Orange County’s two largest printed circuit board makers are taking a bruising Tuesday on Wall Street amid softening demand and profit concerns.

Shares of Anaheim-based Multi-Fineline Electronix Inc. were down 21.6% in afternoon trading to a market value of $397.1 million after the company cut its margin outlook for the recently ended quarter.

The company said gross margins are projected at roughly 8.5%, below its prior forecast in late 2012 of 10% to 12%.

Sales in the December quarter are pegged to top $290 million, up 21% from a year earlier and beating Wall Street estimates of $270.2 million.

The company plans to release complete financial results on Feb. 7.

Investors seized upon the news that M-Flex recently scaled back production, which likely reflect a projected dip in Apple Inc.’s iPhone sales in the coming quarters.

Stifel Nicolaus analyst Aaron Rakers in a recent note to investors said the disclosure could “further fuel to the concerns over supply chain order cuts from Apple.”

Rakers noted that M-Flex generated 86% of its $201.5 million in sales in the September quarter from a single customer, believed to be Apple.

M-Flex makes circuit boards used in cell phones, smart phones and other mobile devices. The boards are flexible, which makes them easier to design into phones, barcode scanners and other devices.

TTM shares were down 14.5% to a market value of $647.2 million after Stifel Nicolas analysts downgraded the company to “hold” from “buy,” citing “myriad near and long-term issues, including soft demand, excess industry capacity, and ongoing margin pressure related to rising labor costs and increased pricing competition.”