Everyone knows AI needs chips. Fewer know that a finished AI accelerator isn’t one chip — it’s a chip and its high-bandwidth memory stitched together on a single package. The stitching is called advanced packaging, and TSMC’s version, CoWoS, became a bottleneck the industry didn’t see coming.
What packaging actually is
CoWoS — chip-on-wafer-on-substrate — places the logic die and the memory stacks side by side on a silicon interposer, wired together with enormous bandwidth. Without a slot on a packaging line, a perfectly good chip and perfectly good memory can’t become a usable product. For stretches of the build-out, packaging capacity — not chips — was the thing capping supply.
Why it’s so hard to add
Packaging capacity is concentrated, capital-intensive and slow to expand, and it leans on a small set of substrate and equipment suppliers upstream. That concentration is exactly what gives the companies who own it leverage when demand runs hot.
Following it through the chain
The interesting read-through isn’t just the packager — it’s the substrate makers and equipment names one step upstream, who get pulled tight whenever packaging does. THE ENTITY traces those links so a packaging squeeze becomes a visible list of exposed names, not a mystery. Research, not advice.
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