Abstract
The trend toward heterogeneous integration of optoelectronic, electronic, and micromechanical components favors three-dimensional (3D) integration in which the components are not arranged side-by-side but rather in vertical stacks. This presents a particular challenge due to the fact that the stacked components have different geometric dimensions, and their contact surfaces are also dissimilar. Therefore, an intermediate substrate, the so-called interposer, with different formats (i.e., flip-chip, wire-bond, and hybrid flip-chip/wire bond) comes into play. Currently, the interposers are mainly made of silicon or glass, which incur huge additional costs to the packaged components. In this study, the unique advantages of additive manufacturing (AM) are exploited to realize organic interposers. The proposed interposers provide easy signal probing and flexible die-to-board integration in lower costs without any lithography process, drilling, plating, or any waste. Accordingly, the two state-of-the-art 3D printers (i.e., a monomaterial 3D printer and a bimaterial 3D printer) were utilized for the manufacturing of the interposer parts. The complementary circuitry for vias and through-holes was facilitated by also additive technologies, i.e., 2D-inkjet printing and microdispensing. Moreover, and to manifest the unique possibilities within AM for the next generation of interposers, two examples for 3D-printed interposers with incorporated added-features, i.e., pillars for flip-chip bonding and cavities for face-up die-attachment were realized. The assemblies were consequently assessed by electrical examinations. Conclusively, the main opportunities and challenges toward the full implementation of AM technology for the fabrication of organic interposers with added-features such as integrated multipurpose vias were discussed. Based on the results obtained from this study, it was found that bimaterial 3D printer was more efficient and powerful for the construction of interposers.
