Combined Manufacture Methods for High Density LTCC Substrates: Thick Film Screen Printing, Ink Jet, Postfiring Thin Film Processes, and Laser-Drilled Fine Vias

Abstract

This paper highlights the possible combination of technologies such as 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 interlayer connections, fine vias of 30 μm in diameter formed by UV laser were 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, for example, for flip chip device mounting.