Amkor Technology's stock experienced a significant pre-market plunge, dropping 5.27% as trading opened on Friday. The semiconductor packaging and testing services provider saw sharp selling pressure during the early session.

The decline came after the company announced the pricing of a secondary offering of 10 million shares of common stock by the Kim family, significant shareholders, at a public offering price of $48.75 per share. Secondary offerings typically create downward pressure on stock prices due to concerns about dilution and increased share supply in the market.

Despite the offering, the Kim family will continue to own over 49% of Amkor's common stock, maintaining their controlling interest in the company. The market reaction reflects investor apprehension about the additional shares entering circulation and potential dilution effects on existing shareholders.