Free standing tapes of donor doped BaTiO₃for multilayer positive temperature coefficient thermistors

A disruptive method of fabricating free-standing tapes of La-doped (BaCaSrPb)TiO3 thermistors is demonstrated. The greatest advantage is that the free-standing tapes do not require high temperature co-firing of electrodes or reduced environment cofiring-soft oxidation cycle to obtain thermal sensitivity. The approach thus solves the long-standing problem with the ceramic thermistor technology that eluded its compatibility with surface mount technology (SMT) and miniaturization. Stencil printing is employed that can fabricate up to 500 μm thick tapes in a single step, saving huge cost and processing steps for application requiring thicker films. The pastes suitable for freestanding tapes are reported. The method provides a novel route to integrate PTC elements into the chips of passive components and would lead to a massive reduction in cold resistivity when developed in multilayer laminated stacks.