Rv. Shende et al., Supercritical extraction of binder containing poly(vinyl butyral) and dioctyl phthalate from barium titanate-platinum multilayer ceramic capacitors, J MAT S-M E, 12(11), 2001, pp. 637-643
Supercritical extraction using carbon dioxide was examined for the removal
of binder from multilayer ceramic capacitors. The binder contained poly(vin
yl butyral) (PVB) and dioctyl phthalate (DOP), and the dielectric and metal
electrode materials were barium titanate and platinum, respectively. At 40
MPa of carbon dioxide at 95 degreesC, approximately 55 wt % of the binder
could be removed, and this was mainly the dioctyl phthalate component. The
use of entrainers such as 2-propanol, methyl isobutyl ketone, and n-hexane
was seen to have negligible effect on the degree of binder removal. The die
lectric constant, loss tangent, and breakdown voltage of devices processed
by supercritical extraction were similar as compared to devices processed b
y thermal oxidation alone. Although it was not possible to extract all of t
he binder with supercritical carbon dioxide, removal of the DOP fraction in
creases the pore space in the body by a factor of two. Transport model calc
ulations indicate this partial removal of binder mitigates the buildup of p
ressure in the subsequent thermal processing step and can reduce the proces
sing time for thermal removal of the remaining binder by a factor of 25. (C
) 2001 Kluwer Academic Publishers.