Who makes glass-core substrates for AI data centers

Glass-core substrates are a still-emerging alternative to conventional ABF substrates (ABF / high-layer package substrates), aimed at the flatness, size, and layer-count limits that the largest AI accelerator packages are starting to run into. They occupy the same position in the chain as ABF substrates — between the interposer and the server board — but represent a materials shift rather than an incremental improvement on the existing substrate supply base, with a different set of suppliers, some overlapping with existing substrate and materials makers and others entirely new to the space. For investors, this is a call-option-shaped position rather than a current-revenue one: adoption depends on which upcoming accelerator generations qualify glass-core substrates as viable at volume, a decision made jointly by chip designers and packaging houses rather than by the substrate makers alone. Because it's an emerging technology rather than an established one, supplier lists here are the least settled of anywhere in this layer and should be treated as leads to verify rather than confirmed production relationships.