# Substrate materials

Part ID: 1.14 · Layer 1 (Compute silicon & packaging)

The films, resins, glass cloth, and other specialty chemicals that go into building an ABF package substrate.

These are the raw material inputs to substrate manufacturing (ABF / high-layer package substrates): the resin film, glass cloth, and specialty resins that get layered and cured into a finished substrate. It's a step further upstream than the substrate makers themselves, and the taxonomy notes that at least one input — the ABF film itself — is effectively sole-sourced from a single supplier, which makes this one of the tightest single-point dependencies in the entire compute-silicon chain, upstream of every AI accelerator package that uses it.
For investors, a sole-source or near-sole-source material position is about as concentrated as supply chain exposure gets: it means substrate output, and by extension advanced packaging output, and by extension finished accelerator supply, can be gated by a single material producer's capacity decisions. That's a structural point the taxonomy makes explicitly rather than a market-share estimate, and it's worth treating as a genuine chain constraint rather than a hedge-able diversification risk, since there is reportedly no readily qualified alternative supplier at scale.

**AI delta:** Rising AI substrate volume and larger, higher-layer-count substrate designs pull directly on the limited capacity of the specialty films, resins, and cloth that go into them.

## Companies

| Company | Role | Confidence | Ownership | Ticker | Note |
|---|---|---|---|---|---|
| Ajinomoto | manufacturer | inferred | public | 2802.T | ABF film (effectively sole source) |
| Asahi Kasei | manufacturer | inferred | public | 3407.T |  |
| Mitsubishi Gas Chemical | manufacturer | inferred | public | 4182.T | BT resin |
| Nittobo | manufacturer | inferred | public | 3110.T | low-Dk T-glass cloth |
| Sumitomo Bakelite | manufacturer | inferred | public | 4203.T |  |

Confidence tags: disclosed = company/filing statement; reported = trade press or partner list; inferred = taxonomy lead.