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.

“Multiple component package structures are described in which an interposer chiplet is integrated to provide fine routing between components. In an embodiment, the interposer chiplet and a plurality of conductive vias are encapsulated in an encapsulation layer.”— U.S. Patent No. 10,943,869 source

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.