Aerosol deposition for post-LTCC

Abstract

Embedded capacitor technology is one of the most promising methods to achieve miniaturization, reduced costs and higher performance in rf wireless communication products. Much R&D on embedded capacitors has been conducted using different circuit board technologies; however, none of the circuit boards developed to date satisfy all of the requirements of embedded passive integration with high performance at low cost. Our unique method of aerosol deposition (ASD) can provide passive ceramic elements embedded in the resin substrate because it can produce ceramic dielectric film by accelerated ceramic nanoparticle aerosol bombardment at room temperature. We present our novel ASD approach to embedded capacitors in FR-4 resin and discuss the correlation between the microstructure and dielectric properties of ASD dielectric films deposited under various conditions. We confirmed that dense BaTiO 3 dielectric films with a dielectric constant of 400, tan δ of less than 2%, and a higher breakdown voltage, exceeding 80 kV/mm, could be formed on the resin substrates. The embedded capacitors on the FR-4 substrate, fabricated as a prototype using this ASD film, demonstrated a capacitance density of 300 nF/cm 2. We also clarified that variations in ASD film dielectric properties after thermal cycle testing between −55 and 160 °C for 2000 cycles was within 10% compared with as-deposited film.