Glass-LTCC-Interposer, a New Plattform for HF-Applications

This publication introduces a new interposer made from a thin glass substrate and a multilayer LTCC compound. Combination of these two material classes into an interposer substrate enables the application of thin-film and thick-film technology in one substrate. In this study thin
$(\mathbf{100}-\mathbf{200}\ \boldsymbol{\mu} \mathbf{m})$
Borosilicate glass AF45® is applied. The glass substrate includes through glass vias, filled with Au-paste to provide the electrical connection from the glass surface to the underlying electrical structures on the LTCC uppermost layer. The multilayer LTCC green tapes DuPont™ 9K7 are prepared with ground structures on the uppermost layer. After the final lamination of the LTCC-multilayers to the glass, a sintering step causes the mechanical joint of the two materials as an interposer substrate. To demonstrate the Glass-LTCC-Interposer for HF-applications, microstrip line, coplanar waveguide and ring resonator were simulated, designed and fabricated. For the fabrication of fine lines and spaces, the semi-additive technology applying Auresinate paste in combination with Au-galvanic deposition was utilized. Finally, the realized structures were characterized up to 60 GHz. The HF-investigations of the realized structures on the glass-LTCC-interposer confirm the accuracy of this structuring method. Furthermore, these investigations approve the new interposer as a proper substrate for HF-applications.