Amkor stock tumbles after warning on sales

SAN FRANCISCO (Reuters) - Amkor Technology Inc shares tumbled 10 percent on Thursday after the microchip packaging and testing company said revenue in its current quarter would fall below its previous forecast.

Amkor (AMKR.O) expected sales in the second quarter to decline by 1 percent to 2 percent from the first quarter. It previously forecast revenue would increase by 1 percent to 3 percent.

It cited previously disclosed disruptions in production arising from installing an enterprise resource planning (ERP) software system at its Philippine operations.

ERP software, such as that made by German software giant SAP AG, helps companies automate production, manufacturing and supply chain functions, often referred to as "back office" operations.

Amkor, based in Chandler, Arizona, said it currently was not able to gauge the impact of the sales shortfall on its previous forecast for gross margin and net income.

Gross margin is the percentage of revenue remaining after subtracting product costs and is a widely used measure of profitability at corporations.

Prior to the sales warning, Amkor was expected to have revenue in the second quarter of $703.8 million and a per-share profit of 30 cents, according to Reuters Estimates.

The company's stock rose 56 cents, or 6.3 percent in regular trading to close at $9.52. In extended trading after the revenue warning, the stock fell 10 percent to $8.56.

(Reporting by Duncan Martell; Editing by Andre Grenon)