Fabrication of Smallest Vias in LTCC Tape

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Electronic products are getting smaller and smaller, this at the same time, when their functionality seems to rise continuously. The basis for that development is continuing miniaturization, function integration and high density interconnection in electronic packaging. Ceramic interconnection technology, such as low temperature cofiring ceramics (LTCC), may be a niche technology, but one which offers a range of unique features. It is used for applications, where reliability, miniaturization, and RF capability is of premier importance, such as automotive, military, space and medical electronics. Although the potential of high interconnection density is one of LTCCs current advantages, a further reduction in feature size is postulated. As one consequence, layer to layer interconnections (vias) have to be reduced in size. Via diameters down to 100 microns are already common in state of the art production lines. Scientific papers have recently reported the fabrication of micro vias with a diameter of 50 microns. But roadmaps indicate the need for an even further reduction of via diameters well below 50 microns. The presented paper deals with research works to fabricate vias in LTCC-tape with diameters of 50 microns and below. The fabrication of the via hole itself by mechanical punching or laser drilling is discussed. The subsequent process steps of via filling, fine line printing, stacking, lamination and sintering are addressed as well. Test substrates with 50 micron vias and 80 micron lines on HeraLocktrade tapes have been produced. The overall goal of the works is to assess the fabrication of smallest vias in LTCC tape and explore the feasibility and current technological limits of today's manufacturing technologies