Taiwan's biggest IC substrate maker Unimicron was searched by prosecutors, and its stock crashed from an all-time high — bad news for shareholders and a warning sign for the hot AI supply chain.

• Prosecutors raided Unimicron and took away two vice presidents, an accountant, and four laptops.
• The suspected issues are faked accounts by senior managers, disguising the origin of goods, and insider trading.
• The stock hit a record high in the morning, then dived close to the daily limit-down and closed sharply lower.
• Taoyuan prosecutors confirmed the search but gave no details, and the company has stayed silent so far.

Outlook: More details from prosecutors and a company response are the next things to watch, and the shares are likely to stay shaky until the scope of the case is clear.