Silicon Interposer 2.5D is passive silicon substrate with embedded interconnects routing signals between chiplets, enabling heterogeneous integration — dense signal routing layer. Function bridges chiplets: receives, routes, delivers signals. Through-Silicon Vias vertical copper vias (10-50 μm diameter) route signals/power. TSV Pitch 10-100 μm via spacing. Finer: higher density. Micro-Bumps chiplets bonded via micro-bumps (10-20 μm pitch). Copper Bonding direct Cu-Cu bonding low-resistance interface. Substrate Thickness 100-200 μm silicon; mechanically robust, thermally conductive. Metal Layers multiple interconnect layers (M1-M6) for routing. Routing Density fine-pitch wires enable complex routing between dozens of chiplets. Signal Integrity impedance-controlled traces; crosstalk mitigation. Power Delivery dedicated power/ground vias; low impedance distribution. Clock Distribution low-skew tree distributes clock. Test integrated test logic enables testing interposer, connectivity. Thermal silicon conducts heat downward; 10-50°C junction temperature improvement. Thermal Vias extra vias for heat dissipation under hot spots. Mechanical silicon rigid; warping minimal. Supports chiplets. Stress CTE mismatch creates stress; underfill mitigates. Reliability TSVs stress at via; thermal cycling life important. Cost scales with TSV density, yield. Rework defective chiplets thermally reworked; interposer reused. Silicon interposers enable high-density 2.5D integration for advanced systems.