ASE Technology Holding is the world's largest outsourced semiconductor assembly and test (OSAT) provider, specializing in the back-end manufacturing steps that convert bare silicon wafers into finished chips. ASE operates two businesses: ATM (Assembly, Testing, and Materials), which accounts for roughly 60% of consolidated revenue, and EMS (Electronic Manufacturing Services), which accounts for the remaining 40% and is operated through USI Group. The ATM segment covers semiconductor packaging and testing — packaging encapsulates silicon dies and creates electrical connections, while testing validates chips at multiple stages of production. ASE offers a wide range of packaging formats, from traditional wire bonding for mainstream chips to advanced LEAP technologies (including 2.5D, 3D IC, and System-in-Package) that are critical for AI accelerators and high-performance computing. LEAP revenue reached roughly $1.6B in FY25 and is targeted to double in FY26. The EMS segment provides contract manufacturing of finished electronics across computing, communications, automotive, and industrial applications, but operates at thin margins with gross margins around 9% vs. 23-24% for ATM. ASE's customers are primarily fabless chip designers and IDMs. ASE is in an aggressive CapEx cycle, directing investment toward LEAP capacity and test equipment, with a strategic focus on scaling advanced packaging, expanding testing, and pivoting USI toward AI-adjacent applications like server power delivery and silicon photonics.