[News] TSMC Reportedly Expands Outsourcing of Key CoWoS Front-End Step to OSATs Amid Rising NVIDIA, ASIC Demand

TSMC is broadening its advanced packaging outsourcing. According to ETNews, sources say the company has decided to expand outsourcing of CoW (Chip-on-Wafer), a key step in its CoWoS packaging technology for AI chips, to OSAT companies including ASE. Unlike its previous practice of primarily outsourcing WoS (Wafer-on-Substrate), the latest move is intended to boost production capacity with key OSAT partners and help relieve packaging bottlenecks.

As the report explains, CoW (Chip-on-Wafer) refers to the process of attaching the chip to the interposer, while WoS (Wafer-on-Substrate) involves bonding the interposer to the main substrate. OSAT companies including ASE, Amkor, and SPIL have long manufactured WoS packages under technology licenses from TSMC. Although the company has also outsourced some CoW production, the outsourced volumes have reportedly remained limited.

The reported move to significantly expand CoW outsourcing is viewed as an effort to ease persistent bottlenecks in AI chip production. The report notes that demand has surged as both global AI chip developers led by NVIDIA and AI data center operators increasingly develop and deploy their own custom AI chips.

As noted by Mydrivers, NVIDIA has reportedly reserved approximately 800,000 to 850,000 wafers of TSMC’s CoWoS capacity for 2026, accounting for more than 50% of the company’s total CoWoS capacity for the year. Meanwhile, the report notes that TSMC’s monthly CoWoS capacity is projected to increase from approximately 70,000 wafers in 2025 to 130,000–140,000 wafers by the end of 2026. Even so, the report estimates that the CoWoS supply-demand gap will remain at approximately 20% in 2026.

Following TSMC’s reported outsourcing expansion, major OSAT providers are placing equipment orders for new production lines, ETNews says. Sources also say purchase order (PO) discussions are underway with South Korean materials, components, and equipment suppliers for CoW equipment, with investment expected to focus on dicing equipment for cutting wafers and interposers and bonding equipment for joining them.

OSAT Providers Prepare for Broader CoWoS Roles

OSAT companies had reportedly been laying the groundwork for broader CoWoS capabilities. According to a Mirror Daily report from June, sources say that with strategic backing from customers such as AMD, ASE and SPIL have allocated a portion of their 2026 advanced packaging capital expenditures to build their own CoW (Chip-on-Wafer) production lines, rather than focusing solely on oS (Wafer-on-Substrate) lines.

Sources cited by Mirror Daily say the initiative is not being led by TSMC, but instead reflects a new approach proposed by major chipmakers to address TSMC’s capacity constraints. Under this model, chipmakers would continue outsourcing wafer fabrication to TSMC before shipping completed wafers directly to ASE or SPIL for end-to-end CoWoS packaging.

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(Photo credit: TSMC)