Veeco Instruments Inc. said Thursday it has agreed to purchase a California-based technology company for $815 million.

Veeco expects to close on its purchase of Ultratech Inc. in the second quarter, the company said in a news release.

The company will pay Ultratech shareholders $21.75 per share in cash and 0.2675 of a share of Veeco common stock for each Ultratech common share outstanding. Based on Veeco’s closing stock price on Wednesday, the transaction is valued at about $28.64 per Ultratech share, Veeco said.

Veeco said the deal’s value is about $550 million, net of Ultratech’s net cash balance as of Dec. 31.

Plainview-based Veeco’s stock price fell 90 cents to close at $24.85 on Thursday, a decline of 3.5 percent. Over the past 12 months, Veeco’s stock has risen more than 33 percent.

Ultratech, whose headquarters are in San Jose, makes lithography, laser-processing and inspection systems used to manufacture semiconductor devices and LEDs, the Veeco statement said.

advertisement | advertise on newsday

“We believe our complementary end-market exposure and customer relationships will create the ideal platform to accelerate growth,” Veeco chairman and CEO John R. Peeler said in a statement. “Ultratech is a great fit with our strategy to profitably grow our business and diversify our revenue.”

Veeco produces tools to make light-emitting diodes, hard drives and chips for wireless devices.

The boards of both companies have approved the plan, the Veeco statement said. The companies expect that Ultratech’s shareholders will own about 15 percent of the combined company once the deal closes. A Veeco spokesman said it is too soon to say whether the transaction will have any effect on the company’s Long Island workforce.