Laser micromachining of barium titanate (BaTiO3)-epoxy nanocomposite-based flexible/rollable capacitors:: New approach for making library of capacitors

This paper discusses laser micromachining of barium titanate (BaTiO3)-polymer nanocomposite thin films. In particular, recent developments on high-capacitance, large-area, thin, flexible, embedded capacitors are highlighted. A variety of barium titanate (BaTiO3)-epoxy polymer nanocomposite-based flexible/rollable thin films ranging from 2 to 25 pm thick were processed on large-area substrates (330 mm x 470 mm, or 495 mm x 607 mm) by liquid coating processes. The electrical performance of composites was characterized by dielectric constant (Dk), capacitance, and dissipation factor (loss) measurements. Nanocomposites provided high capacitance density (10-100 nF/in(2)) and low loss (0.02-0.04) at 1 MHz. Scanning electron microscopy (SEM) micrographs showed uniform particle distribution in the coatings. Uniform mixing of nanoparticles in the epoxy matrix results in high dielectric (> 3 x 10(7) V/m) and mechanical strengths (> 3700 PSI). Reliability of the capacitor was ascertained by thermal cycling. Capacitance change was less than 5% after baking at 140 degrees C for 4 h, and 1100 cycles from -55 degrees C to 125 degrees C (deep thermal cycle). A frequency-tripled Nd:YAG laser operating at a wavelength of 355 nm was used for the micromachining study. The micromachining was used to generate arrays of variable-thickness capacitors from the nanocomposites. The resultant thickness of the capacitors depends on the number of laser pulses applied.