Low‐Sintering High‐k Materials for an LTCC Application

High‐k LTCC tapes with ultralow sintering temperatures were developed from lead‐free perovskite powders. Lowering of the sintering temperature from 1250°C down to 900°C has been achieved by means of ultrafine ceramic powders in combination with suitable sintering aids. The tape‐casting process has been optimized for ultrafine powders with an enhanced sintering activity. Low‐sintering high‐k tapes of a thickness down to 40 μm, suitable for LTCC processing, were obtained. The sintering behavior of these high‐k tapes has been studied and compared with other LTCC materials. Dielectric properties of the high‐k material have been investigated on a multilayer test structure consisting of up to 20 dielectric layers. After metallization with an Ag conductor, the green tapes were stacked and laminated. Sintering of these multilayer stacks at 900°C gives dense ceramic samples. Permittivities up to 2000 have been obtained, together with low dielectric losses. Material compatibility with several Ag/Au‐thick‐film‐paste systems has been tested.