Integration of Photo-Imaging Technology and Microvias in LTCC for Enhanced High-Frequency Applications and Packaging

In low-temperature co-fired ceramic (LTCC) technology, there is a growing demand for higher resolution of printed structures, particularly below <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$50 \mu \mathrm{m}$</tex>, to meet the miniaturization needs of high-frequency applications such as 5G, 6G, or radars. To address these challenges, Fraunhofer IKTS employs photo-imaging (PI) technology, achieving resolutions down to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$15 \mu \mathrm{m}$</tex> in the cofiring process. In addition to planar structuring, the miniaturization of vias is essential, as standard pastes are insufficient for filling diameters below <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$100 \mu \mathrm{m}$</tex>. This work aims to establish a robust micro-multilayer technology process chain that combines PI-based fine-line metallization with microvias <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(30-50 \mu \mathrm{m})$</tex> in LTCC. Two approaches for via formation were investigated: picosecond laser drilling and the use of dielectric PI pastes. The laser direct imaging (LDI) process demonstrated high structural quality and enabled spatially resolved shrinkage compensation during sintering. This allows for precise realization of microstructures ensuring the geometric accuracy required for high-frequency circuit applications.