EXHIBIT 32.2

                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

      In connection with the Annual Report of Plexus Corp. (the "Company") on
Form 10-K for the fiscal year ended September 30, 2004 as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), I, F.
Gordon Bitter, Chief Financial Officer of the Company, certify, pursuant to 18
U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley
Act of 2002, that to the best of my knowledge:

      (1)   The Report fully complies with the requirements of Section 13(a) or
            15(d) of the Securities Exchange Act of 1934; and

      (2)   The information contained in the Report fairly presents, in all
            material respects, the financial condition and results of operations
            of the Company.

/s/ F. Gordon Bitter
------------------------------------------
F. Gordon Bitter
Vice President and Chief Financial Officer
December 8, 2004

A signed original of this written statement required by Section 906, or other
document authenticating, acknowledging, or otherwise adopting the signature that
appears in typed form within the electronic version of this written statement
required by Section 906, has been provided to Plexus Corp. and will be retained
by Plexus Corp. and furnished to the Securities and Exchange Commission or its
staff upon request.

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