Porosification behaviour of LTCC substrates with potassium hydroxide

The demand to meet advanced substrate requirements in terms of electrical, mechanical, thermal, and dielectric properties has led to an increasing interest in low temperature co-fired ceramics (LTCC). However, LTCC materials suffer from high permittivity. We recently showed that the wet-chemical porosification under acidic conditions allows the reduction of the permittivity of LTCCs in the as-fired state. In the present study, potassium hydroxide solution was employed as an alternative etchant which features a suitable bearing plane for further metallization lines. Various characterization techniques, including scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, and electron energy loss spectroscopy were used for investigation of the morphology and chemical composition of the substrates. Three-dimensional information of the surface topography was acquired by means of MeX^® Alicona software and the obtained roughness parameters confirmed the advantage of the proposed approach over acid treatment when targeting an enhanced surface quality.