The layer of the semiconductor industry that gets paid per package assembled and per die tested had an unusually good July. ASE Technology Holding, the Taiwanese firm that is the largest chip packager outside Taiwan Semiconductor Manufacturing Company (TSMC) itself, reported July consolidated revenue of NT$73.8bn, up 43.2% year over year and 12.2% on June. ChipMOS Technologies, a Hsinchu house that assembles memory, mixed-signal and display-driver chips, reported July revenue up 43.6% year over year, its highest month since 2014, and attributed it explicitly to an artificial-intelligence-driven imbalance between demand and available capacity. Both prints landed after their shares had already fallen.

What these companies do, and what happened to them

Outsourced assembly and test firms — OSATs — take finished silicon wafers from foundries and turn them into packaged, tested chips. In the AI era that work has moved up the value chain: 2.5D silicon interposers, fan-out wafer-level packaging and the chip-on-wafer-on-substrate (CoWoS) process that binds accelerator dies to high-bandwidth memory.

Seven such companies fell together in the 30 days to 10 August: ASE (-9.8%), Amkor Technology, the Arizona-based packager and the only large American one (-22.8%), ChipMOS (-28.0%), Powertech Technology, a Hsinchu memory-packaging specialist (-9.8%), China's JCET Group (-23.3%) and Tongfu Microelectronics (-10.6%), and Korea's Hana Micron (-15.9%). The breadth is real; the path was not gradual. Every one took a 28-47% peak-to-trough drawdown inside three weeks, and every one has since rebounded 20-35% off its low. The trigger was mostly external — chip stocks shed more than $1 trillion in the week to 29 July as investors questioned hyperscaler returns — but these names fell three times as far as Nvidia or TSMC did over the same sessions.

The businesses: CONTRADICTS

Every member with reported numbers accelerated in the window the prices fell. ASE's revenue growth ran 7.8%, 9.2%, 17.4% and then 34.1% year over year across four quarters, with gross margin climbing from 17.1% to 21.0%. Its assembly, test and materials segment — 66% of revenue and 94% of operating profit — set a record, up 36%, and management guided the third quarter up 21-22% sequentially with advanced capacity running at 80-85% utilisation and pricing it called "very friendly." Amkor grew 25.6% with gross margin up 4.75 points and utilisation moving from the low-70s to the high-70s. Powertech grew 28.0% with margin up 5.85 points and net income nearly tripled; it also agreed in July to invest in a joint venture with Broadcom. Taiwan's OSAT industry as a whole grew 23.7% year over year in June.

One genuine company event sits inside the selloff. Amkor's largest division, legacy communications packaging, was guided down high single digits on phone-assembly migration to Vietnam and Android weakness, taking total third-quarter guidance to $1.95-2.05bn against $2.11bn consensus; the stock fell 24.7% in a day despite beating on revenue and earnings. Its AI-exposed computing segment set a record and was guided up roughly 30% sequentially, and it announced a ten-year advanced-packaging agreement with TSMC and a multi-year Nvidia partnership in the same print.

The structural fear — that TSMC keeps the AI packaging work for itself — did not hold up either. TrendForce reported on 5 August that TSMC is expanding outsourcing of the chip-on-wafer front-end step it had previously retained, on top of an estimated 240,000-270,000 CoWoS wafers already slated to outside partners in 2026.

The valuations: split three ways

Amkor is where the arithmetic is cleanest. At $54.43 it trades at 22.0x consensus 2026 earnings of $2.48 a share, against 32.3x for the same estimate at its 1 July peak — a ten-turn de-rating with the number unchanged — on 10.4x enterprise value to EBITDA and a 3.8% free-cash-flow yield, the only positive one here. The consensus target rose to $75.50 after results, in a $60-92 range. Its 2027 estimate implies only 7.9% growth, the Arizona depreciation drag showing through. Powertech sits at 22.7x forward against 28.6x trailing, and targets mass production of through-silicon-via memory packaging in the fourth quarter.

At the other end, JCET trades at 109.7x trailing earnings and Tongfu at 75.4x, both up over three months, after Tongfu's RMB 4.4bn placement to expand memory and computing packaging. ASE is inconclusive: its forward figures are currency-corrupted, and on trailing metrics (45.3x earnings, 19.3x EBITDA) it is the dearest of the Taiwan-US trio. Hana Micron, which supplies packaging to Samsung and SK Hynix, has no usable multiple at all — and faces KRW 120tn of in-house Korean packaging and memory investment announced on 2 July.

The cost is cash. ASE raised 2026 capital spending by $2bn to $10.5bn and expects negative free cash flow into 2027; trailing free-cash-flow yields are -1.1% at ASE and -6.0% at Powertech. Verdict: the business CONTRADICTS the month's tape; the valuation CONFIRMS only at Amkor and Powertech, and CONTRADICTS at the two Chinese listings.

The setup

Where it stands — Monthly revenue at the Taiwanese packagers accelerated through July while their shares fell, with only Amkor's phone division actually guided lower.

Would confirm — August monthly revenue at ASE and ChipMOS holding above 40% year-over-year growth, and ASE's third-quarter assembly gross margin printing 28-29%.

Would invalidate — ASE deferring any part of the $10.5bn 2026 capital plan, or advanced-capacity utilisation slipping below the 80-85% it reported.

Watch next — September monthly revenue releases in the first ten days of the month; Amkor's third-quarter results against $1.95-2.05bn guidance.

Valuation — Amkor 22.0x forward earnings versus 24.3x trailing and 32.3x at its 1 July peak; ASE 45.3x trailing, JCET 109.7x.