{"id":"cowos-r-l-routing","level":"package","name":"CoWoS-R and CoWoS-L: RDL and local silicon","shortName":"CoWoS-R and CoWoS-L: RDL and local silicon","role":"Distinguishes polymer/copper redistribution from RDL combined with dense local silicon links.","description":"CoWoS-R and CoWoS-L are different routing arrangements within TSMC’s package family. CoWoS-R uses an RDL interposer composed of polymer and copper routing. CoWoS-L combines an RDL-based interposer with embedded local silicon interconnects where denser connections are needed. These distinctions change the geometry and material system compared with a broad silicon interposer. A useful comparison keeps the same logic and memory endpoints while exposing where each route carries dense signals and distributes power. Larger package capability alone does not establish better yield, lower cost or interchangeable production capacity; those require a complete configuration and manufacturing boundary.","specs":[{"label":"CoWoS-R","value":"Polymer/copper RDL interposer","context":"A routing construction, not the same as a full silicon interposer."},{"label":"CoWoS-L","value":"RDL plus local silicon interconnects","context":"Dense local silicon and wider-area redistribution have different roles."}],"interfaces":[{"name":"Logic, memory and routing components","direction":"in","signal":"Compatible endpoints and route-specific fabricated structures"},{"name":"Integrated routing assembly","direction":"out","signal":"Dense local links plus package-wide signal/power paths"}],"tradeoff":"Concentrating fine routing locally can reduce the need for a broad fine-routing silicon plane while adding placement and heterogeneous-material integration tasks.","whyAI":"As accelerators need more logic and memory within a package, routing location and material choices become system design decisions.","related":["cowos-s-silicon-interposer","rdl-fanout-integration","emib-local-bridge","package-thermomechanical-reliability"],"sources":[{"title":"TSMC — CoWoS","url":"https://3dfabric.tsmc.com/english/dedicatedFoundry/technology/cowos.htm"}],"scale":"Multi-die package to selected joint; not dimensionally identical alternatives","kind":"integration","branch":"Packaging / Interposers, bridges and stacking","subbranch":"Alternative integration routes","mechanism":["Hold the compute and memory endpoint requirements fixed for the route comparison.","For CoWoS-R, identify the polymer/copper RDL interposer that connects those endpoints.","For CoWoS-L, place local silicon interconnects at dense-link locations and connect the wider RDL network.","Integrate compatible dies and substrate connections while controlling alignment and material deformation.","Compare complete routing, power, thermal, test and manufacturing requirements rather than one advertised package dimension."],"misconception":"CoWoS-S, CoWoS-R and CoWoS-L are not merely three names for identical geometry.","check":{"question":"Which feature distinguishes the CoWoS-L description from an RDL-only interposer?","options":["All memory is fabricated inside the logic die","Embedded local silicon interconnects for dense links","The absence of any conductive routing"],"answer":1,"explanation":"CoWoS-L combines local high-density silicon routing with a broader RDL-based structure."},"science":[{"title":"Dense-routing footprint accounting","equation":"A_dense = ΣA_local; fraction = A_dense/A_package","explanation":"Areas use the same unit and fraction is dimensionless.","assumptions":"Geometric bookkeeping only; lower dense-silicon area does not directly predict cost, yield, bandwidth or capacity."}],"prerequisites":["cowos-s-silicon-interposer","rdl-fanout-integration"],"learningObjective":"Identify the material and routing differences among CoWoS-S, R and L.","workstream":"W05","visualFamily":"package-route","engineeringExample":"Synthetic diagram: four local routing pieces of 10 mm² total 40 mm² inside a 1,000 mm² package outline. The 4% area fraction describes placement only; it is not a 96% cost or yield improvement.","evidenceNotes":"Public route definitions are checked; variant-specific tool capacity and customer queues are unknown. Production-history dates remain separate evidence entries.","labId":"library","scope":"Use the manufacturing investigation to trace compatible inputs, assembly and operating constraints; no current standalone calculator models this lesson’s full mechanism.","investigationId":"manufacturing","labScope":"Use the manufacturing investigation to trace compatible inputs, assembly and operating constraints; no current standalone calculator models this lesson’s full mechanism."}