IC substrate maker Unimicron is trying to calm investors after a raid on its offices, but the stock still crashed — bad news for holders, and a scare for the AI supply chain.

• Taiwanese prosecutors searched Unimicron over a dispute about where some products were labeled as made.
• Unimicron rarely comments publicly, but issued a statement saying the products in question are ordinary circuit boards, not the ABF substrates used in AI chips.
• Investors dumped the stock anyway: it opened limit-down with a huge pile of unfilled sell orders and dropped out of Taiwan's club of stocks trading above NT$1,000.
• The worry is that a supply hit at Unimicron would ripple into the global chip packaging chain, since it is the top maker of these substrates.

Outlook: The investigation is still open, so the stock is likely to stay under pressure until prosecutors clarify how wide the case is.