Study On Doping Modification And Mechanism Of MgO-Al₂O₃-SiO₂ Glass-Ceramics

The advancement of information technology continues to increase,which creates a vigorous development of the integrated circuit industry and causes electronic packaging to become a current hot field.It is urgent to seek LTCC packaging substrate materials with excellent performance.MgO-Al₂O₃-Si O₂ glass-ceramics have gradually become the focus of attention because of their excellent properties.However,there are still problems such as high sintering temperature,difficulty in co-firing with electrodes of low melting point,unstable flexural strength and thermal expansion coefficient.Therefore,this paper takes MgO-Al₂O₃-SiO₂ glass-ceramics as the object.The effects of different elements on the crystal phase composition,microstructure and comprehensive properties of the system are studied through doping modification.The corresponding theoretical analysis of the sintering and crystallization process is also carried out.This experiment uses four kinds of rare earth oxides for doping.The results show that Y₂O₃ can reduce the sintering temperature of MgO-Al₂O₃-SiO₂ glass-ceramics,promote the precipitation of crystal phases,and improve mechanical properties.When the doping amount of Y₂O₃ is 1wt%,the crystallinity of the sample is the highest.So that the flexural strength is 211MPa,the Young’s modulus is 89GPa,the thermal expansion coefficient is 4.68×10^-6/℃,the dielectric constant is 5.99,and the dielectric loss is 1.99×10^-3.Sm₂O₃ can inhibit the formation of MgAl₂O₄ phase,promote the conversion of(Mg Al₂Si₃O₁₀)_0.6 phase into Mg₂Al₄Si₅O₁₈ phase,improve the microstructure,and significantly enhance the mechanical properties.When 2wt%Sm₂O₃ is doped,the performance of the sample is the best.The flexural strength is 229MPa,the thermal expansion coefficient is 4.58×10^-6/℃,the dielectric constant is5.93,and the dielectric loss is 1.64×10^-3.Dy₂O₃ has little effect on the composition of the crystal phase,but it can promote sintering densification and overall crystallization,thereby reducing the thermal expansion coefficient.Doping 3wt%Dy₂O₃ can reduce the thermal expansion coefficient to 3.55×10^-6/℃,which is close to the Si chip.At the same time,the flexural strength is 181MPa,the Young’s modulus is 99GPa,the dielectric loss is 0.68×10^-3,and the dielectric constant is 5.78.Lu₂O₃ can obviously promote the precipitation of the Indialite phase,thereby adjusting the thermal expansion coefficient,but has a small effect on the dielectric properties.When the doping amount of Lu₂O₃ is 0.5wt%,the sample obtains the best performance,in which the flexural strength is 172MPa,the Young’s modulus is 94GPa,the thermal expansion coefficient is 4.17×10^-6/℃,the dielectric loss is 0.87×10^-3,and the dielectric constant is 5.33.Secondly,the sintering kinetics of the Y₂O₃ and Sm₂O₃ doped MgO-Al₂O₃-SiO₂glass-ceramics with different contents were analyzed and studied.With a constant heating rate model based on the Arrhenius equation,the sintering activation energy was calculated accordingly.The results showed that 1wt% Y₂O₃ or 2wt%Sm₂O₃ could significantly reduce the sintering activation energy of MgO-Al₂O₃-SiO₂ glass-ceramics and promote the densification of the system.Finally,this paper discussed the principle of the Aügis-Bennett model and introduced three parameters that characterized the stability of the glass.The crystallization kinetics of Y₂O₃ doped MgO-Al₂O₃-SiO₂ glass-ceramics with different contents was analyzed and calculated.The results showed that 1wt%Y₂O₃ could produce the effect of nucleating agent and greatly reduce the crystallization activation energy of MgO-Al₂O₃-SiO₂ glass-ceramics.Meanwhile,it could destroy the stability of the glass network and promote the overall crystallization of MgO-Al₂O₃-SiO₂glass-ceramics.