Taiwan's ABF substrate makers have flipped from years of oversupply to a shortage, and that is good news for their profits and shareholders.

• ABF substrates — the boards that carry AI chips — are now in short supply, so makers can raise prices instead of cutting them.
• AI chip designers and cloud companies are locking in long-term supply deals to reserve capacity, turning this into a sellers' market.
• Unimicron, Nan Ya PCB, Kinsus and Zhen Ding are all expected to hit record results this year and next.
• Unimicron already gets over 60% of sales from AI products and is a top supplier for Nvidia's next Rubin platform, with Intel's new packaging substrates due to ramp next year.
• Companies are spending heavily on new plants, with Unimicron and Nan Ya each committing tens of billions of Taiwan dollars, most of it aimed at ABF.

Outlook: Prices look set to keep climbing quarter after quarter with no ceiling in sight, as long as AI server demand holds up.