Plexus Corp.
Sixth Amendment To Credit Agreement

This Sixth Amendment to Credit Agreement (herein, the “Amendment”) is entered
into as of June 30, 2005, by and among Plexus Corp., a Wisconsin corporation
(the “Borrower”), the Subsidiaries listed on the signature pages hereof, as
Guarantors, the several financial institutions listed on the signature pages
hereof, as Lenders, and Harris N.A., as successor by merger to Harris Trust and
Savings Bank, as Administrative Agent for the Lenders.

Preliminary Statements

A. The Borrower, the Guarantors, the Lenders and the Administrative Agent are
parties to a Credit Agreement dated as of October 22, 2003, as amended (the
“Credit Agreement”). All capitalized terms used herein without definition shall
have the same meanings herein as such terms have in the Credit Agreement.

B. As a result of the requirements under GAAP that the Borrower periodically
test goodwill for impairment, the Borrower has requested that the Lenders amend
the definition of “Adjusted EBITDA” set forth in Section 5.1 of the Credit
Agreement to exclude certain charges against income reflecting impairment of
goodwill, and the Required Lenders have agreed to do so, all on the terms and
conditions hereinafter set forth.

Now, Therefore, for good and valuable consideration, the receipt and sufficiency
of which is hereby acknowledged, the parties hereto agree as follows:

Section 1. Amendment.

Subject to the satisfaction of the conditions precedent set forth in Section 2
below, the Credit Agreement shall be and hereby is amended as follows:

1.1. Section 5.1 of the Credit Agreement is hereby amended by deleting the
definition of “Adjusted EBITDA” set forth therein and replacing it with a new
definition, to read in its entirety as follows:

“Adjusted EBITDA” means, with reference to any period, the sum of (a) EBITDA for
such period, (b) without duplication of amounts included in clause (a), EBITDA
of the Acquired Business subject of any Permitted Acquisition consummated during
such period for that portion of such period prior to the consummation of such
Permitted Acquisition, (c) one-time non-cash restructuring charges incurred
during such period (but limited to such charges incurred during the fourth
fiscal quarter of 2004 or the first or second fiscal quarters of 2005) as
described in the Borrower’s presentation to the Lenders dated October 19, 2004
in an amount not to exceed $13,000,000 in the aggregate, (d) all non-cash
restructuring and other non-recurring non-cash charges for such period other
than those included within Adjusted EBITDA pursuant to another clause of this
definition (not to exceed $20,000,000 in aggregate from July 13, 2004 through
the Revolving Credit Termination Date), provided that, for the purposes of this
clause (d), one-time charges representing accruals for Operating Lease payments
shall be deemed by the parties hereto to be non-cash charges notwithstanding any
contrary treatment of such charges under GAAP, and (e) non-cash charges of up to
$35.2 million (subject to adjustments due to currency fluctuations which affect
the Buyer’s goodwill accounts) which may be taken from time to time as a result
of impairment charges arising from SFAS No. 142 (Goodwill and Other Intangible
Assets) in connection with the Borrower’s goodwill.

Section 2. Conditions Precedent.

Upon the satisfaction of the following conditions precedent, this Amendment
shall become effective as of and with effect from and after the date first above
written:

2.1. The Borrower, the other Guarantors and the Required Lenders shall have
executed and delivered this Amendment.

2.2. The Borrower shall have paid to the Administrative Agent for the ratable
account of the Lenders an amendment fee in the amount of 0.05% of the aggregate
Revolving Credit Commitments.

2.3. The Borrower shall have paid to the Administrative Agent such fees as are
required to be paid pursuant to the terms of a letter between the Administrative
Agent and the Borrower dated June 22, 2005.

Section 3. Representations.

In order to induce the Lenders to execute and deliver this Amendment, the
Borrower hereby represents to the Lenders that as of the date hereof the
representations and warranties set forth in Section 6 of the Credit Agreement as
amended hereby are and shall be and remain true and correct (except that the
representations contained in Section 6.5 of the Credit Agreement shall be deemed
to refer to the most current financial statements of the Borrower delivered to
the Lenders) and that the Borrower is in compliance with the terms and
conditions of the Credit Agreement as amended hereby and no Default or Event of
Default has occurred and is continuing under the Credit Agreement as amended
hereby or shall result after giving effect to this Amendment.

Section 4. Miscellaneous.

4.1. The Borrower and the other Guarantors (collectively, the “Credit Parties”)
have heretofore executed and delivered to the Lenders the Collateral Documents.
The Credit Parties hereby acknowledge and agree that the Liens created and
provided for by the Collateral Documents continue to secure, among other things,
the Obligations arising under the Credit Agreement as amended hereby; and the
Collateral Documents and the rights and remedies of the Lenders thereunder, the
obligations of the Borrower, and the other Guarantors thereunder, and the Liens
created and provided for thereunder, remain in full force and effect and shall
not be affected, impaired or discharged hereby. Nothing herein contained shall
in any manner affect or impair the priority of the liens and security interests
created and provided for by the Collateral Documents as to the indebtedness
which would be secured thereby prior to giving effect to this Amendment.

4.2. By executing this Amendment in the place provided for that purpose below,
each Guarantor hereby consents to the Amendment to the Credit Agreement as set
forth herein and confirms that its obligations thereunder remain in full force
and effect. Each Guarantor further agrees that the consent of such Guarantor to
any further amendments to the Credit Agreement shall not be required as a result
of this consent having been obtained.

4.3. Except as specifically amended herein, the Credit Agreement shall continue
in full force and effect in accordance with its original terms. Reference to
this specific Amendment need not be made in the Credit Agreement, the Notes, or
any other instrument or document executed in connection therewith, or in any
certificate, letter or communication issued or made pursuant to or with respect
to the Credit Agreement, any reference in any of such items to the Credit
Agreement being sufficient to refer to the Credit Agreement as amended hereby.

4.4. The Borrower agrees to pay on demand all reasonable third party costs and
expenses incurred by the Administrative Agent in connection with the
negotiation, preparation, execution and delivery of this Amendment, including
the reasonable fees and expenses of counsel for the Administrative Agent.

4.5. This Amendment may be executed in any number of counterparts, and by the
different parties on different counterpart signature pages, all of which taken
together shall constitute one and the same agreement. Any of the parties hereto
may execute this Amendment by signing any such counterpart and each of such
counterparts shall for all purposes be deemed to be an original. This Amendment
shall be governed by the internal laws of the State of Illinois.

[Signature Pages to Follow]

1

This Sixth Amendment to Credit Agreement is entered into as of June 30, 2005.

Borrower

Plexus Corp.

By /s/ George W.F. Setton

      Name George W.F. Setton
Title Corporate Treasurer and Chief Treasury Officer

Guarantors

Plexus Services Corp.

     
By
  /s/ George W.F. Setton
George W.F. Setton
Treasurer

Plexus Intl. Sales & Logistics, LLC

     
By
  /s/ George W.F. Setton
George W.F. Setton
Treasurer

Plexus QS, LLC

     
By
  /s/ George W.F. Setton
George W.F. Setton
Treasurer
 
   

2

Plexus International Services, Inc.

By /s/ Angelo Ninivaggi

      Name Angelo Ninivaggi
Title President

PTL Information Technology Services Corp.

By /s/ Angelo Ninivaggi

      Name Angelo Ninivaggi
Title President

3

Lenders

Harris N.A., successor by merger to Harris Trust and Savings Bank, in its
individual capacity as a Lender and as Administrative Agent

By /s/ Thad D. Rasche

      Name Thad D. Rasche
Title Vice President

LaSalle Bank National Association

By /s/ Lou D. Banach

      Name Lou D. Banach
Title Senior Vice President & Senior Banker

National City Bank

By /s/ Tiffany Cozzolino

      Name Tiffany Cozzolino
Title Vice President

The Bank of Tokyo — Mitsubishi, Ltd., Chicago Branch

By /s/ Tsuguyuki Umene

      Name Tsuguyuki Umene

Title Deputy General Manager

4

Wells Fargo Bank, National Association

By /s/ Joan F. Kurate

      Name Joan F. Kurate
Title Vice President

Royal Bank of Canada

     
By
  /s/ Suzanne Kaicher
Name Suzanne Kaicher
Title Attorney-In-Fact

Bank of America, N.A.

By /s/ Sugeet Manchanda Madan

      Name Sugeet Manchanda Madan
Title Senior Vice President

KeyBank National Association

     
By
  /s/ Daniel DiMarco
Name Daniel DiMarco
Title Assistant Vice President

U.S. Bank National Association

     
By
  /s/ Caroline V. Krider
Name Caroline V. Krider
Title Vice President and Senior Lender
 
   

5