Self-constraining method for low shrinkage of low-temperature-cofired ceramic devices

Abstract

A new technique developed for the low shrinkage of low-temperature-cofired-ceramics (LTCCs) is proposed; this technique is based on a self-constraining mechanism, which relies on composite green tapes formed by two laminated glass layers, each of which has a distinct softening point (onset shrinkage temperature, OST) and a crystallization temperature (CRT). Each layer works as a constraining layer for the other layer in a distinct temperature range to prevent excessive linear shrinkage along the layer plane. The OSTs ranging from 802 to 606 degrees C are adjusted by controlling the amount of Na2O (0-1.0 wt %) added to the CaO-SiO2 glass. The OST and CRT of the two glass layers as well as the heating profile have strong effects on shrinkage ratio, the lowest of which is found to be only 0.2% after sintering up to 880 degrees C. The measured dielectric constant of the sintered samples is approximately 6.0 within a narrow variation range even when the samples have a wide range of shrinkage ratios.