OKI Circuit Technology (OTC), the printed circuit board business unit of the OKI Group, has developed design and production technologies for 180-layer, 15 mm-thick PCBs intended for wafer testing equipment used with high bandwidth memory (HBM) mounted on AI semiconductors.
The new configuration represents an approximate 45% increase in layer count and roughly doubled board thickness compared with the prior 124-layer, 7.6 mm-thick design. OTC plans to establish mass production technology and install required equipment at its Joetsu Plant in Joetsu City, Niigata Prefecture, with mass production and shipments scheduled to begin in October 2026. The plant has established capabilities in high multilayer, high-precision, large-format PCBs for semiconductor testing equipment.
Rising signal counts in latest AI semiconductors and increased chip density on wafers have driven requirements for higher-density (reduced pitch) and higher-layer-count PCBs in testing equipment. However, greater board thickness creates challenges in controlling via characteristic impedance, maintaining power supply performance where vias pass through power layers, and drilling fine, deep via holes. These constraints had previously limited practical single ultra-high-multilayer PCBs to 124 layers and 7.6 mm thickness.
OTC addressed the limitations through two new technologies: sintering paste for via bonding, which enables stacking and electrical connection of multiple multilayer PCBs by joining surface vias, and ultra-high-thickness PCB manufacturing technology supporting boards up to 15 mm thick. The company combined these approaches to create 180-layer, 15 mm-thick PCBs by stacking and connecting three 60-layer PCBs. This method applies established conventional technologies for via characteristic control, signal quality, and power supply performance to each individual multilayer PCB before stacking, achieving both higher layer counts and required performance.
The technologies target applications in AI semiconductors, AI servers, aerospace and defense, and next-generation communications. OTC will continue development of PCBs and related manufacturing technologies to align with ongoing advancements.
OTC is scheduled to exhibit the technologies at PCB East 2026 (Booth 313) at the DCU Convention Center in Worcester, Massachusetts, from April 28 to May 1, 2026.
OTC is headquartered in Tsuruoka City, Yamagata, with President Masaya Suzuki. HBM refers to next-generation high-bandwidth memory consisting of multiple stacked DRAM chips with a dedicated high-speed interface. A via is a hole that electrically connects layers within a multilayer PCB. Characteristic impedance represents the ratio of voltage to current in an AC circuit.
