OKI Breaks New Ground with 124-Layer PCB for AI Testing

I was recording a podcast with Steve Sandler yesterday, and he was expressing how crazy the acceleration of the "speed curve" has become over the last couple of years, and the unprecedented demands on engineers he's been witnessing. To drive his point home, he asked me if I'd seen the news about the latest breakthrough announcement about the 124-layer PCB. Since I'd missed the news, I went looking for it this morning, and what I learned is worth sharing.

OKI Circuit Technology, Japan, has just made a big move in the world of advanced PCB design by releasing a 124-layer PCB, now the highest known commercial stack for semiconductor test equipment.

The kicker? They achieved this without increasing the conventional 7.6 mm board thickness (just shy of 1/3"), a long-standing constraint for these kinds of builds.

Image from OKI Circuit Technology

This is more than a step up, it’s a leap forward in wafer-level testing of high bandwidth memory (HBM) for AI chips. With ultra-thin 25 µm dielectric layers and low-loss materials (maybe Megtron 7?), this stack supports the kind of high-speed protocols AI engineers dream about: PCIe Gen6, CXL 3.0, and beyond.

With potential applications in AI, aerospace, defense, and high-frequency comms, OKI is showing what’s possible when materials science and manufacturing precision come together. While this is rarified air that most engineers will never see, I found the trickle-down implications to be interesting for the rest of us.

👉 Read the full article at The EEcosystem Substack page

Ref: All About Circuits, “OKI Reaches New Heights With a 124-Layer PCB,” by Luke James (May 9, 2025).