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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ejor.2007.06.007 Byline: Tao Yuan (a), Way Kuo (b) Keywords: Quality control; Stochastic processes; Pattern recognition; Semiconductor manufacturing Abstract: Defects on semiconductor wafers tend to cluster and the spatial defect patterns contain useful information about potential problems in the manufacturing process. This study proposes to use model-based clustering algorithms via Bayesian inferences for spatial defect pattern recognition on semiconductor wafers. These new algorithms can find the number of defect clusters as well as identify the pattern of each cluster automatically. They are capable of detecting curvilinear patterns, ellipsoidal patterns and nonuniform global defect patterns. Promising results have been obtained from simulation studies. Author Affiliation: (a) Department of Industrial and Information Engineering, The University of Tennessee, Knoxville, TN 37996, United States (b) College of Engineering, The University of Tennessee, 124 Perkins Hall, Knoxville, TN 37996, United States Article History: Received 24 August 2006; Accepted 3 June 2007

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ejor.2006.11.002 Byline: J. Ashayeri (a), W. Selen (b) Keywords: Production; Scheduling; Sequencing; Printed circuit boards Abstract: A planning and scheduling model is developed for the onsertion-phase in printed circuit board (PCB) assembly. PCBs are manufactured by machines that mount components, such as chips, on a PCB. On an onsertor machine, a certain number of component types can be stored. These components are subsequently used for the production of a certain PCB batch type. This research develops a production planning and scheduling formulation to determine the component-machine allocations, as well as a PCB sequence. Two strategies are proposed; one focusing on minimal number of changeovers (C-strategy), and the other on minimal process time (P-strategy). Both strategies were validated in a pilot study with real company data, with encouraging results for potential implementation. Author Affiliation: (a) Department of Econometrics and Operations Research, Tilburg University, P.O. Box 90153, 5000 LE Tilburg, The Netherlands (b) Institute for Logistics and Supply Chain Management, VictorEia University, Melbourne VIC 8001, Australia Article History: Received 17 January 2005; Accepted 1 November 2006

A simple analytical model is proposed and shown to be effective in predicting the nonlinear behavior of single-ended amplifiers, as well as Doherty amplifiers implemented with GaAs heterojunction bipolar transistors (HBTs) for handset applications. The analytical model is based on linear and nonlinear components extracted from a vertical bipolar inter-company model for Skyworks Solutions Inc.'s InGaP/GaAs HBT devices. Equations derived from the model provide insights into effects of individual components on the gain and phase of both the single-ended and Doherty amplifiers. The model indicates that tuning the phase delay inserted in front of the auxiliary power amplifier (PA) within the Doherty can improve linearity at a high input power. The efficacy of the model is demonstrated by experimental results in which, for a Doherty PA with a tuned phase delay at the auxiliary PA side, the measured gain and phase agree with the simulation results. Furthermore, the third-order intermodulation distortion performance is improved as much as 8 dB when compared with a Doherty PA without phase delay tuning. Index Terms--Code division multiple access (CDMA), Doherty amplifier, heterojunction bipolar transistor (HBT).

US Mil-Hnbk-217 contains models that determine the failure rate of electronic components as the product of base failure rate and adjustment factors. A statistical approach for computing the differences in base failure rate and the adjustment factor i, two critical variables for reliability prediction, is presented. Applicable for lifetime approximation of electronic packages using the US Mil-Hnbk-217, it also facilitates confirmation of the current values of base failure rate and adjustment factor i.

A new approach for transient simulation of lossy interconnects terminated in arbitrary nonlinear elements is presented. The approach is based on convolution simulation. By making use of the Pade approximations of each line's characteristics or each multiconductor lines' modal functions, we derive a recursive convolution formulation, which greatly reduces the computation used to perform convolutions. The approach can handle frequency-varying effects, such as skin effects, and general coupling situations. In this paper, we analyze the errors introduced by Pade approximations and develop a scheme to determine the necessary order for an approximation. We have incorporated the proposed approach to the stepwise equivalent conductance timing simulator (SWEC) (1), (2) for digital CMOS circuits. The comparisons with SPICE3.e (7) indicate that SWEC, which gives accurate results, can be one to two order-of-magnitudes faster.

A one-dimensional, analytical model is developed for characterizing the rise of thermal gradients across solder interconnections during the power-on transient phase. Derived for thermal stress analysis of multichip electronic packages, the model's validity is confirmed through finite element solutions on a single problem and measurements of an semiconductor package. Results indicate that the thermal gradients peak before steady-state is attained.

A spatial-domain mixed-potential integral equation method is developed for the analysis of microstrip discontinuities and antennas of arbitrary shape. The algorithm is based on roof-top basis functions on a rectangular and triangular mixed grid and analytical evaluation of the quadruple moment integrals involved. The algorithm is successfully implemented into an accurate, efficient and versatile computer program. The numerical results agree with the measured ones very well.

A computer aided optimization procedure is introduced to enable the addition of extra channels to an already existing waveguide manifold multiplexer, without changing any of the existing multiplexer elements. The process provides the important advantage of the ability to expand the number of channels as required, a property which was only feasible before for channel dropping type multiplexers. The process is illustrated by practical examples that show its validity. Analysis of the effect of mechanical tolerances on the multiplexer performance is also presented to provide guide lines for the tolerance ranges in manifold multiplexer fabrication.

The scattering and transmission matrix representations of the mode-matching technique are generalized for multiguide junctions with arbitrarily shaped coupling apertures. A comparison between both representations is given with respect to the CPU time. The relative convergence phenomenon arising in cascaded discontinuities of multiguide junctions is investigated. A numerical criterion for choosing the correct mode ratio among the guides is presented. Also studied is the application to a kind of multiguide junction between a circular waveguide and a coaxial waveguide with hollow inner.

Optimized all-metal E-plane finned waveguide components are designed with the rigorous method of modal field expansion into the ridged eigenmodes, which includes both the higher order mode interaction between the step discontinuities and the finite thickness of the fins. The design which combines the advantage of constant fin thickness with that of the optimum matching potential of different waveguide inner cross-section dimensions and fin heights achieves very broad-band transformers and evanescent-mode filters with improved performance. Computer optimized data demonstrate the efficiency of the method by typical design examples: Compact transformers for WR112, WR42, WR15, and WR12 input waveguides to E-plane finned waveguides achieving return losses of more than 33 dB, or 20 dB, respectively, for the whole waveguide bands; corrugated lowpass filters designed for a cutoff frequency in the waveguide Ku- (12-18 GHz) and U-band (40-60 GHz) with return losses of better than 20 dB together with a stopband attenuation of more than 60 dB; and an evanescent-mode bandpass filter with unequal fin heights achieving 33 dB return loss for about 2% bandwidth at 56.5 GHz. The theory is verified by available measurements.