The contested question in chip packaging this year has been who gets to do the work. Packaging — the step that bonds finished silicon into a working part, stacks memory beside a processor and tests the result — has become a harder constraint on artificial-intelligence hardware than wafer fabrication itself. The assumption underneath a lot of trading was that Taiwan Semiconductor Manufacturing Co. (TSMC), which fabricates most of the world's accelerators, would keep the high-value packaging in its own plants and leave the independent contractors with low-margin wirebonding and test hours.

The past three weeks made that assumption harder to hold. TrendForce, a Taiwanese research house, reported on 5 August that TSMC is expanding its outsourcing of the chip-on-wafer front-end step — the part of its CoWoS (chip-on-wafer-on-substrate) flow that had stayed almost entirely in-house — to ASE, Amkor and SPIL. TSMC's own monthly CoWoS capacity is set to roughly double by the end of 2026, and the supply gap is still projected near 20%. Separately, DigiTimes has put TSMC's 2026 outsourced CoWoS volume at 240,000 to 270,000 wafers, the bulk of it to Amkor.

The businesses agree

ASE Technology Holding, the world's largest outsourced packaging and test provider and a supplier of flip-chip, fan-out and 2.5D interposer services to fabless chip designers, reported second-quarter revenue of TWD 191.06bn, up 34.1% year over year. That was an acceleration from 17.4% in the prior quarter. Gross margin reached 21.0%, against 16.1% a year earlier; gross profit grew 75.5% and operating income more than doubled. On the 30 July call management put utilization at 80-85%, described pricing as "very friendly," and said fourth-quarter margin in the assembly and test business should break through the 30% ceiling it has historically treated as structural.

Amkor Technology, the Arizona-headquartered number two and the main independent alternative to TSMC's in-house packaging, grew revenue 25.6% to $1.898bn. Gross margin rose to 16.8% from 12.0%, and factory utilization moved from the low 50s to the high 70s. Its Computing segment set a record and was guided to grow about 30% sequentially in the third quarter. In July it announced a multi-year, $1.5bn agreement with NVIDIA, with NVIDIA prepaying to fund US capacity, alongside a ten-year packaging partnership with TSMC.

ChipMOS Technologies, a Hsinchu-based specialist in memory test and display-driver packaging, is the sharpest turn of the three. Revenue rose 28.7% to TWD 7.38bn, its highest quarterly level since 2014, with memory revenue up more than 46%. Gross margin went to 18.0% from 6.6%, and a loss a year ago became TWD 892m of net income.

The capital spending says the same thing. ASE raised 2026 capex by $2bn to a record $10.5bn, with 70% of equipment spending aimed at leading-edge capacity, and its SPIL subsidiary broke ground on 11 August on a plant near NT$100bn dedicated to integrating CoWoS. Among the Asian names, JCET of Shanghai reported first-quarter net profit up 42.7% and has committed RMB 7.8bn to a high-end packaging plant in Lingang; Tongfu Microelectronics is part of the same wave of Chinese expansion, which totalled over RMB 27bn in the first half. Powertech Technology of Taiwan and Hana Micron of Korea, both memory-weighted packagers, do not publish comparable figures in our data.

What the shares did, and what they cost

All seven fell hard between 28 July and 3 August, inside the sector-wide rout that shed more than $1trn from chip stocks on reports SK Hynix was slowing high-bandwidth memory expansion. Intel, AMD and Micron fell with them; this was not a judgment on packaging. Every one of the seven has since rallied off its trough, by an average near a third — Hana Micron by 48%, Amkor by 38%, ASE by 27% — which leaves the group up about 180% over twelve months.

The interesting number is what did not recover. Amkor is priced at 12.7 times trailing gross profit and 12.3 times forward, against 18.8 times in May, when its market value was $19.1bn versus $14.7bn now. Its forward price/earnings ratio of 23.8 sits below its trailing 26.3, EV/EBITDA is 11.3, and it is the only one of the three generating positive free cash flow, at a 3.5% yield. ASE has de-rated too, despite a higher share price: trailing P/E of 44.3 against 52.6 in May, because earnings outran the stock. ChipMOS is the cheapest on cash profits at 8.7 times EV/EBITDA.

The honest bear threads are not about AI. Amkor's Communications division, still its largest, was guided down high single digits sequentially and faces headwinds into the first half of 2027, and depreciation on the Arizona campus is expected to dilute margins in 2027-28. ASE expects negative free cash flow to persist into 2027 while it runs roughly 20 construction projects at once, and says execution — not demand — is the risk.

The setup

Where it stands — Advanced packaging capacity is a binding constraint on AI hardware, and the foundries are outsourcing more of it, not less. Would confirm — Amkor third-quarter revenue landing at or above the $2.05bn top end of guidance, with Computing up near 30% sequentially. Would invalidate — ASE's fourth-quarter assembly-and-test gross margin failing to exceed 30%, or its 2027 leading-edge doubling target being pulled back. Watch next — Amkor and ASE third-quarter results in late October 2026, and the first CoWoS output from newly outsourced lines. Valuation — Amkor at 26.3x trailing and 23.8x forward earnings; 12.7x gross profit against 18.8x in May. ASE 44.3x trailing, versus 52.6x in May.