Study On Preparation And Performance Of Low Temperature Sintered Silver Nanoparticle Paste

With the development of electronic products in the direction of miniaturization, high-density, and high-power, as well as the industrial application of Si C as the representative of the third generation of wide band gap semiconductor devices, it is important to develop new bonding materials and joining technologies with good mechanical, electrical and th ermal conductivity performance, high temperature stability and environmental friendliness. Currently, the most promising option for Si C die attach is the use of silver nanoparticles sintered at low temperatures, which allows a relatively low processing temperature and can operate at high temperatures. However, most of the currently developed bonding materials with nano silver particles are in the form of slurry, which has low viscosity and can not meet the industrial applications such as stencil printing or needle point dispensing. Based on the problems above, this dissertation explores the improvement measures for proper viscosity of low-temperature sintering silver nano particle paste. The deposition behavior and bonding process of silver nano particle paste were studied to fabricate the joints with suitable microstructures and mechanical properties. In addition, systematic investigations have been carried out on the sintering mechanisms of silver nano particle paste and the relationship between the sintering degree of nano particles and the mechanical properties of joints.In this dissertation, silver nano particles were prepared by chemical reduction of aqueous, a residual organic component system was selected which includes PGMEA as solvent, EC as binder, modified hydrogenated castor oil as thixotropic agents and a certain amount of hydrogenated rosin. A no residual organic component system which only contains 1,2-propanediol was also developed. Two types of low-temperature sintering nano silver pastes with suitable viscosities of a solid content of 70% were prepared for stencil printing. After sintering at 250℃, nano silver paste showed a good electrical conductivity and thermal conductivity, with electrical resistivity and thermal conductivity are respectively up to 5.89μΩ·cm and 367.90W/m·K.Using the residual nano silver paste to sinter at 250℃ with 10 MPa pressure for 30 min according to different temperature curves to connect the chip and silver-plated copper substrate, to obtain the impact of volatile organic components of the nano silver paste sintering connections through the analysis and testing of the interconnection joint, and made it possible by controlling the evaporation or decomposition of the organic components to improve mechanical properties of a sintered connection joint.Orthogonal experiment was designed to study the relationship between joining technology and mechanical properties of the low-temperature sintered joint of the metal substrate connected by two types of nano silver paste sintering, observed the microstructure of joints, analyzed the test results considering the influence of process parameters on organic compounds volatile as well as joining principle of low-temperature sintering metal nanoparticles.