Mineral Sillimanite-Based Hard Substrates for HTCC Applications

Sillimanite is a naturally occurring mineral with an orthorhombic structure. A suitable concentration of tape casting slurry with a pseudoplastic nature has been formulated using sillimanite (Al2SiO5) (filler) and organic additives. The green tape has a tensile strength of 1.5 MPa. The Al2SiO5 (5 layers) high-temperature co-fired ceramic (HTCC) tape sintered at 1500 degrees C shows a dielectric constant (epsilon(r)) of 4.59 with a loss tangent (tan delta) of 0.0008 at 5 GHz. The mineral has a coefficient of thermal expansion of 4.3 ppm/degrees C. The low cost Al(2)SiO(5 )tape from natural sources can be a suitable option for low epsilon(r) HTCC substrate applications.