-The objective of this paper is to show how stretchable conductive composites can be utilized for the fabrication of ultra-low cost stretchable RF devices. We show a method to produce biocompatible highly conductive stretchable silicone composites via an in-situ nanoparticle formation and sintering process. Furthermore, we develop a simple, low cost, processing technique to fabricate stretchable RF transmission lines. These RF transmission lines are highly flexible, stretchable and robust. The S-parameter measurements show stable performance during mechanical deformation up to 6 GHz. Future development of this technology will enable ultra low cost consumer RF devices serving as a platform for future stretchable electronic devices.
Future electronics will undoubtedly require natural integration at the system, device and package level in the form of a functional, flexible package. Functional, flexible electronics expand the functionality of devices allowing morphological-electronic response for ergonomic and natural interfaces between the device and its surroundings. Recent technological successes have been able to fabricate functional, flexible electronics, however have all failed to develop a package capable of meeting the stringent cost, reliability and performance required of consumer electronics.We demonstrate the application of electrically conductive adhesive technology to produce low cost, flexible electronics without metallization. We have shown the capability of fabrication of highly conductive Poly(dimethlysiloxane) (PDMS) (ρ~7x10 -4 Ω•cm) by incorporation of 80 wt% bimodal distribution of micron sized silver flakes. PDMS is both the ideal substrate and composite matrix material due to its unique properties; PDMS is optically transparent, viscoelastic, chemically and thermally stable, highly flexible, hydrophobic and can easily be molded with high resolution and aspect ratio. These unique properties of PDMS allow for high resolution molds to be prepared from photolithographically defined substrates. Screen printing of electrically conductive PDMS into these molds with microsized features creates a low cost, flexible electronic package. We have coined this package PDMS-in-PDMS.We show that PDMS ECA can be prepared by curing a novel formulation of PDMS at curing temperatures of 150 °C for 15 minutes. Upon curing, the ECA undergoes a transition from insulating to conductive. TMA results have shown that this transition is due to ECA shrinkage >20%. Furthermore, we show simultaneous conductivity and tensile strain measurements to show the electrical properties of PDMS ECA are unaffected by tensile strains of >40%. We show the feasibility of this technology to create low cost, flexible devices without the need for metallization.
IntroductionThe future of electronics will not be constrained to the simplicity of planarity. The electronics of the future will be designed on flexible substrates enabling functionality impossible within the confines of a ridged planar surface. This transformation from the simplicity of planarity to complex curved and flexible surfaces will require eloquent materials and design of component, integration and interconnection at the system, device and package level. Current electronic design and interconnection technologies have been unable to meet the stringent cost, reliability and performance required for application in a flexible, functional package. New
Anisotropically conductive adhesives (ACA) are a promising alternative to solder interconnects for high performance electronic devices due to their increased I/O capabilities and reduced form factor. Previous studies have shown that modification of Au coated Ni/Cu bumps with conjugated self-assembly monolayers (SAMs) increases conductivity, current carrying capacity and reliability of ACA interconnects [1][2][3]. In this study, we kinetically control the assembly of p-Terphenyl-4,4"-dithiol (TPD) monolayers on Au bumps. Using a custom designed test vehicle we show how TPD SAMs can either increase or decrease the single bump resistance depending on the kinetics of the monolayer formation and its resulting structure. Future studies focusing on controlling monolayer assembly will determine the efficacy of conjugated SAMs at enhancing the conductivity and current carrying capacity of ACA interconnects.
A study of curved beams having eccentrically positioned circular-arc boundaries is reported upon in this paper. The study involves some mathematical considerations as well as a photoelastic investigation of the stresses in such beams. The results comprise a method of design using the ordinary straight-beam theory but involving stress factors. Both curves and expressions that can be used to obtain the required factors are presented.
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