Study Of The Random Distribution Of Multi-Scale Silver Particles Based On Molecular Dynamics

High performance of wide band gap semiconductors been fully applied are largely depends on the packaging technology and the packaging materials.With the promotion of the lead ban around the world,the researchers found that sintered silver technology is an ideal alternatives to chip bonding technology for high temperature applications.However,the cost of preparation and preservation of silver paste,and process reliability etc have become the major obstacle to the wide application of silver sintering technology.For this reason,in this study,we are mainly studies the material preparation of silver paste,optimizing sintering process,and study the micro mechanism of particle diffusion during the silver sintering,Takes optimizing the formula of sintered silver paste as the core,which can reduces the material cost,and provides a favorable reference basis for promoting the largescale application of sintered silver technology in wide band gap semiconductors.The main research results in this paper are as follows:(1)Through the reaction between different reducing agents with the silver nitrate during the preparation experiment of silver nanoparticles,the study found that the particle size ratio will be different at different reduction reaction rates.(2)In order to verify the feasibility of silver paste sintering,we used a traditional vacuum reflux system for pressureless sintering to eliminate the sintering voids.The results show that the vacuum chamber pressure has a significant effect on the formation of sintering cavity defects in the drying process of sintered silver layer.This sintering method can not only eliminate the voids during the sintering,but also avoid the oxidation of other packaging components.(3)Based on molecular dynamics,a random algorithm was used to establish a model to simulate the initial coating morphology of silver coating.The effects of particles with different sizes on sintering porosity were analyzed.Compared with the sintering process using large-size silver particles,the results show that the sintering process using multi-scale silver particles will improve the degree of densification under the same sintering conditions,which theoretically verifies the feasibility of adding small-size silver particles to large-size silver particles.(4)Based on the above study of sintered multi-scale particles,in order to further study the effect of heterogeneous silver paste on sintering densification,the sintering densification of flake-particle silver paste had been studied.The results show that the addition of nano particles to flake silver can help the sintering densification,while the appropriate addition of flake silver to micron particles can help the sintering densification.In this paper,in order to obtain a better sintering scheme and silver paste formula guidance scheme of sintering silver technology,we studied from many aspects such as particle preparation,micro mechanism research of cost ratio in silver paste,and then process setting,which provides a certain commercial reference value for the wide application of sintering silver technology.