Process Integration of Inkjet Printing and Electroless Plating for LTCC Substrates

This paper reports on our latest development in mask-less patterning of conductors on LTCC (Low Temperature Co- fired Ceramic ) by integrating inkjet printing with electroless plating process. The objective of this process integration is to realize reliable, high aspect interconnections and passives on LTCC substrates. Due to the intrinsic properties of the inkjet printable ink, the printed ink typically forms thin film. Hence the resistance of the traces is much higher than conventional bulk metal traces. In this study, we aim to alleviate these limitations by integrating the inkjet printing process with electroless plating process. Co-fired LTCC was used as the substrate, and silver nano-particle colloidal solution was used as printing ink. Conductive lines were inkjet printed on LTCC substrates, followed by curing in conventional oven. Thickness of the conductive traces was successfully plated up to 76 mum. The optimization of inkjet printing process, surface study of inkjet printed seed layer and process integration are presented with details.