[News] HBM5 Expected to Feature Immersion Tech as Cooling Becomes Key to HBM Race

As leading memory makers advance in HBM development, cooling technology is expected to become a key competitive factor once HBM5 enters commercialization—likely around 2029—according to Joungho Kim, a KAIST professor cited by The Elec.

As noted in the report, Kim explains that while packaging is currently the main differentiator in semiconductor manufacturing, the importance of cooling will rise significantly with the arrival of HBM5. He further points out that cooling is becoming increasingly critical as the base die begins taking on part of the GPU’s workload starting with HBM4, resulting in higher temperatures.

Kim emphasizes that the current liquid cooling method used in HBM4—where coolant is applied to the heat sink at the top of the package—will face limitations going forward. In response, HBM5 structures are expected to adopt immersion cooling, submerging both the base die and the entire package in coolant.

KAIST Teralab, headed by Professor Kim, unveils a technology roadmap for HBM4 through HBM8, covering the years 2025 to 2040. The roadmap outlines advancements in HBM architecture, cooling methods, TSV density, interposers, and more. Kim also notes that base dies are expected to shift to the top of the HBM stack through heterogeneous and advanced packaging technologies, as the report indicates.

Future HBM Architectures and Cooling Innovations

For HBM7, embedded cooling will be required to allow coolant to flow between the stacked DRAM dies, with fluidic TSVs introduced to enable this, according to the report citing Professor Kim. In addition to standard TSVs, new types of vias will be adopted—including through thermal vias (TTVs), gate TSVs, and TPVs.

HBM7 is also expected to integrate with new architectures such as high-bandwidth flash (HBF), where NAND flash is stacked in 3D similarly to DRAM in HBM. Looking ahead, HBM8 will feature direct mounting of memory on top of the GPU, as highlighted in the report.

Bonding Technology as a Key to HBM Performance

Moreover, Kim states that beyond cooling, bonding will emerge as another crucial factor in determining HBM performance. Beginning with HBM6, a hybrid interposer combining glass and silicon will be introduced, Kim indicates, as cited by the report.

TrendForce notes that the focus on HBM products in the DRAM industry is increasingly turning attention toward advanced packaging technologies like hybrid bonding. Major HBM manufacturers are considering whether to adopt hybrid bonding for HBM4 16hi stack products but have confirmed plans to implement this technology in the HBM5 20hi stack generation.

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(Photo credit: Micron)