SK Hynix (000660.KS), the world's largest supplier of high-bandwidth memory (HBM) for AI accelerators, on May 26 disclosed a new in-package cooling architecture it calls iHBM, claiming a more than 30% reduction in thermal resistance versus existing HBM packages. The company said the technology is slated for deployment starting with HBM5, its next-generation product after HBM4 (Yonhap, May 26; ETNews, May 26; SK hynix press release via PR Newswire, May 25 US time).
\nThe disclosure matters because the next leg of the HBM contest, by SK Hynix's own framing and that of industry coverage, is no longer about how many DRAM die a vendor can stack but about how aggressively it can drain heat out of that stack without redesigning customers' boards. Businesskorea, summarizing the announcement, wrote that 'the core of the next-generation HBM competition is shifting beyond simple stacking technology to thermal control' (Businesskorea, May 26).
\nWhat iHBM actually does
\niHBM places silicon-based Integrated Cooling Elements (ICEs) inside the HBM package itself, sitting in the D2D PHY region — the die-to-die physical interface area that SK Hynix identifies as the hottest spot in a stacked HBM die. The ICEs are described as electrically non-conductive but highly thermally conductive silicon structures that open an additional heat-dissipation path out of the package, in effect acting as an embedded heat-spreader block (ETNews, May 26; Hankyung, May 26; SK hynix release).
\nThe company says the structure rides on its existing Mass Reflow-Molded Underfill (MR-MUF) wafer-level packaging flow rather than a new process, which it argues lowers the customer-side qualification burden because the System-in-Package footprint is unchanged (Businesskorea, May 26; SK hynix release). Kangwook Lee, senior vice president and head of package development at SK Hynix, said iHBM 'is an optimal solution for thermal management, combining our memory design capabilities with advanced packaging technology' (SK hynix press release via PR Newswire).
\nSizing the move against SK Hynix's franchise
\nThe announcement lands while SK Hynix still controls the bulk of the HBM market it helped define. The company's own 2026 outlook, citing third-party research, puts its share at 62% of HBM shipments as of Q2 2025 and 57% of HBM revenue as of Q3 2025, and points to roughly 70% projected share in the emerging HBM4 segment (SK hynix Newsroom, '2026 Market Outlook,' published on news.skhynix.com).
\nOther tallies of Q3 2025 cited by industry trackers give SK Hynix 53%, Samsung Electronics (005930.KS) 35%, and Micron Technology around 11% (Astute Group market summary, 2026). The two readings are not directly comparable — one measures shipments, the other a later-quarter revenue mix — but both leave SK Hynix as the incumbent that any thermal-led HBM5 transition has to dislodge rather than the challenger trying to break in.
\nThe 30%-plus thermal-resistance number is the only headline performance figure SK Hynix disclosed for iHBM; the company did not publish power-draw, bandwidth, or capacity claims tied specifically to the cooling element (ETNews, May 26; SK hynix release).
\nWhy a fund desk should care: the Samsung and Micron angle
\nThe HBM4 generation is precisely the cycle in which Samsung and Micron are trying to narrow SK Hynix's lead. Per industry reporting summarized this year, Samsung's HBM3E parts have been moving through customer qualification, and its HBM4 share with Nvidia is reported in the mid-20% range against SK Hynix in the mid-50% range, with Micron around 20% but with a mass-production schedule said to lag competitors by one to two quarters (TrendForce, February 2026; Astute Group, 2026). Micron has begun shipping HBM4 samples rated up to 11 Gbps, while SK Hynix has said its HBM4 development is complete with data rates around 10 Gbps and roughly 40% better power efficiency than the prior generation (Astute Group market summary, 2026).
\nIn that context, iHBM is essentially SK Hynix moving the goal posts from HBM4 stacking and speed — where competitors have closed in — to HBM5 thermal architecture, where it is asserting an in-package, drop-in advantage that does not force AI-accelerator customers to redesign cold plates or board layouts. Whether Samsung and Micron answer with their own in-package cooling structures, or with external liquid-cooling partnerships, is the open question the announcement creates.
\nA separate, smaller story in the same tape
\nOn the same day, Samsung Asset Management ('Samsung Unyong,' the asset management arm of the Samsung Group) launched a pair of 2x leveraged ETFs tracking Samsung Electronics and SK Hynix individually, with a third product tracking both names — colloquially dubbed 'Samjeon-Nix' by Korean retail press. Maeil Business Daily reported that 144,357 retail investors had registered for the mandatory pre-trading education required for single-stock leveraged ETFs in Korea (Maeil Business Daily, May 26; Yonhap, May 26; Hankyung, May 26).
\nThe fund launch is a flow story rather than a fundamental one, and the cluster of news services treated it as a separate Samsung Asset Management product release rather than an SK Hynix event. It is noted here only because it sits in the same news cluster and shows the depth of domestic retail positioning around the two memory names on the day of the iHBM disclosure.
\nWhat to watch next
\nThe near-term confirmation point for the iHBM thesis is not a financial release but a customer one: whether the first HBM5 design wins, expected to be announced by AI accelerator vendors as they detail their post-HBM4 roadmaps, name SK Hynix as the supplier of the cooling-integrated variant. SK Hynix has not published an HBM5 mass-production date in the iHBM disclosure (SK hynix press release; ETNews, May 26).
\nA second checkpoint is whether Samsung Electronics or Micron Technology unveils an in-package thermal-control answer at the next major industry events. Neither has announced an equivalent structure as of this disclosure, according to the coverage reviewed (Businesskorea, May 26; Astute Group, 2026).
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This article is for informational purposes only and does not constitute investment advice or a recommendation to buy or sell any security. All figures are sourced from company disclosures and reporting cited inline; readers should verify against primary sources before relying on them.
\nSources
\n- Yonhap — SK Hynix unveils iHBM thermal management, May 26, 2026
- ETNews — SK Hynix reveals iHBM cutting thermal resistance 30%, May 26, 2026
- Hankyung — SK Hynix embeds "ICE" inside HBM to tame heat, May 26, 2026
- SK Hynix press release via PR Newswire — iHBM thermal solution to boost AI performance, May 25, 2026
- Businesskorea — Next-gen HBM contest shifts from stacking to thermal control, May 26, 2026
- SK Hynix Newsroom — 2026 Market Outlook: HBM-led memory supercycle
- Astute Group — SK Hynix holds 62% of HBM; 2026 battle pivots to HBM4
- TrendForce — Samsung HBM4 initial share projected mid-20%, Feb. 9, 2026
- Maeil Business Daily — 144,357 retail investors line up for Samjeon-Nix 2x ETFs, May 26, 2026
- Yonhap — Samsung Asset Management launches single-stock 2x leveraged ETFs, May 26, 2026