osat (outsourced semiconductor assembly and test)

OSAT (Outsourced Semiconductor Assembly and Test) Overview OSATs are third-party companies that provide semiconductor packaging (assembly) and testing services for fabless chip companies and IDMs that choose to outsource these back-end operations. Why OSATs Exist - Capital Efficiency: Packaging and test equipment costs hundreds of millions of dollars. OSATs spread this cost across many customers. - Specialization: OSATs focus exclusively on packaging/test, achieving higher expertise and efficiency. - Flexibility: Fabless companies avoid owning assembly capacity—scale up or down with demand. - Technology Breadth: OSATs offer many package types, while an in-house facility might support only a few. Major OSATs - ASE Group (ASE + SPIL): #1 globally. Headquartered in Taiwan. Full range of packaging and test. - Amkor Technology: #2. Strong in advanced packaging (flip-chip, fan-out, SiP). - JCET Group: #3. China-based. Acquired STATS ChipPAC for advanced packaging capabilities. - PTI (Powertech Technology): Major DRAM/NAND memory packaging. - Tongfu Microelectronics: Growing China-based OSAT. Services Offered - Wafer Probe/Sort: Test every die on the wafer before dicing. - Assembly: Die attach, wire bonding, flip-chip bumping, molding, singulation. - Advanced Packaging: Fan-out, 2.5D/3D integration, SiP, chiplet packaging. - Final Test: Functional test, burn-in, reliability screening. - Drop Ship: Ship tested parts directly to end customers. Industry Trend Foundries (TSMC, Intel) are moving into advanced packaging (CoWoS, InFO, Foveros), overlapping with OSAT territory. For cutting-edge AI chips, foundry-integrated packaging is becoming preferred. OSATs remain strong for mainstream and mid-range packaging.