| At present,the Ceramic Ball Array Package?CBGA?technology is widely used in chip packaging processes.In order to solve the thermal mismatch problem between printed circuit board?PCB?with high thermal expansion coefficient and substrate in the packaging process,it is necessary to research and develop the low temperature co-fired ceramic?LTCC?substrate material with high thermal expansion coefficient and high strength.Lithium disilicate glass-ceramics own good mechanical properties,dielectric properties and controllable thermal expansion coefficient,which make it possible to be used as the CBGA package substrate material.In this paper,lithium disilicate glass-ceramics were synthesized by the pressureless sintering method.The sintering temperature range of glass-ceramics was tested by sample shrinkage at various temperature points.The flexural strength of samples were tested by three-point bending method.The thermal expansion coefficient at 20-500?of samples were tested by Thermal expansion coefficient tester and the phase composition and morphology of the samples were analyzed by X-ray diffractometry and scanning electron microscopy?SEM?respectively;The dielectric properties of the samples were tested by the Impedance Analyzer.The results show that the introduction of different molar ratios of SiO2/Li2O in the glass-ceramics based on Li2O-SiO2 system can adjust the flexural strength of the glass-ceramic.When the molar ratio of SiO2/Li2O is 2.28,the comprehensive performance of glass-ceramics is good,the sintering temperature range is820±15°C,the flexural strength is 266.7 MPa in the sintering temperature range,the thermal expansion coefficient is 10.92×10-6/°C,the dielectric constant and electrical loss of the sample is 1.33and 3.51×10-3 at 1 MHz respectively.P2O5 is used as the nucleating agent to precipitate Li3PO4 grains during the sintering process,which provides nucleation sites to promote the precipitation of crystals in the system.However,when the content of P2O5 is too high,the viscosity of the lithium-rich region will increase,which will hinder the precipitation of crystals.Na2O as the alkali metal oxide can reduce the sintering temperature of the glass ceramics,but it will seriously deteriorate the dielectric properties of the system,and a small amount of addition should be used to improve the sintering temperature.The glass/quartz composites were prepared from glass powder and quartz powder.The types of crystal phases and thermal expansion coefficients,mechanical properties and dielectric properties were analyzed and discussed.The results show that the addition of quartz will increase the content of?-quartz in the system and raise the coefficient of thermal expansion.However,the increase of quartz content will increase the sintering temperature,the density will decrease,and the mechanical properties will deteriorate.When 15 wt.%quartz powder is blended,the comprehensive performance is the best.The sintering temperature range is 840±20°C.When the sintering temperature is 820°C,the flexural strength of sample is 222.4 MPa and the thermal expansion coefficient is11.82×10-6/°C,dielectric constant is 4.13,dielectric loss is 0.11?at 1 MHz?. |
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