Combined Manufacture Methods for high density LTCC-substrates: thick film screen-printing, ink-jet, post-firing thin film processes and laser-drilled fine-vias

摘要

This paper highlights the possible combination of technologies like thick film screen-printing, ink-jet, and post-firing thin film processes in conjunction with laser-drilled fine-vias to produce high-density, miniaturized LTCC substrates. To obtain the silver pattern on the inner layers, both conventional thick film printing and ink-jet printing (using nano-silver particle dispersed ink) were applied on the ceramic green sheets. The ink-jet process made it possible to metallize fine lines with line / space = 30 / 30 μm. For inter-layer connections, fine-vias of 30 μm in diameter formed by UV laser was used. Then, these sheets were stacked on top of each other and fired to obtain a base substrate. On this base substrate, fine copper patterns for flip chip mounting were formed by a thin film process. The surface finish consisted of a nickel passivation and a gold layer deposited by electroless plating. The combination of the three patterning processes for conducting traces and UV laser drilling of fine-vias make it appear possible to realize fine pitch LTCC, e.g. for flip chip device mounting.