Study On The Preparation And Properties Of Modified Epoxy Resin Based Filled Thermal Conductive Adhesive

With the rapid development of science and technology,electronic products more and more widely used and the power is increasing,so the heat dissipation of electronic equipment still has many problems,the matrix of many electronic packaging materials is resin adhesive,and its toughness is poor and fragile,which seriously affects the performance and effective use time of products.Therefore,the electronic packaging material should have a certain heat dissipation function,while ensuring the stability and toughness of the material to prolong the service life and performance of the product.Based on these two points,the polyurethane modified epoxy resin with good toughness has been prepared.Based on this,a thermal conductive adhesive with good thermal conductivity has been synthesized.The influence of different factors on the properties of modified adhesive and thermal conductive adhesive has been analyzed.1)Toluene diisocyanate?TDI?and polypropyiene glycol?PPG?are used as raw materials for polyurethane?PU?prepolymer.The effects of raw material ratio,reaction temperature and reaction time on the synthesis of PU prepolymer were investigated.Through the content of-NCO,the optimum synthesis condition of PU prepolymer was 1.5h at 75?C.The effect of moisture on the synthesis of PU prepolymer is discussed.It is concluded that the presence of water can cause the side reaction of isocyanate group and affect the stability and quality of the prepolymer.Finally,it is concluded that the PU prepolymer is the end-NCO based PU prepolymer by FI-IR analysis.2)The polyurethane modified epoxy resin was prepared by graft copolymerization of polyurethane prepolymer with epoxy resin.The influence of the structure and amount of polyurethane prepolymer on the mechanical properties of the modified epoxy resin was studied.The results showed that the toughening effect of polyurethane on epoxy resin was the best when the molecular weight of PPG was 1000 and TDI:PPG=2:1.Besides,when the amount of polyurethane prepolymer is 10%,the strain and the tensile strength of the modified epoxy resin were respectively 84.7%and 27.1 MPa,30.47 times and 3.04 times of unmodified epoxy resin.The toughening mechanism of polyurethane was studied by scanning electron microscope.It was found that the epoxy resin was brittle fracture before modification,and the crazing of polyurethane modified epoxy resin increased obviously,which was ductile fracture.3)The modified epoxy resin was used as the matrix,and Al₂O₃ and graphite powder were added to prepare the heat conductive adhesive for the mixed packing.The effects of size and dosage of Al₂O₃ and graphite,surface modification of Al₂O₃ and the amount of diluent on viscosity,thermal conductivity and mechanical properties of thermal conductive adhesive were investigated.The results show that the thermal conductivity reaches 1.53 W/?m K?when the filling amount of 10?m KH-560 modified Al₂O₃ is 60%and the filling amount of 20?m is 5%,which is about 7.7 times that of the matrix epoxy resin.The mechanical properties and viscosity of the heat conductive adhesive are determined to determine the epoxy resin:diluent=10:1.At this point,the tensile strength of the thermal conductive adhesive is 26.3 MPa,and the mechanical properties are excellent.