1
                                                                    Exhibit 99.3

                       AMENDMENT NO. 3 TO RIGHTS AGREEMENT

         AMENDMENT NO. 3, dated as of April 17, 2000 (the "Amendment"), to the
RIGHTS AGREEMENT, dated as of August 22, 1995 between HADCO CORPORATION, a
Massachusetts corporation (the "Company"), and THE FIRST NATIONAL BANK OF
BOSTON, a national banking association, as Rights Agent, as amended by Amendment
No. 1 dated March 18, 2000 and as amended by Amendment No. 2 dated March 28,
2000 (as so amended, the "Rights Agreement"). All terms not otherwise defined
herein shall have the meanings given such terms in the Rights Agreement.

                              W I T N E S S E T H:

         WHEREAS, on August 22, 1995, the Board of Directors of the Company (the
"Board") authorized and declared a dividend distribution with respect to each
share of Common Stock of the Company (the "Common Stock") outstanding as of the
close of business on September 11, 1995 constituting the right to purchase one
share of Common Stock of the Company, as reflected in the Rights Agreement; and

         WHEREAS, pursuant to Section 27 of the Rights Agreement, the Company
may cause the Rights Agreement to be amended at any time prior to the Final
Amendment Date (as defined in the Rights Agreement) without the approval of any
holders of certificates representing shares of Common Stock; and

         WHEREAS, on April 17, 2000, the Board authorized and approved the
further amendment of the Rights Agreement.

         NOW, THEREFORE, in consideration of the premises and the mutual
agreements herein set forth and for other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereby
agree as follows:

         1. The first sentence in Section 1(a) shall be amended and restated in
its entirety as follows:

                  "Acquiring Person" shall mean any Person who or which,
                  together with all Affiliates and Associates of such Person,
                  shall be the Beneficial Owner of more than 20% of the shares
                  of Common Stock then outstanding, but shall not include the
                  following Persons (each individually called an "Exempt
                  Person"): (i) the Company or any Subsidiary of the Company,
                  (ii) any employee benefit plan of the Company or of any
                  Subsidiary of the Company, (iii) any Person or entity
                  organized, appointed or established by the Company for or
                  pursuant to the terms of any such plan, (iv) Horace H. Irvine
                  II, Andrea P. Irvine and John O. Irvine (including any spouses
                  of any of the foregoing Persons; any lineal descendants,
                  including children and adopted children, of any of the
                  foregoing Persons or of any of their spouses; and, in addition

   2
                  to but not in limitation of the foregoing, any donees that are
                  blood relatives of any of the foregoing Persons or of any of
                  their spouses) and any or all of his or her or their heirs,
                  personal representative(s), trustee(s), executor(s),
                  administrator(s) and estates, as well as any trust created in
                  the past or future by or for the benefit of any or all of the
                  foregoing Persons referred to in this Section 1(a)(iv)
                  (including any trustees or successor trustees of any such
                  trusts or any successor trusts thereto), except that Horace H.
                  Irvine II shall not be deemed an Exempt Person at any time as
                  he (not including any of the other Persons referred to in this
                  Section 1(a)(iv)) should acquire (except by reason of any
                  inheritance or gift from any Person, or by reason of any
                  acquisition from any spouse and/or child and/or sibling of
                  his) the outstanding Beneficial Ownership of an additional 1%
                  or more of the outstanding Common Stock of the Company beyond
                  that of which he (not including any of the other Persons
                  referred to in this Section 1(a)(iv)) has Beneficial Ownership
                  on August 22, 1995, and further provided that any percentage
                  increase in his Beneficial Ownership of outstanding Common
                  Stock of the Company by reason of share purchases by the
                  Company shall not be deemed to be part of any such additional
                  1% or more or (v) Sanmina Corporation, a Delaware corporation,
                  and/or any of its subsidiaries.

         2.       That Section 7(a) shall be amended and restated in its
                  entirety as follows:

                  Subject to Section 7(e) hereof, the registered holder of any
                  Rights Certificate may exercise the rights evidenced thereby
                  (except as otherwise provided herein including, without
                  limitation, the restrictions set forth in Section 9(c),
                  Section 11(a)(iii) and Section 23(a) hereof) in whole or in
                  part at any time after the Distribution Date upon surrender of
                  the Rights Certificate, with the form of election to purchase
                  set forth on the reverse side thereof and the certificate
                  contained therein completed and duly executed, to the Rights
                  Agent at the office of the Rights Agent designated for such
                  purpose, together with payment of the aggregate Purchase Price
                  with respect to the total number of shares of Common Stock (or
                  other securities, cash or other assets, as the case may be) as
                  to which such surrendered Rights are then exercisable, at or
                  prior to the earlier of (i) the Final Expiration Date, (ii)
                  the time at which the Rights are redeemed as provided in
                  Section 23 hereof, (iii) the time at which the Rights expire
                  pursuant to Section 13(d) hereof, (iv) the time at which such
                  Rights are exchanged as provided in Section 26 hereof, or (v)
                  immediately prior to the Effective Time, as defined in the
                  Agreement and Plan of Merger, dated as of April 17, 2000 among
                  Sanmina Corporation, a Delaware corporation ("Sanmina"), a
                  wholly owned subsidiary of Sanmina and the Company, as may be
                  amended from time to time (the earliest of (i), (ii), (iii),
                  (iv) or (v) being herein referred to as the "Expiration
                  Date").
   3
         3.       Except as amended hereby, the Rights Agreement shall continue
                  in full force and effect.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]
   4
         IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. 3
to be duly executed, all as of the day and year first above written.

Attest:                                    HADCO CORPORATION

By: /s/ Patricia Randall                   By:/s/ F. Gordon Bitter
    ----------------------------------        ---------------------------------
     Name: Patricia Randall                   Name: F. Gordon Bitter
           --------------------------               ---------------------------
     Title: Vice President                    Title: Sr. Vice President and CFO
           --------------------------               ---------------------------


Attest:                                    FLEET NATIONAL BANK (As Successor to
                                           the First National Bank of Boston)



By: /s/ Paul L. Fori                        By: /s/ Katherine Anderson
    ---------------------------------          --------------------------------
     Name:  Paul L. Fori                       Name:   Katherine Anderson
           --------------------------               ---------------------------
     Title: Senior Account Manager              Title: Managing Director
           --------------------------               ---------------------------