Artur Wymyslowski

Advanced numerical prototyping methods in modern engineering applications

Numerical prototyping methods based on numerical simulations and optimization are nowadays a key success factor for cost effectively and timely development, manufacturing of competitive products and processes. The typical numerical prototyping procedures are based on a sequence of numerical simulations/experiments done in an iterative form in order to achieve usually sub-optimal designs. These experiments are usually selected according to the knowledge and experience of an engineer or defined according to experimentally orientated methodologies. The current paper describes part of our preliminary research results of numerical prototyping, specialty focusing on the optimized numerical DOE approach, which leads to substantial reduction of numerical experiments for the specified accuracy of the response surface model.

Numerical Approach to Characterization of Thermally Conductive Adhesives

Thermally conductive adhesives (TCA) and electrically conductive adhesives (ECA) are one of the major concerns of the contemporary micro-electronics. They are especially important in application where e.g. effective heat dissipation is the key factor for reliability issues. Currently there is a lot of ongoing research in order to improve the basic thermal property of adhesives, which is mainly heat conductance. According to the literature data the heat conductance can vary from 0.1 up to 60 W/m-K. It depends not only on the filler material, its content and configuration but also on thermo-mechanical properties of matrix. On the other hand numerical simulation becomes nowadays an inevitable tool for rapid non-destructive and low-cost experiments. The basic problem of numerical experiments is accuracy. Nevertheless the error can be minimized by combining the numerical and traditional experiments. This can be achieved by means of partial validation of numerical results by traditional experiments or by precise and appropriate material properties measurement. In fact, the above approach was applied in current work in order to simulate the influence of curing temperature and time on the thermal conductance of polymers. Thermally conductive adhesives belong to polymer materials. In order to apply numerical simulation it is required to have an appropriate description of the thermal and mechanical behavior of polymers. Most often polymers are described by cure dependent or independent linear viscoelastic model (Jansen, 2004). Having this model, which parameters in fact can be measured experimentally, it is possible to simulate the stress and strain field caused by polymer curing and shrinkage phenomena and finally assess the thermal conductance accordingly. Current paper focuses on a problem of numerical simulation of TCA in order to recognize the trend dependence of thermal conductivity due to viscoelastic model of polymers and filler particles contact area

A procedure for validating the finite element model of a piezoresistive ceramic pressure sensor

In this paper, we describe our experimental approach to the electromechanical characterization of thick-film resistors, the estimation of the resistive materials properties, and the validation of the finite element (FE) model used for the numerical analysis of ceramic pressure sensors (CPS). In order to improve the accuracy of the numerical models and increase the reliability of the simulation results a special test device containing all the essential construction details of the CPS was designed. Both the deflection of the ceramic diaphragm of the device under test and the resistance changes were measured. The numerical and experimental analyses of the specially designed test device indirectly confirmed the correctness of the FE model, which could be convenient for further virtual prototyping analyses.

Smart and Sequential Approach to Numerical Prototyping in Micro-Electronic Applications

Numerical prototyping methods based on numerical simulations are nowadays a key factor to successful cost effective and timely design for optimized products and processes. The typical prototyping procedure would be based on a sequence of numerical simulations/tests done in an iterative form in order to achieve usually sub-optimal designs. These tests are usually selected according to the knowledge and experience of an engineer or defined standard with little or no help from effective methodologies. In contrast, this paper presents the elaborated optimized approach to numerical prototyping based on smart and sequential algorithm. The major advantage of the presented approach is that it can improve the quality of the response model at a fraction of the number of experiments compared to the classical methodologies. Details of the methodology are presented along with a selected example concerning micro-electronic packaging.

Reliability analysis of solder joints due to creep and fatigue in microelectronic packaging using microindentation technique

Solder joints in microelectronic are used for electrical signals transmission, heat conduction and structural support. One of the key problems referring to solders in microelectronics is reliability due to typical failure modes as creep and fatigue. The above paper focuses on the experimental measurements and corresponding analysis with the microindentation tests of the SAC 405 solder alloy due to creep and fatigue. The creep, resulting from the application of a constant load during a long time, is represented by an original law between the indenter displacement and time. The fatigue due to repeated loading–unloading cycles is characterized by the law of Manson–Coffin which is adapted for connecting the plastic indentation strain to the number of cycles.

Parametric Approach to Numerical Design for Optimization of Stacked Packages

The main aim for development of smaller packages is mainly due to ongoing development of portable communications devices. Thin silicon die improves device performance and reliability. Novel technological processes allow for the thinning of wafers to 2 mils without residual damage to the backside silicon or topside circuitry. Stacked packages reduce packaging cost and cycle-times. Wafers are stacked to form 3D multi-chip packages. On the other hand the electronic market requires novel and efficient designing tools as numerical design for optimization. The goal of the work was to design a reliable numerical model of the stacked package and afterwards perform numerical design for optimization in reference to a number of variables, which influence the package reliability. The numerical model of the analyzed stacked package was elaborated in ABAQUS with an embedded Python script language. The design for optimization was done by two alternative approaches: direct and indirect design for optimization. The direct approach was based on genetic algorithms while indirect approach was achieved by combination of design of experiments (DOE) with response surface modeling (RSM) methods

Simulated annealing as a global optimization algorithm used in numerical prototyping of electronic packaging

There are many optimization algorithms, which can be used to find the extremum of a function. However, in optimizing the function, which is obtained from the numerical calculations, it is necessary to apply the proper global optimization algorithm. It is caused by the high nonlinearity of the numerical functions response. The nonlinear function with not known analytical form may have many local extrema and only one global extremum. Such problems occur in numerical prototyping, when the finite element method is used, for example in numerical optimization in electronic packaging in order to inmprove the components reliability.

An approach of numerical multi-objective optimization in stacked packaging

The main aim for the development of small electronic packages is supported by an ongoing development of portable communication devices. Thin silicon dies are believed to improve the device performance as well as its reliability. Additionally, novel packaging techniques such as stacked packaging reduce packaging cost and size, and improve the functionality and reliability. In the case of the stacked packages, wafers are stacked to form a 3D multi-chip package. On the other hand, the electronic market requires novel and efficient numerical designing tools to deal properly with the optimization. The goal of the current work was to design a reliable numerical model of the stacked package and afterwards perform numerical multi-objective optimization in reference to a number of variables, which influence the stacked package reliability.

Advanced numerical prototyping methods in modern engineering applications – Optimisation for micro-electronic package reliability

Numerical prototyping methods based on numerical simulations and optimization are nowadays a key success factor for cost effectively and timely development, manufacturing of competitive products and processes. The typical numerical prototyping procedures are based on a sequence of numerical simulations/experiments done in an iterative form in order to achieve usually sub-optimal designs. These experiments are usually selected according to the knowledge and experience of an engineer or defined according to experimentally orientated methodologies. The current paper describes part of our preliminary research results of numerical prototyping, specialty focusing on the optimized numerical DOE approach, which leads to substantial reduction of numerical experiments for the specified accuracy of the response surface model.

Adhesion work analysis through molecular modeling and wetting angle measurement

Abstract The above paper contains a description of the numerical and experimental analysis in order to evaluate the adhesion work. The goal was to calculate the work of the adhesion between solutions of water, isopropyl alcohol (IPA) and silicon. The work of adhesion was calculated by using two computational methods and were compared with the experimental results based on a wetting angle measurement. The surfactants, as solution of water with IPA, are used in a process of silicon etching. The presented analysis could help in better understanding of the adhesion phenomena, which can result in improvement of silicon etching and the same can lead to higher quality of, e.g. MEMS (Micro Electro Mechanical Systems) devices, as well as reduce their production cost. The numerical analysis of the adhesion work is a challenge, where wetting angle and other methods are used in order to determine the adhesion work between for example IPA and silicon.