Development of process modeling methodology for flip chip on flex interconnections with non-conductive adhesives

This paper presents a comprehensive methodology to model the assembly process of flip chip on flex interconnections with non-conductive adhesives (NCAs). The methodology combines experimental techniques for material characterization, finite element modeling, and model validation. A non-conductive adhesive has been characterized using several techniques. A unique experimental technique has been developed to measure the cure shrinkage. A 2D axisymmetric finite element model is used for analysis of flip chip on flex package with the non-conductive adhesive (NCA), which takes into account assembly force, cure shrinkage, adhesive modulus buildup, removal of assembly force, and cooling down to room temperature. The relationship between the bump contact resistance and the bump pressure has been established through the development of a dedicated experimental setup, which uses a micro-force tester combined with a digital multimeter and a nano-voltmeter. The process modeling has been validated by comparing the predicted bump contact resistance value and the measured bump contact resistance value after assembly process. The approach developed in this paper can be used to provide guidelines with respect to adhesive material properties, assembly process parameters, and good reliability performances.     

A class of model equations for bi-directional propagation of capillary-gravity waves

A class of model equations that describe the bi-directional propagation of small amplitude long waves on the surface of shallow water is derived from two-dimensional potential flow equations at various orders of approximation in two small parameters, namely the amplitude parameter α=a/h₀ and wavelength parameter β=(h₀/l)², where a and l are the actual amplitude and wavelength of the surface wave, and h₀ is the height of the undisturbed water surface from the flat bottom topography. These equations are also characterized by the surface tension parameter, namely the Bond number τ=Γ/ρgh₀², where Γ is the surface tension coefficient, ρ is the density of water, and g is the acceleration due to gravity.The traveling solitary wave solutions are explicitly constructed for a class of lower order Boussinesq system. From the Boussinesq equation of higher order, the appropriate equations to model solitary waves are derived under appropriate scaling in two specific cases: (i) β?(1/3−τ)?1/3 and (ii) (1/3−τ)=O(β). The case (i) leads to the classical Boussinesq equation whose fourth-order dispersive term vanishes for τ=1/3. This emphasizes the significance of the case (ii) that leads to a sixth-order Boussinesq equation, which was originally introduced on a heuristic ground by Daripa and Hua [Appl. Math. Comput. 101 (1999) 159] as a dispersive regularization of the ill-posed fourth-order Boussinesq equation.     

Scaling estimations of thermal and flow field in gas-stirred ladles

To obtain a better understanding of the physical process involved in gas stirring of a steelmaking vessel, a scaling analysis approach is developed that accounts for the effects of natural convection and axisymmetric bottom gas injection in the vessel. The orders of magnitude of some important quantities such as the transient velocity scale, thermal boundary layer thickness, and the critical flow rate to homogenize the thermal stratification in the molten steel are predicted successfully.     

Analysis of Performance of BPSK in an Additive Combination of Impulsive and Gaussian Noise

We analyze the bit error rate (BER) performance ofa correlation receiver subject to impulsive plusGaussian noisewith coherent binary phase-shift keying (BPSK). The impulsive component of the noise is assumed to be due torandom occurrences of impulses following a Poisson arrival process.Using the moments of theimpulsive component, aseries expression for the BERis derived by a Taylor's series approach. From this expression, approximate formulae for extreme valuesof signal-to-noise ratio (SNR) and impulse arrival rate (IAR)are obtained. Numerical results show thatwhen the square root raisedcosine pulse is used, (1) the BER performance improves with increaseof the rolloff factor, but the improvement becomes more significantwith decrease of the Gaussian-to-total noise ratioor increase of the IAR,(2) as the rolloff factor increases, a decrease of the IARdegrades the BER performance for low SNRs, but improves it for high SNRs.     

Genetic Algorithms in Optimization of Strength and Ductility of Low-Carbon Steels

A comparative study between the conventional goal attainment strategy and an evolutionary approach using a genetic algorithm has been conducted for the multiobjective optimization of the strength and ductility of low-carbon ferrite-pearlite steels. The optimization is based upon the composition and microstructural relations of the mechanical properties suggested earlier through regression analyses. After finding that a genetic algorithm is more suitable for such a problem, Pareto fronts have been developed which give a range of strength and ductility useful in alloy design. An effort has been made to optimize the strength ductility balance of thermomechanically-processed high-strength multiphase steels. The objective functions are developed from empirical relations using regression and neural network modeling, which have the capacity to correlate high number of compositional and process variables, and works better than the conventional regression analyses.     

Optimal control limits for CCC charts in the presence of inspection errors

The control chart based on cumulative count of conforming (CCC) items between the occurrence of two non‐conforming ones, or the CCC chart, has been shown to be very useful for monitoring high‐quality processes. However, as in the implementation of other Shewhart‐type control charts, it is usually assumed that the inspection is free of error. This assumption may not be valid and this may have a significant impact on the interpretation of the control chart and the setting of control limits. This paper first investigates the effect of inspection errors and discusses the setting of control limits in such cases. Even if inspection errors are considered, the average time to alarm increases in the beginning when the process deteriorates. Since this is undesirable, the control limits in the presence of inspection errors should be set so as to maximize the average run length when the process is at the normal level. A procedure is presented for solving this problem. Copyright © 2003 John Wiley & Sons, Ltd.     

Comparison of p–n junction formed by BF2 and B implantation in silicon microstrip detector with low and high thermal budget: impact of fluorine on electrical characteristics

The influence of crystal damage on the electrical properties and the doping profile of the implanted p⁺–n junction has been studied at different annealing temperatures using process simulator TMA-SUPREM4. This was done by carrying out two different implantations; one with implantation dose of 10¹⁵ BF₂⁺ ions/cm² at an energy of 80 keV and other with 10¹⁵ B⁺ ions/cm² at 17.93 keV. Substrate orientation 1 1 1 of phosphorus-doped n-type Si wafers of resistivity 4 kΩ cm and tilt 7° was used, and isochronally annealing was performed in N₂ ambient for 180 min in temperature range between 400°C and 1350°C. The diode properties were analysed in terms of junction depth, sheet resistance. It has been found that for low thermal budget annealing, boron diffusion depth is insensitive to the variation in annealing temperature for BF₂⁺-implanted devices, whereas, boron diffusion depth increases continuously for B⁺-implanted devices. In BF₂⁺-implanted devices, fluorine diffusion improves the breakdown voltage of the silicon microstrip detector for annealing temperature upto 900°C.For high thermal budget annealing, it has been shown that the electrical characteristics of BF₂⁺-implanted devices is similar to that obtained in B⁺-implanted devices.     

Four Input Single Output based third order universal filter using Four Terminal Floating Nullor

This paper presents a Four Input Single Output based third order universal filter that offers all five sections of filter frequency responses with some passive components using active block named as Four Terminal Floating Nullor (FTFN). The design schematic uses two number of Four Terminal Floating Nullor (FTFN) with three numbers of resistors and capacitors each. The proposed universal filter is realised with CMOS implementation of FTFN as well as Current Feedback Operational Amplifier (CFOA) namely IC AD844 for FTFN realisation. The viability of the universal filter circuit is justified with PSPICE simulation that includes both CMOS and AD844 based realization of FTFN. Also theoretical verification is well performed for the sustainability of the proposed circuit along with experimental verification by using IC AD844.     

Embedded macroporous elastomers by hydrostatic fracturing for flexible strain‐sensor applications

A method is proposed for fabricating flexible materials embedded with macroporous regions by inducing fractures under point loading. Possible use of these structures in strain sensing is demonstrated. Injecting air at high pressure through a needle‐tip generates 3‐dimensional fractures in homogeneously crosslinked polydimethylsiloxane (PDMS) media, whereas a 2‐dimensional planar fracture is generated in a sandwich‐like structure wherein a softer layer is bounded by two stiffer layers. Size‐dependence of 3‐dimensional fractures on stiffness of the media which is controlled by the crosslinker concentration shows a maximum, suggesting an optimal stiffness for generating largest fracture. The size of the 2‐dimensional fractures (～5 cm) generated inside the sandwiched layer is huge as compared to the 3‐dimensional fractures (～1 mm) under the similar conditions. Two dimensional fractured surfaces show ridges with feature length monotonically becoming smaller with stiffness. Embedded rough planar domains are created by introducing 2‐dimensional fractures at distances close enough to overlap. Using this method an embedded 2‐dimensional porous domain of polyaniline nanostructures is realized in flexible PDMS matrix. An Ohmic nature of these embedded polyaniline domains with an ability to change resistance under compression establishes their suitability for developing inexpensive and flexible strain sensors. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43681.