Multi-Stacking Fan-Out Package I/O Density and Warpage

The patent transitions from planar fan-in packaging to three-dimensional fan-out packaging by stacking multiple semiconductor dies vertically. This dimensional change allows I/O pads to be redistributed across multiple layers, effectively increasing I/O pad density without compromising the throughput advantages of WLP technology.

The patent implements multi-stacking configurations where semiconductor dies are nested vertically one above another. This nesting approach allows multiple I/O interfaces to be packed into a smaller footprint area, resolving the contradiction between maintaining high throughput and increasing I/O pad density.

By moving to vertical stacking, the patent increases the spatial separation between I/O pads in the horizontal plane while maintaining high density through the third dimension. This effectively prevents solder bridging by distributing pads across multiple layers rather than crowding them in a single plane.

The patent introduces intermediate structures such as redistribution layers and buffer layers between stacked dies. These intermediary elements provide mechanical support and electrical redistribution, allowing I/O pads to be densely packed without direct solder contact that would cause bridging.

The patent divides the packaging process into discrete, standardized stages: die attachment, molding, planarization, and stacking. This segmentation of the complex fan-out process into manageable steps reduces overall process complexity while achieving high I/O pad density through systematic repetition of these modules.

The patent optimizes material parameters such as polymer composition, filler content, and curing conditions to simplify the molding and planarization processes. By carefully controlling these parameters, the patent achieves effective fan-out packaging with reduced process complexity.

The patent employs composite polymer materials with carefully selected filler content and composition in the molding compound. These composite materials provide mechanical compliance that absorbs thermal expansion mismatches between stacked dies, reducing stress and warpage while maintaining high I/O pad density.

The patent introduces buffer layers with specific mechanical properties at critical interfaces between stacked dies. These localized regions with tailored quality provide stress relief at points of highest stress concentration, preventing overall warpage while preserving the benefits of multi-stacking.