The Bonders — Advanced Packaging Outliers
Modern AI chips aren't single chips — they're stacks of chips fused into one package.
To make AI chips faster, manufacturers stopped just shrinking transistors (that got too hard). Instead, they stack multiple chips on top of each other and fuse them with copper threads finer than a human hair. The machines that do that fusion (hybrid bonders) come from essentially one Dutch company . Around it sits a small group of specialty equipment names — wafer-level burn-in (Aehr), thermo-compression bonding (Kulicke & Soffa), 1.6T linear pluggable optics (AAOI). These are the 'outlier' picks: niche but irreplaceable.
4 names on the watchlist
The hybrid bonder duopoly — fusing chips at the nanometer
Dutch company that makes the machines that fuse two chips together with nanometer accuracy (called 'hybrid bonders'). Required to build the most advanced AI chips. Q1 2026 orders €269.7M — a record. Applied Materials owns 9% of them and may try to buy them outright. ADR is on the pink sheets, which is why most American investors have never bought it.
1.6T LPO — single hyperscaler order play
AAOI is positioned to be one of the very few suppliers of next-gen 1.6T 'linear pluggable optics' (LPO) — a cheaper, lower-power alternative to traditional transceivers. A single $200M+ hyperscaler order would re-rate the stock. Lumpy, binary, but huge optionality.
Wafer-level burn-in monopoly
Aehr makes the only volume machines that 'burn in' chips at the wafer level — running them hot to weed out defective ones before they're cut and packaged. Critical for SiC power chips and increasingly for high-reliability AI silicon. Tiny float, niche monopoly.
TCB transition + wire-bond cash cow
Kulicke & Soffa runs the legacy wire-bond business that funds their next-gen 'TCB' (thermo-compression bonding) machines — the alternative path to BESI's hybrid bonders for connecting stacked chips. Either TCB takes share or it doesn't, but the wire-bond cash flow underwrites the bet.
- Dylan Bristot, AI Bottlenecks · whatllm.org · May 2026