A 2.5D integrated circuit (2.5D IC) combines multiple integrated circuit dies in a single package without stacking them into a

three-dimensional integrated circuit A three-dimensional integrated circuit (3D IC) is a MOS (metal-oxide semiconductor) integrated circuit (IC) manufactured by stacking as many as 16 or more ICs and interconnecting them vertically using, for instance, through-silicon vias (TSVs) or ...

(3D-IC) with

through-silicon via In electronic engineering, a through-silicon via (TSV) or through-chip via is a vertical electrical connection (via) that passes completely through a silicon wafer or die. TSVs are high-performance interconnect techniques used as an alternative ...

s (TSVs). The term "2.5D" originated when 3D-ICs with TSVs were quite new and still horrendously difficult. Chip designers realized that many of the advantages of 3D integration could be approximated by placing bare dies side by side on an interposer instead of stacking them vertically. If the pitch is very fine and the

interconnect In telecommunications, interconnection is the physical linking of a carrier's network with equipment or facilities not belonging to that network. The term may refer to a connection between a carrier's facilities and the equipment belonging to ...

very short, the assembly can be packaged as a single component with better size, weight, and power characteristics than a comparable 2D

circuit board A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich struc ...

assembly. This half-way 3D integration was facetiously named "2.5D" and the name stuck. Since those early days, 2.5D has proven to be far more than just "half-way to 3D." Some benefits: * An interposer can support heterogeneous integration – that is, dies of different pitch, size, material, and process node. * Placing dies side by side instead of stacking them reduces heat buildup. * Upgrading or modifying a 2.5D assembly is as easy as swapping in a new component and revamping the interposer to suit; much faster and simpler than reworking an entire 3D-IC or

System-on-Chip A system on a chip or system-on-chip (SoC ; pl. ''SoCs'' ) is an integrated circuit that integrates most or all components of a computer or other electronic system. These components almost always include a central processing unit (CPU), memor ...

(SoC). Some sophisticated 2.5D assemblies even incorporate TSVs and 3D components. Several

foundries A foundry is a factory that produces metal castings. Metals are cast into shapes by melting them into a liquid, pouring the metal into a mold, and removing the mold material after the metal has solidified as it cools. The most common metals pr ...

now support 2.5D packaging. The success of 2.5D assembly has given rise to "chiplets" – small, functional circuit blocks designed to be combined in mix-and-match fashion on interposers. Several high-end products already take advantage of these LEGO-style chiplets; some experts predict the emergence of an industry-wide chiplet ecosystem.

References

{{reflist Integrated circuits