Taiwan's three big ABF substrate makers fell hard as institutions sold, a short-term setback for holders even though the long-term AI story is intact.

• Unimicron, Nan Ya PCB and Kinsus all dropped more than 4% early before trimming losses to around 2%.
• The selling is about messy short-term positioning and thin buying interest, not weak demand.
• The group broke below its one-month trend line, and buyers are being told to wait rather than catch a falling knife.
• Analysts still see a supply shortage building in 2027–2028 as AI servers need bigger, thicker substrates — Nvidia's Rubin platform needs 71% more substrate area than Blackwell.
• Unimicron carries an extra weight: it was searched by prosecutors over suspected origin-of-goods fraud, a trust problem in a tightening US–China trade fight.

Outlook: Price targets are being raised on the shortage story, but the shares look shaky near-term until selling pressure clears.