Eco-friendly tape casting of borosilicate glass/Al2O3 sheets for LTCC applications

This work reports the innovative development of a borosilicate glass/Al 2 O 3 tape for LTCC applications using an eco-friendly aqueous tape casting slurry. Polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA) were the respective dispersants, while carboxymethyl cellulose (CMC) and styrene acrylic emulsion (SA) were the respective binders. The results showed that PVP was more suitable than PAA as the dispersant for the aqueous casting slurry, and that 1.5 wt% PVP would achieve well dispersion of CABS glass/Al 2 O 3 powder in the aqueous slurry. Moreover, a small amount of 2.0 wt% CMC binder could yield smooth CABS glass/Al 2 O 3 tapes crack free. A high-quality CABS glass/Al 2 O 3 tape with a smooth surface was made from an aqueous slurry containing 1.5 wt% PVP dispersant, 2.0 wt% CMC binder, and 2.0 wt% PEG-400 plasticizer. The density, tensile strength, and surface roughness of the green tape were 2.05 g/cm 3 , 0.87 MPa, and 148 nm, respectively. The resulting CABS glass/Al 2 O 3 composites sintered at 875 °C exhibited a bulk density of 3.14 g/cm 3 , a dielectric constant of 8.09, a dielectric loss of 1.0 × 10 −3 , a flexural strength of 213 MPa, a thermal expansion coefficient of 5.30 ppm/ ° C, and a thermal conductivity of 3.2 W m −1 K −1 , thus demonstrating its broad prospects in LTCC applications.