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A new type of low-temperature co fired ceramic (LTCC) material with a medium dielectric constant was developed in this study (MK, er = 20.9). MK can be co fired with a high-dielectric-constant material (HK, er = 44.5) and a low-dielectric-constant material (LK, er = 8.1) previously reported. Glass and ceramic materials similar to HK and LK were used. The compositions of glass and ceramic materials for MK were designed to set the adequate dielectric constant and low-temperature coefficient of the dielectric constant (τer). The coefficient of thermal expansion (CTE) was matched with those of both the previous materials. MK was confirmed to match well electrically with both the previous materials, had no mechanical defects, and showed minimal inter diffusion. With the addition of MK, the three types of LTCC material system contribute to the enhancement of the performance and the downsizing of electronic components for high-frequency communication.

We found that the co-firing low temperature co-fired ceramic (LTCC) materials of different dielectric constants (εr) with Cu wiring is achievable using a novel, original design. It was confirmed that the dielectric characteristics of the dielectrics designed in this study are very suitable for the use of the dielectrics in electronic components such as filters mounted in high-speed radio communication equipment. The dielectric constants of the lower- and higher-dielectric-coefficient materials were 8.1 and 44.5, respectively, which are sufficiently effective for downsizing LTCC components. Observing the co-fired interface, it was confirmed that excellent co-firing conditions resulted in no mechanical defects such as delamination or cracks. On the basis of the results of wavelength dispersive X-ray spectrometry (WDX) and X-ray diffractometry (XRD), it was confirmed that co-firing with minimal interdiffusion was realized using the same glass for both dielectrics. It is concluded that the materials developed are good for co-firing in terms of the mechanical defects and interdiffusion that appear in them.

Amorphous (Tb1-x Gd x )30Fe70 thin films were prepared at various substrate temperatures (T sub) and with various thicknesses, and their magnetic properties were investigated. The films prepared at T sub=77 K show only in-plane anisotropy, and those prepared at T sub=473 K only perpendicular anisotropy. The films prepared at T sub=300 K are found to simultaneously have two components of anisotropy, the in-plane and the perpendicular. Since the absolute value of K u decreases linearly with the fraction of Gd substitution for Tb, the single-ion anisotropy of Tb is considered to be closely connected with the anisotropy of these films. Thickness dependence of perpendicular anisotropy and that of angular dispersion of the easy axis of the local anisotropy of amorphous Tb15Gd15Fe70 films suggest the formation of small microcrystals in the films to produce the perpendicular anisotropy.