Study On Novel Modified Graphite/Epoxy Resin Conductive Adhesives

With the rapid development of the science and technology nowadays,the electronic products tend to be more miniaturized,more portable and more integrated.Traditional technique of welding with tin and lead can no longer satisfy modern integrated circuit which requires a high I/O number.Meanwhile,as the global electronics industry have to be completely lead-free,it is very important to explore a novel conductive adhesive which is lowenergy consuming,good to the environment,advanced in electrical excellent performance and bonding intensity.In this paper,conductive adhesive(CA) contains the conductive filler,matrix materials, curing agent,as well as other additives.Normal flake graphite can be turned into activated flake graphite(AFG) through chemical methods.The blend of nano-Aluminium/AFG(nano-AI /AFG) can be made through physical methods,by mixing nano-Aluminum powder and AFG together evenly.It is possible to get nano-graphite(nano-G) by expanding the normal expandable graphite in a high-temperature,then breaking the resulting product into pieces through ultrasonic system.Reduced nano-graphite(R-nano-G) can be made using the nano-G and reducing agent:hydrazine hydrate.Nano-G can be modified and transferred silver plating nano-G(Ag-nano-G) by plating the silver on the surface of nano-G through electroless silver plating method.We use the above five modified graphite respectively as the conductive filler, epoxy resin(E-51)as the matrix materials,triethanolamine as a curing agent and the combination of diluting agent propylene oxide tert-butyl ether as other additives.All these components are necessary for the novel modified graphite/epoxy CA series:AFG/E-51 CA, nano-Al/AFG/E-51 CA,nano-G/E-51 CA,R-nano-G/E-51 CA,Ag - nano-G/E-51 CA.It has been discovered by mechanical property test and the fourier transform infrared spectrometer(FT-IR) that the most appropriate condition for the conductive adhesive curing is 120℃,150min.In order to explore the hydrazine hydrate reduction method and the technology of chemical silvering,we use the X-ray energy dispersion spectrometer(X-EDS) to analysis the reduction of oxygen element on the surface of the nano-G and the content of silver on the surface of the Ag-nano-G.By scanning electron microscope(SEM) to observe the morphology of modified graphite,it is possible to explore the relationship between the morphological character of conductive filler and the main applying performance of CA.Using the low potential D.C potentiometer set-instrument(D.C-LPPS) to estimate the volume resistivity(ρ_v) of CA,and we can get the electrical property parameters-the percolation concentration(Φ_c) and the applied resistivity(ρ_a).We use the universal testing device(UTD) to test CA's tensileshear strength(T) and subsequently receive the mechanic property parameter-the applied adhesive strength(T_a);By drawing the graph of CA's TG and DTG curves with thermogravimetry analysis(TGA),we can get the thermal property parameter-the initial temperature of heat degradation(t₀) and the maximum weight loss rate(D_m).The principal applied performance parameters(Φ_c/ρ_a/ T_a/ t₀/ D_m) of novel modified graphite/epoxy CA series are as follows——AFG/E-51 CA:20wt%/0.0569Ω·cm/ 6.2MPa/ 349.05℃/-8.80%·min^-1;nano-Al/AFG/E-51 CA:20wt%/0.4883Ω·cm/ 11.1MPa/337.21℃/-4.92%·min^-1;nano-G/E-51 CA:17wt%/ 0.3439Ω·cm/ 12.6MPa/ 342.58℃/ -7.19%·min^-1;Rnano -G/E-51 CA:17wt%/0.0968Ω·cm/ 12.3MPa/344.94℃/-6.22%·min^-1;Ag-nano-G/E-51 CA:17wt%/1.553×10^-3Ω·cm/ 13.2MPa/346.04℃/-5.69%·min^-1.All these are able to meet the packaging requirements of the mid-low-end electronic products in various fields.