Planar inductors on an LTCC substrate realized by the gravure-offset-printing technique

The fabrication and properties of planar inductors on a low-temperature co- fired ceramic (LTCC) substrate are studied together with computational simu lations of their properties. One-and two-layer inductors with both square a nd spiral shapes were fabricated with and without a ground plane. The narro west line width of conductors was 60 mum and the size of the inductors was limited to 2.5 x 2.5 mm(2). Inductors were printed on the LTCC sheet by the gravure-offset printing. Via holes needed in the two-layer structures were made by excimer and Nd-YAG lasers, The layers were aligned and laminated a t 70 degreesC with a pressure of 20 10(8) N/mm(2) for 15 min, and the lamin ated layers were co-fired at a peak temperature of 850 degreesC. The dependence of the electrical values on the geometrical dimensions and m aterial properties of the inductor structures was studied both experimental ly and by simulation. The electrical measurements were made by an LCR meter and a network analyzer, and the dimensions of the printed conductors were measured by a surface profilometer. The measured inductance values varied f rom a few nH to hundreds of nH depending on the structure and the resonant frequencies of the coils ranged from 300 MHz for the microstrip coils up to several GHz for the one-layer inductor structures. The measured inductance values were higher than the calculated ones and the variation of the measu red electrical values was in the range of +/-10%.