Preparation And Performance Study Of Low Temperature Sintered Nano-Silver Paste

With the development of high-power electronic appliances,more and more requirements are needed to meet for interconnection materials in the field of electronic packaging.Packaging interconnection materials with excellent performance play an important role in heat dissipation of high-power integrated chips and other components.The traditional alloy solder and conductive adhesive can't keep up with the requirements of high power components because of their defects.As a new type of interface interconnection material,low-temperature sintered nano-silver paste has high thermal conductivity,,low process temperature and high interconnection reliability,which are not possessed by other traditional interconnection materials.It is more suitable for the packaging of high-power components.The research contents of this paper are as following:preparation of nano silver particles with appropriate particle siz for low-temperature sintering nano-silver paste.e and the preparation and performance study of low-temperature sintering nano silver paste with the prepared nano silver particles.The research content of this paper is divided into the following two aspects:(1)Preparation of nano silver particles:nano silver particles were prepare through liquid-phase reduction method,in whichsilver nitrate,ferrous sulfate heptahydrate and sodium citrate were served as silver sourcereducing agentand protective agent repectively.The nano silver particlewere characterized by XRD and TEM.The effects of the ratio of silver nitrate to sodium citrate,the initial concentration of silver nitrate,the reaction temperature and the drop speed of the reaction solution on the particle size of nano silver were studied.The best experimental conditions for the preparation of silver nanoparticles were obtained and selected to prepare nano silver particles.(2)Preparation of sintered nano silverpaste:anhydrous ethanol solution containing organic additives were added into the ultrasonic-dispersed nano silver paticles ethanol solution,and then the desired silver paste were obtained by removing the excess ethanol though low temperature vacuum drying.The prepared silver paste is holded between two electronic copper sheets as interconnection material for low-temperature pressure sintering.The sintering performance of the silver paste is characterized by cross-section analysis.In this paper,the effects of different organic binders and their dosage on the properties of sintered silver paste were studied.The experimental results show that when the ratio of Ag⁺:C₆H₅Na₃O₇is 1:5,the concentration of silver ion is 0.037mol/L,the experimental temperature is 10?,and the drop acceleration is 1.17m L/min,the size of the silver nanoparticles is 20 nm,and the distribution is uniform.XRD analysis showed that the nano-silver had high purity and no other impurities.The nano-silver slurry with different organic binder content was sintered at 200?,the bonding structure was observed by optical microscope,and the best silver slurry was selected.Through SEM observation of the sintered silver slurry,the surface sintering and the surface shrinkage were observed carefully,and no obvious shrinkage cracks were found.X-ray diffraction was used to analyze the composition of the sintered silver slurry The melting temperature of nano-silver was190?,and the sintering resistance was 3.90M?.