OKI Develops 180-Layer, 15 mm PCB for AI Semiconductor Test Equipment

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OKI Circuit Technology, the OKI Group’s printed circuit board (PCB) business company, has successfully developed design and production technologies for 180-layer, 15 mm-thick PCBs intended for use in wafer testing equipment for high bandwidth memory (HBM) mounted on AI semiconductors. This represents an approximate 45% increase in layer count and approximately doubled board thickness compared to the previous 124-layer, 7.6 mm-thick configuration. OTC is pushing ahead with establishing mass production technology and setting up the required equipment at its Joetsu Plant, with the aim of starting mass production and shipment in October 2026. The plant, located in Joetsu City, Niigata Prefecture, which has a proven track record and advanced development and production capabilities in the field of high multilayer, high-precision, large-format PCBs for semiconductor testing equipment.

Due to the enormous numbers of signals handled by the latest AI semiconductors as well as rising number of chips mounted on wafers accompanying process miniaturization, PCBs for testing equipment must feature ever higher densities (reduced pitches) and layer counts. However, increasing the board thickness makes the characteristic impedance of vias more difficult to control; the power supply performance drops due to vias passing through power supply layers; and the drilling process for accurately boring fine, deep via holes involves technical limitations. Due to these constraints, the practical limits for single ultra-high-multilayer PCBs to address all these challenges had been 124 layers and 7.6 mm thickness, unable to meet future demand for high-speed, high-frequency, and high-density data transfer.

This time, OTC developed two technologies: Sintering Paste for Via Bonding, a conductive paste inter-substrate via bonding technology that allows multiple multilayer PCBs to be stacked and connected (by joining the vias on their surfaces); and a technology for manufacturing ultra-high-thickness PCBs measuring up to 15 mm thick. OTC combined these two technologies to establish design and production technologies for proprietary 180-layer, 15 mm-thick PCBs formed by stacking and connecting three 60-layer PCBs. By addressing via characteristic control, signal quality, and power supply performance issues for each multilayer PCB using well-established conventional technologies, individual multilayer PCBs can be stacked, enabling both ultra-high multilayering and superior performance and quality. This technology provides customers with the performance and quality needed to meet future demand for high-speed, high-frequency, and high-density data transfer.

OTC has developed these new technologies with an eye on fields expected to see significant growth—AI semiconductors, AI servers, aerospace and defense, and next-generation communications. OTC will continue to adapt to technological advancements and actively work on further development of PCBs and manufacturing technologies.