Glass substrates and glass-core packaging — the post-organic-substrate path for HBM4/HBM5-class advanced packaging. Glass offers flatter surfaces, superior dimensional stability, lower CTE mismatch, and finer through-glass via (TGV) pitches than ABF organic substrates, all of which become essential at 14+ reticle-size interposers carrying 24 HBM5E stacks (TSMC 2029 roadmap). Pilot ramps are happening through 2026-2028 at Ibiden, Unimicron, Hoya (substrate blanks), and Samsung. Intel announced glass-core substrates for second-half 2020s; AMD and TSMC are co-developing with substrate partners.