Taiwan's biggest maker of chip carrier boards is under criminal investigation for relabeling China-made products as Taiwanese, a bad turn for a stock that had been one of the market's hottest AI plays.

• Prosecutors and investigators raided Unimicron's Taoyuan headquarters and a second plant in late August over suspected false country-of-origin labels.
• The tip-off came from named staff inside the company, angry after being told the aging Hejiang plant would be shut and sold with layoffs or transfers on the table.
• Sending half-finished boards from China to Taiwan for final work is not illegal on its own — the question is whether the extra work was substantial enough to count as Taiwanese-made, and whether the company meant to dodge US tariffs.
• Splitting production between China and Taiwan is an open secret across Taiwan's circuit-board and computer hardware industry, so rival makers are now nervously watching how the case is handled.
• Investors briefly pushed Unimicron past NT$1,000 a share on AI board demand; the raid has thrown that story into doubt.

Outlook: The ruling in this case will set the line for what counts as Taiwan-made in cross-strait production, with consequences reaching across Taiwan's whole AI supply chain.