> ## Content Index > Fetch the complete content index at: https://www.sotkn.com/llms.txt > Use this file to discover other available public pages before exploring further. # Who Makes Advanced Packaging? OSAT Companies and TSMC CoWoS - URL: https://www.sotkn.com/explained/who-makes-advanced-packaging/ - Published: 2026-10-13T01:23:31.000Z - Updated: 2026-10-13T01:23:31.000Z - Description: OSAT companies are paid to package and test chips they did not make. For AI accelerators the scarce finish is advanced packaging — ASE, Amkor and JCET on the outsourced side, TSMC CoWoS on the captive side. Packaging slots are the stuck step. - Author: Sean - Tags: Players, #desk-explained EXPLAINED · Players · Last reviewed: 13 Oct 2026 · Next review: after TSMC Q3 2026 results (mid-Oct 2026) and ASE / Amkor next prints OSAT companies (outsourced semiconductor assembly and test) are firms paid to package and test chips made by someone else — attaching dies, memory and substrates into a finished module before it ships. **In short.** OSAT companies package and test chips made by others. For AI accelerators the money finish is advanced packaging: ASE, Amkor and JCET on the outsourced lane, and TSMC’s captive CoWoS on many leading GPUs. ASE’s ATM packaging took in NT$100.3 billion in Q2 2026; Amkor’s advanced products were $1.56 billion of $1.90 billion sales. The stuck step is packaging slots — TSMC’s chairman said in July 2026 that packaging capacity was limiting customers’ growth. Why an investor cares: a wafer is not a shippable AI GPU until packaging joins the compute die to HBM. OSAT companies and captive foundry packaging are paid at that finish. When slots bind, modules wait even if wafer starts look fine. For the mechanism, see [what CoWoS is](https://www.sotkn.com/explained/cowos-explained/) and [foundry and advanced packaging](https://www.sotkn.com/explained/foundry-advanced-packaging-explained/). ## Who makes advanced packaging? Four names matter for the AI finish line. Three are OSAT companies. One is a foundry packaging lane that is not an OSAT. | Player | Role | Latest dated print | | ---------------------------- | ------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------- | | TSMC (Taiwan) | Captive foundry packaging (CoWoS family). Not an OSAT — finishes its own wafers | Q2 2026 call (16 Jul): packaging so tight it limited customer growth | | ASE (Taiwan; ATM incl. SPIL) | Largest OSAT ATM lane; packaging + test for many customers | ATM packaging NT$100.3B; ATM revenue NT$126.1B, +36.3% YoY (30 Jul 2026) | | Amkor (US HQ) | OSAT; advanced products (flip chip, memory, wafer-level) majority of sales | Q2 sales $1.90B; Advanced products $1.56B; FY CapEx guide \~$2.5–3.0B (27 Jul 2026) | | JCET (China) | OSAT; heterogeneous integration and advanced packaging expansion | Q2 revenue RMB 10.36B; H1 computing electronics +40.4%; RMB 7.8B Shanghai plant (20 Aug 2026) | *Sources: ASE PR 30 Jul 2026; Amkor Form 8-K exhibit 27 Jul 2026; JCET PR 20 Aug 2026; TSMC Q2 2026 call. Roles only — not a market-share ranking or a tip sheet.* Think of two lanes. The outsourced lane: ASE, Amkor and JCET take wafers from many customers and return finished packages. The captive lane: TSMC runs CoWoS on wafers it already printed. Leading AI GPUs often need that captive lane. OSAT advanced lines add capacity beside it, but they are not a free substitute for every CoWoS-class SKU (our read). ## What do OSAT companies actually do? They assemble and test. After a foundry prints dies on a wafer, someone must cut, attach, wire or bump, place memory where needed, mount on a substrate, and test. OSATs specialise in that back-end work. Chip designers and foundries pay them per package and per test hour. ASE is the largest ATM (assembly, test and materials) name in the OSAT lane. In Q2 2026 its ATM packaging revenue was NT$100.3 billion and ATM segment revenue was NT$126.1 billion, up 36.3% year over year. Packaging was about 52% of ASE’s consolidated revenue that quarter. It spent US$840 million of its Q2 CapEx on packaging operations — tools and buildings before those lines ship more modules. Our Analysis on [ASE’s packaging stuck step](https://www.sotkn.com/analysis/ase-packaging-stuck-step-what-price-assumes/) maps what price already assumes about that CapEx. Amkor is the largest US-headquartered OSAT. In Q2 2026 it reported record net sales of $1.90 billion, up 26% year over year. Advanced products — flip chip, memory and wafer-level processing and related test — were $1.56 billion. Mainstream wirebond was $341 million. Packaging services were 88% of sales; test was 12%. It guided third-quarter sales of $1.95–2.05 billion and full-year CapEx of about $2.5–3.0 billion as it expands advanced packaging capacity. JCET is a China-listed OSAT with plants in China, Korea and Singapore. In Q2 2026 group revenue was RMB 10.36 billion, up 11.7% year over year. Computing electronics revenue rose 40.4% in the first half. In June 2026 it announced a RMB 7.8 billion investment in a new advanced packaging and testing plant in Shanghai — a capacity-add clock, not proof that AI package queues have cleared. ## Where does TSMC CoWoS fit if it is not an OSAT? CoWoS is TSMC’s branded advanced packaging family. It places a compute die and HBM stacks on a shared base, then onto a substrate. TSMC runs it as captive packaging on wafers from its own fabs. That is why this Players page includes TSMC beside the OSAT companies: for many AI accelerators, the scarce finish is still that captive slot. Full mechanism: [CoWoS explained](https://www.sotkn.com/explained/cowos-explained/). On TSMC’s Q2 2026 earnings call on 16 July 2026, chairman C.C. Wei said packaging capacity was “so tight that now it’s limiting my customers’ growth.” That is a primary IR statement: the attach step can throttle shippable AI modules even when front-end wafer commentary sounds fine. Markets door when capacity is the story: [TSMC CoWoS capacity](https://www.sotkn.com/markets/taiwan/tsmc-cowos-capacity/). ![Who makes advanced packaging — ASE ATM packaging, Amkor advanced products, JCET revenue, TSMC CoWoS slots as stuck step](https://storage.ghost.io/c/cd/10/cd10e222-131f-4ba4-b4a9-ca4214e8c12d/content/images/2026/10/osat-chart.png) Roles and dated prints, not a share ranking. ASE 30 Jul · Amkor 27 Jul · JCET 20 Aug · TSMC 16 Jul 2026. ## Who gets paid first? The packagers — OSAT or captive — when a package ships and is accepted. Toolmakers and substrate makers are often paid earlier, when lines and materials are built. Chip designers and cloud buyers earn later, when finished modules are installed and billed. ASE’s Q2 packaging CapEx of US$840 million is money paid to equipment and facility suppliers before those lines fill. Amkor’s $2.5–3.0 billion CapEx guide is the same clock. For the tools that print wafers before packaging, see [who makes wafer fab equipment](https://www.sotkn.com/explained/who-makes-wafer-fab-equipment/). For the memory that must match the package, see [who makes HBM](https://www.sotkn.com/explained/who-makes-hbm/). ![Who makes advanced packaging — who gets paid and where modules wait: ASE, Amkor, JCET, stuck step CoWoS slots](https://storage.ghost.io/c/cd/10/cd10e222-131f-4ba4-b4a9-ca4214e8c12d/content/images/2026/10/osat-infographic.png) Stuck step: CoWoS-class packaging slots. Sources: company Q2–H1 2026 materials; TSMC Q2 2026 call. ## Where is the stuck step? Packaging slots for CoWoS-class AI modules. TSMC’s captive lane is still the bind named in primary IR. OSAT advanced packaging is expanding — ASE’s packaging CapEx, Amkor’s CapEx guide, JCET’s Shanghai plant — but expansion plans are not the same as open slots for every AI SKU this quarter (our read). A second bind sits beside the slot: IC substrates, including ABF. A reserved packaging line without a matched substrate still waits. See [IC substrates and ABF](https://www.sotkn.com/explained/ic-substrates-abf-explained/). Hybrid bonding is the next attach style on some stacks: [hybrid bonding explained](https://www.sotkn.com/explained/hybrid-bonding-explained/). ## What to check next TSMC’s third-quarter 2026 results, expected mid-October 2026 — any update on packaging tightness versus the July “limiting growth” language. Then ASE’s and Amkor’s next quarterly prints for ATM packaging and advanced-product growth against CapEx. Our Wire on [CoWoS-L through 2028](https://www.sotkn.com/wire/cowos-l-mainstream-through-2028-wire/) tracks the architecture path. ## Common misconceptions - **People assume OSAT companies print the chip.** Actually foundries print the wafer. OSATs package and test. - **People assume TSMC CoWoS is an OSAT service.** Actually CoWoS is captive foundry packaging. TSMC is not an OSAT. - **People assume more OSAT CapEx means open AI package supply now.** Actually CapEx is tools and buildings first. Qualified slots for a named GPU SKU can still lag. - **People assume packaging and HBM are the same bottleneck.** Actually they are neighbours. Either can bind on a different clock. ## FAQ **What are OSAT companies?** OSAT companies are outsourced semiconductor assembly and test firms. Chip designers and foundries send them wafers; the OSAT packages the dies, often with memory, and tests the finished modules. They are paid for that finish work, not for printing the wafer. **Who makes advanced packaging for AI chips?** Two lanes. Captive: TSMC runs CoWoS packaging on many leading AI accelerators. Outsourced: ASE (including SPIL), Amkor and JCET sell advanced packaging and test as OSAT services. Roles differ; densest AI packages still often queue at TSMC. **What is the difference between an OSAT and a foundry’s packaging line?** An OSAT packages chips made by others. A foundry packaging line such as TSMC CoWoS is captive — it finishes wafers the foundry already printed. Both can bind AI module supply; they are not free substitutes for every package style. **How big is ASE’s packaging business?** In the second quarter of 2026 ASE’s ATM packaging revenue was NT$100.3 billion, and ATM segment revenue was NT$126.1 billion, up 36.3% year over year. Packaging was about 52% of ASE’s consolidated revenue that quarter. **Where is the stuck step in advanced packaging?** Packaging slots for CoWoS-class AI modules, especially at TSMC. On TSMC’s Q2 2026 call the chairman said packaging capacity was so tight it was limiting customers’ growth. Substrates (ABF) can bind beside that slot. **Is this a list of stocks to buy or sell?** No. Second Order Explained pages explain who does what and how the money moves. They do not give buy or sell calls. ## Related terms - [CoWoS](https://www.sotkn.com/explained/cowos-explained/) — TSMC’s captive packaging family. - [Foundry and advanced packaging](https://www.sotkn.com/explained/foundry-advanced-packaging-explained/) — the wider finish line. - [Who makes HBM](https://www.sotkn.com/explained/who-makes-hbm/) — memory that must match the package. - [Who makes AI chips](https://www.sotkn.com/explained/who-makes-ai-chips/) — designers and foundries upstream. ## Stack doors Layer: [Semiconductors](https://www.sotkn.com/stack/semiconductors/). Markets: [Taiwan](https://www.sotkn.com/markets/taiwan/) · [TSMC CoWoS capacity](https://www.sotkn.com/markets/taiwan/tsmc-cowos-capacity/). Analysis: [ASE packaging stuck step](https://www.sotkn.com/analysis/ase-packaging-stuck-step-what-price-assumes/). [Get the Wire](https://www.sotkn.com/#/portal/signup) — short daily notes when packaging CapEx, CoWoS slots or OSAT prints move. **How we check this** Figures come from ASE’s, Amkor’s and JCET’s own results releases and from TSMC’s Q2 2026 IR materials, listed under References. Each was re-checked against the saved source on 13 Oct 2026\. Roles describe what each company is paid to do; they are not market-share rankings. Where we judge how the lanes fit together, the wording says “our read”. This page explains how the money moves. It does not give buy or sell calls. **Last reviewed:** 13 Oct 2026 · **Next review:** after TSMC Q3 2026 results (mid-Oct 2026) and ASE / Amkor next prints Spot an error? [Tell us](mailto:sean@thekopinotes.com) and we will correct it and note the change here. [Our editorial standards →](https://www.sotkn.com/editorial-standards/) ## References 1. [ASE Technology Holding — Q2 2026 results (PR Newswire, 30 Jul 2026)](https://www.prnewswire.com/news-releases/ase-technology-holding-co-ltd-reports-its-unaudited-consolidated-financial-results-for-the-second-quarter-of-2026-302838714.html?ref=sotkn.com) — ATM packaging NT$100.3B; ATM revenue NT$126.1B (+36.3% YoY); Q2 packaging CapEx US$840M 2. [Amkor Technology — Q2 2026 results, Form 8-K exhibit 99.1 (27 Jul 2026)](https://www.sec.gov/Archives/edgar/data/1047127/000104712726000043/amkr6302026erex-991.htm?ref=sotkn.com) — Net sales $1.90B; Advanced products $1.56B; Q3 guide $1.95–2.05B; FY CapEx \~$2.5–3.0B 3. [JCET Group — H1 / Q2 2026 results (PR Newswire, 20 Aug 2026)](https://www.prnewswire.com/news-releases/jcet-reports-79-4-yoy-growth-in-h1-2026-net-profit-attributable-to-shareholders-accelerates-advanced-packaging-expansion-302856590.html?ref=sotkn.com) — Q2 revenue RMB 10.36B; H1 computing electronics +40.4%; RMB 7.8B Shanghai advanced packaging plant 4. [TSMC — Q2 2026 quarterly results hub (16 Jul 2026)](https://investor.tsmc.com/english/quarterly-results/2026/q2?ref=sotkn.com) — Earnings materials and call; packaging tightness cited on call 5. [TSMC — Q2 2026 Management Report (16 Jul 2026)](https://investor.tsmc.com/english/encrypt/files/encrypt%5Ffile/reports/2026-07/6f49632674bd2d0fd48cb65aaf89ec6ab510b559/2Q26%20ManagementReport.pdf?ref=sotkn.com) — Q2 CapEx US$15.70B; advanced packaging in technology mix 6. [TSMC — CoWoS technology page](https://3dfabric.tsmc.com/english/dedicatedFoundry/technology/cowos.htm?ref=sotkn.com) — Captive CoWoS-S / -R / -L family description 7. [Second Order — CoWoS explained (last reviewed 20 Sep 2026)](https://www.sotkn.com/explained/cowos-explained/) — C.C. Wei Q2 2026 call: packaging capacity limiting customer growth S **[Sean](https://www.sotkn.com/author/sean/)** Writes Second Order by TKN — a plain-English map of AI infrastructure and semiconductors for non-specialist investors. Focus: who gets paid, where money sticks, and which step is stuck. Covers AI infrastructure, semiconductors, and second-order stack reads. [Author page →](https://www.sotkn.com/author/sean/) · [Editorial standards →](https://www.sotkn.com/editorial-standards/)