Developing And Performance Research Of Die Attach Solder Paste For LED Flip Chip Based On SnAgCu Lead-free Solder

With the increasing development of the LED industry,it is increasingly moving towards miniaturization.A series of requirements have been put forward for heat dissipation and packaging technology,including improving the flip-chip structure and developing connection materials suitable for fine pitch and high thermal conductivity.Due to the low thermal conductivity of die bond glue,it has not met the heat dissipation requirements of high-power LEDs.Die attach solder paste has higher thermal conductivity and bonding strength than die bond glue,which can meet the heat dissipation and strength reliability requirements of highpower LEDs,and is gradually favored by the packaging material industry.However,the die attach solder paste on the market is used for fine pitch applications.Because of its poor printing performance and welding performance,defects such as bridging and collapse will occur during printing,and there will be tin beads and more residues after welding.In response to this problem,this article starts with the film-forming agent,thixotropic agent,and activator in the flux components,and evaluates the printing performance,anti-collapse performance and soldering performance of the die attach solder paste under different flux components,and uses the viscosity Rheological testing methods such as testing,thixotropy testing,hysteresis loop testing and oscillating stress testing further explore the effects of different rheological parameters on the rheological properties of solder paste.Finally,the performance of self-made solder paste had been analyzed compared with that of commercial solder paste.In this thesis,by selecting different types of thixotropic agents,film-forming agents and active agents,the printing,collapse and soldering properties of die attach solder paste under different components were tested.The results show that the solder paste prepared with succinic acid has relatively good anti-collapse performance,soldering performance and printing performance.For the selected film-forming agent,the solder paste prepared by choosing rosin(KE604)with large acid value and large softening point has better soldering performance and printing performance.For the selected thixotropic agent,it is found that the amide wax thixotropic agent(J630)has better printing performance than the hydrogenated castor oil thixotropic agent.The rheological properties of solder pastes containing different flux components were tested.The results show that for thixotropic agents,amide wax thixotropic agents have a stronger thixotropic recovery ability than hydrogenated castor oil thixotropic agents.The solder paste containing amide wax thixotropic agent(J630)has an excellent thixotropic recovery index and good flow properties.For the film-forming agent,choose the solder paste made of rosin(KE604)with the larger softening point,which has higher thixotropic recovery ability,and choose the solder paste made of rosin(KR610),which has better Small loss factor and better structural stability.As for the active agent,among the linear dicarboxylic acids,the lower the number of molecules of the active agent,the better the structural stability of the solder paste.In addition,compared with film formers and active agents,thixotropic agents have a greater impact on rheological properties,especially on viscosity,thixotropic recovery index and flow stress.In this thesis,the self-made solder paste was tested and compared with the commercial solder paste.the printing performance and collapse resistance of the self-made solder paste are better than those of the commercial solder paste.The self-made solder paste has mechanical properties equivalent to those of the commercial solder paste,and it can meet the requirements of the pad Welding requirements with spacing above 75 ?m.