Influence of substrate thickness on performance of LTCC micro-transformer

This paper presents one aspect of research regarding various possibilities for performance improvement of integrated passive components. The paper deals with influence of substrate thickness on properties of spiral micro-transformer fabricated in LTCC technology. Designed geometry represents an interleaved spiral transformer printed on the top of one LTCC dielectric tape embedded in seven separate substrates that incorporate one to seven bottom tape layers. Obtained results of experimental characterization show trend of transformer performance improvement with increase of substrate bottom layers of transformer module. Inductance, Q-factor and coupling coefficient of transformer windings exhibit more than double enhancement of their values, while mutual inductance increases almost four times, in the lower RF frequency range. However, after certain limit increase of substrate thickness does not contributte much to transformers performance. This implies that optimal substrate thickness can be determined in order to obtain the best properties of micro-transformers.