Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    A novel hermetic encapsulation approach for the protection of electronics in harsh environments
    ( 2022-11-11)
    Spanier, Malte
    ;
    Pawlikowski, Jakub
    ;
    Ziesche, Steffen
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    Kappert, Holger
    ;
    Ostmann, Andreas
    ;
    Jägle, Martin
    ;
    Schneider-Ramelow, Martin
    Technologies and building blocks for the realization of reliable electronic systems for the use in harsh environments are attracting increasing intention. Harsh environments are for instance high temperature, pressure, mechanical stress and/or submerge into corrosive liquids, or the combination thereof. In the first place electronic components like integrated circuits or passive components which constitute the electronic system need to be operational under harsh conditions. On system level also the interconnections and package materials need to withstand the loading conditions. Printed circuit board embedding technology is a highly promising approach to realize this kind of electronic systems. Embedded semiconductors and passive components are mechanically protected from the environmental stresses by the epoxy/glass fibre compound into which they are encapsulated. Furthermore, novel types of high temperature laminate materials are commercially available since a few years. In an electroless plating process a fully hermetic metallic encapsulation can be added to the modules. This encapsulation acts as a protective barrier when they are immersed into corrosive liquids or gases. The external electrical connections out of the package are realized by ceramics with metallic feed throughs. They are assembled onto the modules (prior to the metallic encapsulation) using sinter-lamination-technology, i.e. the simultaneous build-up lamination and a sintering process. Two application demonstrators were realized in order to show the general viability of the encapsulation process. All used materials are commercially available. Industrial process equipment was used throughout the manufacturing. Subsequent reliability tests provide evidence for the general robustness and functionality of the modules under harsh environmental conditions. This work was part of the Fraunhofer lighthouse project “eHarsh” which was funded by the Fraunhofer Society.
  • Publication
    Experimental and simulative study of warpage behavior for fan-out wafer-level packaging
    ( 2022)
    Dijk, Marius van
    ;
    Huber, Saskia
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    Stegmaier, Andreas
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    Walter, Hans
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    Wittler, Olaf
    ;
    Schneider-Ramelow, M.
    Controlling warpage effects in fan-outwafer-level packaging (FO-WLP) is of key importance for realizing reliable and cost-efficient system in packages (SiPs). However, warpage effects can occur during the manufacturing process, caused by a combination of different processing temperatures, different materials, and the changing properties of the materials (e.g. polymerization and related cure shrinkage). One approach to controlling warpage could be realized by assessing a numerical simulation workflow of the FO-WLP process chain, in which the relevant material properties and geometry are used as input. Since there are many different steps included in the FO-WLP process, accompanied by complex material behavior, this workflow is not straight-forward. In the present paper, the first FO-WLP processing steps are investigated in detail by performing extensive thermo-mechanical material characterization, temperature-dependent warpage measurements, and numerical simulations. The investigation focuses on two epoxy mold compound (EMC) materials with completely different physical properties. The warpage measurements of bi-material (EMC and silicon) samples reveal an irreversible effect after passing certain processing temperatures, which are significant for final warpage at room temperature. A new approach to measuring the coefficient of thermal expansion (CTE) is discussed, using a temperature profile based on the temperature in the process, instead of the three identical temperature ramps suggested by the typical standards. This new approach makes it possible to determine possible shrinkage effects. Within the simulation model, the hysteresis effect observed in the experiment is taken into account by adding a shrinkage strain as well as changing the CTE values during the process. A very good agreement between the experiment and simulation is achieved, which is shown for several demonstrators with different epoxy mold compound materials and thicknesses.
  • Publication
    Design of dual-frequency piezoelectric MEMS microphones for wind tunnel testing
    ( 2021)
    Wu, Lixiang
    ;
    Chen, Xuyuan
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    Ngo, Ha-Duong
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    Julliard, Emmanuel
    ;
    Spehr, Carsten
    The demand for aeroacoustic measurement microphones is surging in recent years as new rules on noise reduction and environmental compliance are getting tougher. However, the state-of-the-art microphones including classical measurement microphones and micro-electro-mechanical systems (MEMS) microphones cannot fully meet the strict requirements for wind tunnel testing (WTT) in terms of form factor, acoustic performance, and product price. To break through the bottleneck, a new type of piezoelectric MEMS microphones with dual frequency bands was designed as key part of a dedicate WTT solution, which aims to capture the unsteady pressure fluctuations underneath the turbulent boundary layer and predict the cabin noise excitation. The finite element method (FEM) was applied to analyze and optimize the MEMS design at the system level. The feasibility of the new MEMS design has been preliminarily verified by characterizing the mechanical and electrical properties of first batch of dual-frequency piezoelectric MEMS microphones. The acoustic characterization was conducted to evaluate the overall performance and the system-level FEM model was refined based on the measurement results.
  • Publication
    Design and modeling of a novel piezoresistive microphone for aero acoustic measurements in laminar boundary layers using FEM and LEM
    ( 2021)
    Erbacher, Kolja
    ;
    Ngo, Ha-Duong
    ;
    Mackowiak, Piotr
    ;
    Wu, Lixiang
    ;
    Julliard, Emmanuel
    ;
    Spehr, Carsten
    In this paper the modeling and simulation results of a piezo-resistive microphone are presented and a possible fabrication process flow and characterization concept of the sensor are described. The main objective in this funded AEROMIC project is to develop a thin and small in size microphone, which can be integrated into a flexible array, that can be mounted onto an airplane hull for flight tests. The microphone array should be no thicker than 2 mm and should contain more than 80 flush mounted single microphones, allowing acoustic measurement without disturbance of the laminar boundary layer. The pitch of the microphone sensors in the array enable high spatial resolution of the pressure fluctuation. The optimization of geometry of single sensor microphone has been done using FEA (Finite Element Analysis). For the optimization of the geometry of the single microphone chip, FEA of the air damped dynamic behavior of the diaphragm is modeled in Ansys Harmonic Response Analyses with Acoustics ACT package. To model the array on system level, a lumped-element model (LEM) is set up to predict spatial resolution and signal to noise ratio. Derived from the FEA results, a sensor chip layout with three membrane sizes is presented.