Search

In this paper, we present our results of experimental and numerical pull-out tests on carbon nanotubes (CNTs) embedded in palladium. We prepared simple specimens by employing standard silicon wafers, physical vapor deposition of palladium and deposition of CNTs with a simple drop coating technique. An AFM cantilever with known stiffness connected to a nanomanipulation system was utilized inside a scanning electron microscope (SEM) as a force sensor to determine forces acting on a CNT during the pull-out process. SEM-images of the cantilever attached to a CNT have been evaluated for subsequent displacement steps with greyscale correlation to determine the cantilever deflection. We compare the experimentally obtained pull-out forces with values of numerical investigations by means of molecular dynamics and give interpretations for deviations according to material impurities or defects and their influence on the pull-out data. We find a very good agreement of force data from simulation and experiment, which is 17 nN and in the range of 10-61 nN, respectively. Our findings contribute to the ongoing research of the mechanical characterization of CNT-metal interfaces. This is of significant interest for the design of future mechanical sensors utilizing the intrinsic piezoresistive effect of CNTs or other future devices incorporating CNT-metal interfaces. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the transport of water molecules at the interface of an epoxy molding compound to a SiO2 (chip surface) is investigated by molecular modelling. Experi-mental results of bulk diffusion of H2O into a DGGOA/DAIIBA epoxy/hardener system at several temperatures are compared to molecular dynamics results at elevated (artificial) temperatures with respect to activation energies. Molecular modelling allows to trace individual molecules over time. The recorded traces are evaluated in a semi-quantitative way with respect to jump-distances and comparisons are made between bulk diffusion, diffusion at an interface and diffusion at open surfaces of the involved materials. Results show reasonably agreeing activation energies in experiment and simulation and an enhanced transport at open surfaces. A significantly enhanced transport at a perfect interface could not be confirmed in this investigation. [Copyright &y& Elsevier]

Abstract: In this work we present a procedure for the construction of 3D networked epoxy moulding compounds and an estimation of basic thermodynamic properties by molecular dynamics simulations. Our investigations present part of general trend to extend failure analysis, reliability assessment and the development of packaging materials from the conventional discrete usage of simulation techniques to a more holistic approach of an interconnected multimethods-procedure, enabling bottom-up simulation of complex microsystems. Within that framework, the task at hand for detailed atomistic molecular modelling is to develop practical methods in order to take materials development as well as materials failure analysis to the nanoscale level. This paper reports a cross linking scheme for the construction of three dimensionally cross linked simulation packages and presents a first property analysis of an industry-oriented moulding compound material. First models and results are presented of model packages of ideal epoxy/silicon-dioxide interfaces. [Copyright &y& Elsevier]

Liquid crystal polymer (LCP) has gained wide interest in the electronics industry largely due to its flexibility, stable insulation and dielectric properties and chip integration capabilities. Recently, LCP has also been investigated as a biocompatible substrate for the fabrication of multielectrode arrays. Realizing a fully implantable LCP-based bioelectronic device, however, still necessitates a low form factor packaging solution to protect the electronics in the body. In this work, we investigate two promising encapsulation coatings based on thin-film technology as the main packaging for LCP-based electronics. Specifically, a HfO 2 -based nanolaminate ceramic (TFE1) deposited via atomic layer deposition (ALD), and a hybrid Parylene C-ALD multilayer stack (TFE2), both with a silicone finish, were investigated and compared to a reference LCP coating. T-peel, water-vapour transmission rate (WVTR) and long-term electrochemical impedance spectrometry (EIS) tests were performed to evaluate adhesion, barrier properties and overall encapsulation performance of the coatings. Both TFE materials showed stable impedance characteristics while submerged in 60 °C saline, with TFE1-silicone lasting more than 16 months under a continuous 14V DC bias (experiment is ongoing). The results presented in this work show that WVTR is not the main factor in determining lifetime, but the adhesion of the coating to the substrate materials plays a key role in maintaining a stable interface and thus longer lifetimes.

We report on the cure characterization, based on inline monitoring of the dielectric parameters, of a commercially available epoxy phenol resin molding compound with a high glass transition temperature (>195 °C), which is suitable for the direct packaging of electronic components. The resin was cured under isothermal temperatures close to general process conditions (165-185 °C). The material conversion was determined by measuring the ion viscosity. The change of the ion viscosity as a function of time and temperature was used to characterize the cross-linking behavior, following two separate approaches (model based and isoconversional). The determined kinetic parameters are in good agreement with those reported in the literature for EMCs and lead to accurate cure predictions under process-near conditions. Furthermore, the kinetic models based on dielectric analysis (DEA) were compared with standard offline differential scanning calorimetry (DSC) models, which were based on dynamic measurements. Many of the determined kinetic parameters had similar values for the different approaches. Major deviations were found for the parameters linked to the end of the reaction where vitrification phenomena occur under process-related conditions. The glass transition temperature of the inline molded parts was determined via thermomechanical analysis (TMA) to confirm the vitrification effect. The similarities and differences between the resulting kinetics models of the two different measurement techniques are presented and it is shown how dielectric analysis can be of high relevance for the characterization of the curing reaction under conditions close to series production.