HBM 2.5D / 3D Advanced Packaging (TSV, Interposer, KGSD) — OSAT package + memory stack

HBM 2.5D / 3D Advanced Packaging (TSV, Interposer, KGSD) — OSAT package + memory stack

**Companies committing:** tsmc, amkor-technology, amd, cerebras-systems, ase-technology, astera-labs.

**Opportunity:** HBM3E/HBM4 supply is the gating reagent for every AI accelerator (NVIDIA, AMD, Cerebras, hyperscaler ASICs). The packaging/test loop (CoWoS, KGSD, interposer reliability) is the real bottleneck — not the DRAM die.

The four-corner stack is hiring in sync: foundry (TSMC TSV), OSAT (Amkor, ASE), accelerator owner (AMD, Cerebras), and a 2.5D fabless (Astera). The hires are reliability + KGSD test + chiplet architecture — i.e. ramp/yield, not exploration. Whoever ships uHAST-clean HBM4 packages first owns 2027.

_Evidence caveat: A1-only on this product; A4/A5 not separable from broader semis._