Passive RF band-pass filters in an LTCC module made by fine-line thick-film pastes

Low-temperature co-fired ceramic (LTCC) materials offer a good possibility to bury passive components and to produce compact electronic circuits. Thes e properties were utilised in this study to realise a passive band-pass RF filter in the LTCC module. The filter consisted of planar inductors, capaci tors and microstrip lines. The component values of the filter structure wer e determined by using the APLAC circuit simulator, Commercial fine-line thi ck-film Au paste and shrinkage-matched LTCC Ag pastes were used to print na rrow conductor lines by gravure-offset-printing on different LTCC sheets. N arrow conductor lines down to 50 mum wide were printed successfully without shrinkage mismatch during firing. A network analyser and different microsc opes were used to study, respectively, the electrical and material properti es of the patterns and filters. Variations of the printed line widths and o f the electrical values of the patterns and filters were about +/- 10%. The highest centre frequency of the realised filters was about 2 GHz. (C) 2001 Elsevier Science Ltd. All rights reserved.