The MgO-Al₂O₃-SiO₂ Glass-ceramics For LTCC And The Tape-casting Technics

Low temperature co-fired ceramics (LTCC) developed rapidly as a kind of microelectric packaging technology. The substrate materials as the most important part of LTCC technology was broad attentioned. The substrate materials technology was kept as secret by DuPont and Ferro company to earn huge profits. Study of the inorganic materials in LTCC substrate and the corresponding tape-casting technics was seriously significative. In this paper, the properties targets and typical materials were introduced systemattically. The MgO-Al₂O₃-SiO₂ glass-ceramic green tape with properties near to the mature product was prepared. The influence factors to this green tape were mastered. The influence of oxide additives and the periodic properties of elements were studied . And the application fields of green tape were spread such as the preparing of the curve metal/ceramic composite materials.Series of MgO-Al₂O₃-SiO₂ glass-ceramics were designed and prepared. The contents of MgO, Al2O3 and SiO2 corresponded to the stoichiometric cordierite (Mg2Al4Si5O18) or not. The influence factors in crystallization kinetics of glass-ceramics includ the components, the melting temperatures of glass, the state of glass and the granularity of glass powder. The peak temperatures Tp and the crystallization rate constant k(Tp) of glass were used to analyze the influence by way of differential scanning calorimetry (DSC). Increasing the content of MgO can decrease the Tp and increase the k(Tp) of MgO-Al₂O₃-SiO₂ glass-ceramics. The rising of melting temperature can increase the Tp and decrease the k(Tp). The ground glass powder has lower peak temperatures than massive glass. And the finer glass powder has lower peak temperatures.The stoichiometric MgO-Al₂O₃-SiO₂ glass which had better properties was chosen to be heat-treated with different treat system. The main influence factors of heat treatment includ nucleating temperature, nucleating time, crystallizing temperature and crystallizing time. Such factors could influence the sintering properties, the dielectric properties and the coefficient of thermal expansion (CTE) of glass-ceramics. Increasing the nucleating temperature can raise the relative density of MgO-Al₂O₃-SiO₂ glass-ceramics. The influence of the nucleating temperature on the dielectric constant of glass-ceramics is not obvious. The highest CTE as 4.93×10-6K-1 and the highest softening point of glass as 838℃appear when the nucleating temperature is 750℃. The nucleating time has little influence to the relative density and dielectric constant of glass-ceramics. The highest CTE as 4.93×10-6K-1 appears when the nucleating time was 60 minutes. And the highest softening point as 840℃appears when the nucleating time is 90 minutes. The CTE of glass-ceramics increases with the inceasing of the crystallizing temperature. When the crystallizing temperature was 950℃, the maximal relative density as 98.85%, the maximal dielectric constant as 5 and the highest softening point as 838℃appears. The influence of crystallizing time to relative density of glass-ceramics is not obvious. The dielectric constant decreases and the CTE increase with the prolongation of crystallizing time. The highest softening point of glass as 838℃appears when the crystallizing time is 60 minutes.Three kinds of oxides, which are P2O5, ZrO₂ and Yb₂O₃, were chosen to be addtives of MgO-Al₂O₃-SiO₂ glass-ceramics. The nucleating ability of such oxides were determined by studing the crystallization kinetics, the kind and shape of crystal of the glass-ceramics with such oxides. The influence of such oxides to the crystallization kinetics of glass-ceramics is not obvious. P2O5 can promote the phase separation of glass and farther can promote the crystallization. The temperature of cordierite separating decreases with the adding of P2O5. ZrO₂ and Yb₂O₃ can restrain the separation of crystal. The adding of P2O5 and ZrO₂ can decrease the flexural strength of MgO-Al₂O₃-SiO₂ glass-ceramics. When the quantity is big enough (6wt% P2O5 and 4wt% ZrO₂) the dielectric constant and the loss tangent of glass-ceramics increase rapidly. Yb₂O₃ can enhance the flexural strength of glass-ceramics. At the same time the dielectric properties keep stable with the adding of Yb₂O₃. The CTE of glass-ceramics is influenced little by these oxides.The same mole of MgO, CaO, SrO and BaO were chosen to prepare RO-Al₂O₃-SiO₂ glass-ceramics for the periodic properties of such oxides. The influence of the periodic properties on glass-ceramics was studied by analyzing the crystallization kinetics, the sintering temperature range and the physical properties of such glass-ceramics. As the periodicity of alkaline earth ion R2+ increases, the peak temperatures of glass decrease, the sintering temperature ranges reduce, the flexural strengthes decrease firstly, and then increase.At the same time, the dielectric constants increase, and the CTE increases too. The prolongation of crystallization time makes the values of flexural strengthes centralized. The dielectric constants decrease and the CTE increases with the prolongation of crystallization time.The MgO-Al₂O₃-SiO₂ glass-ceramics tape casting slurry was prepared. The factors such as the size of glass powder, the content of glass powder, the content of binder, the ratio of binder to plasticizer (R) and the content of dispersing agent which would influence the rheology of slurry were studied. The results announce that if such conditions could be satisfied as the D50 of glass powder is 2.23μm, the volume content of glass powder is between 20% and 25%, the volume content of binder is between 15.5% and 19%, the R is 0.65 and the dispersing agent is 2wt% of glass powder, the slurry with best rheological properties can be gained.The MgO-Al₂O₃-SiO₂ glass-ceramics green tape was prepared by tape casting technics. The influence factors to properties of green tape were studied. The strength and flexibility of unfired green tape were measured by standard tensile strength test. The relative density and shrinkage of fired green tape were measured to estimate the sintering properties of green tape. The benefit factors to properties of unfired green tape include the increasing of the content of binder, a proper R value and the fine glass powder. And the benefit factors to sintering properties include the decreasing of the content of binder, a proper R and the coarse glass powder.As a kind of transitional technics, the development of green tape technics was influenced by the application field. Some work which can expand the application field is attempted in this paper. This work includes the preparing of curve surface metal/glass-ceramics composites and the Ag/glass resistance green tape that can substitute the resistance paste in LTCC technics.