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Since many years, the University of Liege is involved in micro-electronics and micro-electromechanical systems modelling, design and integration. Recently, the University of Liege had received the opportunity to build a brand new infrastructure (clean rooms - ISO 7) with specific equipments for packaging and MEMS characterisation. This new facility (clean rooms and equipments) enables the University...
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...
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...
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...
This investigation is aimed at the stability of press-fit interconnections for MID. Moulded interconnect devices (MID) are 3-dimensional substrates produced by thermoplastic injection moulding for large-series applications. The assembly process of press-fit interconnections has been correctly modelled with a FE-Software. With this model the behaviour of the mechanical contact pressure, which decreases...
The scope of the paper is to present the result of combining experimental and simulation methodologies to determine mechanical material properties at high strain rates. Miniature bulk specimens which have a diameter comparable to BGA joints are used in the experiments. Stress-strain data recorded at high strain rates proof the high resolution capability of a novel tensile setup. A FEM model of the...
This paper deals with the problem of accurate evaluation of global quantities related to the electrostatic fields in micro-electro-mechanical systems (MEMS). In particular, the capacitance and the electrostatic force play often an important role in the design of micro-machines. In spite of the fact that some simplified formulas have been proposed so far, in many cases it is necessary to improve the...
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,...
3D integrated circuit technology is an emerging technology for the near future, and has received tremendous attention in the semiconductor community. With the 3D integrated circuit, the temperature and thermo-mechanical stress in the various parts of the IC are highly dependent on the surrounding materials and their materials properties, including their thermal conductivities, thermal expansivities,...
Nanoindentation technique is commonly used to characterize the mechanical properties of thin films. However, the validity of the measurements is greatly affected by the indentation depth and the substrate properties. The purpose of this study is to understand the influence of the substrate properties, the thin film thickness and the mechanical properties of the thin film itself on force-displacement...
This paper presents the model for the design optimization of an aluminum Thermal Linear Motor (TLM) for high bandwidth positioning systems. The aluminum TLM is the crucial driving element for our Hard Disk Drive thermal micro actuator. It occupies less area than an electrostatic actuator with the same driving force while still reaching 3-5 kHz bandwidth for positioning accuracy better than 5 nm. Optimized...
This paper presents a combined numerical and experimental methodology for predicting moisture-induced effects in Package-on-Package (PoP) assemblies. The hygroscopic warpage of the assembly "PoP" is measured. Its behavior is compared with the individual components "top" and "bottom". The assembly "PoP" absorbs more moisture than the sum of the two individual...
The temperature dependent driving force for stress induced voiding of Cu dual damascene interconnects has been studied using finite element modeling. Both 2D axisymmetric and 3D models have been investigated. Interconnect test structures have been simulated at temperatures ranging from 25 to 300degC and a stress free temperature for the structure is demonstrated, consistent with analytical modeling...
This work will present case studies of three types of flexible printable circuits subjected to different loading conditions in order to evaluate their technologies regarding mechanical reliability. Typical causes of failure in electronic devices are associated with mechanical stress, moisture, heat from transportation and field use. Typically manufacturers carry out tests to evaluate the reliability...
The transient process of filling the mold cavity in microelectronics packaging has been simulated applying the finite element method (FEM). The results have been compared to those of so-called dasiashort shotpsila experiments, in which the molding process is interrupted at predefined points in time. After determining the quantitative discrepancies between the simulation and the experimental results,...
The purpose of this research is to enhance the structure of the 204-pin small outline dual in-line memory module (SODIMM) against the drop impact. According to the JEDEC regulations, the enhancement of PCB clips should be attempted to increase the resistance against drop impact. From high speed camera observation, the SODIMM module is pushed away from the PCB clips during drop impact. Therefore, the...
Computational approaches, opportunities and challenges in reduced order modelling based on mode superposition method of the coupled electrostatic-structural domains, including effective model generation and geometrical parameterization, as well as physical and system design of MEMS component are presented and discussed.
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...
When assessing the mechanical durability of electronic assemblies, the focus is generally on the solder interconnect. However, in many package styles, such as BGAs (ball grid arrays), LGAs (land grid arrays), MLFs (micro lead frame) and QFNs (quad flat no-lead), the Cu trace emanating from the solder pad may be the weakest failure site, especially if the solder joint is copper-defined rather than...
Commercial FEM software codes do not directly support the cure dependency of polymers behavior. In electronics packaging, for example, cure shrinkage of the molding compound is consequently treated as a surplus to thermal contraction and its changes in visco-elastic behavior during curing are usually ignored. This give rise to inaccurate results and may cause difficulties even in recognizing factors...
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