The Preparation And Performance Of Calcium Aluminum Boron Glass-ceramics With Low Dielectric And Low Loss

In our day-to-day lives in which all things are connected,microwave dielectric ceramics play an indispensable role in the electronics,communications and other fields.Further developments of electronic gadgets and millimeter-wave technology guarantee wide prospects of dielectric ceramics with permittivity lower than 10.One of the areas is electronic packaging.Therefore,it is of great significance to study high-performance electronic substrate materials that can be applied to electronic packaging technology to promote the development of packaging technology.In this thesis,based on CaO-Al₂O₃-B₂O₃ glass ceramics,it is expected to obtain electronic substrate materials suitable for LTCC process with low dielectric constant and low dielectric loss.The effects of the content of elements on the phase composition,crystallization behavior and dielectric properties of the glass-ceramics were systematically studied.It is found that the sintering temperature will affect the main crystal phase of the calcium aluminum boron glass ceramics,and the element content also has a certain influence.When the aluminum content is 0.5 mol%,the microwave dielectric ceramic samples with low permittivity and low dielectric loss can be obtained after sintering at 900℃(ε_r=4.35,tanδ=2.94×10^-4,Q×f=53085 GHz@15.618 GHz,_f=-33.95 ppm/℃).The dielectric properties(ε_r=4.3,tanδ=7.72×10^-4,Q×f=19808GHz@15.294 GHz)were obtained by sintering at 900℃when Ca was 1.25 mol%.When boron content is 1.75 mol%and sintered at 925℃,the samples with the lowest dielectric constant and better microwave dielectric properties(ε_r=3.50,tanδ=7.55×10^-4,Q×f=27879 GHz@16.378GHz,f=-25.24 ppm/℃).According to the theory of crystallization kinetics,the stability parameters and crystallization activation energy of cal-Al-B glass-ceramics with different aluminum content were calculated.The variation trend of stability parameter S and crystallization activation energy is consistent,which is suitable for the stability judgment of calcium-aluminum-boron glass-ceramics.The results calculated by the two crystallization activation energy models show consistent variation rules and the error is less than 2%.When the content of aluminum is 0.5 mol%,the crystallization activation energy is the lowest,which is 308.607 kJ/mol,which is consistent with the calculation result of crystallinity.The calculated crystallization index is about 2～3,indicating that it is mainly one-dimensional and two-dimensional crystallization,which is consistent with the SEM results.It indicates that Ozawa method and Kissinger method are suitable for the crystallization kinetics analysis of calcium-aluminum-boron glass system.Finally,the thermal contraction curves and sintering activation energy calculations show that the amount of aluminum content can influence the glass transition temperature and the composition of the precipitated crystalline phase leading to rapid densification.The sintering activation energy of the sample decreases from 1021 kJ/mol to 733 kJ/mol with the increase of alumina content,and then increases to 1040 kJ/mol.The appropriate aluminum content can promote the sintering process and densification of calcium aluminum boron glass-ceramics,making it easier to precipitate crystals.