Gf Securities released a research report stating that glass substrates and their related TGV (Through Glass Via) processes have become an important development direction for advanced packaging. Glass substrates enable board-level optical interconnection and 3D integration; these two technologies can achieve CPO (Co-Packaged Optics) system-level integration through co-design. The TGV process is a crucial technique for glass substrate processing, involving steps such as laser drilling, metal filling, and high-density wiring. The firm suggests focusing on (1) the demand for laser equipment driven by the processing of high aspect ratio glass micro-vias, and (2) other process segments. The main viewpoints from Gf Securities are as follows:
Glass substrates offer significant advantages and are expected to become the next-generation packaging material. Compared to traditional silicon and organic materials, glass possesses benefits including a low coefficient of thermal expansion, high mechanical strength, excellent electrical isolation properties, and low high-frequency signal loss. According to information from Chengdu MICC's official account, the thermal expansion coefficient of glass substrates is highly compatible with silicon chips, potentially reducing high-temperature warping issues by 70%. Additionally, their low surface roughness allows interconnect density to reach approximately ten times that of conventional substrates.
Taiwan Semiconductor Manufacturing Company (TSMC) is actively advancing its CoPoS packaging technology, with a pilot line expected to be fully constructed by June. TSMC's primary current packaging technology is CoWoS, which uses a silicon interposer as the interconnect material. CoPoS (Chip-on-Panel-on-Substrate) is TSMC's new generation advanced packaging technology, utilizing a rectangular glass substrate to replace silicon as the interposer. On one hand, glass substrates offer superior electrical performance, lower warpage, and enable larger packaging areas, leading to more efficient and stable connections. On the other hand, glass material costs are lower, and using large rectangular panels instead of traditional round silicon wafers can significantly improve wafer material utilization and production efficiency, thereby reducing costs. According to a report by Commercial Times cited by Chengdu MICC's official account, equipment delivery for the TSMC CoPoS pilot production line began in February, with the full line expected to be completed in June. Mass production is anticipated to gradually commence between 2028 and 2029.
The application potential of glass substrates in the CPO field is also considerable. Glass substrates enable board-level optical interconnection and 3D integration; co-design of these technologies can achieve CPO system-level integration. According to a presentation by Corning's research team at the 2025 IEEE 75th Electronic Components and Technology Conference, on one hand, using a thermal ion exchange process, a research collaboration between Corning NY and Fraunhofer IZM successfully fabricated a panel-level fan-out glass waveguide circuit for the first time, which can replace optical fibers to achieve efficient interconnection between computing units and CPO modules. On the other hand, utilizing the TGV process, glass substrates can enable 3D packaging of optical and electrical chips, achieving high-density integration for co-packaged optics and electronics. With further optimization, such as reducing waveguide loss to below 0.04 dB/cm and increasing the TGV aspect ratio, glass substrates are expected to become a key technological pathway for CPO applications at 102.4 Tbps and higher bandwidths.
Risk warnings include potential slower-than-expected progress in glass substrate processes, volatility in the semiconductor industry, and slower-than-expected growth in the advanced packaging market.
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