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Thermal, Mechanical and Multi-Physics simulation and Experiments in Microelectronics and Microsystems, 2009. EuroSimE 2009. 10th International Conference on

Date 26-29 April 2009

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Displaying Results 1 - 25 of 114
  • Influence of the microstructure on the stress state of solder joints during thermal cycling

    Publication Year: 2009 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1059 KB) |  | HTML iconHTML  

    The lifetime of a solder joint is mainly determined by its creep behaviour. Creep arises from the stresses inside the solder joints as a consequence of the thermomechanical mismatch of the board and the substrate. The stress state is heavily influenced by the anisotropy of tin. To understand the damage process in solder joints, the influence of the anisotropic microstructure must be understood. In this paper the influence of different grain sizes, shapes and orientations on the stress state is evaluated, based on numerical experiments. View full abstract»

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  • Pull-in curves determined with monolithic FEM models

    Publication Year: 2009 , Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5041 KB) |  | HTML iconHTML  

    This paper gives an overview of the different monolithic approaches to compute the pull-in curve for discretized models of electrostatically actuated microsystems that are currently available in the literature. A method to implement monolithic charge loading combined with path-following is proposed. The performance of the algorithms is tested with some numerical experiments: FEM models of microbeams, used to model micro-switches. The results show that the charge loading scheme provides a fast converging alternative to the traditional path-following approaches. Finally it is shown that the algorithm can be easily extended to handle bifurcations. View full abstract»

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  • A conformal mapping based approach for fast two-dimensional FEM electrostatic analysis of MEMS devices without re-meshing

    Publication Year: 2009 , Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (541 KB) |  | HTML iconHTML  

    In this paper, a methodology is proposed for expediting the coupled electro-mechanical two-dimensional finite element modeling of electrostatically-actuated MEMS. The proposed methodology eliminates the need for repeated finite element meshing and subsequent electrostatic modeling of the device during mechanical deformation. With the reference domain defined to be the device geometry in the absence of electrostatic actuation, we eliminate the need for repeated finite element meshing. We achieve this by mapping the deformed electrostatic domain in which the electrostatic problem must be solved to the reference undeformed domain dasiaconformallypsila. A dasiaconformalpsila map preserves the form of the Laplace equation and the boundary conditions; thus, the finite element matrix for the electrostatic problem is solved only once in the reference undeformed electrostatic domain. The conformal map itself is generated through the solution of the same Laplace equation on the reference undeformed domain geometry and with displacement boundary conditions dictated by the movement of the mechanical domain. The proposed methodology is demonstrated through its application to the modeling of two MEMS devices with varying length-to-gap ratios, multiple dielectrics and complicated geometries. The accuracy of the proposed methodology is confirmed through comparisons of its results with results obtained using the conventional finite element solution from ANSYS. View full abstract»

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  • Assaembly induced failures in thin film MEMS packages

    Publication Year: 2009 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (15185 KB) |  | HTML iconHTML  

    In the growing MEMS market wafer level thin film packages can be applied to an increasing number of MEMS devices. This paper discusses the effects of common assembly processes on wafer level thin film packages. All assembly processes are discussed and the effects of the process on the structures is presented. From the assembly tests the grinding process poses the largest hazards followed by dicing, moulding, wire bonding and finally die attachment. A number of improvements related to etch holes and sealing structures are proposed to enhance the crack resistance and robustness. View full abstract»

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  • Design for reliability methodology for micro laser welding of pigtail fibres

    Publication Year: 2009 , Page(s): 1 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (14366 KB) |  | HTML iconHTML  

    This paper discusses the effect of five process parameters on the generation of post weld stresses in the pigtail fibre optic. The alignment of the fibre optic and the laser in the butterfly module become misaligned during the laser welding process of the sleeve to the ferrule. This is primarily due to post welding stresses in the fibre optic which develop during the cooling process. The mechanical stresses resulting in the post welded fibre optic are estimated using Finite Element Analysis and response surface methodology. Integrated Design of Experiments (DoE) and Finite Element Analysis (FEA) are used to determine the distribution of the post welding stresses in the fibre optic. The DoE data is used to construct an explicit reduced order model to perform a sensitivity analysis. The influence of the manufacturing tolerances and variation of the design variables on the residual stresses in fibre is assessed using a Monte Carlo simulation. The initial design of the fibre optic is used to evaluate the important process parameters and to assess the capability of the welding process. A particle swarm optimisation algorithm is used to undertake design optimisation of fibre optic and to determine the optimal process conditions. View full abstract»

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  • Effects of geometry and material properties for stacked IC package with spacer structure

    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (15362 KB) |  | HTML iconHTML  

    As the electronic industry is making its progress to miniaturize high performance, smaller and lower-priced IC packages, 3D packaging technologies are presently used to achieve these goals. Although 3D packaging technologies are vastly studied and applied to perform better performance, low power consumption and smaller packaging size of IC packages, thermo-mechanical problems occur as well due to the 3D stacking feature. Because chips are vertically stacking in 3D packages, higher thermal resistances are resulted and their corresponding induced thermal stresses and heat dissipations are becoming major reliability concerns. In order to realize thermal stresses distributions in stacked IC packages with spacer structures, the three dimensional finite element analysis (FEA) modeling has been employed. For the purpose of studying effects of geometry and material properties of stacked IC package with spacer structure, several comparisons of variations of geometry and materials are discussed in this paper. Through these comparisons, effects of material properties of spacer structures in stacked IC packages and those resulted in stresses distributions of copper TSV (through-silicon-vias), dies and spacers can be presented. Moreover, effects of geometry of die and copper TSV size, die stacking number, TSV distributions as well as TSV/bump pitch and spacer/bump thickness are also illustrated. These results will be helpful design guidelines to engineers if optimization designs for stress solutions in stacking IC package with spacer structure are needed. View full abstract»

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  • Fatigue life prediction models developed for Green Electronics in Aeronautical and Military Communication Systems (GEAMCOS)

    Publication Year: 2009 , Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (10493 KB) |  | HTML iconHTML  

    This paper presents in details the fatigue life prediction models developed for lead-free assemblies in harsh environments during the 3-year European LIFE project GEAMCOS. The approach uses advanced finite element modelling as well as experimental fatigue data. It is also based on a complete material characterisation for a wide range of stress conditions. It focuses on the most critical packages of the full lead-free GEAMCOS test board and of the functional demonstrator developed for military communication. View full abstract»

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  • Modeling cure shrinkage and viscoelasticity to enhance the numerical methods for predicting delamination in semiconductor packages

    Publication Year: 2009 , Page(s): 1 - 8
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6135 KB) |  | HTML iconHTML  

    Interfacial adhesion between the Epoxy Molding Compound (EMC) and the copper-based leadframe is one of the major concerns in the qualification of plastic packages. Since the conventional shear testing methods used in industry do not consider the residual stresses in the shear samples, they are only used as a qualitative testing method for the EMC qualifications. However, since these tests are based on the maximum force leading to interface delamination, they may cause erroneous results because of neglecting process-induced stresses, which may alter the required force needed to break the samples at the interface. Even classical fracture mechanics, based on mechanical load leading to crack propagation, may not fully characterize the interfacial fracture toughness, because the residual stresses available in the sample impede or facilitate the crack progress, depending on the state of the stresses at the crack tip. The aim of this work is to propose an effective selection criterion for finding the most suitable epoxy molding compound in terms of the intrinsic interfacial adhesion. The effect of residual stresses on the interfacial fracture toughness was investigated by performing an empirical approach to calculate the amount of the cure shrinkage by warpage measurement of the bi-material beams. The effective cure was implemented in the Finite Element Analysis (FEA) of the experimental fracture test to estimate the real interface adhesion. It was observed, that the proper molding compound candidate to fulfill the adhesion requirements was not the one which showed the maximum fracture force and material selection may be done wrongly, if the process-induced stresses are not considered in the FEA of the fracture tests. View full abstract»

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  • Simulation of large-scale periodic circuits by a homogenization method

    Publication Year: 2009 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1589 KB) |  | HTML iconHTML  

    Actuation, sensoring and control in arrays of MEMS require spatially distributed periodic electronic circuits. For very large sized arrays, say 1000 times 1000 MEMS or cells, on the same chip, simulation requirements for electronics are far away from standard algorithm capabilities. One of the authors has shown in a theoretical paper, that a homogenization modeling method, previously developed for composite materials, can be extended to arrays of electronic circuits, at least in the linear static case. When it is applied to a set of periodic network equations, the simplified resulting model turns to be a system of few partial differential equations. Its properties are inherited on the one hand from the periodic cell composition, and on the other hand from electric conditions imposed at the boundaries. Its numerical solution, a vector of few mean voltages, is weakly dependent of the array size. Actual voltages, at all nodes of the whole periodic circuit, are computed through a fast post-processing procedure. We present the implementation of the model. View full abstract»

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  • Investigation of mixed SAC and SnPb solder balls under high speed ball shear and pull tests

    Publication Year: 2009 , Page(s): 1 - 8
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (31679 KB) |  | HTML iconHTML  

    Due to environmental consciousness and legislative regulations, Pb-free solders have been increasingly used for replacement of conventional SnPb solders in the microelectronic industry. However, during the transition period from SnPb to Pb-free solders, some products will potentially consist of mixtures of Pb-free with SnPb solders. This paper presents the results of microstructural analysis of mixed solder joints which are formed by attaching different alloys of solder balls and pastes on the OSP pad finish. The effect of thermal aging on the strength and fracture energy of the mixed solder balls during high speed ball shear/pull tests was also investigated in the study. The test specimens were aged at 125degC for durations of 200, 500 and 1000 hours. The correlations between the solder ball fracture force/energy, failure modes and intermetallic compound (IMC) thickness of the mixed alloy solder joints are also established. View full abstract»

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  • Development of a submodel technique for the simulation of solder joint fatigue of electronic devices mounted within an assembled ECU.

    Publication Year: 2009 , Page(s): 1 - 8
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5893 KB) |  | HTML iconHTML  

    The thermomechanical fatigue of solder joints on the system level is more complex to predict than on the board level. The damage of the solder joints of an electronic device in an ECU (electronic control unit) depends on the thermal expansion mismatch between the materials of the device and the PCB (printed circuit board), so called local mismatch, as well as on the global deformation of the PCB induced by the casing of the ECU. Therefore we have performed a transient sequentially coupled thermal-mechanical simulation on the system level. We used a two-step submodel approach. In the first step the electronic device with a PG-LQFP package was included in the entire ECU model, though the creep behaviour of its SnAgCu solder joints was omitted. In the second step the simulation of the solder joints fatigue was carried out with the help of the submodel. The submodel technique allowed to reduce the simulation model of a system to the electronic device model with a piece of the PCB underneath and at the same time maintain realistic PCB deformations and the realistic temperature field in the entire submodel during the temperature cycle. The simulation is validated with the temperature and strain gage measurement. The simulation predicts a loss of the life time by a factor of 0,5 for the solder joints in the ECU compared to the the board level tests. View full abstract»

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  • 3D Multi-Frequency MEMS Electromechanical Resonator Design

    Publication Year: 2009 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (8528 KB) |  | HTML iconHTML  

    Microelectromechanical systems (MEMS) are intensively studied since many years due to their high potential performances and their integration possibilities. In particular, electromechanical resonators realized at the CMOS level could allow the emergence of integrated multi-frequency architectures suitable for future multiband wireless communication devices that might require many reference frequencies to address multiple communication standards. This paper presents a new 3D multi-frequency MEMS resonator design based on Lame-mode plate resonators. Mechanisms and finite element modeling (FEM) simulations are detailed. The silicon on nothing process (SoN) can be used to realize such 0-stress 3D structures. View full abstract»

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  • A multiscale model of mMicro cantilever arrays

    Publication Year: 2009 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6607 KB) |  | HTML iconHTML  

    We present a simplified model of mechanical behavior of large cantilever arrays with discoupled rows in the dynamic operating regime. Since the supporting bases are assumed to be elastic, cross-talk effect between cantilevers is taken into account. The mathematical derivation combines a thin plate asymptotic theory and the two-scale approximation theory, devoted to strongly heterogeneous periodic systems. The model is not standard, so we present some of its features. We explain how each eigenmode is decomposed into a products of a base mode with a cantilever mode. We explain the method used for its discretization, and report results of its numerical validation with full three-dimensional finite element simulations. Finally, we provide a short description of parameter updating and identification techniques developed for the model. View full abstract»

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  • Probabilistic effects in thermal cycling failures of high-I/O BGA assemblies

    Publication Year: 2009 , Page(s): 1 - 7
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (11278 KB) |  | HTML iconHTML  

    This paper presents a study of the probabilistic effects that act in addition to deterministic (mechanistic) effects to reduce the thermal cycling durability of ball grid array (BGA) interconnects as the component I/O count increases. The mechanistic drivers include increasing thermal expansion mismatch with increasing package size and increasing stress levels with decreasing solder joint size. The most critical joint from this deterministic perspective is usually the one at the outer corner of either the die foot-print or the package foot-print. The probabilistic factors include variabilities in microstructure, interfacial intermetallic layers, joint geometry and void distributions; all of which can place several joints around the critical one at risk, and further reduce the durability of the entire package. Thus, durability can drop as the number of joints in series increase, even if the stress levels do not change. Thus, for large BGAs the mechanistic prediction can overestimate component life. In this paper PBGA-1156 assemblies are subjected to temperature cycling tests and the failure statistics are identified. Using a partitioned daisy-chain design, the durability is found to decrease, as more and more joints are nested together in the critical regions at the package corners. Since all the failed joints do not experience the same thermal expansion mismatch, finite element analysis and fatigue analysis is conducted to normalize all the failure data to a uniform damage level, by quantifying the deterministic (mechanistic) effects. The additional drop in durability with increasing number of joints, after the mechanistic normalization, is attributed to the probabilistic effect of interest. The results suggest that for this example, the probabilistic effects can reduce the deterministic prediction by an order of magnitude, as the number of I/O in the critical region reaches 100. View full abstract»

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  • Rigid-Flexible Printed Circuit structure optimization by simulations

    Publication Year: 2009 , Page(s): 1 - 4
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2585 KB) |  | HTML iconHTML  

    Rigid-flexible printed circuit boards (RFPCB) has the advantages of providing not only the flexibility and bendability required by many electronic products, but also the reliability required by the key electronic components. In this study, based on one kind of RFPCB which would be used for a wearable device prototype, the structure optimization was performed by simulations. Through the structural analysis, it is found that there are some risk places for potential failures, such as the corners of the connecting part of the RFPCB. Normally, the stress concentrations would locate on these places if the circuit boards encounter the bending, twisting or tension conditions during the assembly process or usages. Hence the three load conditions are simultaneously considered in the optimization. To reduce the stress concentration in the corners of connecting part, the structure of the FPC cross section were optimized. The various optimization proposals are presented firstly. Then the simulations were executed. At last, by comparing the maximum Von Mises stress of different simulation cases, the optimized structure was attained. Appending substrate layers on top and bottom layer of FPC and setting air gap between the appending substrate and FPC is suggested using tension and twisting cases. The original design is better used under the loading condition of bending. View full abstract»

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  • Thermal analysis based on the environmental tests of STN display

    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (16875 KB) |  | HTML iconHTML  

    Environmental test is widely used to verify the adaptability and reliability of various electronic products in the last decades. The sharp change of temperature and humidity in certain situations could pose a serious reliability issue on the electronic components. This paper presents an experimental study of one kind of plastic substrate based flexible display called STN (super-twisted nematic). The study focuses on the reliability of display under various temperature and humidity conditions. Considering the range of temperature and humidity changed in applications, the experiments are divided into four subgroups: cold test, cyclic damp heat test, the steady state damp heat test and dry heat test. Through all the tests, the STN display reliability was evaluated and the failure modes were obtained. Based on these tests, the thermal-structural simulation model was built. By the simulation, part of the experiment phenomenon were explained. It provides a solid foundation for further reliability study of the STN display in the practical applications. View full abstract»

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  • FEA based design optimization of exciting sensitivity for micromachined piezoelectric transducer

    Publication Year: 2009 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (8461 KB) |  | HTML iconHTML  

    This paper is to perform a design optimization of micromachined piezoelectric transducer by maximizing the system exciting sensitivity. The transducer is a membrane-based micromachined transducer with the piezoelectric film to excite the membrane vibrating. In this study, the exciting sensitivity is taken as the optimization objective. Specifically, when fixing the exciting signal, the transducer structure is optimized to maximize the vibrating magnitude of the membrane. The shape and size of the piezoelectric film are selected as the design parameters to optimize the structure of the transducer. Through analysis, four different piezoelectric structure designs were proposed and explored for optimizing the exciting sensitivity of the transducer. To perform the analysis and the subsequent optimization, finite element simulation was taken and all the FEA models were built on ANSYS software. The optimal design and sensitivity analysis are performed from the results of simulations on ANSYS; the corresponding structural parameters of the piezoelectric film for optimal design are identified. Finally, the optimization results of the exciting sensitivity for the transducers of these different piezoelectric film structures are compared; the design method to improve the exciting sensitivity of the transducer is provided. View full abstract»

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  • Numerical approach to extraction of elasto-plastic material models and corresponding properties of thin layers through nanoindentation technique

    Publication Year: 2009 , Page(s): 1 - 7
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB) |  | HTML iconHTML  

    Current developments and trends in microelectronics are focused on thin layers and novel materials. This leads to application of different test and measurement methods, which are capable to measure basic mechanical properties of such materials on micro-scale and nano-scale. The presented project focuses on application of the nanoindentation technique in order to extract the basic elastic and elasto-plastic mechanical properties of aluminium through analytical and numerical approaches. The results allowed to select the most appropriate elastoplastic material model that would be capable of fitting the experimental and numerical results. According to the performed analysis it was concluded that Ramberg-Osgood model fulfil the above criteria and can be used to predict the nanoindentation results in case of very thin aluminium layers. View full abstract»

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  • Analytical model of electrostatic membrane-Based actuators

    Publication Year: 2009 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB) |  | HTML iconHTML  

    In the design process, modelling is a fundamental stage which allows the designer to obtain a general overview of the device performance. Very often, this phase is very time-consuming, especially if a well optimized device which fulfils very specific requirements is to be fabricated. Hence, a fast and reliable technique of simulation is needed and accurate tools have to be used to achieve this goal. In this paper, a simple method of electrostatic actuator modelling based on reduced analytical equations is presented and compared to commonly used FEM simulations. This method, despite some limitations, gives accurate results in much shorter time which might be crucial during the optimization phase. View full abstract»

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

    Publication Year: 2009 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2428 KB) |  | HTML iconHTML  

    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 function's 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 component's reliability. There is a group of optimization methods, which can solve such nonlinear problem with success. These methods are capable to avoid of being trapped in local extemum. To this group belongs: simulated annealing, evolutionary algorithms, tabu search, ant search, etc. In this paper the simulated annealing algorithm is described and applied to optimize the electronic passive elements. View full abstract»

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  • Drop test simulation study of flexible devices

    Publication Year: 2009 , Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (19141 KB) |  | HTML iconHTML  

    In this paper, a wrist device conception was selected to study the reliability of flexible devices by drop test simulation. In the conception device, all of the components cannot be made flexible immediately. Some of them are still rigid, such as the ball grid array (BGA), the connector, and some other big components like the vibrator. The reliability of the device, where such rigid components are mounted on a flexible plastic substrate, is anything but guaranteed. In this study, a system level simulation model of a drop test was developed. In this simulation model, there are some challenges, such as the uncertain initial shape of the assembled products, the long impact time, and the unknown mechanical behaviours of new materials. To solve these problems, some manual work and some model simplification were performed. For the flexible device, the reliability study focussed on the electrical connection and the assembly processes. Before building the model, structural analysis of this device had been carried out first. Based on this analysis, some points of potential concern were identified. Based on these points, several submodels were refined such as the display, the BGA solder joint, and the flexible printed circuit (FPC) copper trace. Seven drop simulations had been executed with different drop directions. There were six basic orthogonal drop directions and one additional drop direction, that was anticipated to have a serious impact on the reliability of the device. Through the simulations, some weak locations were pointed out by the observation of the stress level of Von Mises in the drop test. The results were delivered to the electronical and mechanical designer for reference in the new design and some actions were taken to optimize the design. View full abstract»

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  • Wire bonding degradation induced by temperature gradients under active cyclic loading

    Publication Year: 2009 , Page(s): 1 - 5
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    It is well known that high temperature storage can degrade wire bonding contacts significantly due to interdiffusion of pad metal and bonding wire. Looking at harsh applications such as engine management we notice an additional failure mode caused by the temperature gradient during the pulsed active cycling period. Especially when we aim at components with high temperature capability and we substitute the power aluminium metallisation with power copper in order to avoid the formation of lifetime limiting intermetallics, the degradation of wire bonds (Au, Al, Cu) must be assessed with respect to the electrical pulse width, the dissipated power and the number of active cycles, which can exceed 500 millions in automotive applications. This paper presents experimental data with different temperature stress. The time dependent temperature distribution in the device is determined with an electrothermal simulator (TESI). The calculated temperature gradients will be used to enable a thermal-mechanical simulation (ANSYS). As a result a prediction, which kind of pulses can reduce the lifetime of the components under investigation, should be possible. View full abstract»

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  • Sensitivity analysis of technological fabrication tolerances on the lifetime of flip-chip solder joints

    Publication Year: 2009 , Page(s): 1 - 7
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (867 KB) |  | HTML iconHTML  

    In this paper we discuss the influence of solder joint geometry on the lifetime of a flip chip assembly. Geometry variations caused by variations of solder volume, pad configuration, and pad size on the printed circuit board (PCB) were taken into account. Typically these parameters vary due to technological fabrication tolerances. Consequently, the influence of such design aspects on system reliability was studied in detail by using finite element analysis (FEA) models. Selected solder joint geometry variations were assembled and tested in a thermal cycling chamber. Simulation and experimental results were compared and some advice is given regarding their evaluation. View full abstract»

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  • Modelling of jet-impingement cooling for power electronics

    Publication Year: 2009 , Page(s): 1 - 5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (834 KB) |  | HTML iconHTML  

    The use of an innovative jet impingement cooling system in a power electronics application is investigated using numerical analysis. The jet impingement system, outlined by Skuriat et al, consists of a series of cells each containing an array of holes. Cooling fluid is forced through the device, forming an array of impingement jets. The jets are arranged in a manner, which induces a high degree of mixing in the interface boundary layer. This increase in turbulent mixing is intended to induce higher Nusselt numbers and effective heat transfer coefficients. Enhanced cooling efficiency enables the power electronics module to operate at a lower temperature, greatly enhancing long-term reliability. The results obtained through numerical modelling deviates markedly from the experimentally derived data. The disparity is most likely due to the turbulence model selected and further analysis is required, involving evaluation of more advanced turbulence models. View full abstract»

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  • In-situ observation of SAC305 degradation during isothermal mechanical cycling of joint-scale samples

    Publication Year: 2009 , Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (16472 KB) |  | HTML iconHTML  

    This paper investigates the degradation behaviour of lead-free Sn96.5Ag3.0Cu0.5 solder. A series of isothermal mechanical cycling tests under different conditions has been conducted. The tests were monitored in-situ with a high magnification camera system. Optical observations are presented from selected tests, showing the surface morphology during testing. In addition to the optical investigation, the load drop behaviour of the samples is analysed. The result is a deeper insight into the microscale failure behaviour of SAC305 during isothermal cycling. View full abstract»

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