Issue link: https://iconnect007.uberflip.com/i/1541367
72 PCB007 MAGAZINE I NOVEMBER 2025 The definition of the term "interposer" is broaden- ing for a variety of technological reasons. • Chiplet architectures: Companies want to connect dies from different process nodes, foundries, or vendors. Interposers are becoming more than "wiring boards"—they are integration platforms. • Heterogeneous integration: Logic + memory + analog + photonics + RF can all sit on/ through the same interposer. • Power delivery & thermal constraints: Active interposers may help manage local power/ heat at the package level. Evolution of Interposers in Electronics Manufacturing 1. Early Generation (2000s – early 2010s): Classical Silicon Interposers • Definition: Passive silicon plates with through-silicon vias (TSVs) and redistribution layers. • Use case: 2.5D packaging, where multiple dies (e.g., logic + HBM memory) are mounted on an interposer and then onto a package substrate. • Examples: Xilinx FPGAs, AMD GPUs with HBM. Industry View: Interposers were synonymous with TSV-based silicon. 2. Broadening (mid-2010s): Organic & Glass Interposers Organic Interposers: • Built from laminates (Ajinomoto build-up film, BT resin). • Lower cost, coarser pitch than silicon. • Used where TSV density wasn't essential. Glass Interposers: • Entered research and early adoption. • Benefits: dimensional stability, low electrical loss, potential for very fine-pitch drilling. Industry Impact: "Interposer" now covered multiple material classes, not just silicon. 3. Redefinition (late 2010s – early 2020s): Bridges & RDL Fan-Out Fan-Out RDL Interposers: • Redistribution layers on reconstituted wafers or panels. • Function like interposers without TSVs. • Found in advanced fan-out wafer-level pack- aging (FOWLP). Embedded Bridges (localized interposers): • Intel's EMIB is the flagship example. • Small interposer "slivers" embedded only where needed, reducing cost vs. full silicon interposers. Industry Impact: The word "interposer" broadened to include partial/localized connection platforms. 4. Next-Gen (2020s → future): Active Interposers Definition: Interposers that not only redistribute signals, but also integrate active circuits: • Power management (voltage regulators). • Clock distribution and signal re-timing. • Possible security or interconnect logic for chiplet ecosystems. Example: Research in Europe (CERN, CEA-Leti) and commercial development by foundries and OSATs. Industry Impact: Blurring of lines between "substrate," "interposer," and "system-on-inter- poser." The industry now uses "interposer" as a broad umbrella term for anything that sits between dies and substrates to enable high-density integration. The definition is no longer limited to passive silicon with TSVs. Common Ground: HDI Substrates in advanced semiconductor packag- ing are, in many ways, miniature HDI PCBs. They use laser-drilled microvias, fine-line routing, and multilayer stack-ups, all of which are technologies pioneered in HDI PCB manufacturing.