UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): April 21, 2015

TTM TECHNOLOGIES, INC.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (714) 327-3000

(Former name or former address if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Beginning on April 21, 2015, executives of TTM Technologies, Inc. (the “Company”) will present information about the Company, including the information described in the slides furnished as Exhibit 99.1 to this Current Report on Form 8-K, to various potential lenders in connection with the proposed financing arrangements related to the Company’s proposed acquisition of Viasystems Group, Inc. (“Viasystems”).

The information in this Current Report (including the exhibit) is furnished pursuant to Item 7.01 and shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that section. This Current Report will not be deemed an admission as to the materiality of any information in this Current Report that is required to be disclosed solely by Regulation FD.

The Company does not have, and expressly disclaims, any obligation to release publicly any updates or any changes in its expectations or any change in events, conditions, or circumstances on which any forward-looking statement is based.

Forward-Looking Statements

Certain statements in this communication may constitute “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. The Company cautions you that such statements are simply predictions and actual events or results may differ materially. These statements reflect the Company’s current expectations, and the Company does not undertake to update or revise these forward-looking statements, even if experience or future changes make it clear that any projected results expressed or implied in this or other Company statements will not be realized. Further, these statements involve risks and uncertainties, many of which are beyond the Company’s control, which could cause actual results to differ materially from the forward-looking statements. These risks and uncertainties include, but are not limited to, general market and economic conditions, including interest rates, currency exchange rates and consumer spending, the ability of the Company and Viasystems to consummate the proposed Merger and realize anticipated synergies, demand for the Company’s products, market pressures on prices of the Company’s products, warranty claims, changes in product mix, contemplated significant capital expenditures and related financing requirements, and the Company’s dependence upon a small number of customers. Additional factors that may cause results to differ materially from those described in the forward-looking statements are set forth in the Annual Report on Form 10-K of the Company for the year ended December 29, 2014, which was filed with the SEC on February 27, 2015, under the heading “Item 1A. Risk Factors” and in the Company’s other filings made with the SEC available at the SEC’s website at www.sec.gov.

The Company does not undertake any obligation to update any such forward-looking statements to reflect any new information, subsequent events or circumstances, or otherwise, except as may be required by law.

Use of Non-GAAP Financial Measures

In addition to the financial statements presented in accordance with U.S. GAAP, TTM and Viasystems use certain non-GAAP financial measures, including “adjusted EBITDA.” The companies present non-GAAP financial information to enable investors to see each company through the eyes of management and to provide better insight into its ongoing financial performance.

Adjusted EBITDA is defined by TTM as earnings before interest expense, income taxes, depreciation, amortization of intangibles, stock-based compensation expense, gain on sale of assets, asset impairments, restructuring, costs related to acquisitions, and other charges. Adjusted EBITDA is

defined by Viasystems as earnings before interest expense, income taxes, depreciation and amortization, stock-based compensation, restructuring and impairment charges, costs relating to acquisitions and equity registrations, and other non-recurring items. Adjusted EBITDA is not a recognized financial measure under U.S. GAAP, and it does not purport to be an alternative to operating income or an indicator of operating performance. Adjusted EBITDA is presented to enhance an understanding of operating results and is not intended to represent cash flows or results of operations. The Boards of Directors, lenders, and management of TTM and Viasystems use adjusted EBITDA primarily as an additional measure of operating performance for matters including executive compensation and competitor comparisons. The use of this non-GAAP measure provides an indication of each company’s ability to service debt, and management considers it an appropriate measure to use because of the companies’ leveraged positions.

Adjusted EBITDA has certain material limitations, primarily due to the exclusion of certain amounts that are material to each company’s consolidated results of operations, such as interest expense, income tax expense, and depreciation and amortization. In addition, adjusted EBITDA may differ from the adjusted EBITDA calculations reported by other companies in the industry, limiting its usefulness as a comparative measure.

The companies use adjusted EBITDA to provide meaningful supplemental information regarding operating performance and profitability by excluding from EBITDA certain items that each company believes are not indicative of its ongoing operating results or will not impact future operating cash flows, which include stock-based compensation expense, gain on sale of assets, asset impairments, restructuring, costs related to acquisitions, and other charges.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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