Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration IZM

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  • Publication
    On the Radiation Characteristics of Full-Loop, Half-Loop and Quasi Half-Loop Bond Wire Antennas
    ( 2018)
    Ndip, I.
    ;
    Lang, K.-D.
    ;
    Reichl, H.
    ;
    Henke, H.
    The theory, modeling, measurement and analysis of the radiation characteristics of bond wire antennas (BWAs) is presented in this work. We commence with rigorous formulations, and derivations of analytical models for calculating the vector potential, radiated electromagnetic fields and directivity of full-loop BWAs (FL-BWAs), considering non-constant current distribution along the BWAs. Based on the image theory, we derive an analytical model for calculating the directivity of half-loop BWAs (HL-BWAs) from that of FL-BWAs. Very good correlation is obtained between the directivities calculated analytically using the derived models, and numerically using commercial full-wave solvers, thus validating our analytical approach. We apply the verified models to thoroughly analyze the radiation characteristics of FL-BWAs and HL-BWAs. The radiation characteristics of a HL-BWA is based on the assumption that its reference plane is infinitely large and perfectly conducting. However , for the development of wireless systems, reference planes of finite sizes are required. Therefore, we investigate the impact of realistic dimensions of reference planes. Our results reveal that the radiation characteristics of BWAs referred to as ""HL-BWAs"" in published literature differ significantly from those of true HL-BWAs. Hence, we introduce the term ""quasi half-loop BWA (QHL-BWA)"" to describe BWAs with small reference planes. Finally, we analyze the radiation characteristics of QHL-BWAs, and compare their radiation patterns to that of HL-BWAs. For experimental verification, QHL-BWAs were fabricated and measured in the 60 GHz band. Very good correlation was obtained between measurement and simulation results.
  • Publication
    Experimental verification and analysis of analytical model of the shape of bond wire antennas
    ( 2017)
    Ndip, I.
    ;
    Huhn, M.
    ;
    Brandenburger, F.
    ;
    Ehrhardt, C.
    ;
    Schneider-Ramelow, M.
    ;
    Reichl, H.
    ;
    Lang, K.D.
    ;
    Henke, H.
    In this Letter, the authors present the experimental verification of an analytical model, which captures the realistic shape of bond wire antennas (BWAs) in dependence on the wire bonding and design parameters. Using the verified model, the impact of the shape of the wires on the performance of BWAs is quantified.
  • Publication
    Analytical models for calculating the inductances of bond wires in dependence on their shapes, bonding parameters, and materials
    ( 2015)
    Ndip, I.
    ;
    Oz, A.
    ;
    Reichl, H.
    ;
    Lang, K.D.
    ;
    Henke, H.
    Novel analytical models for accurately and efficiently calculating the inductances of bond wires in dependence on their shapes, bonding parameters, and materials are derived. For verification, the inductances of bond wires having different geometrical dimensions and material properties were analytically calculated using our proposed models, and compared to those numerically extracted using Ansys Q3D. An excellent correlation was obtained, with a maximum discrepancy of approximately 1%. These models can be applied to rapidly predict the impact of the bonding parameters and their process variations right at the beginning of the design process. For example, using the models, we could predict within seconds that the loop inductance of a ground-signal bond wire configuration can be reduced by approximately 14%, 19%, or 37%, respectively, if the loop height, pitch or the distance between the bonding positions is reduced by 50%. To quantify the impact of the reductions in inductance on realistic signal transmission characteristics of the wires, we fabricated and measured bond wire interconnects up to 40 GHz.
  • Publication
    On the optimization of the return current paths of signal vias in high-speed interposers and PCBs using the M3-approach
    ( 2014)
    Ndip, I.
    ;
    Löbbicke, K.
    ;
    Tschoban, C.
    ;
    Ranzinger, C.
    ;
    Richlowski, K.
    ;
    Contag, A.
    ;
    Reichl, H.
    ;
    Lang, K.-D.
    ;
    Henke, H.
    In this paper, the return-current paths of signal vias transiting multilayered stack-ups are optimized using the M3-approach (methodologies, models, measures). A methodology for suppressing the excitation of parallel-plate modes in these stack-ups is first proposed. The result of this methodology is a stack-up with well-defined paths for the returning conduction currents. Secondly, a model of the stack-up is developed and experimentally verified using measurement results. The model is then applied to study the impact of the impedance of the return-current paths on the effectiveness of the proposed stack-up in suppressing the excitation of cavity resonance modes. Based on the results of this study, appropriate designs measures for optimizing the return-current paths of the signal vias are derived. To demonstrate the advantages of these measures, they are applied to fabricate a new test board with the proposed stack-up. The measurement results show excellent signal transmission and no dips in the insertion loss of the signal via for frequencies up to 20 GHz.
  • Publication
    A modeling approach for predicting the effects of dielectric moisture absorption on the electrical performance of passive structures
    ( 2014)
    Curran, B.
    ;
    Ndip, I.
    ;
    Engin, E.
    ;
    Bauer, J.
    ;
    Pötter, H.
    ;
    Lang, K.-D.
    ;
    Reichl, H.
    In this paper a modeling approach for predicting the electrical behavior of nonresonant and resonant structures under the influence of the absorption of moisture into the dielectric is presented. The paper focuses on the encapsulation materials used for printed circuit boards (PCBs) as a case study. For the investigated cases, analytical modeling shows that the loss of electrical insulation resulting from moisture absorption has minimal effects on the losses in transmission lines (TMLs), which would only cause system failure when combined with other aging effects. However, potential cases are discussed where the loss of electrical insulation could be significantly increased. Full-wave modeling shows that moisture absorption can cause the detuning of passive components, specifically antennas and impedance-controlled TMLs, that can have significant effects on system performance. Antenna resonance frequencies shift by up to 3-5%.
  • Publication
    Design and evaluation of a passive self-breathing micro fuel cell for autonomous portable applications
    ( 2013)
    Weiland, M.
    ;
    Wagner, S.
    ;
    Hahn, R.
    ;
    Reichl, H.
    A micro fuel cell system designed to power complex autonomous systems with dynamic pulse-shaped loads like wireless sensor nodes is presented in this work. The requirements posed by the corresponding pulse load profiles are considered for the design of the passive self-breathing micro fuel cell. The performance of the fuel cell is mainly affected by the oxygen and water management which is influenced by the openings in the cathodic current collector. Due to the comparatively low average cell current the performance can be strongly improved by retaining water within the cell using a reduced opening ratio and thus improving the ionic conductivity of the electrolyte. The impact of the opening ratio is studied in the range between 54% and 0.007%. The total active area of the fuel cell is only 0.1 cm(2). Prototypes are realized using printed circuit board technology and wet chemical etching of the micro-structured current collectors. The cells were characterized with an exemplary load profile with a 10 ms load pulse and a 1 s pulse period. Successful operation was demonstrated for all cells for different current densities. A significant power improvement was achieved by reducing the opening ratio down to 0.3%. Under these circumstances a power density of 220 mW cm(-2) could be generated during the pulse. This is more than twice in comparison to cells with large opening ratios of 54% where only approx. 100 mW cm(-2) was obtained.
  • Publication
    Modeling and minimizing the inductance of bond wire interconnects
    ( 2013)
    Ndip, I.
    ;
    Öz, A.
    ;
    Guttowski, S.
    ;
    Reichl, H.
    ;
    Lang, K.-D.
    ;
    Henke, H.
    In this paper, a novel analytical model for calculating the partial self-inductance of bond wires in dependent on bonding parameters such as loop height, distance between bonding positions and the thickness of the metallization on which the wire is bonded, is derived for the first time. An excellent correlation is obtained between inductances extracted using our proposed model and those extracted using Ansys Q3D, with a maximum deviation of approximately 1%. Furthermore, methods for minimizing the inductance of bond wires, based on the definitions of loop and partial inductances are discussed. Test bond wire structures are designed, fabricated and measured to quantify the implemented method.
  • Publication
    Impact of process tolerances on the performance of bond wire antennas at RF/microwave frequencies
    ( 2012)
    Ndip, I.
    ;
    Öz, A.
    ;
    Tschoban, C.
    ;
    Schmitz, S.
    ;
    Schneider-Ramelow, M.
    ;
    Guttowski, S.
    ;
    Reichl, H.
    ;
    Lang, K.-D.
    Due to the multitude of advantages bond wire antennas have over conventional planar antennas (especially onchip planar antennas), they have received much research attention within the last four years. The focus of the contributions made so far has been on exploiting different configurations of single-element and array bond wire antennas for short-range applications at RF/microwave frequencies. However, the effects of process tolerances of bond wires on the radiation characteristics of bond wire antennas have not been studied in published literature. Therefore in this paper, we investigate the impact of up to 20% fluctuations in the parameters of bond wires on the performance of 42 GHz and 60 GHz bond wire antennas. Our results reveal that the length and radius of bond wires are the most and least sensitive parameters, respectively. Furthermore, the severity of the impact of process tolerances depends on the impedance bandwidth of the original antenna, before considering the tolerances. For example, a 10% change in the length of a bond wire causes the resonance frequency of a 42 GHz antenna to be shifted out of the specified 3GHz bandwidth (40.5 GHz-43.5 GHz) required for point-to-point communication. However, although a 10% change in length of a bond wire yields a 2.5 GHz shift in the resonance frequency of a 60 GHz bond wire antenna, it doesn't completely detune the antenna because of the original 6 GHz bandwidth available, prior to the fluctuation. Therefore, to prevent the impact of process tolerances from severely degrading the performance bond wire antennas, these antennas should be designed to have larger bandwidths than specified. For experimental verification, a bond wire antenna was designed, fabricated and measured. Very good correlation was obtained between measurement and simulation.
  • Publication
    Characterization of interconnects and RF components on glass interposers
    ( 2012)
    Ndip, I.
    ;
    Töpper, M.
    ;
    Löbbicke, K.
    ;
    Öz, A.
    ;
    Guttowski, S.
    ;
    Reichl, H.
    ;
    Lang, K.-D.
    As a result of their myriad of advantages over silicon and other conventional substrate technologies, glass substrates have received significant attention from the electronic packaging and system integration community worldwide. So far, most of the research effort on glass has concentrated on developing methods for fabricating cylindrical through glass vias (TGVs). However, to fully evaluate the potential of glass as an interposer material for microelectronic systems with computing and communication functions, an extensive characterization of interconnects and RF components on these substrates must be carried out. In this contribution, we go beyond state-of-the-art research and present an in-depth characterization of TGVs, coplanar lines and 60 GHz coplanar excited patch antennas on two glass substrates. One of these substrates has a low alkaline content (Borofloat33®) and the other is alkaline-free (AF32®). The effects of these glass materials on the RF performance of TGVs, coplanar lines and 60 GHz antennas are extensively studied, and recommendations for performance optimization are proposed. For experimental verification, test samples are fabricated and measured. Very good correlation is obtained between the measurement and simulation results from 100 MHz to 100 GHz.
  • Publication
    Modelling the shape, length and radiation characteristics of bond wire antennas
    ( 2012)
    Ndip, I.
    ;
    Oz, A.
    ;
    Tschoban, C.
    ;
    Guttowski, S.
    ;
    Reichl, H.
    ;
    Lang, K.D.
    ;
    Henke, H.
    Novel analytical models for accurately modelling the shape and length of bond wires in dependence on the loop height (Lh(max)), distance between the bonding positions (d(bp)) and the thickness of the metallisation (t(met.)) on which the wires are bonded, are derived in this work. These analytical models, which are based on the Gaussian distribution function, are applied to (i) develop realistic three-dimensional electromagnetic models of bond wire antennas and study their radiation characteristics and (ii) study the impact of process tolerances of bond wire parameters on the performance of the antennas. For these studies, a 42 GHz half-loop bond wire antenna is considered as an example. It is designed, fabricated and measured. Our results reveal that dbp has the most significant impact on the antenna performance. For example, -10% fluctuations in dbp causes similar to 2.5 GHz shift in the resonance frequency and 24% reduction in the maximum realised gain. Since this may completely detune the antenna, it is recommended that fluctuations in d(bp) should be kept below 10% during the manufacturing process. Good correlation is obtained between measurement and simulation results.