China is moving ahead of Korea in commercializing glass substrates. While Korean companies are validating individual processes and reviewing investments in mass production, Chinese companies have moved first to build production lines and are accelerating product manufacturing and customer qualification.
WG Tech recently began investing in a second-phase production line for through-glass via (TGV) glass substrates, according to industry sources on Sept. 26. The company entered the glass substrate business through TGV Circuits, its Hubei-based subsidiary established in 2022, and is now expanding mass-production facilities. Initial applications will target artificial intelligence (AI) computing chips and optical communications for data centers, including TGV glass substrates for 1.6-terabit-per-second optical modules and co-packaged optics (CPO).
WG Tech previously invested about 500 million yuan, or roughly 100 billion won, in the first phase to build a TGV glass substrate line with annual capacity of 100,000 square meters. It completed qualification with multiple customers in the first half of this year, with some products entering small-volume supply. The company plans to invest a total of 1.216 billion yuan, or about 250 billion won, to eventually expand annual capacity to 1 million square meters.
That is about eight times the annual capacity of 12,000 square meters at the first-phase plant built by SKC subsidiary Absolics in Georgia. Absolics plans to expand its second-phase high-volume manufacturing (HVM) line to about 72,000 square meters a year. But delays in stabilizing mass production at the first-phase plant have pushed back a detailed investment timetable and equipment installation plans.
Samsung Electro-Mechanics also remains in the process-validation stage for the first production line of GlaSSEM, its joint venture with Dongwoo Fine-Chem. Most equipment for individual processes has been selected, but validation is still required to link processes including glass cleaning, TGV processing, metallization and chemical mechanical polishing (CMP). Process stabilization and customer qualification will follow. LG Innotek has yet to begin full-scale construction of a production line.
"Korea is taking a long time to actually build production lines because companies are trying to validate each process, from front-end glass cleaning to processing, metallization and CMP, before making investment decisions," a Korean glass substrate industry official said. "China builds the equipment first, makes products and then has customers evaluate them, so in terms of commercialization speed, China is moving faster than Korea."
The difference in pace is also visible at trade shows in China. Chinese companies have displayed not only glass samples with vias but also finished assemblies that have undergone subsequent processes such as chip packaging. "Chinese companies are already showing finished glass substrates and final assemblies at exhibitions," an industry official said. "They are rapidly improving their technology by producing actual products and repeatedly going through trial and error based on customer qualification."
Investment in glass substrates has expanded in China, backed by government policies supporting advanced semiconductors and packaging. According to TrendForce, more than 18 listed Chinese companies, including WG Tech, have entered the glass substrate supply chain, spanning raw glass materials, TGV processing, metallization and process equipment.
BOE has invested about 993 million yuan, or roughly 180 billion won, to build a glass substrate pilot line. It has produced large-format, 24-layer glass substrates measuring more than 100 by 100 millimeters and is evaluating products incorporating central processing units (CPUs) and graphics processing units (GPUs) with customers. It plans to decide whether to invest in a mass-production line in the first half of next year. TCL subsidiary CSOT has also formed a dedicated glass substrate organization and is working to unveil prototypes and build a pilot line in the second half of this year. Optical components maker Crystal-Optech is developing TGV glass substrates for CPO and is a key supplier of waveguide components used to create optical paths for Corning's Glass Bridge.
China is accelerating glass substrate commercialization with a focus on its domestic market. It has built its own ecosystem spanning display, printed circuit board (PCB) and equipment suppliers, with domestic semiconductor and telecommunications companies such as Huawei serving as end customers. The country has effectively internalized processes ranging from glass pretreatment and TGV processing to metallization, redistribution layers (RDLs) and buildup.
"The technological level of glass substrates in Korea and China is now almost equivalent," an industry official said. "While Korea is improving the maturity of individual processes, China is accumulating mass-production experience by making actual products." The official added, "Because securing yield and reliability during mass production is critical for glass substrates, experience with customer qualification is key to advancing the technology."
