Preparation Of Low Temperature Sintered Nanoscale Silver Paste

Thermal interface materials play an important role for the heat dissipation of integrated chips and other elements in electronic packaging. The heat-conducting property of traditional thermal interface materials such as thermally conductive adhesive and solder have not been competent, so that they have restricted the heat dissipation. Low-temperature sintered nanoscale silver paste which acts as a kind of thermal interface materials has high heat conducting property which the other thermal interface materials do not possess. However, this kind of thermal interface material has not been studied systematically inland. What is more, the related dispensation and technique abroad are still secretive. So, the content of this thesis is to study the recipe of this kind of thermal interface material and test the properties of low-temperature sintered nanoscale silver paste.Low-temperature sintered nanoscale silver paste is comprised of organic components and nanoscale silver particles. The fundamental principle of nanoscale silver paste is that with the temperature rises, the organic components burn out and the nanoparticles are sintered together. Moreover, the nanoparticles were connected with the substrate which is plated with silver by the mechanism of diffusion. The sintered silver layer has high heat conducting property. The thermal conductivity is 193.7W/(K·m). The shear strength of sintered joint is 37.5MPa.Because of the heat-proof restriction of the other materials in the system of electronic packaging, the sintering temperature must be controlled within a lower temperature range. The reason why we choose nanoparticles is that they possess so high surface energy that can reduce the needed sintering driving force which is sintering temperature dramatically.The main content of this thesis are as followed:(1) Resolve the problem that the agglomeration of nanoparticles. Both chemical approach and physical approach are adopted. Disperse the nanoparticles by adjusting the kind, dosage of dispersive and the time of supersonic.(2) The selection of organic components. The organic components must be stable chemically when they are mixed with nanoparticles. They also should be able to burn out at the temperature which below the sintering temperature so that they can not affect the heat conducting property of sintered silver layer. Moreover, they should not volatilize so quickly that make the screen-printing hard to be done. On the other hand, too slowly to volatilize will result in more defects after sintering process.(3) Observe the microstructure and test the properties of the low-temperature sintered nanoscale silver paste. Verify whether or not such thermal interface material is suitable for electronic packaging.