is shown in a series of in vivo experiments that reconstructions based on the priors, which tend to emphasize the "sparseness" of the tissue structure, result in solutions of higher resolution and contrast.     

A simple model for the mode I popcorn effect for IC packages

A simple model for the Mode I popcorn effect is presented here for packages with rectangular die pad (P-DSO). A package “stability parameter”, relating to its moisture sensitivity, is derived from the popcorn model. It describes the critical factors for a robust package - molding compound properties and package, leadframe design for a given preconditioning and soldering process. Furthermore, nomograms generated from the model enable an easy estimation of moisture sensitivity levels (between 1 and 5) of packages with different die pad sizes and molding compound underpad thicknesses and for different soldering temperatures ranging from 220°C to 260°C (Pb-free soldering).