Review on ceramic multilayer circuit carriers for monolithic sensor integration

Abstract:
Within available technologies for ceramic circuit carriers, Low Temperature Cofired Ceramics (LTCC) is a proven technology for smart system integration in harsh environmental conditions. This review explores the monolithic integration of capacitive interdigital sensors on LTCC substrates, emphasizing design strategies and material compatibility. While LTCC enables direct integration of heaters and sensor elements, its surface characteristics, such as roughness, warping, and thickness variation, limit the achievable resolution for fine sensor electrodes. To overcome these limitations, two approaches are examined: mechanical polishing and surface planarization using low-softening-point electronic glass pastes. Polishing improves surface uniformity, allowing feature sizes down to 6 µm. Overprinting with glass pastes enhances resolution to 3 µm, though compatibility with high-temperature thin-film processes remains a challenge. We show that LTCC technology enables advanced sensor integration and benefits from ongoing technological improvements.