OSATs (Outsourced Semiconductor Assembly and Test) are the factories that package and test chips for fabless and foundry customers. What they do: take finished wafers and turn them into usable chips through dicing, assembly, packaging, and final test. For [[What Is Advanced Packaging|Advanced Packaging]], this means building 2.5D/3D packages, integrating [[HBM and Package Integration]], and handling [[Chiplets and Heterogeneous Integration]]. Key players: [[Amkor - AMKR]], [[ASE Technology - ASX]], and others. These companies compete on technology capability, scale, and customer relationships. Why they matter for investors: OSATs are the direct beneficiaries of [[Packaging Capacity Bottleneck]]. When demand exceeds supply, utilization stays high and pricing improves. The challenge is capex intensity and customer concentration. [[OSAT Value Investing Framework]] explains how to underwrite these businesses. They trade like cyclical industrials but benefit from structural demand growth in advanced packaging. The economics: lower gross margins than chip design or foundries, but more stable than pure-play equipment. Cash flow visibility comes from multi-year capacity contracts with hyperscalers and chip companies. Links: [[Advanced Packaging MOC]], [[Packaging vs Foundry Economics]], [[Why Advanced Packaging Matters Now]] --- #semiconductors #investing