Electrically Conductive Adhesives with Low Ag Content Prepared by Ag Self-Activated Plating and PEDOT:PSS

Abstract

Silver-plated graphite powder, poly (3,4-ethylenedioxythiolphene):poly(styrenesulfonate) (PEDOT:PSS), and organic additives were employed to reduce the electrical resistivities of epoxy-based adhesives. A novel silver self-activated electroless deposition using conductive graphite particles as filler in electrically conductive adhesives (ECAs) was investigated to develop high-performance ECAs with low silver content. Adding silver-plated graphite powders to the conductive adhesives reduced their electrical resistivities by at least two orders of magnitude compared with those filled with graphite powders only. The silver content of the adhesive with PEDOT:PSS decreased to 24.7 wt%, and its resistivity was 1.2 × 10 −3 cm. The best electrical resistivity of the epoxy-based conductive adhesives with 70 wt% silver-plated graphite powders was 4.36 × 10 −4 cm. The weight percentage of silver in this epoxy-based adhesive decreased to 43.3 wt%, which is much lower than that of conventional silver conductive adhesives. Polymer-based conductive adhesives have been utilized widely in many applications, for example, electronic interconnects, lightemitting diode and photovoltaic technologies.1 Electrically conductive adhesives (ECAs) have acquired prominence as potential substitutes for solder interconnects. They not only provide a lead-free replacement for solder, but these highly conductive materials also offer feasible alternatives to problems arising from insufficient solder. ECAs are chiefly composed of organic/polymeric binder matrices and conductive fillers. Intrinsically conductive polymers can conduct electric current without requiring addition of conductive media, and extrinsically conductive polymers require the addition of conductive media in order to be more electrically conductive. Extrinsically conductive polymers are divided into isotropic conductive adhesives and anisotropic conductive adhesives according to filler concentration. 2The electrical resistivities of extrinsically conductive polymers are influenced by the amount of conductive fillers, degree of resin curing and cross-link density, diameter and shape of conductive fillers, degree of dispersion, and so forth.3-8 Poly(p-phenylene), polyaniline, polypyrrole, polythiophene, and polyacetylene are conjugated conductive polymers. Their electrical conductivities can be increased dramatically by dopants. [9][10][11][12][13][14][15] The conducting polymer polypoly(3,4-ethylenedioxythiolphene):poly(styrenesulfonate) (PEDOT:PSS) is usually synthesized using an electrochemical method or by chemical synthesis. Particularly promising results have been obtained with electrochemically synthesized poly(3,4-ethylenedioxythiophene) (PE-DOT) doped with PF 6 or with other small-molecule dopants; the room-temperature conductivity of PEDOT-PF 6 films could reach 200-300 S cm −1 . 16Conductive fillers confer excellent electrical properties to ECAs, and polymeric matrixes impart their physical and mechanical properties. Therefore, selection of suitable materials and prepara...

Selective Patterning of Conductive Silver on Polyimide Film by Localized Microplasma Reduction and Electroless Deposition

“…It can be seen that the diffraction peaks, corresponding to [111], [200] and [220], are in accordance with the JCPDS data of crystal planes of face centered cubic silver, indicating that the silver is well crystallized in the metallic state with high quality. [33][34][35] Moreover, more detailed information about the chemical compositions and states of microplasma reduced Ag(0) nanoparticles layer and electroless metallized silver film is obtained using XPS (Fig. 3d).…”

Synthesis of Highly Conductive, Uniformly Silver-Coated Carbon Nanofibers by Electroless Deposition

“…Electroless deposition was successfully used to metallize complicated microstructures , and to fabricate surface plasmon resonance sensors and surface-enhanced Raman scattering substrates. , Deposition on carbonaceous substrates has been attempted with varying success. The conductivity of graphite-filled ICAs was shown to increase by up to 2 orders of magnitude with electroless silver deposition , and a uniform coating was obtained on carbon spheres, , but the deposition on nanosized particles proved to be more challenging. The process applied to carbon nanotubes resulted in mere decoration, , a discontinuous coating − or loss of aspect ratio. , Arai et al did show convincingly that pure nickel and Ni–B alloy electroless deposition on vapor-grown nanofibers could yield an excellent coating uniformity. , The same group attempted silver electroless deposition with silver iodide and dimethylaminoborane as a reducing agent.…”

“…27,28 Deposition on carbonaceous substrates has been attempted with varying success. The conductivity of graphitefilled ICAs was shown to increase by up to 2 orders of magnitude with electroless silver deposition 29,30 and a uniform coating was obtained on carbon spheres, 31,32 but the deposition on nanosized particles proved to be more challenging. The process applied to carbon nanotubes resulted in mere decoration, 33,34 a discontinuous coating 35−38 or loss of aspect ratio.…”

Effect of Solution Aging on Temperature Sensitivity of CNT/PEDOT:PSS

“…Numerous studies have investigated PEDOT:PSS for blending or modification with various materials. [27][28][29][30][31][32][33] Tsai et al 34 added sodium hydroxide (NaOH) for controlling pH values to dedope the pristine PEDOT:PSS. By changing the pH values, the Seebeck coefficient and conductivity of PEDOT:PSS can be greatly improved by the dedoping process.…”