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38 I-CONNECT007 MAGAZINE I JULY 2026 of the vertical interconnect structure increases. For power-intensive applications, this requires ex- plicit thermal simulation and, in some cases, the strategic retention of thermal vias even within an ELIC architecture. Design to a Real Process Window This principle governs every other decision in ELIC. The right design target is not the best-case geom- etry on a capability chart. It is the actual process window the fabricator can repeatedly hold across production panels, material lots, and environmental variation. Preserving an extra increment of capture pad size, mask dam width, or layer-to-layer spac- ing where possible often has an outsized impact on yield and repeatability, and far greater than its ap- parent cost in routing space. Early engagement with the fabricator answers the questions that matter most before the layout is locked: Is this mask strategy realistic? Is this capture pad too aggressive? Where is registration most likely to drive yield loss? Which areas would benefit from a little more margin? That collaboration, before routing is complete, is where the most impactful DFM improvements happen. Reviewing for Movement, Not Just for Clearance Traditional design review asks: Do these features clear each other? ELIC review should ask: Do these features still work if they move slightly? That shift surfaces the right issues, where copper is barely protected, mask margin is smallest, vias are landing with the least tolerance, and structures depend on near-perfect alignment. It is a simple habit change with an outsized impact on first-build yield. How Do Yield, Cost, and Cycle Time Scale? Yield in ELIC is driven primarily by the cumulative defect opportunity at each sequential build cycle. Figure 2: At UHDI pitch, a 30 µm mask shift can reduce dam width to near zero and partially mask an adjacent pad. Solder mask strategy, including SMD/NSMD pad definition, dam width targets, and alignment tolerances, is a design decision, not a fabrication variable.