Preparation Of Lead-free And Low-melting Point Glass Powder And Study Of Nano Silver Coating

Low-melting point glass powder has many advantages such as low melting temperature,low melting viscosity and good chemical stability,etc,so that it’s widely used in packaging or connection in metal or non-metal materials,for example,in the case of inorganic binder in electronic paste.In recent years,the application of electronic paste in fields of semiconductor,integrated circuit and automobile parts requires the paste can be sintered at medium or low temperature conditions,which could promise that the base materials or components are free from the effect of high temperature environment,which could avoid producing harmful phenomena inside materials or parts,such as micro cracks or deformation,damage,etc.Therefore,the research and development of lead-free,environmental protection and low melting point glass powder has an important significance for the development and application of the electronic paste.Bismuth system low-melting point glass powder is considered to be the best substitute of low-melting point glass powder system with lead element.The studying of glass forming properties,crystallization ability,characteristic temperature,chemical stability is of great significance in promoting the development and application of the glass system.By doping other oxides and optimizing the glass component,this article try to lower the glass transition temperature of glass and improve the overall performance of the glass such as the feature of impermeability of glass and the integrity of the glass structure.The inorganic glass powder act as an insulator which does not conduct electricity.The electrode material is made through printing and sintering by conductive paste which electrical conductivity is affected by inorganic glass powder largely.Usually,in order to reduce body resistance of electrode materials,the inorganic glass powder is reduced as much as possible,but the adhesion between the electrode and the substrate will drop out,besides the phenomenon of falling off and other harmful phenomena is now.Glass powder covered with nano silver particles on the surface by electroless plating could reduce the resistance of electrode material and could improve the efficiency of working devices for example in the case of crystalline silicon solar cell.Therefore,developing lead-free and low-melting point conductive glass powder is of great significance.The design experiments are based on triple component diagram of Bi2O3,B2O3 and Si O2.And the glass forming ability,crystallization and glass transition temperature are studied.The results show that the glass forming performance is good.And the glass transition temperature of the glass is 330~400 Deg.C.The glass is low-melting point glass by main components of Bi2O3,B2O3,Si O2 and the addition of 5 wt.% R2O(obtaining 2.5 wt.% Na2 O and 2.5 wt.% K2O).The mole ratio of main components of Bi2O3,B2O3,Si O2 is 30~60:30~60:10~30.In addition,the basic glass components of the oxides of Bi2O3 and alkali metal oxides could reduce the transition temperature of the glass significantly,but the more its content,the more crystallization of glass after heat treatment.In view of the based components of 40% Bi2O3-30% B2O3-30% Si O2-x R2O(x1=2 wt.%,x2=5 wt.%),the effects of amount of Te O2 and Sb2O5 are studied on the structure and properties of glass.The results show that when the amount of Te O2 is less than 6 wt.%,the glass forming performance is good,and the addition of Te O2 can significantly reduce the glass transition temperature,but the thermal expansion coefficient of glass is increased.When the amount of alkali metal oxide R2 O is 5 wt.%,the impermeability of glass decreased obviously after adding Te O2.The results also show that when the amount of Sb2O5 is less than 6 wt.%,the glass forming performance is good,and the change of glass transition temperature is not obvious,but glass thermal expansion coefficient decreases after adding Sb2O5.When the amount of alkali metal oxide R2 O is 5 wt.%,adding Sb2O5 can improve the impermeability of glass significantly.The final system of Bi2O3-B2O3-Si O2-R2O-Te O2-Sb2O5 low-melting point glass is prepared,which forming performance and impermeability are good.Two kinds of silver coated glass powder are prepared by electroless plating reaction with two different reducing agents of Glucose and formaldehyde on the surface of self-made glass powder.The characterization and properties are characterized with the help of X-rad Diffraction(XRD),Field-Emission Scanning Electron Microscope(FE-SEM),Transmission electron microscope(TEM),Energy Dispersive Spectrometer(EDS)and Four Probe Tester.In Glucose reduction of silver ammonia solution,the article explore the effects about the content of ammonia,p H value of the plating solution,the reaction temperature and other parameters respectively.Finally,the appropriate reaction conditions are selected with adding surfactant.And its silver coated glass powder has good performance,wherein the silver particle particle size is 10~30 nm and the average particle size is about 15 nm.In Formaldehyde reduction of silver ammonia solution,by adjusting the content of ammonia,p H value of the plating solution and adding surfactant PVP,several groups of silver coated glass powder are prepared.Firstly,the results show that the size of nano silver particles coating on the surface of glass powder gradually increases and the coating uniformity decreases with the increase of ammonia concentration.The average particle size of nano silver is about 20~40 nm.Secondly,the size of nano silver particles coating on the surface of glass powder gradually decreases and the coating uniformity increases with the increase of the p H value of plating solution.The average particle size of nano silver is about 20~40 nm.Lastly,the coating uniformity and density increase by adding surfactant PVP,which nano silver particle size is about 50 nm.In addition,a few nanocrystalline silver rod grow out on the surface of glass powder after adding surfactant PVP.With the content of adding PVP increase,the number of rod structure and the size gradually increase and the volume resistance of silver coated glass powder decreases.The volume resistance value is(0.3~1.5×103)Ω·cm.