Study On The Preparation Of Several Kinds Of Conductive Fillers And Effect On The Conductive Properties Of Condutive Adhesive

Silver conductive filler and copper conductive filler is commonly used in conductive adhesives, but the price of silver conductive filler is higher and electromigration phenomenon occurs easily in moist environment, which reduce the reliability of the conductive adhesive. Copper conductive adhesive is prone to oxidation, and electrical conductivity greatly reduced after oxidation. These shortcomings and defects affect the practical application of conductive adhesive. Ni based conductive fillers were prepared in conductive adhesives. Nickel conductive filler of spherical nickel powder, nickel nanowires, nickel coated carbon fibers and nickel coated expanded graphite was introduced in this paper. The conductive fillers were added to the resin matrix and different kinds of fillers and effects of the content on the conductivity of conductive adhesive were researched. Finally the conductive adhesive with better optimized proportion and conductive properties were preparation. Specific content is as follows:Ultrafine nickel particles were prepared by liquid phase reduction method, and we studied the effects of different kinds and amount of reducing agent, different kinds of solvent, concentration of reactants on nickel particle size, morphology, crystal structure and magnetic properties. Studies show that when sodium borohydride as reducing agent, water as solvent, the product is amorphous. When the hydrazine hydrate used as reducing agent, water as the solvent, reaction temperature is higher and the product Morphology is ball chain. With the increase of nickel salt concentration the particle size gradually improve and the crystal structure is face-centered cubic. When hydrazine hydrate used as reducing agent and ethylene glycol as solvent, the product is ball chain particles with smooth surface and uniform particle size. When the composite with sodium borohydride and hydrazine hydrate used as reductant, the particle size in water solvent is greater than the ethylene glycol. Product made in the water system is the mixture of nickel and nickel hydroxide and product made in ethylene glycol is product of face-centered cubic metal nickel. In ethylene glycol system, with sodium borohydride and mole ratio of nickel sulfate, nickel particle size increases gradually. With the increase of nickel salt concentration, the size of nickel particle increases gradually. Nickel particles in different concentration of reactants are face-centered cubic crystal structure metal nickel.The nanowires were prepared by liquid phase reduction method and under a uniform magnetic field of0.3T, with ethylene glycol as solvent. In a uniform magnetic field, nickel particles were reduced and growth along magnetic field lines and the orientation shape anisotropy is more apparent. When hydrazine hydrate used as reducing agent and nickel salt concentration is0.05mol/L, the diameter of nickel nanowire is about100nm, coercive force is238Oe; the saturation magnetization is42emu g-1. When the composite with sodium borohydride and hydrazine hydrate used as reductant, and Nickel salt concentration is0.5mol/L, and the molar ratio of nickel sulfate and sodium borohydride change from1:10to1:1000, the diameter of the nanowires is about100nm and coercive force is185Oe, the saturation magnetization is38emu g-1.By contrasting the sensitization and activation technology and chemical plating process without palladium, the carbon fiber plated nickel plating mechanism was researched. Two methods both can succeed in the carbon fiber surface plating. Chemical plating technology can be used without palladium and sensitization activation pretreatment process in carbon fiber and expanded graphite surface chemical nickel plating, and can obtain good quality of nickel plating. Optimum process conditions of electroless plating:NiSO430g/L，Na3C6H5O712g/L，NH4Cl30g/L，NaH2PO230g/L，thiourea trace, pH for9~10, temperature of60℃.In the same amount of resin matrix, respectively, different amount of nickel particles, nickel nanowires and nickel plating expanded graphite were added. When the same amount of conducting fillers were added, the resistivity change from high to low in turn for nickel nanowires, nickel, nickel plating, expanded graphite particles. When the amount of conductive fillers added is23wt%, the resistivity are10.56Ω·cm,3.93Ω·cm,0.67Ω·cm, respectively. In42g conductive adhesive with nickel particles quantity of16wt%and with the resistivity of30.53Ω·cm, adding0.3g nickel plating carbon fiber can make the resistivity dropped to1.21Ω cm and adding3g nickel coated expanded graphite can make the resistivity dropped to1.23Ω·cm. In42g conductive adhesive with nickel nanowires quantity of16wt%, adding3g nickel coated expanded graphite can make the resistivity dropped from66.88Ω·cm to2.15Ω·cm.