For AuthorsIf you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation.*Related content and download information correct at time of download. Purpose -This paper aims to show that simple geometry-based hp-algorithms using an explicit a posteriori error estimator are efficient in wave propagation computation of complex structures containing geometric singularities. Design/methodology/approach -Four different hp-algorithms are compared with common h-and p-adaptation in electrostatic and time-harmonic problems regarding efficiency in number of degrees of freedom and runtime. An explicit a posteriori error estimator in energy norm is used for adaptive algorithms.Findings -Residual-based error estimation is sufficient to control the adaptation process. A geometry-based hp-algorithm produces the smallest number of degrees of freedom and results in shortest runtime. Predicted error algorithms may choose inappropriate kind of refinement method depending on p-enrichment threshold value. Achieving exponential error convergence is sensitive to the element-wise decision on h-refinement or p-enrichment.Research limitations/implications -Initial mesh size must be sufficiently small to confine influence of phase lag error. Practical implications -Information on implementation of hp-algorithm and use of explicit error estimator in electromagnetic wave propagation is provided. Originality/value -The paper is a resource for developing efficient finite element software for high-frequency electromagnetic field computation providing guaranteed error bound.
In this paper, research activities on the reliability for bare die connections on molded interconnected devices (MID) and flexible substrates are presented. The results were achieved by experimental, thermo-mechanical stress characterization combined with finite element analysis (FEA) of the assembly during application specific environmental conditions. Aim of the work is to determine the influence of thermo-mechanical stress on different assembly variants. Therefore, four different assemblies are examined each on four different substrates: Aluminum wire bonded chip, flip-chip with 200 µm SAC305 solder balls for reflow soldering, flip-chip with gold stud bumps for an isotropic conductive adhesive configuration and flip-chip with gold stud bumps for a non-conductive adhesive configuration. For flip-chip assemblies an additional underfill was used to mechanically strengthen the connection between chip and substrate. To gain data from the real assemblies, aspecial stress detection chip with boron doped solid state resistors has been adapted for the requirements of the research project. The matching of numerical analysis and real assembly was done by measuring the mechanical stress in the chip during thermal cycling of the assemblies. The real time stress data of the piezo resistive resistors were recorded and compared to the thermo-mechanical FEA results.
This investigation is aimed at the modeling of both the fabrication process and the reliability of press-fit interconnections on moulded interconnect devices (MID). These are multifunctional three-dimensional substrates, produced by thermoplastic injection moulding for large-series applications. The assembly process and subsequently the durability of press-fit interconnections has been modeled and proved with a finite element software. Especially, a simulation tool for process optimizations was created and applied. In order to obtain realistic results, a creep model for the investigated base material, a liquid-crystal polymer (LCP), was generated and verified by experiments. Required friction coefficients between metal pin and base material were determined by adapting simulations and experiments. Retention forces of pins pressed into substrate holes during as well after the assembly process, and after temperature loads were predicted by simulations. Additionally, the decreasing extraction forces over time due to creep in the thermoplastic base material have been predicted for different storage temperatures as well with finite element analyses. Following, the numerical results of the process and reliability modeling were verified by experiments. It is concluded that the behavior of the mechanical contact of the pin-substrate system, can be suitably described time- and temperature-dependent.
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