Advanced Fan-Out RDL is fine-pitch redistribution layers on substrate enabling dense signal routing from chiplets to package pads — substrate-level wiring at ~10-15 μm pitch. RDL Purpose redistribute signals from micro-bumps to larger package pads. Trace Width 5-10 μm width; advanced lithography. Via Density micro-vias ~5-10 μm diameter at similar pitch. Dielectric low-k polymers (polyimide) or SiO₂. Copper Traces low resistivity routing; oxidation/passivation protected. Pattern Transfer lithography + etching or laser patterning. Multiple Layers stacking 2-4 RDL layers increases density. Via-to-Via spacing 20-50 μm between layers. Signal Integrity impedance control; crosstalk mitigation. Power Distribution large-area traces carry power; low resistance. Solder Mask protective coating; openings for bumps. Fan-Out signals spread from compact chip to larger substrate pads. Density advantage. Test Points integrated test access; online testing. Cost processes mature; volume reduces cost. Panel-Level large substrate processing increases throughput. Advanced RDL enables routing density matching logic for high-density packaging.