Shares of Anaheim-based Multi-Fineline Electronix Inc. closed up about 18% Thursday on news that the printed circuit board maker indicated better-than-expected results for its December quarter.

The run up put the market value of the company, known as M-Flex, at about $615 million.

M-Flex said it expects sales of approximately $239 million for the December quarter, about even with a year earlier. Its gross margin is expected to be 12.2%.

The company’s printed circuit boards go into cell phones and other mobile devices.

Chief Executive Reza Meshgin said margins will likely exceed the company’s prior projections as more orders lead to “improved capacity utilization.”

Meshgin said a recovery from supply-chain disruptions caused by recent floods in Thailand helped drive the company’s sales increase. M-Flex expects year-over-year improvements on sales for the current quarter. Meshgin said margins will likely decline moderately as the pace slows in comparison on the prior quarter.

He said the second half of the year looks strong for M-Flex.

“Demand for our flex assemblies for both smartphones and tablets remains strong and we continue to expect year-over-year top-line growth and sequential gross margin expansion in the second half of 2012," he said.

Final results for the December quarter are expected later this month.

Today’s big gain comes two months after investors sent M-Flex shares down by 18%, to a market value of about $464 million, after it missed Wall Street expectations for its September quarter and lowered its outlook for the December period.

That prompted analyst downgrades from several analysts.