| With the rapid development of information and communication technology, the microwave dielectric ceramic material applied in the Low Temperature Co-fired Ceramics (LTCC) has become the focus and direction. In this dissertation, (Ca18/19Sr1/19)0.2(Li0.5Sm0.5)0.8TiO3 (CSLST) microwave dielectric ceramics using B2O3-GUO-LiCO3 (BCL) as sintering aid was selected as the research objects. The process of aqueous tape-casting and un-aqueous tape-casting were researched. The practical CSLST microwave dielectric ceramics for LTCC was obtained.Aqueous tape casting of CSLST microwave dielectric ceramic powder with sintering aid BCL (CSLST+BCL) which using styrene-acrylic latex as blinder, PVP as dispersant, glycerol as plasticizer, and deionized water as dispersion medium was researched. The influence of pH value, solid content of slurry, and various additives on slurry dispersion and rheological properties were studied. Appropriate formulations of slurry for aqueous tape casting have been obtained:when the slurry pH value is 10, content of ceramic powder is 60.0 -65.6 wt%, dispersant is 0.8 wt%, binder is 10-14 wt%, the ratio of plasticizer and binder is 0.25, the slurry is suitable for tape casting. The both ways of using n-butyl alcohol as defoamer and vacuum defoaming were effectively ruled out the bubble in the slurry. The well uniform film without crazing was achieved after drying between 40 to 60℃.Un-aqueous tape casting of CSLST+BCL was researched by using BM-2 as binder, polyethylene glycol as plasticizer, and dimethylbenzene mixed butyl alcohol as dispersion medium. The effect on proportion of dispersion solvent and solid content on slurry rheological properties was studied. The formula of tape casting slurry was optimized. The high density ceramic substrate has been obtained which was sintered at low temperature. The research shows that, when the solid content of ceramic powder is 55wt%, the ratio of dimethylbenzene to utyl alcohol isl:1, binder was 8～11%, plasticizer was 3-4%, the slurry has fluid characteristics of typical shear-thinning behavior which suitable for tape casting. The well uniform film without crazing by tape-casting is obtained. CSLST+BCL microwave dielectric ceramic film was prepared through tape casting process. According to the TG/DTA analysis, reasonable dumping and sintering procedure was determined. The sintering properties were confirmed through measuring the density of the sintered membrane. The experimental results show that aqueous tape-casting film has excellent microwave dielectric properties after laminated and sintering at 900℃:dielectric constant εr= 55.6, quality factor Q×f=1044 GHz, resonance frequency temperature coefficient τf=-18.39×10-6/℃. The un-aqueous tape-casting film also has better microwave dielectric properties after laminated and sintering at 900℃: dielectric constant εr= 51.8, quality factor Q×f= 1085 GHz, resonance frequency temperature coefficient τf= 19.38×10-6/℃.The co-fired behavior of two kinds of film with adding different content CSLST+BCL ceramic powders of silver slurry was studied. The results show that the diaphragm has good associativity after it co-fires at 900℃ with Ag electrode which contains 5% CSLST+BCL.The research on the two type of tape-casting process of CSLST microwave dielectric ceramic were studied, a series of the microwave dielectric ceramics with the excellent dielectric properties and aqueous green tape would be achieved, which meet LTCC technology. |
PDF Full Text Request