BCB Based Packaging for Low Actuation Voltage RF MEMS Devices

This paper outlines the issues related to RF MEMS packaging and low actuation voltage. An original approach is presented concerning the modeling of capacitive contacts using multiphysics simulation and advanced characterization. A similar approach is used concerning packaging development where multi-physics simulations are used to optimize the process. A devoted package architecture is proposed featuring very low loss at microwave range

Oncostatin m impairs brown adipose tissue thermogenic function and the browning of subcutaneous white adipose tissue

© 2016 The Obesity Society Objective: Since oncostatin m (OSM) is elevated in adipose tissue in conditions of obesity and type 2 diabetes in mice and humans, the aim of this study was to determine whether this cytokine plays a crucial role in the impairment of brown adipose tissue (BAT) activity and browning capacity that has been observed in people with obesity. Methods: C57BL/6J mice rendered obese by high-fat diet, their lean controls, and C57BL/6J mice fed a standard diet and implanted subcutaneously with a mini pump through a surgical procedure to deliver OSM or placebo were used. Preadipocytes or fully differentiated brown adipocytes were treated with OSM or vehicle with or without norepinephrine before harvesting. RNA was extracted and processed for qPCR analysis. Media from mature adipocytes was also collected to measure glycerol levels. Results: Studies demonstrated that OSM gene expression was increased in BAT of mice fed a high-fat diet. In addition, exogenous OSM impaired BAT activity and the browning capacity of white adipose tissue in vitro and in vivo. Conclusions: Overall, the results reveal a negative role for OSM on BAT and on the browning of white adipose tissue. Therefore, further studies are necessary to demonstrate whether OSM inhibition is a potential treatment for metabolic disorders

Vampires in the village Žrnovo on the island of Korčula: following an archival document from the 18th century

Središnja tema rada usmjerena je na raščlambu spisa pohranjenog u Državnom arhivu u Mlecima (fond: Capi del Consiglio de’ Dieci: Lettere di Rettori e di altre cariche) koji se odnosi na događaj iz 1748. godine u korčulanskom selu Žrnovo, kada su mještani – vjerujući da su se pojavili vampiri – oskvrnuli nekoliko mjesnih grobova. U radu se podrobno iznose osnovni podaci iz spisa te rečeni događaj analizira u širem društvenom kontekstu i prate se lokalna vjerovanja.The main interest of this essay is the analysis of the document from the State Archive in Venice (file: Capi del Consiglio de’ Dieci: Lettere di Rettori e di altre cariche) which is connected with the episode from 1748 when the inhabitants of the village Žrnove on the island of Korčula in Croatia opened tombs on the local cemetery in the fear of the vampires treating. This essay try to show some social circumstances connected with this event as well as a local vernacular tradition concerning superstitions

Etude théorique et expérimentale des techniques d'assemblage et de mise en boitier pour l'intégration de microsystèmes radio-fréquences

Radio-Frequency Micro-Electro-Mechanical Systems (RF MEMS) are highly miniaturized devices intended to switch, modulate, filter or tune electrical signals from DC to microwave frequencies. RF Mems switches are characterized by their high isolation, low insertion loss, large bandwith and by their unparalleled signal linearity. Despite these benefits, RF Mems switches are not yet seen in commercial products because of reliability issues, limits in signal power handling and question in packaging. In this context, we put in evidence, a near hermetic packaging based on a micro-machined cap in Foturan sealed onto a photopatternable polymer Benzo-Cyclo-Butene (BCB) as a solution adapted to micro-switches RF. To answer the stakes in conception, we identified needs in multiphysics modelling able to generate behavioural macro-models. Finally, a demonstrator was characterised in terms of return and insertion losses measurements, which assures insignificant impact of the package on the RF losses.La mise sur le marché de Micro Systèmes Electro Mécaniques Radio-Fréquences (MEMS RF) est freinée par leurs manques de maturités au niveau du flot de conception, de la mise en boîtier (packaging) et de la fiabilité. Dans ce contexte, nous mettons en évidence, une solution d'assemblage par report d'un capot avec un scellement en polymère adaptée aux micro-commutateurs RF. Afin de répondre aux enjeux de conception, nous avons identifié des besoins en terme de modélisation éléments finis (EF) multi-physique, permettant de générer des macro-modèles comportementaux. Ainsi, nous discutons des possibilités offertes par deux logiciels EF réellement multi-physique : ANSYS et COMSOL. Finalement, nous proposons une solution (boîtier micro-usiné en Foturan et scellement en polymère BCB) compatible avec les spécifications du cahier des charges. La fabrication et la caractérisation électrique d'un démonstrateur ont permis de valider cette technique simple de packaging quasi-hermétique

Modélisation du contact résistif de micro-commutateurs MEMS RF

Les principales limitations des micro-commutateurs MEMS RF à contact ohmique sont liées à la qualité, à la répétitivité du contact et à sa fiabilité. Afin de proposer de nouvelles générations de structures MEMS RF, il est important d'acquérir de meilleurs connaissances de la physique du contact pour pouvoir choisir des matériaux, une topologie et une architecture les mieux appropriés. Dans ce contexte l'outil de simulation en éléments finis est utilisé pour mesurer l'impact des matériaux constituant le contact et de chaque paramètre de design sur les caractéristiques mécaniques et électriques du contact. Dans ce papier nous présentons notamment une nouvelle approche qui combine la caractérisation de surface avec l'analyse en éléments finis pour simuler le contact entre des profils réels de surface. Cette méthode d'ingénierie inverse nous permet de mesurer l'impact de la rugosité sur la résistance de contact du micro-commutateur

A macro model based on finite element method to investigate temperature and residual stress effects on RF MEMS switch actuation

International audienceTill nowadays, MEMS design suffers from the lake of efficient and easy-to-use simulation tools covering the complete MEMS design procedure, from individual MEMS component design to complete system simulation. Finite element analysis (FEA) methods offer high efficiency and are widely used to model and simulate the behaviour of MEMS components. However, as MEMS are subject to multiple coupled physical phenomena at process level and play, such as initial stress, mechanical contact, temperature, thermoelastic, electromagnetic effects, thus finite element models may involve large numbers of degrees of freedom so that full simulation can be prohibitively time consuming. As a consequence, designers must simplify models or specify interesting results in order to obtain accurate but fast solution. Some multiphysics' softwares, such as COMSOL [3], allow Reduced Order Modeling (ROM) or macro models which considers the global behaviour of the device. Thus designers can create automatically, for example, their own Simulink (Matlab ©) library from a multiphysics finite element modelization, in order to develop a behavioural model of the whole component. This work deals with a Simulink macro model, generated by a three-dimensional multiphysics finite element analysis (FEA) using COMSOL, aiming to investigate the pull-in and pull-out voltage of microswitches

A macro model based on finite element method to investigate temperature and residual stress effects on RF MEMS switch actuation

International audienceTill nowadays, MEMS design suffers from the lake of efficient and easy-to-use simulation tools covering the complete MEMS design procedure, from individual MEMS component design to complete system simulation. Finite element analysis (FEA) methods offer high efficiency and are widely used to model and simulate the behaviour of MEMS components. However, as MEMS are subject to multiple coupled physical phenomena at process level and play, such as initial stress, mechanical contact, temperature, thermoelastic, electromagnetic effects, thus finite element models may involve large numbers of degrees of freedom so that full simulation can be prohibitively time consuming. As a consequence, designers must simplify models or specify interesting results in order to obtain accurate but fast solution. Some multiphysics' softwares, such as COMSOL [3], allow Reduced Order Modeling (ROM) or macro models which considers the global behaviour of the device. Thus designers can create automatically, for example, their own Simulink (Matlab ©) library from a multiphysics finite element modelization, in order to develop a behavioural model of the whole component. This work deals with a Simulink macro model, generated by a three-dimensional multiphysics finite element analysis (FEA) using COMSOL, aiming to investigate the pull-in and pull-out voltage of microswitches

Effect of Contact Force Between Rough Surfaces on Real Contact Area and Electrical Contact Resistance

International audienceUntil nowadays, surface roughness effects were ignored in the analysis, due to the difficulty to generate a rough surface model and also to simplify the model in order to reduce calculation time. However, many engineering fields, such as MEMS, seek to improve the behaviour of the system at the surface level or the interface between surfaces. Thus, with the advance of numerical capabilities, the topography of the surface can be included in finite element simulations. This paper presents two methods for generating rough surfaces, one using the real shape with an original reverse engineering method and the other one by using a parametric design language to generate a normally distributed rough surface. As an application to demonstrate the power of these methods, we choose to predict by simulation the electrical contact resistance and the real contact area between rough surfaces as a function of the contact force. This application is a major concern in RF MEMS ohmic Switches and shows an original approach to extract a guideline in choosing a design, materials and process flow to minimize the contact resistance. The agreement between the numerical model and an analytical model is very good and validates this novel numeric approach

Impact of The Surface Roughness Description on the electrical contact resistance of ohmic switches under low actuation forces

International audienceAt the present time, the insertion of radio frequency microelectromechanical switches into real architecture requires reduced actuation voltages, reduced dimensions, and better control of the electrical and electromechanical behavior that gives more importance to surface effects, their understanding, and modeling. The use of such devices requires the development of methods for estimating the contact performances as a function of surface roughness, contact materials, and contact topologies. With increase in computation capabilities, the rough surface topography can be implemented in the finite element model but implies long calculation times or even calculation overloading if a high definition of the roughness is desired. To reduce these limitations, assumptions on the microgeometry are required. This paper treats, by use of finite element modeling, the influence of the definition of roughness of contacting switch members on the electrical contact resistance of resistive switches, and investigates the error introduced by using a minimum defined atomic force microscope sampling interval of 10 nm. The present numerical analysis is implemented for switch test structures