LTCC Warpage Reduction via Interlayer Shrinkage Mismatch Control for RF Electronic Packaging

Low-Temperature Co-Fired Ceramics (LTCC) are widely used in RF, power, and optical modules due to their low sintering temperature (<900 °C), excellent electrical properties, and multilayer integration capability. However, controlling warpage during co-firing remains a critical challenge, particularly for large-area substrates required in commercial applications. Warpage primarily arises from shrinkage mismatch between the conductive paste and ceramic green sheet, as well as from interlayer metal density asymmetry. This study addresses warpage reduction in a comparatively large LTCC substrate (60 × 30 mm²) to enhance manufacturability for practical deployment. To this end, we propose a comprehensive approach that combines interlayer metal density balancing, shrinkage rate tuning through glass frit and silver particle and the application of mechanical constraint during firing. These strategies were validated through the fabrication and evaluation of a sub-6 GHz band-pass filter (BPF), where reduced warpage directly enabled RF performance closely matching the simulation results. The findings demonstrate the effectiveness of an integrated process scheme for achieving reliable LTCC module fabrication at scale.