Preparation And Mechanism Research Of Ba-Al-B-Si Glass/ceramic Packaging Materilas With High Coefficient Of Thermal Expansion

At present,the ceramic ball grid array?CBGA?packaging technology is widely used in the secondary packaging of the chip.In order to solve the thermal mismatch etc problems cauesed by the different coefficient of thermal expansion between the substrate and the printed circuit board?PCB?,we need to develop the low temperature co-fired ceramic?LTCC?substrate materials with high coefficient of thermal expansion.BaO-Al₂O₃-B₂O₃-SiO₂ galss-ceramics own high coefficient of thermal expansion,good mechanical and dielectric properities,which making it possible to be used as the CBGA packaging material.Therefore,in this paper,we selected it as the research object.In this paper,the BaO-Al₂O₃-B₂O₃-SiO₂ galss-ceramics were synthesized by the traditional ceramic preparation process.Moreover,the microstructure,crystalline phases,coefficient of thermal expansion,flexuarl strength,young's modulus and dielectric properities of the sample were studied.The results show that when the SiO₂ content in the basic glass increased,the flexuarl strength and young's modulus of the samples increased linearly,and other performances were improved.When the content of SiO₂ is50wt%,the sample has the best comprehensive performance.The coefficient of thermal expansion is 13.4×10^-6/°C,the flexural strength is 150MPa,the young's modulus reached 66GPa,and dielectric constant and dielectric loss were 6.0 and 6.2×10^-4,respectively.When the content of Al₂O₃ in the basic glass is 5wt%,the specimen has the highest flexural strength?171MPa?and young's modulus?60GPa?,the comprehensive performance is best.The addition of 0.2wt%Y₂O₃ in the glass-ceramics was significantly improved the flexural strength?200MPa?of the materials.When doped 1wt%V₂O₅ in the glass-ceramics,the comprehensive performance of the sample is best.The flexural strength and young's modulus were 152MPa,63GPa,respectively.Through the above research,we finally obtained the glass-ceramic packaging material with the high coefficient of thermal expansion and excellent comprehensive properties,which can be applied to CBGA packaging of high density chips.At the same time,the sintering kinetics of BaO-Al₂O₃-B₂O₃-SiO₂ glass-ceramics was discussed.The sintering activation energies of samples with different SiO₂ content were calculated by different equations based on the constant sintering rate model,and the results were consistent.The results show that the increase of SiO₂ content can reduce the sintering activation energy and effectively promote the sintering process of the samples,and the sudden increase of the sintering activation can be attributed to the formation of the cristobalite phase in the specimen.In addition,the constant temperature sintering model proposed by Singh was used to calculate the sintering activation energy of samples doped Y₂O₃,and the result show that the doping trace Y₂O₃ can effectively reduce the sintering activation energy of the samples.Finally,the coefficient of thermal expansion of the material was calculated by the method of oxide and crystal phase.The calculated results of crystal phase module,based on the crystal phase and phase content in the material,are much closer to the experimental values and the error range is basically within±10%.The above results show that the coefficient of thermal expansion of the glass-ceramics can be adjusted by controlling the crystal phase content in the sample.