Characterization of Thermal Interface Materials to Support Thermal Simulation

In this paper new characterization equipment for thermal interface materials is presented. Thermal management of electronic products relies on the effec-tive dissipation of heat. This can be achieved by the optimization of the system design with the help of simulation methods. The precision of these models relies also on the used material data. For the determi-nation of this data an experimental set-up for a static measurement is presented, which evaluates thermal conductivity and interface resistance of thermal inter-face materials (e.g. adhesive, solder, pads, or pastes). A qualitative structure-property correlation is pro-posed taking into account particle size, filler content and void formation at the interface based on high resolution FIB imaging. The paper gives an overview over the set-up and the measurement technique and discusses experimental and simulation results.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Combinatorial effects on gene expression at the Lbx1/Fgf8 locus resolve Split-Hand/Foot Malformation type 3

Split-Hand/Foot Malformation type 3 (SHFM3) is a congenital limb malformation associated with tandem duplications at the LBX1/FGF8 locus. Yet, the disease patho-mechanism remains unsolved. Here we investigated the functional consequences of SHFM3-associated rearrangements on chromatin conformation and gene expression in vivo in transgenic mice. We show that the Lbx1/Fgf8 locus consists of two separate, but interacting, regulatory domains. Re-engineering of a SHFM3-associated duplication and a newly reported inversion in mice resulted in restructuring of the chromatin architecture. This led to an ectopic activation of the Lbx1 and Btrc genes in the apical ectodermal ridge (AER) in an Fgf8-like pattern. Artificial repositioning of the AER-specific enhancers of Fgf8 was sufficient to induce misexpression of Lbx1 and Btrc. We provide evidence that the SHFM3 phenotype is the result of a combinatorial effect on gene misexpression and dosage in the developing limb. Our results reveal new insights into the molecular mechanism underlying SHFM3 and provide novel conceptual framework for how genomic rearrangements can cause gene misexpression and disease

Genomic Targets of Brachyury (T) in Differentiating Mouse Embryonic Stem Cells

The T-box transcription factor Brachyury (T) is essential for formation of the posterior mesoderm and the notochord in vertebrate embryos. Work in the frog and the zebrafish has identified some direct genomic targets of Brachyury, but little is known about Brachyury targets in the mouse.Here we use chromatin immunoprecipitation and mouse promoter microarrays to identify targets of Brachyury in embryoid bodies formed from differentiating mouse ES cells. The targets we identify are enriched for sequence-specific DNA binding proteins and include components of signal transduction pathways that direct cell fate in the primitive streak and tailbud of the early embryo. Expression of some of these targets, such as Axin2, Fgf8 and Wnt3a, is down regulated in Brachyury mutant embryos and we demonstrate that they are also Brachyury targets in the human. Surprisingly, we do not observe enrichment of the canonical T-domain DNA binding sequence 5'-TCACACCT-3' in the vicinity of most Brachyury target genes. Rather, we have identified an (AC)(n) repeat sequence, which is conserved in the rat but not in human, zebrafish or Xenopus. We do not understand the significance of this sequence, but speculate that it enhances transcription factor binding in the regulatory regions of Brachyury target genes in rodents.Our work identifies the genomic targets of a key regulator of mesoderm formation in the early mouse embryo, thereby providing insights into the Brachyury-driven genetic regulatory network and allowing us to compare the function of Brachyury in different species

Investigation of thin films by nanoindentation with doe and numerical methods

Nanoindentation is one of the most known method for investigating the properties of thin films. The materials can be assessed by means of elastic mechanical properties (hardness and Young's modulus). However, the author's research works show that it is possible to obtain the elastic as well as the plastic material behavior of the investigated thin layer. It can be done by using the nanoindentation experiment and the numerical simulations. This paper focuses then on investigation of thin metal layers by nanoindentation with a support of numerical methods, such as finite element method and numerical optimization processes. Additionally, the 3-level, full factorial design of experiment (DOE) process was applied. In order to carry out such experiment 27 samples were prepared and taken into account: 3 different materials with 3 different thickness's values sputtered on 3 different substrates. The results were then processed by the numerical methods in order to achieve more i nformation about the materials - mainly the plastic behaviour

Detection of degradation in die-attach materials by in-situ monitoring of thermal properties

This paper presents a method for indicating cracks in die attach materials, which is non-destructive and enables in-situ monitoring of degradation. It is based on the principle that voids or cracks cause the change of thermal behaviour in electronic packages. Therefore the thermal behaviour is due to alter over lifetime. Parametric simulation models have been developed, which enable the prediction of influence of delamination areas on transient thermal properties for different die attach materials in example COB packages. The results show an increase of delamination area, which causes a significant increase of transient thermal resistance. The computational results are validated with experimental measurements, which show a practical feasibility of the proposed method, which can accelerate and simplify lifetime testing of die attach interconnects

Comparative characterization of chip to epoxy interfaces by molecular modeling and contact angle determination

An investigation of interfacial interaction has been performed between three epoxy molding compound materials and a native silicon dioxide layer (SiO 2) usually found at chip surfaces. The epoxy materials were an industry oriented epoxy molding compound Epoxy Phenol Novolac (EPN), its filled variety EPN F (with silica particles) and a model aromatic epoxy 1 (2 1 2). All systems are described in full in [1] and [2]. The free surfaces of the solid materials were experimentally analyzed by contact angle measurements of three different liquids (water, methylene-iodide (MI) and glycerol). Results are compared to interfacial energies obtained by analysis of the interfaces in bimaterial molecular models, yielding reasonable agreement. A qualitative prediction regarding the influence of water on the interfacial strength between chip and molding compound is attempted

Application of multi-criteria optimization algorithms to numerical material extraction of thin layers through nanoindentaion technique

Current developments and trends in microelectronics are focused on thin layers and novel materials. This leads to application of different test and measurement methods, which are capable to measure basic mechanical properties of such materials on micro-scale and nano-scale. The presented paper focuses on application of the nanoindentation technique in order to extract the basic elastic and elasto-plastic mechanical properties through numerical approaches. In order to extract the elasto-plastic material data of the investigated thin layers the numerical process was designed. First of all, the nanoindentation process was elaborated in FEM Abaqus software. Then, the results were compared to the measurements and processed by the numerical optimization algorithms