TSMC's CoWoS (Chip-on-Wafer-on-Substrate) packaging technology now underpins the AI accelerator boom, but its commercial origin, as recounted in a Digitimes retrospective, traces back to a program that started with a 0% yield figure and a customer willing to wait out the crisis.

The Digitimes account frames the episode as TSMC's first advanced packaging win — a milestone that, at the time, looked anything but assured. The packaging line's initial yields sat at zero. That a leading-edge logic foundry, whose entire business model rested on front-end process leadership, chose to iterate through a packaging yield collapse rather than exit the effort, marks the decisive turn in the story.

The context matters for how the commercial picture evolved. For most of the industry's history, packaging was a back-end commodity handled by OSATs (outsourced semiconductor assembly and test providers) such as ASE and Amkor. Foundries sold wafers; someone else cut, placed and molded them. TSMC's decision to move into advanced packaging broke that division of labor, and the 0% yield crisis was the moment the strategy could have died quietly.

It did not. CoWoS ultimately became the mechanism by which TSMC captured not just the wafer fabrication of high-performance compute devices but the integration of them — stacking logic dies beside high-bandwidth memory on an interposer and delivering the assembled module to customers such as Nvidia for its data-center GPUs. That vertical reach into packaging is now central to TSMC's competitive position in AI silicon, because accelerators built on large logic dies paired with HBM stacks cannot ship in volume without comparable capacity on the integration side.

The backstory also illustrates a broader dynamic in semiconductor supply chains. Advanced packaging, once an afterthought in the bill of materials, has become a capacity bottleneck in its own right. The demand signals that once pressured CoWoS availability through the AI boom exist precisely because a foundry invested in a packaging capability during a period when the yields said the investment was failing.

Digitimes presents this as part one of a longer account, positioning the 0% yield episode as the opening chapter of a story that runs through CoWoS's subsequent scaling and the ecosystem that formed around it. The remaining installments are expected to cover how the technology moved from a troubled pilot to a production mainstay — and how the packaging organization inside TSMC evolved from an experiment into a strategic pillar.

For competitors and OSATs, the lesson drawn from the episode is structural rather than technical: packaging yield problems at a foundry did not stay a foundry problem. They redefined who captures the value of integration in advanced-node products, and the share of the AI accelerator supply chain that TSMC now holds in packaging is the direct descendant of a program that once could not produce a single good unit.