Preparation Of Cordierite Glass-ceramics For LTCC And The Tape-casting Technics

Low temperature co-fired ceramics(LTCC) is the most advantaged and fastest developing field in electronic packaging. As the key of LTCC, substrate materials invariably attract attention of many researchers. Glass ceramics have aroused general concern in various substrate materials because of its tunable property and favorable thermostabilization.In this work, Mg F2、Ti O2、P2O5、Ce O2 was chosen as nucleation agent in the research to cordierite glass-ceramics of non-stoichiometric ratio. Advanced materials characterization methods, such as differential thermal analysis(DTA), X-ray diffraction(XRD), scanning electron microscope(SEM), thermal expansion coefficient test, impedance analysis, were used to systematically study how the sintering temperature and addition amount of Mg F2 influence the crystallization properties of glass ceramics, phase composition and phase transition, sintering properties, thermal expansion coefficient, dielectric constant and dielectric loss. Detailed study was also made into influence of nucleation agent(Ti O2, P2O5, Ce O2) on the crystallization properties and phase transition of the materials. The tape casting process was explored.Results show that introduction of Fluorine greatly reduce the glass transition temperature and crystallization peak temperature of the system, achieve sintering densification at relatively low temperature, and promote the precipitation of ɑ cordierite. Besides, merely raising the sintering temperature can also have the same effect. With the introduction of Fluorine affecting the amount and types of crystallization of the system, and sintering temperature affecting crystallization performance of cordierite, both can affect the thermal expansion coefficient of glass ceramics. Thus the adjustment of the thermal expansion coefficient in a certain range can be achieved by changing the content of Fluorine and the sintering temperature. As composition of crystal phase and degree of sintering densification can influence dielectric properties of samples, too high Fluorine content will lead to a surge in dielectric loss. Samples with Fluorine content of 8 wt% can achieve sintering densification under 850℃, and precipitate large amount of ɑ cordierite crystals. The thermal expansion coefficient, dielectric constant and dielectric loss were 3.48×10-6 K-1(25-600℃), 5.2, 0.0032 respectively. Thus make it valuable as substrate materials of low temperature co-fired ceramics.The introduction of a small amount of Ti O2 and Ce O2 facilitates the precipitation of ɑ cordierite, while too much can cause inhibition. Samples with 1 wt% Ti O2 or Ce O2 have small thermal expansion coefficient, matching with silicon and dielectric properties in appropriate range, which make it promising LTCC substrate materials. While, the addition of P2O5 goes against the precipitation of ɑ cordierite and dielectric loss of samples are too high, which make it not suitable for electronic packaging.When content of cordierite glass powder is 24 vol% and dispersant amount is 2 wt% to glass powder, the slurry has appropriate viscosity and uniform stability, which is good for film coating. After sintering, the obtained green tape has shrinkage rate in plane direction of 13.2% and thermal conductivity coefficient of 2.1 W/m·K, which has comparable performance with foreign mainstream products and is expected to be used as LTCC substrate materials.