Advanced packaging can limit how many AI accelerators reach customers, even when their compute chips have been fabricated. A finished 2.5D package needs compatible compute dies, high-bandwidth memory (HBM), interposers, substrates, materials, equipment, and qualified assembly capacity to come together. Manufacturers are expanding facilities, adding suppliers, and developing larger package formats, but announced plans and forecasts are not the same as proven high-volume output.
Why packaging can hold back accelerator output
In 2.5D integration, multiple dies are connected side by side through a high-density interconnect structure, often alongside HBM stacks. TSMC describes its CoWoS technology as a 2.5D approach for high-performance computing (HPC) and AI; its 2025 annual report discusses packages integrating multiple system-on-chip dies with HBM to increase computing capability and memory bandwidth. That makes packaging a specialized production stage, not a generic final assembly step.
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A compute die that is ready but cannot be combined with the necessary memory and interconnects is not a completed accelerator. Packaging capacity therefore contributes directly to the supply of finished systems, alongside wafer fabrication and the availability of the other package components.
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Demand, design commitments, and concentrated supply
TrendForce’s April 2026 analysis connects sustained pressure on CoWoS capacity to the sharp rise in AI demand since 2023. It says customers have been securing wafer capacity, CoWoS, HBM, substrates, and other materials ahead of need. TrendForce also characterizes the supplier concentration as temporary; that is an analyst’s assessment, not a measured market-share conclusion.
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The same analysis says many chip designs are finalized one to three years in advance. Treat that as TrendForce’s description of industry timing, not a universal design-cycle rule. Early commitments can help secure capacity, but decisions made well ahead of production also leave room for a mismatch between planned supply and eventual demand. The analysis does not establish that the commitments are binding purchase orders or quantify that mismatch risk.
Several inputs must be available together
TrendForce identifies constraints beyond CoWoS service capacity, including production equipment, substrates, packaging materials, and other critical components. HBM and silicon interposers are also part of the package architecture and supply picture. In practical terms, the dependencies run from package design and qualification through die and memory availability, interposer and substrate supply, packaging equipment, and integration into a finished package. This is a way to understand the linked dependencies, not a published industry process chart.
If an essential input is unavailable or has not been qualified for a design, adding floor space alone cannot deliver the finished package. Conversely, adding a supplier for one input does not remove constraints elsewhere in the chain.
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Announced capacity is not immediately usable production. A project must move from commitment and construction through equipment installation, qualification, and ramp-up. The available company announcements establish plans and development activity, but do not provide a common ramp schedule or comparable utilization rates across suppliers.
Amkor’s September 2026 announcement says commitments for its second Arizona phase exceeded the 33,000 square meters of cleanroom planned for phase one. It expects phase two to add 60,000 square meters, for about 93,000 square meters across the campus. Those are company plans and commitments, not verified completed operating capacity.
Some constraints are not quantified consistently
The available figures do not provide comparable current data on substrate capacity, HBM output, equipment lead times, yields, labor, or electricity across suppliers. It is therefore not possible to rank those factors by their contribution to the overall constraint. The planned high-voltage substation mentioned in the ASE-WUS project announcement indicates attention to reliable power at that site; by itself, it does not prove that power is a sector-wide bottleneck.
How manufacturers and suppliers are responding
The responses target different parts of the system. New packaging space addresses line capacity; a silicon-interposer agreement adds a source for one input; and panel or interposer developments aim to expand package formats or capabilities. Their maturity and stated output evidence differ.
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| Response | Constraint addressed | Status and what is established |
|---|---|---|
| Amkor Arizona campus expansion | Advanced packaging and test cleanroom capacity in the United States | Amkor announced the plan in September 2026: 33,000 m² planned for phase one, 60,000 m² expected in phase two, and about 93,000 m² across the campus. The figures are planned capacity, not confirmed operating output. |
| ASE-WUS Kaohsiung hub | Regional advanced AI packaging capacity and ecosystem collaboration | The companies announced a planned hub covering chip stacking, chiplet integration, CoWoS, and FOCoS. The announcement does not establish throughput or customer qualification status. |
| GlobalFoundries–TSMC silicon-interposer agreement | Supply diversification for silicon interposers used in TSMC’s CoWoS ecosystem | The companies announced a five-year initial agreement for U.S.-made interposers, with a framework for possible future expansion. It concerns this input, not relocation of the entire CoWoS supply chain. |
| ASE panel-level packaging line | Development of a larger-format approach for heterogeneous integration | ASE announced development of an automated 310 mm × 310 mm panel-level line in May 2026. The announcement does not establish volume output, yield, cost per package, or equivalence to wafer-level interconnect density. |
| TSMC CoWoS-L and larger-reticle packages | Package architecture and support for larger interposer designs | TSMC’s 2025 annual report describes CoWoS-L, combining an RDL interposer with embedded local silicon interconnect. The report said products using larger-reticle interposers were expected to begin volume production in 2026; that forecast is not confirmation that production began. |
Adding packaging facilities
Amkor presented its Arizona campus as a high-volume U.S. advanced-packaging and test site. The announced phases could add substantial planned cleanroom space, but their contribution to production depends on construction, equipment, qualification, and ramp-up.
TSMC’s 2025 annual report describes CoWoS alongside other advanced-packaging technologies, including InFO, SoIC, and COUPE, and says the company intends to add advanced-packaging facilities as part of its U.S. manufacturing investment. The report’s discussion of CoWoS-L and larger-reticle products also shows a technology response: expanding capability is not only a matter of duplicating existing lines.
Broadening regional and supplier options
ASE and WUS announced a planned advanced AI packaging hub in Kaohsiung, framed around demand from HPC, cloud services, and data centers. Their announcement names chip stacking, chiplet integration, CoWoS, and FOCoS. A collaborative hub can add options to the ecosystem, but its eventual capacity and qualification progress are not established by the announcement.
The GlobalFoundries–TSMC agreement addresses a narrower dependency. Its announced five-year initial term is for U.S.-based silicon-interposer supply for TSMC’s CoWoS ecosystem, with a framework for future expansion. It adds a source for an important package component; it does not mean that all CoWoS operations or materials are U.S.-based.
Developing larger-format packaging
ASE’s announced 310 mm × 310 mm panel line is a development effort, not evidence of a production-ready substitute for wafer-level packaging. Panel processing may offer a route to scale, but the announcement does not establish its package density, yield, economics, or qualification for particular products.
CoWoS-L represents a different approach within TSMC’s described CoWoS ecosystem: an RDL-based interposer is combined with embedded local silicon interconnect. TSMC’s 2025 report forecast that products with larger-reticle interposers would start volume production in 2026. Because the report states an expectation, it should not be treated as confirmation of the ramp’s completion.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the available capacity outlook does—and does not—show
TrendForce reported in June 2026 that CoWoS capacity was forecast to grow at a compound annual growth rate of more than 80% from 2022 to 2027, attributing that forecast to TSMC’s May 2026 technology symposium. This is a forward-looking growth estimate, not a realized rate or a measure of finished accelerator output.
TrendForce also expected expansion to narrow the supply-demand gap and said severe 2.5D shortages might moderate from 2027. That is a dated analyst outlook, not evidence that the constraint has been solved. Demand, project execution, qualification, and the availability of linked inputs all affect whether added capacity becomes usable output.
No comparable, independently measured total for global advanced-packaging capacity or current utilization is established in these company announcements and TrendForce analyses. The most defensible reading is that manufacturers are expanding multiple parts of the ecosystem, while the timing and effect on finished-package supply remain dependent on execution and coordinated availability of components.
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