Supercritical extraction of binder containing poly(vinyl butyral) and dioctyl phthalate from barium titanate-platinum multilayer ceramic capacitors

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.