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): November 18, 2014

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 November 18, 2014, executives of TTM Technologies, Inc. (the “Company” or “TTM”) 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 30, 2013, which was filed with the SEC on February 21, 2014, 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. For a reconciliation of adjusted EBITDA to net income, please see the Appendix included in Exhibit 99.1 to this Current Report on Form 8-K. 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.

Additional Information and Where to Find It

This communication may be deemed to be solicitation material in respect of the proposed Merger between the Company and Viasystems. The Company has filed with the SEC a registration statement on Form S-4, which includes a prospectus with respect to the Company’s shares of common stock to be issued in the proposed Merger and a proxy statement of Viasystems in connection with the proposed Merger (the “Proxy Statement/Prospectus”). The Proxy Statement/Prospectus was sent or given to Viasystems’ stockholders when the Proxy Statement/Prospectus was declared effective by the SEC, and it contains important information about the proposed Merger and related matters. VIASYSTEMS SECURITY HOLDERS ARE ADVISED TO READ THE PROXY STATEMENT/PROSPECTUS CAREFULLY BECAUSE IT CONTAINS IMPORTANT INFORMATION ABOUT THE PROPOSED MERGER. The Proxy Statement/Prospectus and other relevant materials (when they become available) and any other documents filed by the Company or Viasystems with the SEC may be obtained free of charge at the SEC’s website at www.sec.gov. In addition, security holders will be able to obtain free copies of the Proxy Statement/Prospectus from the Company or Viasystems by contacting either (1) Investor Relations by mail at TTM Technologies, Inc., 1665 Scenic Avenue, Suite 250, Costa Mesa, CA 92626, Attn: Investor Relations Department, by telephone at 714-327-3000, or by going to the Company’s Investor Relations page on its corporate website at www.ttmtech.com, or (2) Investor Relations by mail at Viasystems Group, Inc., 101 South Hanley Road, Suite 1800, St. Louis, MO 63105, Attn: Investor Relations Department, by telephone at 314-727-2087, or by going to Viasystems’ Investor Info page on its corporate website at www.viasystems.com.

No Offer or Solicitation

The information in this communication is for informational purposes only and is neither an offer to purchase, nor a solicitation of an offer to sell, subscribe for or buy any securities or the solicitation of any vote in any jurisdiction pursuant to the proposed transactions or otherwise, nor shall there be any sale, issuance or transfer of securities in any jurisdiction in contravention of applicable law. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended.

Participants in the Solicitation

The Company and Viasystems and their respective directors and executive officers may be deemed to be participants in the solicitation of proxies from Viasystems’ stockholders in connection with the proposed Merger and may have direct or indirect interests in the proposed Merger. Information about the Company’s directors and executive officers is set forth in the Company’s Proxy Statement on Schedule 14A for its 2014 Annual Meeting of Stockholders, which was filed with the SEC on March 14, 2014, and its Annual Report on Form 10-K for the fiscal year ended December 30, 2013, which was filed with the SEC on February 21, 2014. These documents are available free of charge at the SEC’s website at www.sec.gov, and from the Company by contacting Investor Relations by mail at TTM Technologies, Inc., 1665 Scenic Avenue, Suite 250, Costa Mesa, CA 92626, Attn: Investor Relations Department, by telephone at 714-327-3000, or by going to the Company’s Investor Relations page on its corporate website at www.ttmtech.com. Information about Viasystems’ directors and executive officers is set forth in Viasystems’ Proxy Statement on Schedule 14A for its 2014 Annual Meeting of Stockholders, which was filed with the SEC on March 14, 2014, and its Annual Report on Form 10-K for the fiscal year ended December 31, 2013, which was filed with the SEC on February 14, 2014. These documents are available free of charge at the SEC’s website at www.sec.gov, and from Viasystems by contacting Investor Relations by mail at Viasystems Group, Inc., 101 South Hanley Road, Suite 1800, St. Louis, MO 63105, Attn: Investor Relations Department, by telephone at 314-727-2087, or by going to Viasystems’ Investor Info page on its corporate website at www.viasystems.com. Additional information regarding the interests of participants in the solicitation of proxies in connection with the proposed Merger is included in the Proxy Statement/Prospectus that the Company filed with the SEC.

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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