A Self-Aligned Structure based on V-groove for Accurate Silicon Bridge Placement

As a lower cost alternative to silicon interposers with through silicon vias (TSVs), silicon bridges have been developed for high-performance computing (HPC) and/or heterogeneous integration. One of the most important steps of this advanced packaging technology is the accurate placement of the silicon bridge die with the organic substrate or with the dies requiring the high-density interconnections. In this paper, we demonstrated a novel mechanism for the straightforward and accurate insertion of silicon bridges into substrates. More specifically, mechanical fiducial in the form of V-groove were etch into the back side of functional bridges comprising Cu pillars, high-density Cu traces and insulating layers on their front side. Correspondingly, 4 SAC305 solder spheres were attached onto the substrate through thermal reflow to anchor the bridge. During the silicon bridge placing process, these 4 couples of concave and convex structures would pair and align each other automatically, determining the x, y and z final position of the silicon bridge. Experimental results showed that with such self-aligned structures, the placement drift of the silicon bridge could be confined to 2.5 μm.