Chinese memory makers are slowly but surely adopting the production of high-bandwidth memory (HBM) for AI and HPC processors. This week, Nikkei reported that a third China-based producer, Tongfu Microelectronics, began sampling its HBM products with select customers. Such action indicates that the ecosystem required to make this type of memory is developing. Interestingly, AMD is a major client and shareholder of Tongfu.
Truth to be told, Tongfu Microelectronics is not exactly a DRAM maker. The company is the world's third-largest outsourced semiconductor assembly and test (OSAT) service provider, and its most notable customer is AMD through their TF-AMD joint venture. Participation of a major OSAT in the Chinese HBM race makes its contribution even more intriguing. For now, Tongfu is sampling HBM2 memory packages with select customers, Nikkei claims, citing "multiple" sources.
HBM memory uses specially designed DRAM dies stacked on top of a base die and interconnected through silicon vias (TSVs). Tongfu Microelectronics is not a maker of memory or logic, so it sources DRAM dies, and base dies from third parties and then does another hard part: assembly and testing of these components into HBM2 stacks that can be used with various processors. It is unclear whether Tongfu actually offers HBM2 integration services, but the service is not listed on its website. However, Nikkei claims that it is a supplier of Huawei, which has AI processors with HBM (which does not mean that Tongfu offers Huawei appropriate services).
The history of Tongfu Microelectronics is also interesting. The year 2015 was not exactly AMD's best year as the company was nearly facing bankruptcy, so in late 2015 it agreed to form a joint venture with Nantong Fujitsu Microelectronics (NFME), contributing its assembly and test (ATMP) facilities in Suzhou (China) and Penang (Malaysia) in exchange for $371 million cash and an equity stake in the newly formed entity called AMD's Assembly, Test, Mark, and Packaging (ATMP). Eventually, NFME was integrated into Tongfu Microelectronics through corporate restructuring, and now the latter manages the joint venture TF-AMD together with AMD.
ATMP and then TF-AMD inherited AMD's advanced packaging IP, though it is unclear whether this includes vertically-stacked packaging in general and TSVs. Still, all AMD client CPUs are packaged in China by Tongfu.
Tongfu is not the only HBM assembler in China. ChangXin Memory Technologies (CXMT), China's most advanced DRAM maker, has been producing HBM2 for some time. In addition, Wuhan Xinxin also began to ramp up HBM2 production in March 2024.
