| With the development of miniaturization and portability,conductive adhesive has been widely used in microelectronics packaging and assembly industry.The traditional Pb/Sn materials often result in joint destruction,weak parts or welding problems due to the low resolution,serious pollution and high temperature.The conductive adhesive with low pollution or no pollution has gradually become a research hotspot.So the thesis has been presented.In this paper,aiming at the copper powder's easy oxidation,high cost and easy migration of silver powder,the UV curing paste has been prepared using silver coated copper powder as conductive filler and epoxy acrylic resin as matrix resin,respectively.It can be cured completely using the Irgacure184 and BP are used as the composite photoinitiator system.The cured samples have been characterized by scanning electron microscopy(SEM),four probe resistance tester,tensile testing machine,optical microscope(OM),differential scanning calorimetry thermogravimetric analyzer(TG-DSC)and Fourier transform infrared spectrometer(FTIR),respectively.The main results are as follows:(1)The optimal content of the matrix resin,active diluent system,the light initiator system and silane coupling agent KH-550 were studied by using the blend method.The optimal proportion has been obtained after continuous optimization: W(matrix resin): W(active diluent): W(light initiator): W(KH-550):W(defoamers): W(leveling agent)=50:35:4:2:3.5:0.5,The conductive adhesive made by this formulation has good mechanical and electrical properties.(2)The addition of silver coated copper powder leads to the interconnection of the paste.Results show that when the addition of silver coated copper powder was 75wt%,the resistivity of paste reached a minimum value of 1.377×10-3?·cm.Synchronously,the shear force also reached the maximum value of 5.74 MPa.The optimum UV curing processing was ring powfollowing: the cuer was 400 W,the curing distance was 5cm,and the curing time was 120~180s.In addition,when the optimum film thickness was 140?m and the content of onion-like carbon was 3wt%,the conductive adhesive has good thermal stability below 200?,good oxidation resistance within 40 days,and good chemical resistance.(3)The addition of the AIBN thermal curing agent leads to the the complete curing of the paste.Through the study of thermal and UV curing process,the process formula of dual curing system was determined,For Organic carrier,the content of reactive diluent was 40wt%,the content of light initiator was 4wt%,the content of thermal initiator was 5wt%,For conductive adhesive,the content of conductive filler was 70wt%,the content of carrier was 30wt%,the curing temperature was 60?,and the curing time was 120s~180s.The paste by the dual curing was stable below 250?,which was higher than the that of UV curing paste.The mechanical properties of conductive adhesive were also improved.(4)The reaction mechanism of conductive adhesive has been studied by the nonisothermal DSC method and infrared absorption spectroscopy.By the K issinger method and Crane equation,the apparent activation energy of the light curing conductive adhesive was 15.17KJ/mol,the reaction order was 0.73,and the curing process was 172.3??302.05??369.35?,which was similar to the first stage curing reaction.The reaction activation energy of the double curing conductive adhesive was from 20.52KJ/mol to 20.94 KJ/mol,and the reaction order was 0.78~0.97,Both of which increased than those of UV curing paste,which indicates that the curing process was more complicated. |
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