| With the rapid development of flexible electronic devices and equipment,the solder used in traditional interconnection of electronic industry is limited in the fields of foldable electronics,extensible electronics,three-dimensional packaging because of its high elastic modulus,small elastic deformation limit,low ductility and other shortcomings.The development of corresponding flexible connecting materials and processes has gradually become the field of electronic packaging technology A new trend.Liquid metal gallium indium alloy,as a kind of normal temperature fluid material with high conductivity,has been widely concerned by researchers in the field of flexible connection.In this paper,a new type of flexible joint is realized by using the mobility and conductivity of gallium indium alloy.In this paper,the application of liquid metal in the field of flexible connection is studied.We propose a preparation scheme of liquid metal conductive adhesive,and track and analyze the changes of the morphology of the liquid metal during the preparation process.The electrical properties of the conductive adhesive and the changes of its electrical properties during the curing process are measured.We also study the effects of the content of liquid metal,the curing temperature,the curing pressure and the curing time on the electrical properties of the conductive adhesive.The results show that the percolation threshold of liquid metal is about 90 wt.%.when the percolation threshold of liquid metal exceeds this value,the conductivity of liquid metal conductive adhesive can be realized.The effect of curing temperature on the conductivity of liquid metal conductive adhesive is very small.Generally speaking,the higher the curing temperature is,the smaller the resistivity of conductive adhesive is.There is a threshold value of curing pressure.When the curing pressure exceeds the threshold value,the conductive adhesive will change from nonconductive to conductive state.The effect of curing time on conductive adhesive is not significant.Before the polymer matrix is basically cured,the resistivity of conductive adhesive fluctuates with the curing time.We established a cellular automata model with surface tension and gravity,and simulated the droplet fusion and aggregation process of the liquid metal in the polymer matrix by this model,and successfully simulated the micro morphology of the liquid metal conductive adhesive.The influence of different initial distribution density on the final micro morphology was studied by cellular automata.The percolation threshold was 88 wt.%,which was close to the experimental value.The effect of different surface tension on droplet polymerization was studied,The results show that with the increase of surface tension,the polymerization frequency of droplets is higher,and the diameter of final droplets is smaller.The influence of external force on the distribution of liquid metal in conductive adhesive is analyzed by finite element calculation.By using two-dimensional and threedimensional models,the mechanical performance of conductive adhesive under the action of pressure,tension and shear force is analyzed.The results show that the mechanical properties of the conductive adhesive are mainly affected by the distribution of the internal liquid metal.The higher the content of the liquid metal,the more obvious the mechanical properties of the conductive adhesive decline.When the percolation threshold is exceeded,the mechanical properties of conductive adhesive will be greatly reduced,which will easily lead to collapse,extrusion and other failure.In addition,the uniformity of its internal distribution is also an important factor affecting the mechanical properties of conductive adhesive.The simulation results of different droplet size and radius distribution models show that using smaller droplet size and more uniform density distribution will significantly reduce the overall displacement of conductive adhesive,which ensures its reliability in the service process. |
PDF Full Text Request