Gravure offset printing for fabrication of electronic devices and integrated components in LTCC modules

• Main Author: Lahti, M. (Markku)
• Format: Doctoral Thesis
• Language: English
• Published: University of Oulu 2008
• Subjects: LTCC; LTCC-M; gravure-offset-printing; heat management; passive components
• Online Access: http://urn.fi/urn:isbn:9789514288944; http://nbn-resolving.de/urn:isbn:9789514288944

Abstract The thesis is concerned with the development of gravure-offset-printing and low temperature co-fired ceramic (LTCC) technologies for the miniaturisation of electronic devices and components. The development work has been verified by several applications. Several aspects of gravure-offset-printing have to be optimised in order to make it suitable for fine-line printing and these have been addressed in the study with a focus on the printing inks and plates. Gravure-offset-printing inks were developed from commercial thick-film pastes. The effects of different ink characteristics on some properties of conductor lines, such as line width and resistivity, were studied. The dependence of the conductor lines on the quality of the engravings in the printing plates was also studied. The narrowest line widths obtained were about 30 μm with an accuracy of ±5 μm. Various LTCC compositions and processing steps involved in the production of integrated electronic devices, and the properties of several fabricated devices are discussed. The devices include inductors, band-pass filters and resistors for the 1–2 GHz frequency range. Miniaturisation has been the main focus of attention. For example, the integration of high-permittivity tapes in addition to low-permittivity tapes has made the miniaturisation of filter structures possible. Compatibility between these tapes during firing was found to be good. LTCC technology was further developed by adapting a modified LTCC-on-metal (LTCC-M) approach. A traditional way of guiding heat away from a component is to place a heat-sink under the component and utilise thermal vias and solder balls. In this study high- and low-permittivity tapes were attached directly on a heat-sink. Different heat-sink options were evaluated and the best performance was achieved with an AlN heat-sink which was deposited by screen-printing a Au layer on it. High-power chips were attached directly on the heat-sink through cavities in the LTCC tapes. This approach also restricted the shrinkage of the LTCC tapes. The fabricated test structures and components proved the viability of the approach although the compatibility between the pastes and tapes was not optimal.