Abstract In gravure offset printing, ink is transferred with the help of an offset material from a patterned gravure plate to a substrate. This thesis is concerned with the study and further development of this printing process for electronics; on alumina, glass and polymers. The work has been divided into five parts. In the first section, the printing process is described. The second section describes the composition of the inks for gravure offset printing and the resulting ink properties. It also presents the ink transfer mechanism; the model that explains how the ink is transferred between an offset material and a substrate. The third chapter details the printing process explained by a solvent absorption mechanism. The forth chapter describes the firing/curing of printed samples and their properties. The last chapter describes applications of the method. The inks used to produce conductors on ceramics (ceramic inks) and conductors on polymers (polymer inks) contain silver particles, and were under development for gravure offset printing. The major achieved properties were the high ink pickup to the offset blanket and high transfer percentage to the substrate. 100% ink transfer from blanket to substrate for ceramic inks and almost 100% ink transfer for polymer inks was obtained. The printing of ceramic inks was able to produce 8 μm of relatively thick, 300 μm wide lines with < 10 mΩ/sq. resistance. The minimum line width for conducting lines was 35 μm, with one printing. Multi printing was applied producing as many as 10 times wet-on-wet multiprinted lines with 100 % ink transfer from blanket to substrate resulting in a square resistance of 1mΩ/sq. Polymer inks were able produce a square resistance of 20 mΩ/sq. for 300 μm wide lines after curing at 140 °C for about 15 min, and the minimum width was down to 70 μm. In the optimised manufacturing process, the delay time on the blanket was reduced to 3 s. In addition to ultra-fine-line manufacturing of conductors, the method enables the manufacture of special structures e.g. laser-solder contact pads with 28/28 μm lines/spaces resolution. With industrial printing equipment it is possible to produce 100 m2/h with the demonstrated printing properties.

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.