Co-firing compatibility of LTCC hetero-laminates with low and middle permittivity

This study aimed at developing a good co-firing compatibility between the completely self-developed low-ε_r and middle-ε_r LTCC materials. To evaluate the co-firing results, the sintering dynamics, shrinkage behavior, chemical compatibility, three-dimensional contour, and microstructure of the co-fired composites were analyzed qualitatively and quantitatively. The results showed that the CaTiO₃-TiO₂ ceramic mixed with 50 wt% glass additives tended to have a good co-firing compatibility with low-ε_r composite, especially when the particle size of the CaTiO₃–TiO₂ ceramic was controlled at 3.04 µm. The composite co-fired with low-ε_r material at 875 °C for 20 min presented the best co-firing matching characteristic with an ideal chemical compatibility and the smallest height difference (64.73 µm) along the diameter of the samples. Besides, the sintering dynamics process of the hetero-laminates was simulated for a better understanding of the co-firing process. The simulated schematic was adopted to interpret the co-firing behavior of the hetero-laminates and the crucial factors in achieving a good co-firing compatibility.