Connecting two large dies at fine pitch usually means a silicon interposer - expensive and area-limited. An alternative is a small bridge die embedded only where the dense connection is needed, leaving the rest of the package on cheaper substrate. Apple Inc., which designs its own advanced packaging, claims a fanout version of this in a 2021 grant.
US10943869B2, "High density interconnection using fanout interposer chiplet" (issued 2021-03-09), is classified in H01L 23/5385 (internal electrical connections / redistribution), H01L 25/0655 and H01L 25/105 (stacked/multi-chip assemblies), with a long chain of fanout and bump subclasses. The claim's core is using a fanout interposer chiplet - a small redistribution die - as the high-density bridge between larger components.
Construe the limitation against the alternatives. A full interposer connects everything; an embedded bridge (Intel's EMIB) connects locally; Apple's fanout chiplet uses a fanout-style redistribution die as that local bridge. The distinguishing element is the fanout redistribution structure on the bridge chiplet, not merely the presence of a bridge.
The design-around space is the bridge technology itself. EMIB embeds a passive silicon bridge in the substrate; a competitor could use that, or a glass-core bridge, or a full interposer, and avoid a claim tied specifically to a fanout interposer chiplet with its particular redistribution layers.
Apple's appearance here is notable for a portfolio analyst. Apple is a fabless customer of TSMC, yet it files its own packaging IP - because the package is where it differentiates its SoCs and chiplet-based M-series and A-series parts. This is design-house packaging IP, distinct from the foundry's.
For competitive intelligence, the takeaway is that the chiplet-bridge thicket spans tool makers (Intel), foundries (TSMC's CoWoS-L), and design houses (Apple, AMD). Each owns a slice defined by its bridge implementation, and freedom-to-operate for any 2.5D product means reading across all three.