Study On Doping Modification Of Calcium Borosilicate Glass Ceramics With High Thermal Expansion

Electronic packaging is extremely important for manufacturing large-scale integrated circuit,and especially the mismatch of thermal expansion coefficient between ceramic substrate and printed circuit board becomes the critical problem in secondary packaging.In this thesis,calcium-borosilicate based glass-ceramics were researched and the related theories of doping oxides were explored.The effect of various oxides on the microstructure and properties were studied,and the optimal amount of dopants were obtained,which was expected to be used in the field of packaging substrate.The results indicate that ZnO addition contributes to the crystallization and thus optimizes the mechanical properties of this system.The sample doped with 8 wt%of ZnO posesses excellent mechanical properties,that is,the bending strength and Young's modulus reaches 207.9 MPa and 82.9 GPa,respectively.Moreover,the proper amount of CuO?2 wt%?significantly improves the performance of this system,but an excessive CuO behaves the negative effect.Rare earth elements are very common additives in the area of ceramic materials.It is found that an appropriate amount of Nd₂O₃ inhibits the precipitation of cristobalite in this system.Due to the high thermal expansion coefficient and the phase transition at low temperatures,cristobalite has a significant impact on the thermal and mechanical properties of this system.The sample has the best performance when Nd₂O₃ content is 0.5 wt%.Ho₂O₃ addition greatly inhibits both the crystallization of calcium borosilicate glass-ceramics and the formation of cristobalite.The best comprehensive performance was abtained for the sample doped with 2 wt%Ho₂O₃.Through the modification of calcium borosilicate glass-ceramics,the materials with high coefficient of thermal expansion as well as good mechanical and dielectric properties were prepared,which satisfied the requirement of secondary packaging.In addition,the correlation research on theoretical models was conducted in calcium borosilicate glass-ceramics.In order to study the sintering kinetics of this system,the constant temperature sintering model proposed by Singh was used to calculate the sintering activation energy of samples.The result shows that doping Nd₂O₃reduces the sintering activation energy of this system,which is helpful for the densification during the sintering process.The coefficient of thermal expansion is a key parameter for the secondary packaging material.Furthermore,the theoretical model was built to predict the coefficient of thermal expansion and provide the basis of theory for the experimental design.To verify the applicability of this model,the coefficient of thermal expansion was calculated on the samples doped with CuO and Nd₂O₃.Compared with the experimental value,we found that the small error proved that the calculated model was basically applicable to calcium borosilicate glass-ceramics.