Patterning of electroless copper deposition on low temperature co-fired ceramic

The metallization of low temperature co-fired ceramic (LTCC) is typically done with commercially available silver or gold pastes using conventional screen printing processes. However, for some applications such as substrate integrated waveguides and high performance planar components where the metallization of vertical side walls is required, screen printing is difficult to apply. In such cases, electroless plating of copper can be employed to metallize the fired LTCC, which would also be a promising alternative to the high cost metals such as Ag and Au. In this study, electroless copper plating was combined with KrF excimer laser machining to deposit selective copper patterns on fired LTCC. Using this approach, a functional circuit was fabricated and electrically tested. The mask projection technique of the excimer laser can be used to create complex patterns on LTCC and initial work has been carried out to realize planar passive component layouts, including a capacitor and an inductor. The minimum feature size of the deposited copper that could be achieved in these designs was below 50 μm.