<PAGE>

                                                                   Exhibit 10.51

                                                                  EXECUTION COPY

                                SECOND AMENDMENT



          SECOND AMENDMENT, dated as of December 27, 2000 (this "Amendment"), to
                                                                 ---------
the Credit Agreement, dated as of June 29, 2000 (as the same may be further
amended, supplemented or otherwise modified from time to time, the "Credit
                                                                    ------
Agreement"), among ACT MANUFACTURING, INC., a Massachusetts corporation (the
---------
"Parent Borrower"), the several banks and other financial institutions or
 ---------------
entities from time to time parties thereto (the "Lenders"), CREDIT SUISSE FIRST
                                                 -------
BOSTON, as syndication agent (in such capacity, the "Syndication Agent"),
                                                     -----------------
SOCIETE GENERALE, as documentation agent (in such capacity, the "Documentation
                                                                 -------------
Agent") and THE CHASE MANHATTAN BANK, as administrative agent (in such capacity,
-----
the "Administrative Agent").
     --------------------


                                  WITNESSETH:
                                  ----------

          WHEREAS, pursuant to the Credit Agreement, the Lenders have agreed to
make, and have made, certain loans and other extensions of credit to the Parent
Borrower; and

          WHEREAS, the Parent Borrower has requested, and, upon this Amendment
becoming effective, the Lenders have agreed, that certain provisions of the
Credit Agreement be modified in the manner provided for in this Amendment;

          NOW THEREFORE, in consideration of the premises herein contained and
for other good and valuable consideration, the receipt of which is hereby
acknowledged, the parties hereto hereby agree as follows:

     1.   Defined Terms. Unless otherwise defined herein, capitalized terms used
          -------------
herein which are defined in the Credit Agreement are used herein as therein
defined.

     2.   Amendments to the Credit Agreement. The Credit Agreement is hereby
          ----------------------------------
amended as follows:


               (a)  Amendments to Section 1 of the Credit Agreement.
                    -----------------------------------------------

                    (i)   Section 1.1 of the Credit Agreement is hereby amended
     by adding the following definitions:

               " 'Additional Term Commitment': as to any Lender, the obligation
                  --------------------------
of such Lender, if any, to make an Additional Term Loan to the Borrowers
hereunder in a principal amount not to exceed the amount set forth under the
heading "Additional Term Commitment"
<PAGE>

opposite such Lender's name on Schedule 1.1A. The original aggregate amount of
the Additional Term Commitments is $100,000,000."

               " 'Additional Term Lender': each Lender that has an Additional
                  ----------------------
Term Commitment or that holds Additional Term Loans."

               " 'Additional Term Loan Closing Date': the date on which the
                  ---------------------------------
Additional Term Loans shall be made."

               " 'Additional Term Loan Prepayment Amount': as defined in Section
                  --------------------------------------
2.9(e)."

               " 'Additional Term Loans': as defined in Section 2.1(c)."
                  ---------------------

               " 'Additional Term Percentage': as to any Additional Term Lender
                  --------------------------
at any time, the percentage which such Additional Term Lender's Additional Term
Commitment then constitutes of the aggregate amount of Additional Term
Commitments.

               " 'French Term Percentage': as to any French Term Lender at any
                  ----------------------
time, the percentage which such French Term Lender's French Term Commitment then
constitutes of the aggregate amount of French Term Commitments."

               " 'Indenture': the indenture pursuant to which the Subordinated
                  ---------
Notes are issued."

               " 'Local Thai Term Loans': the term loans to be made by certain
                  ---------------------
local lenders to the Thai Target in respect of the refinancing of the Existing
Thai Facilities."

               " 'Mandatory Prepayment Date': as defined in Section 2.9(e)."
                  -------------------------

               " 'Prepayment Option Notice': as defined in Section 2.9(e)."
                  ------------------------

               " 'Second Amendment Effective Date': the date on which the Second
                  -------------------------------
Amendment, dated as of December 27, 2000, to this Agreement became effective in
accordance with its terms."

               " 'Subordinated Note Documents': the collective reference to the
                  ---------------------------
Indenture, the Subordinated Notes and all other documents executed in connection
therewith."

               " 'Subordinated Notes': the unsecured subordinated notes issued
                  ------------------
pursuant to the Indenture."

               " 'Thai Term Percentage': as to any Thai Term Lender at any time,
                  --------------------
the percentage which such Thai Term Lender's Thai Term Commitment then
constitutes of the aggregate amount of Thai Term Commitments."

                    (ii)  Section 1.1 of the Credit Agreement is hereby amended
          by deleting in its entirety the definition of "Applicable Margin" and
          substituting, in lieu thereof, the following:
<PAGE>

               " 'Applicable Margin': (a) for Alternate Base Rate Loans which
                  -----------------
are (i) Revolving Loans, French Term Loans or Thai Term Loans, 1.50% per annum
and (ii) Additional Term Loans, 2.50% per annum and (b) for Eurocurrency Loans
which are (i) Revolving Loans, French Term Loans or Thai Term Loans, 2.50% per
annum and (ii) Additional Term Loans, 3.50% per annum; provided, that on and
                                                       --------
after the date which is six months after the Initial Closing Date, the
Applicable Margin with respect to Revolving Loans, French Term Loans and Thai
Term Loans will be determined pursuant to the Pricing Grid."

                    (iii) Section 1.1 of the Credit Agreement is hereby amended
     by deleting in its entirety the definition of "Term Commitment" and
     substituting, in lieu thereof, the following:

               " 'Term Commitment': as to any Lender, the sum of (a) such
                  ---------------
Lender's French Term Commitment, (b) such Lender's Thai Term Commitment and (c)
such Lender's Additional Term Commitment."

                    (iv)  Section 1.1 of the Credit Agreement is hereby amended
     by deleting in its entirety the definition of "Term Loans" and
     substituting, in lieu thereof, the following:

               " 'Term Loans': the collective reference to the French Term
                  ----------
Loans, the Thai Term Loans and the Additional Term Loans."

                    (v)   Section 1.1 of the Credit Agreement is hereby amended
     by deleting in its entirety the definition of "Thai Term Commitment" and
     substituting, in lieu thereof, the following:

               " 'Thai Term Commitment': as to any Lender, the obligation of
                  --------------------
such Lender, if any, to make a Thai Term Loan to the Borrowers hereunder in a
principal amount not to exceed the amount set forth under the heading "Thai Term
Commitment" opposite such Lender's name on Schedule 1.1A. The original aggregate
amount of the Thai Term Commitments is $25,000,000."

                    (vi)  Section 1.1 of the Credit Agreement is hereby amended
     by deleting in its entirety the definition of "Subsidiary Borrower" and
     substituting, in lieu thereof, the following:

               " 'Subsidiary Borrower': Bull Electronics Angers or any entity
                  -------------------
successor thereto."

                    (vii) Section 1.1 of the Credit Agreement is hereby further
     amended by inserting the following sentence after the last sentence of the
     definition of "Consolidated EBITDA" therein:

               "For purposes of calculating the Consolidated Leverage Ratio, the
Senior Secured Leverage Ratio and the Consolidated Fixed Charge Coverage Ratio,
each as set forth in Sections 7.1(a), (b) and (c), respectively, Consolidated
EBITDA shall be calculated (i) for the period ending December 31, 2000 by
multiplying the Consolidated EBITDA for the fiscal quarter then ended by four;
(ii) for the period ending March 31, 2001 by adding the Consolidated EBITDA
<PAGE>

for the fiscal quarter then ended and for the fiscal quarter ended December 31,
2000 and multiplying such total by two; (iii) for the period ending June 30,
2001 by adding the Consolidated EBITDA for the fiscal quarter then ended and for
the fiscal quarters ended March 31, 2001 and December 31, 2000, respectively,
and multiplying such total by a fraction the numerator of which is four and the
denominator of which is three."

                    (vii) Section 1.1 of the Credit Agreement is hereby further
     amended by inserting the following sentence after the last sentence of the
     definition of "Consolidated Interest Expense" therein:

               "For purposes of calculating the Consolidated Fixed Charge
Coverage Ratio as set forth in Section 7.1(c), Consolidated Interest Expense
shall be calculated (i) for the period ending December 31, 2000 by multiplying
the Consolidated Interest Expense for the fiscal quarter then ended by four;
(ii) for the period ending March 31, 2001 by adding the Consolidated Interest
Expense for the fiscal quarter then ended and for the fiscal quarter ended
December 31, 2000 and multiplying such total by two; (iii) for the period ending
June 30, 2001 by adding the Consolidated Interest Expense for the fiscal quarter
then ended and for the fiscal quarters ended March 31, 2001 and December 31,
2000, respectively, and multiplying such total by a fraction the numerator of
which is four and the denominator of which is three."

               (b)  Amendments to Section 2 of the Credit Agreement.
                    -----------------------------------------------

                    (i)   Section 2.1 of the Credit Agreement is hereby amended
     by adding, as Section 2.1(c), the following language after Section 2.1(b)
     thereof:

               "(c) Subject to the terms and conditions hereof, each Additional
Term Lender severally agrees to make a term loan (an "Additional Term Loan") to
                                                      --------------------
the Parent Borrower on the Additional Term Loan Closing Date in an amount not to
exceed the amount of the Additional Term Commitment of such Lender. The
Additional Term Loans may from time to time be Eurocurrency Loans or Alternate
Base Rate Loans, as determined by the Parent Borrower and notified to the
Administrative Agent in accordance with Sections 2.2 and 2.10."

                    (ii)  Section 2 of the Credit Agreement is hereby amended by
     deleting in its entirety Section 2.2 and substituting, in lieu thereof, the
     following:

               "2.2 Procedure for Term Loan Borrowing. The Parent Borrower shall
                    ---------------------------------
give the Administrative Agent irrevocable notice (which notice must be received
by the Administrative Agent prior to 10:00 A.M., New York City time, one
Business Day prior to the anticipated French Closing Date, Thai Closing Date or
Additional Term Loan Closing Date, as the case may be) requesting that the Term
Lenders make the Term Loans on the French Closing Date, the Thai Closing Date or
the Additional Term Loan Closing Date, as the case may be, and specifying the
amount to be borrowed. The Term Loans made on each of the French Closing Date,
the Thai Closing Date and the Additional Term Loan Closing Date shall initially
be Alternate Base Rate Loans and, unless otherwise agreed by the Administrative
Agent in its sole discretion, no Term Loan may be converted into or continued as
a Eurocurrency Loan having an Interest Period in excess of one month prior to
the date that is 60 days after the French Closing Date, the Thai Closing Date or
the Additional Term Loan Closing Date, as the case may be. Upon receipt of
<PAGE>

such notice the Administrative Agent shall promptly notify each Term Lender
thereof. Not later than 12:00 Noon, New York City time, on the French Closing
Date, the Thai Closing Date or the Additional Term Loan Closing Date, as the
case may be, each Term Lender shall make available to the Administrative Agent
at the Funding Office an amount in immediately available funds equal to the Term
Loan or Term Loans to be made by such Lender. The Administrative Agent shall
credit the account of the Parent Borrower on the books of such office of the
Administrative Agent with the aggregate of the amounts made available to the
Administrative Agent by the Term Lenders in immediately available funds."

               (iii) Section 2 of the Credit Agreement is hereby amended by
     deleting in its entirety Section 2.3 and substituting, in lieu thereof, the
     following:

          "2.3 Repayment of Term Loans. (a) The French Term Loans of each French
               -----------------------
     Term Lender shall mature in 19 consecutive quarterly installments,
     commencing on December 31, 2000, and ending on the date that is five years
     after the Initial Closing Date in an aggregate amount for each of which
     shall be in an amount equal to such Lender's French Term Percentage
     multiplied by the aggregate amount of French Term Commitments, multiplied
     by the percentage set forth below opposite such installment:

          Installment:                     Principal Percentage Amount:
          -----------                      ---------------------------

          December 31, 2000                3% of French Term Loans
          March 31, 2001                   3% of French Term Loans
          June 30, 2001                    3% of French Term Loans
          September 30, 2001               4% of French Term Loans
          December 31, 2001                4% of French Term Loans
          March 31, 2002                   4% of French Term Loans
          June 30, 2002                    4% of French Term Loans
          September 30, 2002               5% of French Term Loans
          December 31, 2002                5% of French Term Loans
          March 31, 2003                   5% of French Term Loans
          June 30, 2003                    5% of French Term Loans
          September 30, 2003               6.25% of French Term Loans
          December 31, 2003                6.25% of French Term Loans
          March 31, 2004                   6.25% of French Term Loans
          June 30, 2004                    6.25% of French Term Loans
          September 30, 2004               7.5% of French Term Loans
          December 31, 2004                7.5% of French Term Loans
          March 31, 2005                   7.5% of French Term Loans
          June 28, 2005                    7.5% of French Term Loans


          (b) The Thai Term Loans of each Thai Term Lender shall mature in 19
     consecutive quarterly installments, commencing on December 31, 2000, and
     ending on the date that is five years after the Initial Closing Date in an
     aggregate amount for each of which shall be in an amount equal to such
     Lender's Thai Term Percentage multiplied by
<PAGE>

     the aggregate amount of Thai Term Commitments, multiplied by the percentage
     set forth below opposite such installment:

          Installment:                         Principal Percentage Amount:
          -----------                          ---------------------------

          December 31, 2000                    3% of Thai Term Loans
          March 31, 2001                       3% of Thai Term Loans
          June 30, 2001                        3% of Thai Term Loans
          September 30, 2001                   4% of Thai Term Loans
          December 31, 2001                    4% of Thai Term Loans
          March 31, 2002                       4% of Thai Term Loans
          June 30, 2002                        4% of Thai Term Loans
          September 30, 2002                   5% of Thai Term Loans
          December 31, 2002                    5% of Thai Term Loans
          March 31, 2003                       5% of Thai Term Loans
          June 30, 2003                        5% of Thai Term Loans
          September 30, 2003                   6.25% of Thai Term Loans
          December 31, 2003                    6.25% of Thai Term Loans
          March 31, 2004                       6.25% of Thai Term Loans
          June 30, 2004                        6.25% of Thai Term Loans
          September 30, 2004                   7.5% of Thai Term Loans
          December 31, 2004                    7.5% of Thai Term Loans
          March 31, 2005                       7.5% of Thai Term Loans
          June 28, 2005                        7.5% of Thai Term Loans


          (c) The Additional Term Loans of each Additional Term Lender shall
     mature in 19 consecutive quarterly installments, commencing on December 31,
     2001, and ending on the date that is six years after the Initial Closing
     Date in an aggregate amount for each of which shall be in an amount equal
     to such Lender's Additional Term Percentage multiplied by the aggregate
     amount of Additional Term Commitments, multiplied by the percentage set
     forth below opposite such installment:

          Installment:                        Principal Percentage Amount:
          -----------                         ---------------------------

          December 31, 2001                   0.25% of Additional Term Loans
          March 31, 2002                      0.25% of Additional Term Loans
          June 30, 2002                       0.25% of Additional Term Loans
          September 30, 2002                  0.25% of Additional Term Loans
          December 31, 2002                   0.25% of Additional Term Loans
          March 31, 2003                      0.25% of Additional Term Loans
          June 30, 2003                       0.25% of Additional Term Loans
          September 30, 2003                  0.25% of Additional Term Loans
          December 31, 2003                   0.25% of Additional Term Loans
          March 31, 2004                      0.25% of Additional Term Loans
          June 30, 2004                       0.25% of Additional Term Loans
          September 30, 2004                  0.25% of Additional Term Loans
<PAGE>

          December 31, 2004                   0.25% of Additional Term Loans
          March 31, 2005                      0.25% of Additional Term Loans
          June 30, 2005                       0.25% of Additional Term Loans
          September 30, 2005                  0.25% of Additional Term Loans
          December 31, 2005                   0.25% of Additional Term Loans
          March 31, 2006                      0.25% of Additional Term Loans
          June 28, 2006                       95.5% of Additional Term Loans


          (d) To the extent the maturity date of any Term Loan extends beyond
     the maturity date of any subordinated debt of the Parent Borrower existing
     on the date hereof, such maturity date shall be adjusted to be 90 days
     prior to the maturity date of such subordinated debt."

              (iv) Section 2.9 of the Credit Agreement is hereby amended by
     adding, as Section 2.9(e), the following language after Section 2.9(d)
     thereof:

          "(e) Notwithstanding anything to the contrary in Section 2.9(d), with
respect to the amount of any mandatory prepayment described in Section 2.9 that
is allocated to Additional Term Loans (such amounts, the "Additional Term Loan
                                                          --------------------
Prepayment Amount") at any time when either French Term Loans or Thai Term Loans
-----------------
remain outstanding, the Parent Borrower will, in lieu of applying such amount to
the prepayment of Additional Term Loans, as provided in paragraph (d) above, on
the date specified in Section 2.9 for such prepayment, give the Administrative
Agent telephonic notice ( promptly confirmed in writing) requesting that the
Administrative Agent prepare and provide to each Additional Term Lender a notice
(each, a "Prepayment Option Notice") as described below. As promptly as
          ------------------------
practicable after receiving such notice from the Borrower, the Administrative
Agent will send to each Additional Term Lender a Prepayment Option Notice, which
shall be in the form of Exhibit J and shall include an offer by the Parent
Borrower to prepay on the date (each a "Mandatory Prepayment Date") that is 10
                                        -------------------------
Business Days after the date of the Prepayment Option Notice, the relevant
French Term Loans and Thai Term Loans of such lender by an amount equal to the
portion of the Prepayment Amount indicated in such Lender's Prepayment Option
Notice as being applicable to such Lender's Additional Term Loans. On the
Mandatory Prepayment Date, (i) the Parent Borrower shall pay to the relevant
Additional Term Lenders the aggregate amount necessary to prepay that portion of
the outstanding relevant Additional Term Loans in respect of which such
Additional Term Lenders have accepted prepayment as described above and (ii) the
Parent Borrower shall pay to the French Term Lenders and the Thai Term Lenders
an amount equal to the portion of the Additional Term Loan Prepayment Amount not
accepted by the relevant Additional Term Lenders, and such amount shall be
applied to the prepayment of the French Term Loans and Thai Term Loans."

          (c)  Amendment to Section 4 of the Credit Agreement. Section 4.16 of
               ----------------------------------------------
the Credit Agreement is hereby amended by deleting such Section in its entirety
and substituting, in lieu thereof, the following:
<PAGE>

          "4.16 Use of Proceeds. The proceeds of the French Term Loans shall be
                ---------------
used to finance the French Acquisition and to pay related fees and expenses. The
proceeds of the Thai Term Loans, the Additional Term Loans, the Revolving Loans
and the Letters of Credit shall be used to pay certain fees and expenses, to
refinance certain existing indebtedness of the Parent Borrower, its Subsidiaries
and the Thai Target and to finance the working capital needs of the Parent
Borrower and its Subsidiaries in the ordinary course of business."

          (d)  Amendment to Section 5 of the Credit Agreement. Section 5.3(a) of
               ----------------------------------------------
the Credit Agreement is hereby amended by adding "and" at the end of clause (ii)
thereof, deleting "; and" at the end of clause (iii) thereof and substituting,
in lieu thereof, "." and deleting in its entirety clause (iv) thereof.

          (e)  Amendment to Section 6 of the Credit Agreement. Section 6.9 of
               ----------------------------------------------
the Credit Agreement is hereby amended by deleting such Section in its entirety
and substituting, in lieu thereof, the following:

          "6.9 Interest Rate Protection. In the case of the Parent Borrower, no
               ------------------------
later than June 29, 2001, enter into, and thereafter maintain, Hedge Agreements
to the extent necessary to provide that at least the aggregate principal amount
of the Term Loans or $100,000,000, whichever amount is less, is subject to
either a fixed interest rate or interest rate protection for a period of not
less than three years, which Hedge Agreements shall have terms and conditions
reasonably satisfactory to the Administrative Agent."

          (f)  Amendments to Section 7 of the Credit Agreement.
               -----------------------------------------------

               (i)   Section 7.1(a) of the Credit Agreement is hereby amended by
     deleting from the table thereunder the Consolidated Leverage Ratio values
     corresponding to the Fiscal Quarters "09/30/01" through "12/31/01" and
     substituting, in lieu thereof, the following values:

                 "09/30/01                        3.50:1.00
                  12/31/01                        3.25:1.00"

               (ii)  Section 7.1(b) of the Credit Agreement is hereby amended by
     deleting from the table thereunder the Consolidated Senior Secured Leverage
     Ratio values corresponding to the Fiscal Quarters "06/30/01," "09/30/01"
     and "12/31/01" and substituting, in lieu thereof, the following values:

                 "06/30/01                        2.75:1.00
                  09/30/01                        2.75:1.00
                  12/31/01                        2.50:1.00"

               (iii) Section 7.2(b) of the Credit Agreement is hereby amended by
     deleting such Section in its entirety and substituting, in lieu thereof,
     the following:

          "(b) Indebtedness of the Parent Borrower to any Subsidiary, the
Subsidiary Borrower to the Parent Borrower or to any other Subsidiary and of any
Wholly Owned Subsidiary Guarantor or of the Thai Target to the Parent Borrower
or to any other Subsidiary (in
<PAGE>

the case of Indebtedness of the Thai Target, subject to the limitations set
forth in clauses (g) and (i) of this subsection)."

               (iv) Section 7.2(c) of the Credit Agreement is hereby amended by
     deleting such Section in its entirety and substituting, in lieu thereof,
     the following:

          "(c) Guarantee Obligations incurred in the ordinary course of business
by the Parent Borrower or any of its Subsidiaries of obligations of any Wholly
Owned Subsidiary Guarantor, the Subsidiary Borrower or the Thai Target (in the
case of the Subsidiary Borrower, subject to the limitation set forth in clause
(i) of this subsection and, in the case of the Thai Target, subject to the
limitations set forth in clauses (g) and (i) of this subsection)."

               (v) Section 7.2(g) of the Credit Agreement is hereby amended by
     adding the following proviso before the ";" at the end thereof:

               "; provided that any such Indebtedness shall be applied first to
                  --------
reduce the Local Thai Term Loans."

               (vi) Section 7.2 of the Credit Agreement is hereby further
     amended by deleting "and" at the end of clause (i) thereof, by deleting "."
     at the end of clause (j) thereof and substituting, in lieu thereof, "; and"
     and by adding the following new clause (k) thereto:

          "(k) Guarantee Obligations incurred pursuant to the Subordinated Note
Documents."

               (vii) Section 7.8(g) of the Credit Agreement is hereby amended by
     deleting such section in its entirety and substituting, in lieu thereof,
     the following:

          "(g) intercompany Investments by the Parent Borrower in any of its
Wholly Owned Subsidiaries or in the Thai Target, provided that all such
                                                 --------
intercompany Indebtedness shall be evidenced by promissory notes pledged
pursuant to the Guarantee and Collateral Agreement and such intercompany
Indebtedness shall be subordinated in right of payment to the payment in full of
the Obligations hereunder;"

               (viii) Section 7.9 of the Credit Agreement is hereby amended by
     deleting the words "convertible subordinated debt" immediately preceding
     the parenthetical therein and substituting, in lieu thereof, the words
     "subordinated debt".

               (ix) Section 7.14 of the Credit Agreement is hereby amended by
     deleting in its entirety the language immediately following "(a)" therein
     and immediately preceding "(b)" therein and substituting, in lieu thereof,
     the following language:

          "make Restricted Payments in respect of any Capital Stock of such
Subsidiary (other than the prohibition on Restricted Payments made by the Thai
Target pursuant to the Local Thai Term Loans until the Local Thai Term Loans
outstanding have been reduced to $10,500,000 or less) held by, or pay any
Indebtedness owed to, the Parent Borrower or any other Subsidiary of the Parent
Borrower,"
<PAGE>

          (g)  Amendment to Annex A of the Credit Agreement. The Credit
               --------------------------------------------
Agreement is hereby further amended by deleting in its entirety Annex A thereto
and substituting, in lieu thereof, Annex I attached hereto as the new Annex A.

          (h)  Amendment to Schedule 1.1A of the Credit Agreement. The Credit
               --------------------------------------------------
Agreement shall be further amended by adding to Schedule 1.1A thereof an
additional heading entitled "Additional Term Commitment" and inserting
thereunder the Additional Term Commitment of each Additional Term Lender prior
to any borrowing by the Parent Borrower of any Additional Term Loans.

     3. Limited Waiver. Each of the Lenders parties hereto agree that, for the
        --------------
period from the Amendment Effective Date to the Section 3 Termination Date (as
defined below), any Default or Event of Default arising under Section 8(e) of
the Credit Agreement by virtue of the existence of any breach or payment default
(the aggregate principal amount of such payment default not to exceed
$10,500,000) under any of the Existing Thai Facilities is hereby waived. The
"Section 3 Termination Date" shall be the earliest of (i) March 31, 2001 or (ii)
the date on which all defaults under any of the Existing Thai Facilities have
been cured or waived, through amendments to the Existing Thai Facilities or
otherwise or (iii) the date on which a notice of acceleration under any of the
Existing Thai Facilities has been delivered to the Company.

     4. Effectiveness. This Amendment shall become effective on the date (the
        -------------
"Amendment Effective Date") on which the following conditions precedent shall
 ------------------------
have been satisfied or waived:

          (a)  This Amendment shall have been (i) executed by the Parent
Borrower, the Administrative Agent and the Required Lenders and (ii)
acknowledged and consented to by the other Loan Parties, each in accordance with
the terms of the Credit Agreement;

          (b)  If any breach or default under any of the Existing Thai
Facilities shall not have been cured or waived pursuant to Section 3 hereof, the
Parent Borrower (i) shall obtain, or shall cause the appropriate Subsidiary to
obtain, forbearance agreements in connection with all breaches or defaults under
any of the Existing Thai Facilities and (ii) shall deliver to the Administrative
Agent evidence of such forbearance agreements, in form and substance
satisfactory to the Administrative Agent;

          (c)  An amendment fee shall have been paid to the Administrative
Agent, for the ratable account of the Lenders which execute and deliver this
Amendment on or prior to 5:00 p.m. (New York City time) on December 22, 2000 (or
such later date as the Administrative Agent and the Parent Borrower shall
agree), in an amount equal to a percentage, to be determined, of the amount of
the Commitments then in effect and the aggregate then outstanding principal
amount of the Loans;

          (d)  The Administrative Agent shall have received, with a counterpart
for each Lender, the executed legal opinion of Testa Hurwitz & Thibeault, LLP,
counsel to the Parent Borrower (and its Subsidiaries), covering such matters
incident to the transactions contemplated by this Amendment as the
Administrative Agent may require;
<PAGE>

          (e)  The Administrative Agent shall have received a certificate of the
Parent Borrower, satisfactory in form and substance to the Administrative Agent
and its counsel, which shall (i) certify as to the incumbency and signature of
the officers of the Parent Borrower executing and delivering on behalf of the
Parent Borrower this Amendment and any other certificate or document to be
delivered by the Parent Borrower pursuant to this Amendment and (ii) attach
thereto, and certify as true and correct, the resolutions of the Board of
Directors of the Parent Borrower authorizing the execution, delivery and
performance of this Amendment and any borrowing contemplated hereunder; and

          (f)  No Default or Event of Default, other than as waived herein,
shall have occurred and be continuing on the Amendment Effective Date after
giving effect to this Amendment.

     5. Representations and Warranties. The Parent Borrower hereby represents
        ------------------------------
and warrants to the Administrative Agent and to each Lender party to the Credit
Agreement that each of the representations and warranties made by each Loan
Party in or pursuant to the Loan Documents shall be, after giving effect to this
Amendment, true and correct as if made on and as of the date hereof.

     6. Continuing Effect of Credit Agreement. Except as expressly amended
        -------------------------------------
hereby, the provisions of the Credit Agreement are and shall remain in full
force and effect.

     7. Counterparts. This Amendment may be executed in any number of
        ------------
counterparts and by different parties hereto in separate counterparts, each of
which when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement. Delivery of an executed
counterpart of a signature page to this Amendment by telecopier shall be
effective as delivery of a manually executed counterpart of this Amendment.

     8. GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY, AND CONSTRUED AND
        -------------
INTERPRETED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

     9. Expenses. The Parent Borrower agrees to pay or reimburse the
        --------
Administrative Agent for all of its reasonable out-of-pocket costs and expenses
incurred in connection with the preparation, negotiation and execution of this
Amendment, including, without limitation, the reasonable fees and disbursements
of counsel to the Administrative Agent.
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be executed and delivered by their duly authorized officers as of the date first
written above.



                                        ACT MANUFACTURING, INC.




                                        By:  /s/ John A. Pino
                                             --------------------------
                                               Name:  John A. Pino
                                               Title: Chief Executive Officer
<PAGE>

                                           THE CHASE MANHATTAN BANK, as
                                           Administrative Agent and as a Lender




                                           By: /s/ James M. Dailey
                                              -----------------------------
                                                Name:  James M. Dailey
                                                Title: Vice President
<PAGE>

                                            CITICORP USA, INC.




                                            By:  /s/ Suzanne Crymes
                                                 -------------------------------
                                                  Name:  Suzanne Crymes
                                                  Title: Vice President
<PAGE>

                                          CREDIT SUISSE FIRST BOSTON




                                          By:  /s/ Robert Hetu
                                               ---------------------------------
                                                 Name:  Robert Hetu
                                                 Title: Vice President



                                          By:  /s/ Lalita Advani
                                               ---------------------------------
                                                 Name:  Lalita Advani
                                                 Title: Assistant Vice President
<PAGE>

                             DEBIS FINANCIAL SERVICES, INC.




                             By:  /s/ James M. Vandervalk
                                  ----------------------------------------------
                                   Name:  James M. Vandervalk
                                   Title: President, Asset Based Lender Division
<PAGE>

                                              FLEET CAPITAL CORPORATION




                                              By:  /s/ Mark G. Schafer
                                                   -----------------------------
                                                     Name:  Mark G. Schafer
                                                     Title: Vice President
<PAGE>

                                         GMAC COMMERCIAL CREDIT LLC




                                         By:  /s/ Anthony Marsicano
                                              ----------------------------------
                                               Name: Anthony Marsicano
                                               Title:  Executive Vice President
<PAGE>

                                           HARRIS TRUST AND SAVINGS BANK




                                           By:  /s/ Kirby M. Law
                                                --------------------------------
                                                  Name:  Kirby M. Law
                                                  Title: Vice President
<PAGE>

                                            IBJ WHITEHALL BUSINESS CREDIT
                                            CORPORATION




                                            By:  /s/ Bruce Kasper
                                                 -------------------------------
                                                   Name:  Bruce Kasper
                                                   Title: Vice President
<PAGE>

                                          NATIONAL BANK OF CANADA



                                          By:  /s/ A. Keith Broyles
                                               ---------------------------------
                                                 Name:  A. Keith Broyles
                                                 Title: Vice President & Manager



                                          By:  /s/ Peter F. Smith
                                               ---------------------------------
                                                 Name:  Peter F. Smith
                                                 Title: Vice President
<PAGE>

                                            THE PROVIDENT BANK




                                            By: /s/ Jose V. Garde
                                                -------------------------------
                                                 Name:  Jose V. Garde
                                                 Title: Vice President
<PAGE>

                                            SOVEREIGN BANK




                                            By:  /s/ Robert E. Cook
                                                 -------------------------------
                                                  Name:  Robert E. Cook
                                                  Title: Vice President
<PAGE>

                                            SUMMIT BANK




                                            By: /s/ Charles E. Kirschner
                                                -------------------------------
                                                 Name: Charles E. Kirschner
                                                 Title: Vice President
<PAGE>

          The undersigned Loan Parties do hereby consent and agree to the
foregoing Amendment and acknowledge and agree that (i) all obligations of the
Parent Borrower under the Credit Agreement, as amended by the foregoing
Amendment, are Obligations which are secured and guaranteed by the Security
Documents to which each is a party, (ii) all references to the Credit Agreement
in the Security Documents refer to the Credit Agreement, as amended from time to
time (including pursuant to the foregoing Amendment) and (iii) all references to
Loans in the Security Documents refer to the Loans under the Credit Agreement,
as amended by the foregoing Amendment.


                             ACT MANUFACTURING SECURITIES CORPORATION


                             By:  /s/ John A. Pino
                                  ----------------------------------------------
                                  Name: John A. Pino
                                  Title: Chief Executive Officer and President


                             ACT MANUFACTURING US HOLDINGS, LLC


                             By:  /s/ John A. Pino
                                  ----------------------------------------------
                                  Name: John A. Pino
                                  Title: Chief Executive Officer and President



                             CMC INDUSTRIES, INC.


                             By:  /s/ John A. Pino
                                  ----------------------------------------------
                                  Name: John A. Pino
                                  Title: Chief Executive Officer and President
<PAGE>

                                                                      Annex I to
                                                                Second Amendment

                                                                         Annex A
                                                                         -------

              PRICING GRID FOR REVOLVING LOANS, FRENCH TERM LOANS,
                       THAI TERM LOANS AND COMMITMENT FEES

<TABLE>
<CAPTION>
===================================================================================================

    Consolidated                                     Applicable Margin for
      Leverage      Applicable Margin for             Alternate Base Rate         Commitment Fee
       Ratio         Eurocurrency Loans                     Loans                      Rate

---------------------------------------------------------------------------------------------------
<S>                             <C>                          <C>                      <C>
Greater than or                 3.00%                        2.00%                    0.500%
equal to 4.00:1.00
---------------------------------------------------------------------------------------------------
Greater than or                 2.75%                        1.75%                    0.500%
equal to 3.50:1.00
but less than
4.00:1.00
---------------------------------------------------------------------------------------------------
Greater than or
equal to 3.00:1.00
but less than                   2.50%                        1.50%                    0.500%
3.50:1.00
---------------------------------------------------------------------------------------------------
Greater than or
equal to 2.50:1.00
but less than                   2.25%                        1.25%                    0.500%
3.00:1.00
---------------------------------------------------------------------------------------------------
Greater than or
equal to  2.00:1.00             2.00%                        1.00%                    0.500%
by less than
2.50:1.00
---------------------------------------------------------------------------------------------------
Less than
2.00:1.00                       1.75%                        0.75%                    0.375%
===================================================================================================
</TABLE>

     Changes in the Applicable Margin resulting from changes in the Consolidated
Leverage Ratio shall become effective on the date (the "Adjustment Date") that
                                                        ---------------
is three Business Days after the date on which financial statements are
delivered to the Lenders pursuant to Section 6.1 and shall remain in effect
until the next change to be effected pursuant to this paragraph. If any
financial statements referred to above are not delivered within the time periods
specified in Section 6.1, then, until the date that is three Business Days after
the date on which such financial statements are delivered, the highest rate set
forth in each column of the Pricing Grid shall apply. In addition, at all times
while an Event of Default shall have occurred and be continuing, the highest
rate set forth in each column of the Pricing Grid shall apply. Each
determination of the Consolidated Leverage Ratio pursuant to the Pricing Grid
shall be made in a manner consistent with the determination thereof pursuant to
Section 7.1.