Amkor Technology (AMKR) shares tumbled 6.24% over the 24-hour period, as investors reacted to a weaker-than-expected revenue outlook for the third quarter despite the company reporting record second-quarter results. The stock declined during regular trading and extended losses after hours following the earnings release.

The semiconductor packaging and test services provider posted Q2 revenue of $1.9 billion, up 26% year-over-year, and diluted earnings per share of $0.70, easily beating analyst estimates of $0.48. However, the company guided Q3 revenue to a range of $1.95 billion to $2.05 billion, falling short of the $2.10 billion consensus forecast, which sparked selling pressure.

Adding to investor concerns, management flagged a weaker outlook for its communications business due to memory supply constraints and operational disruptions tied to the migration of system-in-package production from Korea to Vietnam. Broader semiconductor sector weakness and profit-taking following the stock's recent rally on a major Nvidia advanced packaging partnership also contributed to the decline.