Search query: rigid flexible CTE

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abstract: Flexible electronics is rapidly finding many main stream applications where low cost, ruggedness, light weight, unconventional form factors and ease of manufacturability are just some of the important advantages over their conventional rigid substrate counterparts. Flexible Electronics: Materials and Applications surveys the materials systems and processes that are used to fabricate devices that can be employed in a wide variety of applications, including flexible flat panel displays, medical image sensors, photovoltaics, and electronic paper. Materials discussed range from polymeric semiconductors to nanotube transparent conductors, highlighting the important characteristics of each system and their target applications. An overview of the performance benchmarks for the different materials is given in order to allow a direct comparison of these different technologies. Furthermore, the devices and processes most suitable for given applications in flexible electronics are identified. Topics covered include: An overview and history of flexible electronics Novel materials for solution processable thin film electronic devices and their properties Low temperature processing of conventional materials and devices on plastic foils Novel techniques, such as printing and roll to roll processing, for large area flexible electronics manufacturing Materials and device physics relevant to flexible electronics Device integration on flexible substrates Mechanical and electronic characteristics for thin film transistors and nano scale transparent conductors on flexible platforms Applications towards flexible displays, sensors, actuators, solar energy, radio frequency identification, and micro electro mechanical systems Written by leading researchers in the field, Flexible Electronics: Materials and Applications serves as a reference for researchers, engineers, and students interested in the characteristics, capabilities, and limitations of these exciting materials and emerging applications.
author_names: William S Wong

Alberto Salleo
title: Flexible Electronics: Materials and Applications
year: 2009

abstract: A new type of flexible microactuator (FMA) has been developed for use in miniature robots. They are constructed using fiber reinforced rubber and are actuated by an electropneumatic or electrohydraulic system. These microactuators have many degrees of freedom (including pitch, yaw, and stretch) making them suitable for robotic mechanisms such as arms, legs, or fingers. Pliant miniature robots can be created by combining FMAs. One example is a robot arm a few millimeters in diameter with seven degrees of freedom. The basic characteristics of the FMAs have been analyzed theoretically and experimentally. It is noted that, since the statistics and dynamics are predicted easily, FMAs can be designed efficiently.<ETX>
author_names: Koichi Suzumori

Shoichi Iikura

H Tanaka
title: Flexible microactuator for miniature robots
venue: [1991] Proceedings. IEEE Micro Electro Mechanical Systems
year: 1991

abstract: Outside of the active device layers, there are a variety of requisite functional layers in flexible organic electronic devices. Whether the application is in displays, lighting, integrated circuits, or photovoltaics, there are materials challenges in implementing flexible and/or organic devices into practical applications. We highlight two topics that are common to most flexible electronic technologies. First, we describe the difficulty in developing suitable permeation barriers on polymer substrates, the approaches being taken to solve this problem, and their current status. Second, we highlight the limited mechanical ruggedness of brittle inorganic films and present approaches for improving overall device flexibility.
author_names: John Lewis
title: Material challenge for flexible organic devices
year: 2006

abstract: In this present work the finite element method has been used for the simulation models in order to develop tools for the early stages of product design. The objective is to develop simulation models for Flexible Printed Circuits Boards (PCBs) in a flex rigid concept in the shape of a wrist device to evaluate its critical stress and strain when this device is submitted to thermal loading considering FR4 and Polyimide substrates as the constitutive materials of the board with BGA attached components. The critical points are the mismatch of the coefficient of thermal expansion of different materials as well as the thermoset viscoelastic nature of the polyimide. In the end of this present study it will be shown that additional research should be done to the final product. In this paper we will show the preliminary results of strain and stress distribution induced by thermo loading using a commercial finite element package.
author_names: Luciano Arruda

Quay Le Chen

Jairo Alonso Quintero Quintero
title: Failure evaluation of flexible rigid PCBs by thermo mechanical simulation
venue: 2009 International Conference on Electronic Packaging Technology High Density Packaging
year: 2009

abstract: A novel cover layer material for flexible printed circuit (FPC) applications was developed in this work. A high molecular weight of polyimide composed of four monomers, pyromellitic dianhydride (PMDA) 3,3',4,4' biphenyltetracarboxylic dianhydride (BPDA) 2,2' bis(trifluoromethyl)benzidine (TFMB) and 2,2 bis(3 amino 4 hydroxyphenyl)hexafluoropropane (BisApAf) was prepared by the one pot polycondensation in N methyl 2 pyrrolidone (NMP) without precipitation and gelation. The polyimide (PI) was highly soluble in various common organic solvents. Interestingly, the PI film formed by simple solution casting of the PI solution had a low CTE value close to that of copper foil, therefore almost no curling of the PI/copper laminate was observed when the PI film was directly formed on a copper foil. The PI film also exhibited other combined properties, including a low CTE, a high T g, high thermal stability, low water absorption, comparatively good transparency, the highest levels of non flammability, good insulation properties and sufficient film flexibility. In addition, fine positive tone patterns could be obtained from DNQ containing PI with a sensitivity of 238 mJ cm 2. The results revealed that the present PI system is a promising candidate as a novel cover layer material.
author_names: Junichi Ishii

Tadashi Akamatsu
title: Organo Soluble Low CTE Polyimides and their Applications to Photosensitive Cover Layer Materials in Flexible Printed Circuit Boards
year: 2009

abstract: Polyimides are attractive mirror candidate materials due to their low mass, solar radiation resistance, and cryogenic flexibility. However, polyimides exhibit high coefficients of thermal expansion (CTE) values (40 70 ppm/K) inducing image distortion from CTE mismatch. Additionally, the temperature of large aperture (10 m) membranes is not uniformly controlled in space, further increasing image distortion from anisotropic deformations. The CTE of the MSRS Novastrat polyimide line was adjusted to exhibit CTEs between 16 ppm/K and 53 ppm/K, including 0 ppm/K, 10 ppm/K, 17 ppm/K, and 25 ppm/K corresponding with CTE matches of graphite/epoxy, carbon steel, copper, and aluminum (respectively) The development of these CTE matched membranes is presented, as well as the effect of the CTE adjustment on the mechanical properties.
author_names: Garrett D Poe

Brian Patrick
title: Zero CTE polyimides for athermal optical membranes
venue: Optical Engineering Applications
year: 2008

abstract: REINFORCEMENT MATERIALS Reinforcement Materials Rigid Glass Glass Composition Glass Fiber Manufacturing From Yarn to Fabric Glass Types and Construction Glass Fabric Weave Surfacing Mat, Paper or Veil Glass Fiber Paper Quartz Properties of Glass Fabrics Aramids Constraining Dielectric Materials (Kevlar(R) RESINS Introduction Polyester Resin Epoxy Polyimide Cyanate Ester and Cyanate Ester Blends (BT Resin) Polyphenylene Oxide (PPO) Epoxy Blends Polytetrafluoroethylene Resin (PTFE) FLEXIBLE FILMS Introduction Types of Flexible Materials Adhesives Cover Coat/Coverlay Bondplies Conductive Materials Copper Clad Laminates COPPER FOILS Introduction Electrodeposited Copper Foil Rolled Copper Foils Grades Nickel Foil LAMINATES, RIGID Introduction NEMA Grades Composite Laminates Rigid Laminates (Glass Reinforced) Laminates, Rigid Glass Reinforced Aramid Laminates Prepreg Additive Laminates HIGH SPEED/HIGH FREQUENCY LAMINATES Introduction High Speed/High Frequency Laminates Thin Laminates Resins High Frequency Laminate Designations Laminate Construction Bonding Dimensional Stability Drilling References METAL CORE AND CONSTRAINING CORE MATERIALS Introduction Copper Invar Copper (CIC) Copper Molybdenum Copper (CMC) Silicon Carbide Reinforced Aluminum (SiC/Al) Coefficient of Thermal Expansion Trade Offs (CTE) APPENDIX INDEX
author_names: Martin W Jawitz

Michael J Jawitz
title: Materials for Rigid and Flexible Printed Wiring Boards (Electrical and Computer Engineering)
year: 2006

abstract: Semi aromatic polyimides (PIs) possessing simultaneously a low dielectric constant (K) and low linear coefficient of thermal expansion (CTE) were molecularly designed. Two PI systems were focused on, i.e. the s BPDA/CHDA polyimide derived from 3,3',4,4' biphenyltetracarboxylic dianhydride with trans 1,4 cyclohexanediamine and CBDA/TFMB derived from 1,2,3,4 cyclobutanetetracarboxylic dianhydride and bis(2,2' trifluoromethyl)benzidine. In the s BPDA/CHDA system, poly(amic) acid (PAA) polymerization using the common procedure was prevented by strong salt formation at the initial stage. However, heating the salt forming reaction mixture at a selected temperature for a short period allowed the system to polymerize and resulted in a high molecular weight PAA (reduced viscosity e red 2 dl g 1) On the other hand, in the CBDA/TFMB system, a high molecular weight PAA (e red 3 dl g 1) was readily obtained by choosing the solid content without any salt formation. The chosen PIs almost achieved the current goal; CTE 20 ppm K 1, K 3.0, and T g 300degC concurrently with adequate film flexibility. In particular, CBDA/TFMB accomplished a very low K ~2.6) Although these PIs have a much lower thermo oxidative stability than wholly aromatic PIs, the results suggested that there is no serious problem for the short term thermal stability required for soldering processes.
author_names: Masatoshi Hasegawa
title: Semi Aromatic Polyimides with Low Dielectric Constant and Low CTE
year: 2001

abstract: Purpose This paper seeks to give an overview on the benefits and challenges of moulded interconnect devices technology and the use of flexible printed circuits (FPC) in electronics production.Design/methodology/approach Each process step was adapted to the boundary conditions of manufacturing three dimensional substrates and FPC. The substrate materials were examined under the specific requirements of electronics production with a special focus on the thermal stability of the materials and the adhesiveness of the metallization.Findings The use of thermoplastics as substrate materials for electronic devices offers high potential but new challenges, e.g. the higher coefficient of thermal expansion of thermoplastics, have to be taken into consideration as well. In most cases, standard machines for surface mount technology can be used with few modifications. Research has shown that even components with very fine pitches can be used successfully on alternative substrate materials.Research limitations/imp.
author_names: Florian Schuessler

Klaus Feldmann

Thomas Bigl
title: Selection and qualification of polymers for rigid and flexible interconnect applications
year: 2007

abstract: A new technique for modeling contact/impact of flexible manipulators with a fixed rigid surface is presented. The manipulator is discretized using the finite element method. The technique is based on the use of the conservation of energy and momentum principles as a local velocity constraint on the nodes in contact with the rigid surface to obtain the post impact velocities of those nodes. Two friction parameters one for the tangential momentum and one for energy can be used. A slight variation of the technique is to use the momentum conservation principle along with Newton's collision rule as the velocity constraint also with two friction parameters one for the tangential momentum and the coefficient of restitution. Momentum conservation/Newton collision rule constraint and momentum/energy conservation constraint are equivalent if friction effects are neglected. Numerical examples are solved to show the accuracy and versatility of the new technique.
author_names: Tamer Wasfy
title: Modeling contact/impact of flexible manipulators with a fixed rigid surface
venue: Proceedings of 1995 IEEE International Conference on Robotics and Automation
year: 1995