TSMC Expands CoW Process Outsourcing, AI Packaging Bottleneck Expected to Ease
Alina Collins
TSMC will outsource the most technically demanding step of its CoWoS packaging — the CoW process — at scale to ASE and other OSAT firms. This means → the packaging bottleneck that has choked AI chip shipments is shifting from a solo capacity push to an industry-wide build-out.
What is CoWoS, and why has it been the bottleneck?
CoWoS — a 2.5D packaging technology that places an AI processor and high-bandwidth memory (HBM) side by side on a silicon interposer — is the standard method for packaging Nvidia and other AI chips. TSMC holds roughly 90% of global capacity.
The process has two stages: CoW (bonding the GPU die onto the interposer) and WoS (joining the interposer to the main substrate). CoW is the harder step; until now TSMC kept nearly all of it in-house.
In plain terms = front-end wafer fabrication can scale, but back-end packaging has been the narrowest pipe in the AI chip supply chain — and TSMC alone could not widen it fast enough.
What exactly changed in this strategy shift?
Previously TSMC outsourced only the simpler WoS step to OSAT firms such as ASE, Amkor, and SPIL. CoW outsourcing was minimal.
The core change: CoW production moves from small-scale trials to large-scale delegation. Multiple OSAT firms have begun procuring equipment for new lines and are negotiating supply orders with South Korean materials and equipment makers.
This means → TSMC is, for the first time, acknowledging that in-house expansion alone cannot close the AI chip supply gap — and handing out the most critical packaging step.
Why is TSMC making this move now?
The fundamental driver is surging AI chip demand: design houses led by Nvidia are placing record orders, while hyperscale data-center operators are also developing custom chips — demand is stacking from both sides.
Despite continued investment in packaging capacity, TSMC's supply-demand gap in packaging has never been fully resolved.
An industry source said: "This expanded outsourcing is TSMC's proactive attempt to lift capacity jointly with its key OSAT partners."
Who benefits most directly?
Equipment makers feel the orders first: demand for CoW-specific tools — wafer and interposer dicing, bonding — is set to surge. South Korean equipment sources say supply negotiations for laser-processing and bonding equipment are already under way.
OSAT firms (ASE, Amkor, SPIL) will significantly expand existing capacity, driving sizable equipment procurement.
This reflects a broader shift: AI packaging capex is spreading from TSMC's solo balance sheet across the entire OSAT supply chain.
Will the bottleneck actually be resolved?
The exact investment scale has not been disclosed; the market has no firm figures yet.
Whether CoW outsourcing materially eases the packaging bottleneck ultimately hinges on two variables: how fast OSAT firms can ramp capacity and what yields they achieve.
In plain terms = TSMC has handed off the work, but whether the partners can match TSMC's own quality bar remains an open question.
Content is for reference only, not financial advice.