As interposers and substrates approach their scaling limits, 2.5D packaging is moving toward 3.5D, with tighter D2D pitch, higher bandwidth density, and lower energy per bit to overcome reticle-driven constraints on lateral scaling.
Higher integration density makes yield increasingly critical to economics. Final yield compounds across process steps, so losses at any stage directly affect overall yield.
More HBM stacks, chiplets, substrates, and bonding interfaces increase integration complexity, while some defects are detected only late in the process flow. This tightens process-control requirements across the integration flow and increases the importance of advanced inspection.