Study On Sintering Process And Conduction Mechanism Of Positive Silver Paste In Solar Cells

The sintering process of silver paste includes glass melting,glass diffusion and infiltration of conductive phase,mobile phase rearrangement of conductive phase,and liquid phase curing.The sintering process of silver paste can get better adhesion and good conductivity.In this paper,through the study on the sintering process of silver paste,the conductive mechanism of silver film formed by silver paste sintering and the change of each component in the sintering process were studied.So as to obtain the composition and sintering process of high performance silver paste.The main contents are as follows:The relationship between the square resistance,adhesion,specific contact resistivity,sintering temperature and holding time of sintered silver film was studied in the range of 450-900℃.At the same time,the changes of silver powder and glass powder in silver paste were analyzed by the micro morphology of silver film surface and cross section.The sintering window and the optimal sintering process are obtained.The conductive mechanism of silver film and Ag-Si contact surface was studied.The effects of different ratios of silver powder and glass powder,spherical silver powder and flake silver powder,spherical micrometer silver powder and nanometer silver powder on sintering process and sintered silver film’s square resistance,adhesion,specific contact resistivity were studied,and obtained optimal mixing ratio.The main conclusions of this paper are there.1.In this paper,the sintering window of the silver slurry system is 700-900℃.The best sintering condition of the silver paste is sintering at 850℃,the holding time is 50 s.At the same time,the optimal performance of silver film is obtained.Silver film’s square resistance is 2.22 mΩ/□,silver film and silicon substrate’s adhesion is 4.61 N,silver film and silicon substrate’s specific contact resistivity is 0.30 Ω·cm2.2.In the middle and high temperature sintering,the silver powder will dissolve in the glass melt,caused the small silver powder dissolved and disappeared,large particles of silver slowly grew up,flake silver powder changes to spherical silver powder.Simultaneously,the silver dissolved on the contact surface of the silver film and the silicon substrate,improved the electrical conductivity of the contact surface.3.During the sintering processd the glass melts infiltrated the surfece of silver powder and silicon substrate,lead to reset silver powder to form a conductive network,determined the silver film’s resistance.Meanwhile,the glass melt provided a connecting medium for the connection of the silver film and the silicon substrate,effected contact properties of silver film and silicon substrate.Glass powder is very important in the process of sintering.In this paper,the optimum content of silver powder is 4.5%.4.The relationship between the content of flake silver powder,silver nanoparticles,and silver film’s properties was obtained.It provided reference for decided the mixing amount of silver powder and nano silver powder in silver paste.