IC substrates serve as the core component in advanced chip packaging, fulfilling three critical functions: chip protection, electrical interconnection, and thermal management. They surpass conventional PCB capabilities to enable ultra-high-density connectivity between chips and mainboards. Utilizing specialized materials like ABF/BT, they support ultra-fine circuits (line/space to 8μm) and incorporate micro-bumps and redistribution layers for precise I/O connections with sub-micron accuracy. This technology meets rigorous signal and power integrity requirements while enabling advanced architectures like 2.5D/3D integration and chiplets, making it essential for AI, high-performance computing, and premium communication chips.