Composition And Properties Research Of CaAlSi Ceramic Materials For Packaging With High Thermal Expansion

The rapid development of the electronic information industry is driving the progress of electronic packaging technology,which has gradually increased the requirements for electronic packaging materials.In the secondary package of the chip,it is necessary to avoid thermal mismatch caused by the difference in thermal expansion coefficient between substrate materials and printed circuit boards,and thus improve the stability of packaging system.CaAlSi glass-ceramics combines excellent mechanical,dielectric and thermal properties,and has always been an important pakaging material.The research in this thesis was based on CaAlSi glass-ceramics.In order to obtain a better overall performance of the chip secondary packaging materials,the effect of oxides doping on the crystal phase composition,microstructure and overall performance of the samples was systematically explored.Studies have shown that the doping of1wt%CeO₂ promotes the phase transformation of quartz to cristobalite,and the thermal expansion coefficient is increased to 12.1×10^-6/℃.At the same time,the mechanical properties have been significantly improved,and its flexural strength,Young’s modulus and microhardness reached 205MPa,78GPa and 7.09GPa,respectively.When the doping amount of Gd₂O₃ is 0.1wt%,the formation of cristobalite phase is inhibited,leading to a decrease in the thermal expansion coefficient,and the stability of the thermal expansion curve is optimized.Meanwhile,the growth of the crystalline phase is promoted,which is beneficial to the enhancement of mechanical properties.With the doping amount of Yb₂O₃ gradually increasing,the crystal phase content of the sample changes and the crystallinity is significantly improved,and the increase in compactness also gradually improves the mechanical and dielectric properties.When the doping amount of Yb₂O₃ reaches 2wt%,the performances of samples are the best.When the content of Mg O（alkaline earth metal oxide）is 6wt%,a new crystalline phase（diopside）is formed in the glass-ceramics,and significantly improves the crystallinity and density of the samples,which enhances the mechanical and dielectric properties,basically meeting the requirements of secondary packaging.Finally,based on various theoretical models,the coefficient of thermal expansion,crystallization and sintering behaviors of CaAlSi glass-ceramics were deeply investigated.For the Mg O-doped glass-ceramics,theoretical model of thermal expansion coefficient was constructed and the theoretical calculated value was obtained.The difference between the calculated value and the measured value is small and shows a same change trend,indicating that this model better reflects the internal law of the thermal expansion coefficient in CaAlSi glass-ceramics,which provides theoretical guidance for further optimizing the coefficient of thermal expansion.According to the non-isothermal crystallization kinetic model,the crystallization activation energy and Avrami exponent of CeO₂-doped samples were calculated,and it was found that CeO₂could reduce the activation energy of glass-ceramics and promote the crystallization of the samples,but the crystallization mechanism has not changed,which still belongs to surface devitrification.According to the theoretical model of isothermal sintering kinetics,the sintering process of CeO₂-doped samples was studied,which showed that CeO₂ can promote the sintering of samples and reduce the sintering activation energy of the system.