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                                                                   EXHIBIT 10.43



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                                CREDIT AGREEMENT


                                     BETWEEN


                             BTU INTERNATIONAL, INC.


                                       AND


                                     USTRUST



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                          DATED AS OF SEPTEMBER 5, 1997



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CREDIT AGREEMENT..............................................................1

ARTICLE 1. -  DEFINITIONS.....................................................1

1.1. DEFINED TERMS............................................................1
1.2. ACCOUNTING AND BANKING TERMS.............................................1

ARTICLE 2. - LOANS AND LETTERS OF CREDIT......................................1

2.1. REVOLVING CREDIT COMMITMENT..............................................1
2.2. PROCEDURE FOR REVOLVING CREDIT BORROWINGS................................1
2.3. INTEREST ON REVOLVING CREDIT LOANS.......................................2
2.4. PREPAYMENT OF EURODOLLAR LOANS...........................................3
2.5. MANDATORY PREPAYMENT.....................................................4
2.6. REVOLVING CREDIT NOTE....................................................4
2.7. REVOLVING CREDIT LOAN PROCEEDS...........................................4
2.8. LETTERS OF CREDIT........................................................4
2.9. CALCULATION OF INTEREST..................................................5
2.10. DEFAULT RATE............................................................5
2.11. INTEREST LIMITATION.....................................................5
2.12. LATE PAYMENT CHARGE.....................................................6
2.13. PAYMENTS................................................................6
2.14. TERMINATION OF CREDIT COMMITMENTS.......................................6
2.15. COMMITMENT FEE..........................................................6

ARTICLE 3. - REPRESENTATIONS AND WARRANTIES...................................6

3.1. FINANCIAL CONDITION......................................................7
3.2. NO CHANGE................................................................7
3.3. ORGANIZATION, EXISTENCE, GOOD STANDING...................................7
3.4. SUBSIDIARIES; CAPITALIZATION.............................................7
3.5. POWER AND AUTHORITY......................................................7
3.6. LEGAL, VALID, BINDING OBLIGATION.........................................8
3.7. CONSENTS.................................................................8
3.8. NO LEGAL BAR.............................................................8
3.9. NO LITIGATION............................................................8
3.10. NO DEFAULT..............................................................8
3.11. ASSETS, NO LIENS; INTELLECTUAL PROPERTY.................................9
3.12. NO BURDENSOME RESTRICTIONS..............................................9
3.13. TAXES...................................................................9
3.14. REGULATION U, ETC.......................................................9
3.15. ERISA...................................................................9
3.16. INVESTMENT COMPANY ACT, ETC............................................10
3.17. INDEBTEDNESS...........................................................10
3.18. CONTINGENT LIABILITIES.................................................10
3.19. CHIEF PLACE OF BUSINESS................................................10
3.20. LAWS INCLUDING ENVIRONMENTAL AND SAFETY MATTERS........................10
3.21. NEGATIVE PLEDGES.......................................................11
3.22. FULL DISCLOSURE........................................................11

ARTICLE 4. - AFFIRMATIVE COVENANTS...........................................11

4.1. FINANCIAL STATEMENTS AND OTHER DOCUMENTS................................11
4.2. EXISTENCE; COMPLIANCE WITH LAWS; ETC....................................12
4.3. MAINTAIN PROPERTY.......................................................12
4.4. INSURANCE...............................................................13
4.5. RECORDKEEPING; RIGHTS OF INSPECTION.....................................13


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4.6. NOTICE OF MATERIAL EVENTS...............................................13
4.7. DEPOSIT ACCOUNTS........................................................14
4.8. NOTICE OF ACQUISITIONS..................................................14

ARTICLE 5. - NEGATIVE COVENANTS..............................................14

5.1. INDEBTEDNESS............................................................14
5.2. CONTINGENT LIABILITIES..................................................15
5.3. LIMITATION ON LIENS.....................................................15
5.4. PROHIBITION OF FUNDAMENTAL CHANGES......................................16
5.5. FINANCIAL MEASUREMENTS..................................................17
5.6. TRANSACTIONS WITH AFFILIATES............................................17
5.7. NEGATIVE PLEDGE.........................................................17

ARTICLE 6. - CONDITIONS PRECEDENT............................................17

6.1. CONDITIONS OF INITIAL EXTENSION OF CREDIT...............................17

LOAN DOCUMENTS:..............................................................18

CORPORATE DOCUMENTS:.........................................................18

MISCELLANEOUS DOCUMENTS:.....................................................18

6.2. CONDITIONS OF ALL REVOLVING CREDIT LOANS AND LETTERS OF CREDIT..........19

ARTICLE 7. - EVENTS OF DEFAULT...............................................20

7.1. EVENTS OF DEFAULT.......................................................20
7.2. LENDER'S REMEDIES.......................................................22
7.3. CROSS DEFAULT...........................................................22
7.4. SETOFF..................................................................22

ARTICLE 8. - MISCELLANEOUS...................................................23

8.1. NOTICES.................................................................23
8.2. NO WAIVER OF RIGHTS.....................................................24
8.3. CUMULATIVE REMEDIES.....................................................24
8.4. SUCCESSORS..............................................................24
8.5. GOVERNING LAW...........................................................24
8.6. SUBMISSION TO JURISDICTION; WAIVER OF TRIAL BY JURY.....................24
8.7. COMPLETE AGREEMENT, AMENDMENTS..........................................25
8.8. EXPENSES................................................................25
8.9. INDEMNIFICATION.........................................................25
8.10. CHANGE IN LAWS.........................................................26
8.11. SURVIVAL OF AGREEMENTS.................................................26
8.12. SEVERABILITY...........................................................26
8.13. DESCRIPTIVE HEADINGS...................................................26
8.14. COUNTERPARTS...........................................................26

SCHEDULE I....................................................................1



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                                CREDIT AGREEMENT

         CREDIT AGREEMENT dated as of September 5, 1997 between BTU
International, Inc., a Delaware corporation ("Borrower"), and USTRUST, a
Massachusetts trust company ("Lender").

         WHEREAS, Borrower has requested that Lender provide it with a revolving
line of credit;

         WHEREAS, Lender is willing, on the terms and subject to the conditions
in this Agreement, to make the revolving line of credit available to Borrower;

         NOW, THEREFORE, in consideration of the mutual promises contained
herein and other good and valuable consideration, the receipt and sufficiency of
which are acknowledged, Lender and Borrower agree as follows.

                            ARTICLE 1. - DEFINITIONS

         1.1.     DEFINED TERMS. The capitalized terms, as used in this
Agreement, shall have the meanings as set forth on Schedule I hereto.

         1.2.     ACCOUNTING AND BANKING TERMS. All accounting and banking terms
not specifically defined herein shall be construed, in the case of accounting
terms, in accordance with GAAP consistently applied and, in the case of banking
terms, in accordance with general practice among commercial banks in Boston,
Massachusetts.

                ARTICLE 2. - LOANS AND STANDBY LETTERS OF CREDIT

         2.1.     REVOLVING CREDIT COMMITMENT. Subject to the terms and
conditions hereof, Lender agrees to make Revolving Credit Loans to Borrower from
time to time during the Commitment Period, provided, however, that the aggregate
principal amount of all outstanding Revolving Credit Loans plus the face amount
of all outstanding Letters of Credit does not exceed the Revolving Credit Limit.
The Revolving Credit Loans may be repaid by Borrower at any time, without
penalty or premium (except as provided in Section 2.4(a)) and reborrowed only
during the Commitment Period, and shall be due and payable on the Termination
Date.

         2.2.     PROCEDURE FOR REVOLVING CREDIT BORROWINGS. Subject to the
terms and conditions hereof, Borrower may borrow under the Revolving Credit
Commitment during the Revolving Credit Commitment Period on any Business Day.
Borrower may request Revolving Credit Loans, from time to time, by submitting
irrevocable Loan requests in such form and manner as Lender may require or
permit (including, without limitation, telephone requests), specifying the
amount to be borrowed, whether the borrowing will be at the Base Rate or the
Eurodollar Rate, the Interest Period, if a Eurodollar Loan is requested, the
requested Borrowing Date, the manner in which Borrower would like the proceeds
of such Loan disbursed and a certification that the Borrower is in compliance
with this Loan Agreement immediately before and after giving effect to the
making of such Loan. If such Revolving Credit Loan request is for a Base Rate
Revolving Credit Loan and is properly made and received by Lender prior to 12:00
noon (Eastern Time) on a Business 



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Day, requesting a Revolving Credit Loan on that Business Day, Lender shall make
such Revolving Credit Loan on the same Business Day. If, however, such Revolving
Credit Loan request is received by Lender after 12:00 noon (Eastern Time) on a
Business Day, Lender shall make the Revolving Credit Loan not later than the
next Business Day. Revolving Credit Loans bearing interest at the Eurodollar
Rate will be made on the second Business Day following receipt of the borrowing
request by Lender. Lender may require telephone requests to be confirmed
promptly in writing and Borrower shall indemnify and hold Lender harmless for
any action, including the making of any advance or any loss or expenses taken or
incurred by Lender in reliance upon any such telephone request. Each borrowing
pursuant to the Revolving Credit Commitment shall be in the amount not less than
$25,000 provided that in any event any such borrowing, together with the
aggregate principal amount of the Revolving Credit Loans and Letters of Credit
then outstanding, shall not exceed the Revolving Credit Limit. Except as
otherwise requested, the proceeds of all Revolving Credit Loans will be made
available to Borrower by Lender by crediting Borrower's deposit account with
Lender or such other account of Borrower at Lender as Borrower may specify.

         2.3.     INTEREST ON REVOLVING CREDIT LOANS.

         (a)      INTEREST RATE. The Borrower shall pay interest on the unpaid
principal amount of each Revolving Credit Loan outstanding at any time, and from
time to time, for the period from the Borrowing Date at a fluctuating rate per
annum equal to one of the following rates as elected by Borrower: (i) the Base
Rate, or (ii) the Eurodollar Rate.

         (b)      EURODOLLAR LOAN NOTICE. To borrow at the Eurodollar Rate, the
Borrower must submit a Eurodollar Loan Notice to Lender prior to 11:00 a.m.
(Eastern Time) on a Business Day at least two (2) Business Days prior to the
commencement of the Interest Period for such Eurodollar Rate borrowing. Each
Eurodollar Loan shall be for an Interest Period of one (1), two (2), three (3),
six (6) or twelve (12) calendar months and shall, upon expiration of the
Interest Period applicable to such Eurodollar Loan, be continued as a Base Rate
Revolving Credit Loan unless Borrower shall have timely provided a Eurodollar
Loan Notice prior to the expiration of such Interest Period. All Eurodollar
Loans shall be subject to prepayment only as provided in Section 2.4.

         (c)      CONVERSION OF REVOLVING CREDIT LOANS. Provided that no Event
of Default has occurred and is continuing the Borrower may, on any Business Day,
convert any outstanding Base Rate Revolving Credit Loan to a Eurodollar Loan in
the same aggregate principal amount and convert a Eurodollar Loan to a Base Rate
Revolving Credit Loan only on the last Business Day of the then current Interest
Period applicable to such Eurodollar Loan. If the Borrower desires to convert a
Revolving Credit Loan, it shall give the Lender not less than two (2) Business
Days' prior written notice, specifying the date of such conversion and the
amount to be converted and if the conversion is from a Base Rate Revolving
Credit Loan to a Eurodollar Loan, the duration of the first Interest Period
therefor.



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         PAYMENT OF INTEREST. Interest on all Revolving Credit Loans shall be
payable in arrears on the first (1st) Business Day of each month commencing on
the first such day to occur after the date of this Agreement, and monthly
thereafter until the Revolving Credit Loans are fully paid.

         2.4.     PREPAYMENT OF EURODOLLAR LOANS. (a) MAKE-WHOLE PAYMENTS. The
Borrower shall pay to Lender on demand such amount or amounts as shall, in the
conclusive judgment of Lender (in the absence of manifest error), compensate
Lender for any loss, cost or expense sustained or incurred by the Lender as a
result of (i) any payment or prepayment of any Eurodollar Loan required or
permitted under this Agreement, if such Eurodollar Loan is prepaid other than on
the last day of the Interest Period for such Eurodollar Loan, (ii) the
conversion, for any reason whatsoever, whether voluntary or involuntary, of any
Eurodollar Loan to a Base Rate Revolving Credit Loan on a date other than the
last day of the applicable Interest Period, or (iii) in the event that after the
Borrower delivers a Eurodollar Loan Notice under Section 2.3(b) in respect of a
Eurodollar Loan, such Eurodollar Loan is not made on the first day of the
Interest Period specified in such notice of borrowing for any reason other than
a breach by the Lender of its obligations hereunder. Such amounts payable by
Borrower shall compensate Lender for any loss or expense incurred or sustained
by Lender including, without limitation, any interest or other amounts payable
by the Lender to other financial institutions in order to make or maintain such
Eurodollar Loan. In the event any such amount is payable by Borrower, the Lender
shall deliver to the Borrower from time to time one or more certificates setting
forth the amount due as determined by the Lender, which certificate shall be
conclusive and binding on Borrower, absent manifest error.

         (b)      LIMITATIONS ON EURODOLLAR LOANS. (i) In the event the Lender
determines that by reason of circumstances affecting the inter-bank Eurodollar
market, adequate and reasonable means do not exist for determining the LIBOR
Rate or Eurodollar deposits in the relevant amount and for the relevant maturity
are not available to Lender in the inter-bank Eurodollar market, with respect to
a proposed Eurodollar Loan, Lender shall give the Borrower prompt notice of such
determination. If such notice is given, then (A) any requested Eurodollar Loan
shall be made as a Base Rate Revolving Credit Loan, unless the Borrower gives
Lender one Business Day's prior written notice that its request for such
borrowing is cancelled; (B) any Revolving Credit Loan which was to have been
converted to a Eurodollar Loan shall be continued as a Base Rate Revolving
Credit Loan; and (C) any outstanding Eurodollar Loan shall, upon the expiration
of the applicable Interest Period, be converted to a Base Rate Revolving Credit
Loan. Until such notice has been withdrawn, Lender shall have no obligation to
make Eurodollar Loans or maintain outstanding Eurodollar Loans and the Borrower
shall not have the right to convert Base Rate Revolving Credit Loans to
Eurodollar Loans.

                  (ii) Notwithstanding any other provisions of this Agreement,
if, after the date of this Agreement, any applicable law, treaty, regulation or
directive, or any change therein or in the interpretation or application
thereof, shall make it unlawful for Lender to make or maintain any Eurodollar
Loans, the obligation of Lender hereunder to make or maintain such Eurodollar
Loans shall forthwith be suspended for the duration of such illegality and the
Borrower shall, if any Eurodollar Loan is outstanding promptly, upon request
from Lender, prepay such advance or convert such Eurodollar Loan to a Base Rate
Revolving Credit Loan. If any such payment is 



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made on a day that is not the last Business Day of the then current Interest
Period applicable to such Eurodollar Loan, the Borrower shall pay Lender, upon
Lender's request, the amounts required under Section 2.4(a).

         2.5.     MANDATORY PREPAYMENT. If at any time the aggregate unpaid
principal amount of the Revolving Credit Loans and Letters of Credit exceeds the
amount of the Revolving Credit Limit, Borrower shall immediately prepay, without
premium or penalty (except for any amount due under Section 2.4(a)), an amount
at least equal to such excess, together with accrued interest on the amount
prepaid to the date of prepayment.

         2.6.     REVOLVING CREDIT NOTE. The Revolving Credit Loans shall be
evidenced by the Revolving Credit Note. Lender shall maintain records of each
(i) Revolving Credit Loan and (ii) payment or prepayment of principal and shall
furnish periodic reports to Borrower showing the outstanding principal balance
of the Revolving Credit Loans. The Lender's records shall constitute PRIMA FACIE
evidence of the accuracy of the information recorded therein and in the event
that Borrower fails to object, within thirty (30) days of receipt of Lender's
periodic reports to Borrower with respect to Revolving Credit Loans, the
information in such reports shall be conclusive and binding as against Borrower;
PROVIDED, HOWEVER, that any failure by Lender to maintain such records or
furnish such reports shall not affect the obligations of Borrower under the
Revolving Credit Note or this Agreement.

         2.7.     REVOLVING CREDIT LOAN PROCEEDS. Borrower shall use the 
proceeds of the Revolving Credit Loans for its working capital purposes, to
support Letters of Credit, for the acquisition of equipment and other assets to
be used in its business and for the acquisition of substantially all of the
assets or capital stock of another Person or Persons pursuant to an Authorized
Acquisition.

         2.8.     LETTERS OF CREDIT.

                  (a) Subject to, and upon the terms and conditions contained
         herein, at the request of Borrower and upon Borrower submitting a
         completed application therefore and other documents required by Lender,
         Lender agrees to provide Letters of Credit for the account of Borrower
         containing terms and conditions acceptable to Lender. Any payments made
         by Lender in connection with the Letters of Credit shall constitute
         additional Base Rate Revolving Credit Loans to Borrower pursuant to
         Section 2.1.

                  (b) Borrower shall pay to Lender a fee equal to five eighths
         of one percent (5/8 of 1.0%) per annum on the face amount of all
         Letters of Credit issued by Lender, which fee shall be paid in full
         upon issuance of each such Letter of Credit and on the anniversary of
         each such issuance. Borrower shall also pay to Lender on demand all
         opening, amendment, drawing and other administrative fees charged by
         Lender from time to time on Letters of Credit.

                  (c) The amount of all outstanding Letters of Credit and all
         other commitments and obligations made or incurred by Lender in
         connection therewith shall not at any 


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         time exceed the Revolving Credit Line less the outstanding principal
         balance of all then outstanding Revolving Credit Loans.

                  (d) Borrower shall indemnify and hold Lender harmless from and
against any and all losses, claims, damages, liabilities, costs and expenses
which Lender may suffer or incur in connection with any Letters of Credit and
any documents, drafts or acceptances relating thereto, including, but not
limited to, any losses, claims, damages, liabilities, costs and expenses due to
any action taken by any beneficiary or correspondent with respect to any Letters
of Credit. Borrower assumes all risks with respect to the acts or omissions of
the drawer under or beneficiary of any Letters of Credit. Borrower assumes all
risks for, and agrees to pay, all foreign, Federal, state and local taxes,
duties and levies relating to any Letters of Credit or any documents, drafts or
acceptances thereunder. Borrower hereby releases and holds Lender harmless from
and against any acts, waivers, errors, delays or omissions, whether caused by
Borrower, by any correspondent or otherwise with respect to or relating to any
Letters of Credit. The provisions of this Section 2.8(d) shall survive the
payment of Obligations and the termination of this Agreement.

                  (e) Nothing contained herein shall be deemed or construed to
grant Borrower any right or authority to pledge the credit of Lender in any
manner. Borrower shall be bound by any interpretation made in good faith by
Lender, or any correspondent under or in connection with any Letters of Credit
or any documents, drafts or acceptances thereunder, notwithstanding that such
interpretation may be inconsistent with any instructions of Borrower.

         2.9.     CALCULATION OF INTEREST. Interest and fees shall be calculated
on the basis of a 360-day year for the actual days elapsed, from and including
the date of such Loan to but excluding the date of any repayment. Any change in
rate resulting from a change in the Base Rate shall become effective as of the
day on which such change in the Base Rate becomes effective.

         2.10.    DEFAULT RATE. Notwithstanding anything to the contrary
contained herein, after maturity (whether at the stated maturity, upon an Event
of Default or otherwise), interest shall be payable on the unpaid principal
balance and on all other obligations of the Borrower to the Lender at a rate
that is two percent (2%) in excess of the rate that is otherwise payable, until
fully paid. If the maturity is a result of an Event of Default, the interest
rate shall revert to the pre-default rate on the first Business Day after such
Event of Default is cured to the satisfaction of the Lender, provided that no
other Event of Default or event or change having a Material Adverse Effect has
occurred.

         2.11.    INTEREST LIMITATION. No provision of this Agreement or the
Notes shall require the payment, or permit the collection, of interest in excess
of the highest rate permitted by applicable law. To the extent that any interest
received by Lender exceeds the maximum amount permitted, such payment shall be
credited to unpaid principal, PROVIDED, however, that any excess amount
remaining after full payment of principal shall be refunded to Borrower.

         2.12.    LATE PAYMENT CHARGE. Any payment of principal or interest not
paid within fifteen (15) days after the date such payment is due shall be
subject to a late charge equal to five percent (5%) of the amount overdue.



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         2.13.    PAYMENTS. All payments (including prepayments) made by
Borrower hereunder or under the Revolving Credit Note shall be made in
immediately available funds not later than 1:00 p.m., (Eastern time), on the due
date at Lender's office located at 40 Court Street, Boston, Massachusetts 02108
(or at such other office as Lender may specify to Borrower in writing). If any
payment becomes due and payable on a day other than a Business Day, such payment
shall be extended to the next succeeding Business Day and, with respect to
payments of principal, interest thereon shall be payable at the applicable rate
during such extension. All payments shall be made without setoff or counterclaim
and free and clear of, and without deduction for, any charge of any kind. All
payments received by Lender after 1:00 p.m. on any Business Day shall not be
deemed received until the next Business Day. On the date any payment of
principal or interest is due on account of the Loans, Lender may, but shall not
be obligated to, effect payment by debiting Borrower's deposit accounts with
Lender in an amount equal to all or any portion of such payment due.

         2.14.    TERMINATION OF CREDIT COMMITMENTS. The Revolving Credit
Commitment and Letter of Credit Commitment are coterminous and may not be
terminated separately by the Borrower. To terminate the Credit Commitments,
Borrower shall give Lender not less than five (5) Business Days prior written
notice and on the termination date prepay in full all Loans together with
accrued interest, fees, and charges thereon to the date of prepayment and either
cause the return of the outstanding Letters of Credit to the Lender or furnish
cash collateral to the Lender in amount deemed sufficient by Lender to pay all
liabilities relating to all outstanding Letters of Credit in full. The Credit
Commitments may be terminated by Lender during the existence of an Event of
Default or automatically as set forth in Article 7.

         2.15.    COMMITMENT FEE. Borrower agrees to pay to Lender for the first
year of the Commitment Period a commitment fee equal to one eighth of one
percent (1/8%) of $6,000,000 ($7,500 at closing), which shall be due and payable
and fully earned on the date hereof. On each anniversary of the date hereof,
Borrower shall pay to the Lender a commitment fee equal to one eighth of one
percent (1/8%) of $6,000,000 plus one sixteenth of one percent (1/16%) of
$8,000,000, which shall be due and payable and fully earned on each anniversary
of the date hereof while this Agreement is in effect.

                   ARTICLE 3. - REPRESENTATIONS AND WARRANTIES

         In order to induce Lender to enter into this Agreement and to make the
Revolving Credit Loans and to issue Letters of Credit, Borrower represents and
warrants to Lender, except as otherwise set forth in the disclosure schedule
attached hereto and made a part hereof (the "Disclosure Schedule"), that:

         3.1.     FINANCIAL CONDITION.

                  (a) The Financial Statements previously delivered to Lender
and attached to the Disclosure Schedule present fairly the financial position of
Borrower and its Subsidiaries on a consolidated basis as of the dates thereof
and its and their results of operations, shareholders' 


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<PAGE>   10

equity and cash flows for the periods then ended. All Financial Statements and
information, including any related schedules and notes, and any other financial
information or statements furnished in accordance herewith, have been prepared
in accordance with GAAP, except as otherwise disclosed therein, subject only in
the case of unaudited interim Financial Statements to normal year-end audit
adjustments and the absence of footnotes. In the case of each Revolving Credit
Loan and Letter of Credit, the representations and warranties in this Section
shall be deemed to have been made in respect of the then most recent Financial
Statements of Borrower furnished to Lender.

                (b) The Borrower is Solvent.

        3.2.    NO CHANGE. There has been no Material Adverse Change since the
Financial Statements dated as of December 31, 1996.

        3.3.    ORGANIZATION, EXISTENCE, GOOD STANDING. Borrower (i) is duly
organized, validly existing and in good standing as a corporation under the laws
of the State of Delaware, (ii) has obtained all licenses, permits, approvals and
consents and has filed all registrations necessary for the lawful operation of
its business, (iii) has the corporate power and authority and the legal right to
own, lease and operate its property and to conduct the business in which it is
currently engaged, and (iv) is duly qualified to do business and is in good
standing as a foreign corporation under the laws of each jurisdiction where its
ownership, lease or operation of property or the conduct of its business
requires such qualification, except where the failure to be so qualified would
not have a Material Adverse Effect. The Disclosure Schedule lists all states
where Borrower is qualified or authorized as a foreign corporation.

        3.4.    SUBSIDIARIES; CAPITALIZATION. Except as set forth on the
Disclosure Schedule, Borrower has no Subsidiaries or Investments in any other
Person on the Initial Borrowing Date. The authorized capitalization and the
number of shares of each class of capital stock issued and outstanding of
Borrower as of August 7, 1997 is set forth in the Borrower's Form 10-Q for the
quarter ended June 29, 1997, a true and correct copy of which has been delivered
to Lender. All outstanding shares of Borrower's stock have been duly authorized,
validly issued, and are fully paid and non-assessable.

        3.5.    POWER AND AUTHORITY. Borrower has (i) full corporate power,
authority and legal right to execute, deliver and perform its obligations under
the Loan Documents to which it is a party and to borrow hereunder, (ii) taken
all necessary actions to authorize the execution, delivery and performance by it
of each Loan Document to which it is a party and to authorize its borrowings
hereunder, and (iii) caused to be duly executed and delivered on behalf of the
Borrower each of the Loan Documents to which Borrower is a party.

        3.6.    LEGAL, VALID, BINDING OBLIGATION. Each of the Loan Documents and
each agreement, certificate, document, instrument or other paper delivered
pursuant thereto, to which Borrower is a party, constitutes the legal, valid,
and binding obligation of Borrower enforceable against Borrower in accordance
with its terms.



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<PAGE>   11

        3.7.    CONSENTS. No consent, permit, license, approval or authorization
of, or registration, declaration or filing with or notice to, any governmental
authority, bureau or agency or any other Person is required in connection with
the execution, delivery or performance by Borrower, or the validity or
enforceability against Borrower, of any Loan Document to which it is a party,
except for the consents and approvals set forth on the Disclosure Schedule and
which have been obtained.

        3.8.    NO LEGAL BAR. The execution, delivery and performance by
Borrower of the Loan Documents, and each agreement, certificate, document,
instrument or other paper delivered pursuant thereto, to which Borrower is a
party, does not and will not conflict with or cause a breach of any provision of
any existing law, rule or regulation, order, judgment, award or decree of any
court, arbitrator or governmental authority, bureau or agency, or of the charter
documents or Bylaws of, or any security issued by, Borrower or of any material
mortgage, deed or trust, indenture, lease, contract or other agreement or
undertaking to which Borrower is a party or by which any of its properties may
be bound, and will not result in the creation or imposition of any Lien on any
of its revenues or properties.

        3.9.    NO LITIGATION. Except as set forth on the Disclosure Schedule,
no litigation, investigation or other proceeding of or before any court,
arbitrator or governmental authority is currently pending nor, to the knowledge
of Borrower, threatened against Borrower or its properties or revenues or
Borrower's Subsidiaries which, if adversely determined, could reasonably be
expected to have a Material Adverse Effect.

        3.10.   NO DEFAULT. Neither Borrower nor any of its Subsidiaries is in
default in any respect, which could reasonably be expected to have a Material
Adverse Effect, in the payment or performance of any of its obligations for
monies borrowed or under any mortgage, deed of trust, indenture, lease, contract
or other agreement or undertaking to which it is a party or by which it or any
of its property may be bound or affected including, without limitation, under
the Hancock Mortgage Documents and no Default or Event of Default has occurred
and is continuing. Neither Borrower nor any of its Subsidiaries is in default
under any order, award or decree of any court, arbitrator or governmental
authority binding upon or affecting it or by which any of its property may be
bound or affected, and no such order, award or decree has or could reasonably be
expected to have a Material Adverse Effect.

        3.11.   ASSETS, NO LIENS; INTELLECTUAL PROPERTY. Borrower has good and
marketable title to, or valid leasehold interest in, all of its real property
and good title to all its personal property, including assets carried on its
books and reflected in the Financial Statements, subject to no Liens except for
(i) Liens described in the Disclosure Schedule and permitted under Section
5.3(f) hereof, and (ii) assets sold or otherwise disposed of in the ordinary
course of its business. Borrower owns or licenses all Intellectual Property
necessary for the conduct of its business and no claims, suit or proceedings are
pending or threatened which would reasonably be expected to impair in any
material respect Borrower's rights in any such Intellectual Property.

        3.12.   NO BURDENSOME RESTRICTIONS. Neither Borrower nor any of its
Subsidiaries is a party to or bound by any contract, agreement or instrument or
subject to any corporate restriction 



                                      -8-

<PAGE>   12

(including any restriction set forth in its Articles of Organization or Bylaws)
that would have a Material Adverse Effect.

        3.13.   TAXES. All federal, state, local and other tax reports and
returns which are required to be filed by Borrower have been filed, except where
extensions have been properly obtained, and Borrower has paid or made adequate
provision for all taxes, interest and penalties shown to be due and payable on
such returns or on any assessments made against it or any of its property and
all other taxes, fees or other charges imposed on its or any of its property by
any governmental authority, including, without limitation, all payroll
withholding taxes, have been paid and no tax liens have been filed and no claims
are being asserted with respect to any such taxes, fees or other charges.

        3.14.   REGULATION U, ETC. Neither Borrower nor any of its Subsidiaries
is engaged and will not engage, principally or as one of its important
activities, in the business of extending credit for the purpose of "purchasing"
or "carrying" any "margin stock" (within the respective meanings of each of the
quoted terms under Regulations U, T, G or X of the Board of Governors of the
Federal Reserve System and any successors thereto as now and from time to time
hereafter in effect), and no part of the proceeds of any Loan hereunder will be
used for "purchasing" or "carrying" any "margin stock" as so defined or for any
purpose which violates, or which would be inconsistent with, the provisions of
Regulation U or Regulation G of the Federal Reserve Board.

        3.15.   ERISA. The Borrower, all Commonly Controlled Entities, and all
their Plans are and have been in substantial compliance with the provisions of
ERISA, the qualification requirements of IRC Section 401(a), and the published
interpretations thereunder. No notice of intent to terminate a Plan has been
filed under Section 4041 of ERISA, nor has any Plan been terminated under
Section 4041(e) of ERISA which resulted in substantial liability to Borrower or
any of its Commonly Controlled Entities. The PBGC has not instituted proceedings
to terminate, or appoint a trustee to administer, a Plan and no event has
occurred or condition exists which might constitute grounds under Section 4042
of ERISA for the termination of, or the appointment of a trustee to administer,
any Plan. Neither Borrower nor any Commonly Controlled Entities would be liable
for any amount pursuant to Sections 4063 or 4064 of ERISA if all Plans
terminated as of the most recent valuation dates of such Plans. Neither Borrower
nor any Commonly Controlled Entities have: withdrawn from a Multiemployer Plan
during a plan year for which it was a substantial employer, as defined in
Section 4001(a)(2) of ERISA; or failed to make a payment to a Plan required
under Section 302(f)(1) of ERISA such that security would have to be provided
pursuant to Section 307 of ERISA. No lien upon the assets of Borrower has arisen
with respect to a Plan. To the best knowledge of Borrower, no prohibited
transaction or Reportable Event has occurred with respect to a Plan. Borrower
and each Commonly Controlled Entities have made all contributions required to be
made by them to any Plan or Multiemployer Plan when due. There is no accumulated
funding deficiency in any Plan, whether or not waived.

        3.16.   INVESTMENT COMPANY ACT, ETC. Borrower is not an "investment
company" registered or required to be registered under the Investment Company
Act of 1940, or a company "controlled" (within the meaning of such Investment
Company Act) by such an "investment company". Borrower is not subject to
regulation under the Public Utility Holding Company Act 



                                      -9-

<PAGE>   13

of 1935, the Federal Power Act, the Interstate Commerce Act or to any other
federal or state statute or regulation limiting its ability to incur
indebtedness for money borrowed. Borrower is in all material respects in
compliance with the reporting requirements of the Securities Exchange Act of
1934, as amended.

        3.17.   INDEBTEDNESS. Borrower and its Subsidiaries have no Indebtedness
of any type except Indebtedness incurred under this Agreement and that which is
permitted under Section 5.1 of this Agreement.

        3.18.   CONTINGENT LIABILITIES. Except as set forth in the notes to the
Financial Statements, Borrower and its Subsidiaries have no material Contingent
Liabilities.

        3.19.   CHIEF PLACE OF BUSINESS. As of the date hereof the chief
executive office of Borrower is located at 23 Esquire Road, North Billerica,
Massachusetts.

        3.20.   LAWS INCLUDING ENVIRONMENTAL AND SAFETY MATTERS. Borrower and
its Subsidiaries are in compliance in all material respects with all laws, rules
and regulations, orders of court or other governmental bodies, applicable to it
including, without limitation, all environmental, health and safety statutes and
regulations and specifically the Federal Resource Conservation and Recovery Act,
the Federal Comprehensive Environmental Response, Compensation and Liability
Act, the Federal Clean Water Act, the Clean Air Act, the requirements and
regulations of the Nuclear Regulatory Commission, and the Federal Occupational
Safety and Health Act. Borrower is not subject to any judicial or administrative
proceedings alleging the violation of any applicable law or regulation which
could reasonably be expected to have a Material Adverse Effect. Except as set
forth in the Disclosure Schedule, Borrower is not the subject of any federal,
state or local investigation regarding, among other matters, the release of any
Hazardous Material into the environment, the results of which could reasonably
be expected to have a Material Adverse Effect. Except as set forth in the
Disclosure Schedule, Borrower has not filed any notice under any applicable law
indicating past or present treatment, storage, disposal, generation,
transportation or reporting a spill or release into the environment of any
Hazardous Material which could reasonably be expected to have a Material Adverse
Effect. Except as set forth in the Disclosure Schedule, Borrower has not placed
or disposed of, used, generated or transported any Hazardous Material in
violation of any applicable law or regulation, upon or over any real property
owned or leased by Borrower and Borrower has no knowledge of such Hazardous
Material on such real property.

        3.21.   NEGATIVE PLEDGES. Except as set forth in the Disclosure Schedule
or pursuant to the Liens permitted under Section 5.3(e) relating to the assets
subject to such Liens, neither Borrower nor any of its Subsidiaries is a party
to or bound by any agreement, indenture, or other instrument which prohibits the
creation, incurrence or allowance to exist of any mortgage, deed of trust,
pledge, lien, security interest or other encumbrance or conveyance upon any of
Borrower's property.

        3.22.   FULL DISCLOSURE. The Financial Statements referred to in Section
3.1, the Disclosure Schedule, nor any of the Loan Documents or any list,
certificate, written statement, 



                                      -10-

<PAGE>   14

instrument, paper or other information furnished by Borrower to Lender in
connection with the Loan Documents, taken as whole, do not contain any untrue
statement of a material fact or omit to state any material fact necessary to
make the statements contained therein and herein, in light of the circumstances
in which they are made, not misleading.

                       ARTICLE 4. - AFFIRMATIVE COVENANTS

        Borrower covenants and agrees that so long as the Revolving Credit
Commitment and Letter of Credit Commitment remain in effect, the Revolving
Credit Note remains outstanding and unpaid, in whole or in part, or any other
amount is owing to Lender hereunder:

        4.1.    FINANCIAL STATEMENTS AND OTHER DOCUMENTS. Borrower shall furnish
or cause to be furnished to Lender:

                (a) ANNUAL STATEMENTS. As soon as available, but in any event
not later than one hundred twenty (120) days after the last day of each fiscal
year of Borrower, audited Financial Statements of Borrower for such fiscal year,
as prepared by the Borrower's independent accounting firm, together with the
audit report of such independent accounting firm which shall not be qualified in
any manner (except for a qualification for a change in accounting principles in
which the accounting firm concurs) together with a copy of the Borrower's
operating statement budget for its next fiscal year;

                (b) QUARTERLY STATEMENTS. As soon as available, but in any event
not later than sixty (60) days after the last day of each of the first three
fiscal quarters of each fiscal year of Borrower, Financial Statements internally
prepared by management of Borrower for such quarter and a Compliance Certificate
as of the end of such fiscal quarter;

                (c) MANAGEMENT LETTER. As soon as available, but in any event
not later than one hundred fifty (150) days after the last day of each fiscal
year of Borrower, copies of any written recommendations concerning the
management, finances, financial controls, or operations of Borrower received
from Borrower's independent public accountants;

                (d) SEC REPORTS. Promptly after sending or filing thereof with
the Securities and Exchange Commission ("SEC"), true and complete copies of all
reports, registration statements, proxy statements, notices and other documents
filed or sent to the SEC, any national securities exchange, or the National
Association of Securities Dealers, Inc.; and

                (e) OTHER INFORMATION. Such other financial and other
information concerning the affairs of Borrower as Lender may from time to time
reasonably request.

        4.2.    EXISTENCE; COMPLIANCE WITH LAWS; ETC.  Borrower shall:

                (a) CORPORATE EXISTENCE. Preserve and keep in full force and
effect its corporate existence and all franchises, licenses and permits material
to the proper conduct of its business;


                                      -11-


<PAGE>   15

                (b) COMPLIANCE WITH APPLICABLE LAWS. Comply and cause its
Subsidiaries to comply with all applicable laws and duly observe all valid
requirements of governmental authorities the breach of which could reasonably be
expected to have a Material Adverse Effect, except when contested with due
diligence, in good faith and in proper proceedings. Without limitation of the
foregoing, Borrower shall file or cause to be filed all tax returns and reports
which are required by law to be filed by it, and pay and discharge, or cause to
be paid and discharged, when due, all taxes, assessments and other governmental
charges and levies imposed upon it or any of its property or any part thereof,
or upon the income or profits therefrom, including, without limitation, payroll
withholding taxes, as well as all claims for labor, materials or supplies which,
if unpaid, might become a Lien upon any of its property (unless and to the
extent only that any such item is being contested in good faith by appropriate
proceedings and adequate reserves have been set aside with respect thereto in
conformity with GAAP). Borrower shall also pay all of its other Indebtedness and
obligations promptly and in accordance with normal terms and trade practices.

        4.3.    MAINTAIN PROPERTY. Borrower shall keep and maintain all property
useful and necessary in its business in good operating condition and repair,
ordinary wear and tear excepted; PROVIDED, HOWEVER, that nothing in this Section
shall prohibit any sale or other disposition of property by Borrower otherwise
permitted hereunder or under the Loan Documents.

        4.4.    INSURANCE. Borrower shall keep adequately insured by financially
sound and responsible insurers (a) all property owned or leased by it and all
property of an insurable nature, such insurance to be in at least such amounts
and covering loss or damage from at least such risks and hazards (including,
without limitation, business interruption insurance and use and occupancy
insurance) as are usually insured against in the same geographic areas by
companies engaged in similar businesses and reasonably acceptable to Lender, and
(b) all liabilities of Borrower for damage to property, death or bodily injury,
including without limitation product liability insurance, insurance required
under all applicable workmen's compensation laws, and insurance for such
liabilities resulting from, caused by or arising out of any product sold by any
predecessor of Borrower or by Borrower, all such insurance to be in at least
such amounts as are usually insurance against by companies engaged in the same
or similar businesses and reasonably acceptable to Lender.

        4.5.    RECORDKEEPING; RIGHTS OF INSPECTION. Borrower shall (i) keep
proper books of record and account in which full, true and correct entries, in
conformity with GAAP, are made of all dealings and transactions in relation to
its property, business and activities; (ii) permit Persons authorized by Lender
to visit and inspect its property, to inspect its books of record and account
and to make photocopies thereof, to review its accounts and to discuss the
affairs, finances and accounts of Borrower with its officers and independent
public accountants, all upon reasonable notice and at such times during normal
business hours and as often as Lender may reasonably request; and (iii) permit
Lender to perform field examinations and audits of such books and records of
account. Prior to an Event of Default hereunder, Borrower shall pay not more
than $1500 per year for field examinations and audits conducted by Lender each
year. Upon and during 



                                      -12-

<PAGE>   16

the continuance of an Event of Default hereunder, Borrower shall pay all of
Lender's reasonable expenses for each such field examination and audit, without
regard to the foregoing limit.

        4.6.    NOTICE OF MATERIAL EVENTS. Borrower will, promptly upon any
officer of Borrower obtaining knowledge thereof, give notice to Lender of (i)
any Default or Event of Default; (ii) any material casualty, loss or
depreciation to any inventory or other property of Borrower or any other force
majeure, or any litigation, investigation or other proceeding against or
involving Borrower the result of any of which might have a Material Adverse
Effect; (iii) any litigation, investigation, other proceeding or dispute
affecting Borrower (A) which relates, in whole or in part, to any of the
transactions contemplated by any of the Loan Documents, (B) which involves an
amount in excess of Two Hundred Fifty Thousand Dollars ($250,000), or (C) which
may exist between Borrower and any governmental body; (iv) any Reportable Event
in respect of any Plan or any other event or change in a Plan which might have a
Material Adverse Effect or (v) any release of any Hazardous Materials at any
location owned or leased by Borrower or any investigation or proceeding by any
governmental body alleging or relating to the violation by Borrower of any
environmental law or regulation. Borrower will furnish to Lender from time to
time all information which Lender shall reasonably request with respect to the
status of any litigation, investigation, other proceeding or dispute to which
Borrower is a party.

        4.7.    DEPOSIT ACCOUNTS. Borrower shall maintain with Lender deposit
accounts or accounts to be used as its principal depository and operating
account(s) and utilize the cash management services of Lender to be provided by
Lender at competitive rates.

        4.8.    NOTICE OF ACQUISITIONS. Borrower shall provide Lender with prior
written notice of any acquisition of substantially all of the assets or stock of
another Person or Persons using the proceeds of the Revolving Credit Loans,
together with pro forma financial information that reasonably demonstrates that
after making the proposed acquisition the Borrower will remain in compliance
with the financial covenants set forth in Section 5.5 (an "Authorized
Acquisition").

                         ARTICLE 5. - NEGATIVE COVENANTS

        Borrower covenants and agrees that, so long as the Revolving Credit
Commitment and Letter of Credit Commitment remains in effect, the Revolving
Credit Note remains outstanding and unpaid, in whole or in part, or any other
amount is owing Lender hereunder, Borrower will not, directly or indirectly, and
Borrower will not permit any of its Subsidiaries to:

        5.1.    INDEBTEDNESS. Create, incur, assume or allow to exist any
Indebtedness, except:

                (a) LOAN DOCUMENT INDEBTEDNESS. Indebtedness evidenced by the
Notes and any other Indebtedness owing to or held by Lender arising under any of
the Loan Documents;

                (b) DISCLOSED INDEBTEDNESS. Indebtedness of Borrower existing on
the Initial Borrowing Date and disclosed in the Disclosure Schedule; PROVIDED,
HOWEVER, that none of such Indebtedness shall be renewed, extended or otherwise
modified in any material respect; PROVIDED, 



                                      -13-

<PAGE>   17

FURTHER, that such Indebtedness may be extended by Borrower on substantially the
same terms and conditions;

                (c) UNSECURED CURRENT LIABILITIES. Unsecured current liabilities
(not the result of borrowing) incurred in the ordinary course of business which
are not evidenced by notes or instruments and which are not more than sixty (60)
days overdue from the original due dates thereof (unless and to the extent only
that any such liability is contested by Borrower in good faith by appropriate
proceedings and adequate reserves have been set aside with respect thereto in
accordance with GAAP);

                (d) CAPITAL LEASES. Capital Leases incurred by Borrower for the
lease of Capital Equipment (and Borrower agrees to furnish copies of the
documentation for its outstanding Capital Leases to Lender upon reasonable
request);

                (e) INTERCOMPANY OBLIGATIONS. Indebtedness of any wholly owned
Subsidiary to Borrower;

                (f) APPEALED JUDGMENTS. Judgments or awards which have been in
force for less than the applicable appeal period so long as execution is not
levied or in respect of which Borrower shall at all times be prosecuting an
appeal in good faith and a stay of execution has been obtained pending appeal;

                (g) PRODUCT WARRANTIES. Product warranties issued in the order
any course of Borrower's business;

                (h) AUTHORIZED ACQUISITIONS INDEBTEDNESS. Indebtedness assumed
after the date of this Agreement in connection with Authorized Acquisitions
provided that Borrower agrees to use its commercially reasonable efforts to
cause all such Indebtedness to be refinanced by the Lender in connection with
the Authorized Acquisition and, in any event, such Indebtedness (other than
Permitted Acquisition Indebtedness) shall be repaid on or before ninety (90)
days following the closing thereof and, unless the Lender otherwise agrees in
writing, Permitted Acquisition Indebtedness. For purposes hereof, Permitted
Acquisition Indebtedness shall mean existing Indebtedness to be assumed by the
Borrower or any Subsidiary of Borrower in connection with Authorized
Acquisitions in respect of specific items of Capital Equipment (including
Capital Lease Obligations) or specific parcels of real property but Permitted
Acquisition Indebtedness shall not include unsecured Indebtedness and
Indebtedness secured by "all assets" Liens or Liens on accounts receivable,
inventory and/or general intangibles acquired by Borrower or any Subsidiary of
Borrower; and;

                (i) APPROVED INDEBTEDNESS. Indebtedness for borrowed money
incurred after the Initial Borrowing Date with prior notice to and the written
consent of Lender.

        5.2.    CONTINGENT LIABILITIES. Except for Contingent Liabilities
existing on the Initial Borrowing Date and disclosed on the Financial Statements
or Disclosure Schedule, create, incur, assume or allow to exist any Contingent
Liabilities.


                                      -14-



<PAGE>   18

        5.3.    LIMITATION ON LIENS. Create, incur, assume or allow to exist,
any Lien upon any of its property, income or profits, whether now owned or held
or hereafter acquired, including attachment, levy, garnishment or other judicial
process relating to such property, except:

                (a) TAXES. Liens for taxes not yet due.

                (b) CARRIER'S; WAREHOUSEMEN'S; MECHANICS' ETC. Carriers',
warehousemen's, mechanics', landlords', materialmen's, repairmen's, workmen's or
other like Liens arising in the ordinary course of business with respect to
obligations which are not yet due.

                (c) SOCIAL SECURITY. Pledges, deposits in connection with
workers' compensation, unemployment insurance and other social security
legislation made in the ordinary course of business;

                (d) EASEMENTS, RESTRICTIONS, ETC. Easements, rights of way,
covenants, consents, reservations, encroachments, variations, and other
restrictions of record, with respect to Borrower's real property which do not
interfere materially with the conduct of Borrower's businesses, and do not
detract materially from the value of such property or impair Borrower's use
thereof;

                (e) CAPITAL LEASES. Liens incurred in respect of Capital Leases
or operating leases permitted under Section 5.1(d); PROVIDED HOWEVER, that the
Lien granted in respect of any Capital Lease or operating lease shall only cover
the Capital Equipment subject to such lease and secure the Indebtedness incurred
in respect of the purchase thereof and so long as such Indebtedness is only
secured by such Lien;

                (f) DISCLOSED LIENS. Liens existing on the Initial Borrowing
Date, disclosed in the Disclosure Schedule; and

                (g) AUTHORIZED ACQUISITIONS. Liens securing Permitted
Acquisition Indebtedness permitted under Section 5.2(h) in respect of (i)
specific items of Capital Equipment (including Capital Lease Obligations) or
specific parcels of real property acquired by Borrower in connection with an
Authorized Acquisition or (ii) Liens on substantially all the assets or on the
accounts receivable, inventory and/or general intangibles of a Person or Persons
to be acquired in connection with an Authorized Acquisition provided that any
such Person or Persons become a Subsidiary of Borrower as a result of the
Authorized Acquisition (so that the Liens do not attach to any of the assets of
the Borrower) and the Indebtedness securing such Liens is repaid and such Liens
are released on or before ninety (90) days following the closing of the
Authorized Acquisition.

        5.4.    PROHIBITION OF FUNDAMENTAL CHANGES. (a) Enter into any
transaction of merger or consolidation or amalgamation unless as a result of
such transaction Borrower is the surviving corporation; (b) liquidate, wind-up
or dissolve itself (or allow any such liquidation or dissolution); (c) convey,
sell, issue, exchange, lease, assign, transfer or otherwise dispose of all or



                                      -15-


<PAGE>   19

any material portion of its business or property (other than sales of inventory
in the ordinary course of business and obsolete equipment or equipment no longer
used or useful in the business of Borrower (but not equipment securing Equipment
Loans); (d) make any Investment in or purchase, lease or otherwise acquire all
or any material portion of the business or property of any other Person except
in connection with an Authorized Acquisition; (e) make any Investment in or loan
or other advances of money to any Person, except for (i) loans and advances (1)
for salary, travel advances, advances against commissions and similar advances
in the ordinary course of business, (2) to Borrower's wholly owned Subsidiaries
and branches existing on the Initial Borrowing Date in accordance with
Borrower's past practices and (3) to wholly owned Subsidiaries of Borrower
incorporated and branches of Borrower organized after the Initial Borrowing
Date, in an aggregate amount not to exceed $1,000,000 at any time and (ii)
Investments in Cash Equivalents, to any Person; (f) change its name or the
location of its chief executive office except on ten (10) Business Days prior
written notice to Lender; or (g) Investments in wholly owned Subsidiaries of
Borrower that are created for the purpose of becoming partners in joint ventures
established by Borrower in an aggregate amount not to exceed $1,000,000.

        5.5.    FINANCIAL MEASUREMENTS.

                (a) CURRENT RATIO. Allow the ratio of Borrower's Current Assets
to Current Liabilities to be less than 1.75 to 1.00 at any time.

                (b) RATIO OF NET WORTH TO SENIOR INDEBTEDNESS. Allow the Net
Worth of Borrower at any time to be less than one and one half (1.5) times the
outstanding amount of all Senior Indebtedness of Borrower.

                (c) RATIO OF TOTAL LIABILITIES TO NET WORTH. Allow the ratio of
(i) Total Liabilities to (ii) Net Worth of Borrower at any time, to be greater
than 1.25 to 1.00.

                (d) DEBT SERVICE COVERAGE RATIO. Allow the ratio of (i) EBITDA
of Borrower minus unfinanced Capital Expenditures minus Dividends and
Distributions, to (ii) Borrower's interest expense plus Current Maturities of
Long Term Debt, calculated retrospectively for the period of the immediately
preceding four fiscal quarters, to be less than 1.20 to 1.00 on the last day of
any fiscal quarter, provided that for purposes of determining the Debt Service
Coverage Ratio unfinanced Capital Expenditures shall not be deducted from the
numerator of the ratio until such time as Loans are outstanding under this
Agreement..

        5.6.    TRANSACTIONS WITH AFFILIATES. Enter into or be a party to any
agreement or transaction with any Affiliate, except in the ordinary course and
pursuant to reasonable requirements of Borrower's business and upon fair and
reasonable terms and conditions which are fully disclosed to Lender and are no
less favorable to Borrower than would obtain in a comparable arm's length
transaction with a Person not an Affiliate of Borrower.

        5.7.    NEGATIVE PLEDGE. Except as set forth in the Disclosure Schedule
or pursuant to the Liens permitted under Section 5.3(e), directly or indirectly,
enter into any agreement, 



                                      -16-

<PAGE>   20

indenture, or other instrument which prohibits the creation, incurrence or
allowance to exist of any mortgage, deed of trust, pledge, lien, security
interest or other encumbrance or conveyance upon any of Borrower's property.

                        ARTICLE 6. - CONDITIONS PRECEDENT

        6.1.    CONDITIONS OF INITIAL EXTENSION OF CREDIT. The obligation of
Lender to make any Revolving Credit Loan and issue Letters of Credit on the
Initial Borrowing Date is subject to the satisfaction of the condition precedent
that Lender shall have received on or before such date, the following items in
form and substance satisfactory to Lender and its counsel executed where
appropriate by a duly authorized officer of Borrower.

LOAN DOCUMENTS:

                (a) CREDIT AGREEMENT. This Agreement;

                (b) REVOLVING CREDIT NOTE. The Revolving Credit Note;

                (c) COMPLIANCE CERTIFICATE. A Compliance Certificate;

CORPORATE DOCUMENTS:

                (d) CORPORATE RESOLUTIONS. Copies of resolutions of the Board of
Directors (and, if necessary, the Stockholders) of Borrower, authorizing the
execution, delivery and performance of the Loan Documents to which Borrower is a
party, and the transactions contemplated thereby, certified as of the Initial
Borrowing Date by the Secretary or Assistant Secretary of Borrower (which
certificate shall state that such resolutions have not been amended, modified,
revoked or rescinded as of such date);

                (e) CORPORATE INCUMBENCY CERTIFICATE. Certificate of the
Secretary or Assistant Secretary of Borrower, dated as of the Initial Borrowing
Date, certifying the names and titles of the officers authorized to execute the
Loan Documents to which Borrower is a party and any other documents related to
any thereof, together with specimen signatures of such officers;

                (f) CHARTER DOCUMENTS. Copies of (i) the charter documents and
all amendments thereto of Borrower, currently certified by the relevant
governmental filing authority, and (ii) the By-Laws of Borrower certified as of
the Initial Borrowing Date by the Secretary or Assistant Secretary of the
Borrower;

                (g) LEGAL GOOD STANDING CERTIFICATES. For Borrower, a
certificate of legal existence and good standing issued by the Secretary of
State of the State of Delaware, and a certificate of foreign qualification and
good standing issued by the Secretary of State of each state of foreign
qualification or authorization, all of which shall be dated currently;



                                      -17-


<PAGE>   21

                (h) TAX GOOD STANDING CERTIFICATES. For Borrower, a certificate
of good tax standing currently dated from each jurisdiction in which such party
is obliged to file tax returns and pay taxes (or, to the extent any such
certificates are unobtainable, because it is not the practice of the taxing
authority to issue such certificate, or because of time delays in the issuance
of such certificate attributable to such taxing authority, a letter from
Borrower's chief financial officer setting forth the nature of the tax
obligation and the relevant jurisdiction, and certifying that all required
returns have been duly filed and all required taxes shown thereon paid;

MISCELLANEOUS DOCUMENTS:

                (i) LEGAL OPINION. A written opinion of counsel for Borrower in
form and content satisfactory to Lender, dated the Initial Borrowing Date,
addressed to Lender and covering such matters related to the Borrower and the
transactions contemplated hereby as Lender may request;

                (j) LIEN SEARCH. Search reports certified by a party acceptable
to Lender, dated a date reasonably close to the Initial Borrowing Date,
confirming the absence of any security interests, tax liens or other Liens made
against Borrower, or any of its assets, wherever located;

                (k) CONSENTS. Copies of all consents or approvals of any Person
that may be required in connection with the transactions contemplated by the
Loan Documents;

                (l) FEES. Payment of the estimated fees and disbursements of
Lender's counsel in connection with the Loan Documents and the transactions
contemplated hereby; and

                (m) CASUALTY AND LIABILITY INSURANCE. Certificates of insurance
or cover notes in respect of insurance required by the provisions of Section 4.4
of this Agreement;

                (n) HANCOCK MORTGAGE DOCUMENTS. A satisfactory review by Lender
and its counsel of the Hancock Mortgage Documents and a Certificate of the Chief
Executive Officer or Chief Financial Officer of Borrower relating to the Hancock
Mortgage Documents and confirming that no defaults or events of default have
occurred thereunder; and

                (o) DISBURSEMENT INSTRUCTIONS. The Borrower's instructions for
wire transfer of the proceeds of its initial borrowing.

        6.2.    CONDITIONS OF ALL REVOLVING CREDIT LOANS AND LETTERS OF CREDIT.
The Lender's obligation to make any Revolving Credit Loan and to issue Standard
Letters of Credit is subject to the fulfillment of the following additional
conditions precedent:

                (a) REPRESENTATIONS. The representations and warranties made by
any party to any Loan Document (other than Lender) in any Loan Document or in
any certificate, document or financial or other statement furnished at any time
under or in connection therewith shall be true 



                                      -18-


<PAGE>   22

and correct in all material respects on and as of the Borrowing Date for such
Loan as if made on and as of such date;

                (b) NO DEFAULT. No Default or Event of Default shall have
occurred and be continuing on the Borrowing Date for such Loan either before or
after giving effect to the Loan made on such date;

                (c) CREDIT LIMIT COMPLIANCE. The aggregate unpaid principal
amount of the Revolving Credit Loans and Letters of Credit outstanding on any
Borrowing Date shall not exceed the Revolving Credit Limit on such date;

                (d) ADDITIONAL MATTERS. Lender shall have received such other
documents, statements, certificates, information and evidence including a
Compliance Certificate as Lender may reasonably request. All documents and legal
matters in connection with the transactions contemplated by this Agreement shall
be reasonably satisfactory in form and content to Lender and its counsel, and
all actions required to be taken on or before the Borrowing Date for such Loan
shall have been taken.

Each request for a Revolving Credit Loan by Borrower hereunder shall constitute
a representation and warranty by Borrower as of the date of such request or
application that the conditions contained in paragraphs (a) through (c) of this
Section 6.2 have been satisfied.

                         ARTICLE 7. - EVENTS OF DEFAULT

        7.1.    EVENTS OF DEFAULT. The occurrence of any of the following shall
constitute an Event of Default:

                (a) FAILURE OF PAYMENT. If Borrower fails to pay any principal
or other amount due, under this Agreement or with respect to any Loan on the
date due (whether on a scheduled payment date or otherwise) and in the manner
provided herein or if Borrower fails to pay any interest with respect to any
Loan within two (2) days of the date due and in the manner provided herein;

                (b) MISSTATEMENTS. If any representation, warranty or other
statement made herein or in any other Loan Document or otherwise in writing by
or on behalf of Borrower in connection herewith proves to be or to have been
incorrect or misleading in any material respect as of the date at which it is
made or deemed to be made;

                (c) PERFORMANCE OF OTHER COVENANTS. If Borrower defaults in the
due performance or observance of (i) any covenant contained in Sections 4.1(a),
4.1(b), 4.1(d), or, 5.1 through and including 5.5 or (ii) any other covenant,
condition or provision to be performed or observed by it under any of the Loan
Documents (other than a covenant default the performance or observance of which
is dealt with specifically elsewhere in this Section 7.1) and the breach of such
other provision is not cured to Lender's satisfaction within thirty (30) days
after the sooner 


                                      -19-


<PAGE>   23

to occur of Borrower's receipt of notice of such breach from Lender or the date
on which such failure or neglect first becomes known to any officer of Borrower.

                (d) OTHER OBLIGATIONS. If Borrower defaults, which default
continues after any applicable grace or cure period, in any payment of principal
of or interest on any Indebtedness for borrowed money in excess of $500,000
including, without limitation, the Indebtedness of Borrower owing to Hancock or
any other default occurs with respect to any Indebtedness for borrowed money
giving the holder thereof the right to accelerate the payment thereof or require
such Indebtedness to be paid before its stated maturity or before any regularly
scheduled date of prepayment; provided, however, that the failure of Borrower to
pay any amount due under any Capital Lease or obligation for the deferred
purchase price of property or services shall not be deemed an Event of Default
hereunder so long as Borrower is contesting such payment in good faith by
appropriate proceedings and adequate reserves have been set aside with respect
thereto in conformity with GAAP);

                (e) JUDGMENTS. If Borrower permits any judgment against it in
excess of $500,000 to remain undischarged for a period of more than thirty (30)
days unless during such period such judgment is effectively stayed or bonded, on
appeal or otherwise;

                (f) LEVY, ATTACHMENTS. If any levy in excess of $500,000 (not
discharged within thirty (30) days), seizure, attachment, execution or similar
process shall be issued on any of the Borrower's cash, accounts or any material
property;

                (g) VOLUNTARY BANKRUPTCY. If Borrower (a) commences a voluntary
case under the Bankruptcy Code (as now or hereafter in effect); or (b) files a
petition or commences any case, proceeding, or action in bankruptcy or seeking
reorganization, liquidation, dissolution, winding-up, arrangement, composition,
readjustment of its debts or any other relief under any other bankruptcy,
insolvency, reorganization, liquidation, dissolution, arrangement, composition,
readjustment of debt or similar act or law of any jurisdiction, now or hereafter
existing; or (c) takes any action indicating its consent to, approval of, or
acquiescence in, any such case, proceeding or other action; or (d) applies for a
receiver, trustee or custodian of it or for all or a substantial part of its
property; or (e) makes an assignment for the benefit of creditors; or (f) is
unable to pay its debts as they mature or admits in writing such inability; or
(g) is adjudicated insolvent or bankrupt;

                (h) INVOLUNTARY BANKRUPTCY. (a) If there is commenced against
Borrower (i) an involuntary case under the Bankruptcy Code (as now or hereafter
in effect); or (ii) any case or proceeding or any other action in bankruptcy or
seeking reorganization, liquidation, dissolution, winding-up, arrangement,
composition, readjustment of its debts or any other relief under any other
bankruptcy, insolvency, reorganization, liquidation, dissolution, arrangement,
composition, readjustment of debt or similar act or law of any jurisdiction, now
or hereafter existing, or seeking appointment of a receiver, trustee or
custodian of Borrower or for all or a substantial part of its property, and any
of the foregoing cases, proceedings, or actions is not dismissed within sixty
(60) days; or (b) if an order, judgment or decree approving any of the foregoing
is entered or a warrant of attachment, execution or similar process against any
substantial part of the property of 


                                      -20-


<PAGE>   24

Borrower is issued, and such order, judgment, decree, warrant, execution or
similar process is not vacated or stayed within sixty (60) days; or (c) if an
order for relief under the Bankruptcy Code (as now or hereafter in effect) is
entered against Borrower; or

                (i) CRIMINAL PROCEEDINGS. If there is an indictment of Borrower
under any criminal statute, or commencement of criminal proceedings against
Borrower, pursuant to which statute or proceedings the penalties or remedies
sought or available include forfeiture of any property of Borrower with a fair
market value in excess of $500,000; or

                (j) NO CHANGE IN CONTROL OF BORROWER. Any change in control of
Borrower such that a "person" or "group" (within the meaning of Sections 13(d)
and 14(d)(2) of the Securities Exchange Act of 1934, as amended) that is not as
of the date of this Agreement the "beneficial owner" (as defined in Rule 13d-3
of the Securities Exchange Act of 1934, as amended) of 5% or more of the total
voting power of all classes of stock outstanding of Borrower entitled to vote in
the election of directors of Borrowers becomes the beneficial owner of 34% or
more of such stock; provided that so long as such Change in Control is not
reasonably likely to constitute a Material Adverse Change, Borrower shall have
forty-five (45) days from the date of occurrence of any such Change in Control
to effect a cure thereof reasonably satisfactory to the Lender.

        7.2.    LENDER'S REMEDIES. Upon the occurrence of any such Event of
Default, Lender may, at Lender's option, immediately exercise one or more of the
following rights: (a) declare all obligations of Lender to Borrower, including,
without limitation, the Revolving Credit Commitment, and Letter of Credit
Commitment to be terminated, whereupon such commitments shall immediately
terminate; and (b) declare all obligations of Borrower to Lender, including,
without limitation, the Loans and all other amounts owing under this Agreement,
the Revolving Credit Note and the Letters of Credit to be immediately due and
payable, whereupon they shall immediately become due and payable without
presentment, demand, protest or notice of any kind, all of which are hereby
expressly waived; PROVIDED, however, that upon the occurrence of any such Event
of Default specified in Sections 7.1(g) or 7.1(h) (a) the Revolving Credit
Commitment and Letter of Credit Commitment shall immediately terminate; and (b)
all obligations of Borrower to Lender, including, without limitation, all
Revolving Credit Loans, Letters of Credit and all other amounts owing under this
Agreement, the Revolving Credit Note and the Letters of Credit shall immediately
become due and payable without presentment, further demand, protest or notice of
any kind, all of which are hereby expressly waived.

        7.3.    CROSS DEFAULT. It is agreed by Borrower that any Event of
Default under this Agreement will constitute an event of default under all of
the Loan Documents and all other agreements and evidences of Indebtedness
between Borrower and Lender, whether now existing or hereafter executed and
whether or not such is an event of default therein.

        7.4.    SETOFF. In addition to any rights and remedies of Lender
provided by law, Lender shall have the right, (a) upon and during the
continuance of an Event of Default pursuant to Section 7.1(a), or (b) upon the
Lender electing to accelerate the Obligations pursuant to Section 7.2, or (c) at
any time, whether or not an Event of Default has occurred and is continuing, in
the event of any attachment, trustee process, garnishment, or other levy or lien
is, or is sought to be 



                                      -21-

<PAGE>   25

imposed, on any cash or deposit and investment accounts of Borrower, and without
prior notice to Borrower, any such notice being expressly waived by Borrower to
the extent permitted by applicable law, and regardless of the adequacy of any
collateral, to set off and apply against any indebtedness, whether matured or
unmatured, of Borrower to Lender, any amount owing or otherwise available under
any applicable agreement or contract (including without limitation all deposits
maintained at Lender, whether general or special, time or demand, provisional or
final, joint or otherwise but excluding payroll accounts) from Lender to
Borrower, and such right of setoff may be exercised by Lender against Borrower
or against any bankruptcy trustee, debtor-in-possession, assignee for the
benefit of creditors, receiver, or execution, judgment or attachment creditor of
Borrower, or against anyone else claiming through or against Borrower or such
Person.

                           ARTICLE 8. - MISCELLANEOUS

        8.1.    NOTICES. Except as otherwise specified herein, all notices to or
upon the parties hereto shall be in writing (including teletransmissions), shall
be given or made to the party to which such notice is required or permitted to
be given or made under this Agreement at the address or telex or telecopier
number set forth below or at such other address or telex or telecopier number as
any party hereto may hereafter specify to the others in writing, and (unless
otherwise specified herein) shall be deemed delivered on receipt, if
teletransmitted or delivered by hand, or three (3) Business Days after mailing,
and all mailed notices shall be by registered or certified mail, postage
prepaid:

                IF TO BORROWER TO

                BTU International, Inc.
                23 Esquire Road
                North Billerica, MA 01862
                Attention:  President
                (Facsimile No. (508) 667-3377)

                WITH A COPY TO

                Peter H. Dodson, Esq.
                Ropes & Gray
                One International Place
                Boston, MA 02110
                (Facsimile No. (617) 951-7050)

                IF TO LENDER TO

                USTRUST
                30 Court Street
                Boston, MA  02108
                Attention:  John Bukala, Vice President



                                      -22-


<PAGE>   26

                (Facsimile No. (617) 932-2849)

                WITH A COPY TO

                Jeffery L. Keffer, Esquire
                Brown, Rudnick, Freed & Gesmer
                One Financial Center
                Boston, MA  02111

                (Facsimile No. (617) 856-8201)

        8.2.    NO WAIVER OF RIGHTS. No failure to exercise nor any delay in
exercising, on the part of Lender, any right, remedy, power or privilege under
the Loan Documents shall operate as a waiver thereof; nor shall any single or
partial exercise of any right, remedy, power, or privilege operate as a waiver
of any further or complete exercise thereof. No waiver shall be effective unless
in writing. No waiver or condonation of any breach on one occasion shall be
deemed a waiver or condonation on any other occasion.

        8.3.    CUMULATIVE REMEDIES. Each of the Loan Documents and the
obligations of Borrower thereunder are in addition to and not in substitution
for any other obligations or security interests now or hereafter held by Lender
and shall not operate as a merger of any contract or debt or suspend the
fulfillment of or affect the rights, remedies, powers, or privileges of Lender
in respect of any obligation or other security interest held by it for the
fulfillment thereof. The rights and remedies provided in the Loan Documents are
cumulative and not exclusive of any other rights or remedies provided by law.

        8.4.    SUCCESSORS. This Agreement shall be binding upon and inure to
the benefit of Borrower, Lender and all future holders of the Notes, and their
respective successors and assigns, except that Borrower may not assign or
transfer its rights or obligations hereunder without the prior written consent
of Lender. Borrower acknowledges that Lender may, from time to time, sell
participation interests in the Loans and Borrower's other obligations hereunder,
to third parties, on such terms and conditions as Lender may determine, and
Borrower specifically consents thereto; provided that so long as no Event of
Default has occurred and is continuing, Lender shall retain at least a majority
interest in the Loans; and provided further that Lender may from time to time at
any time pledge the Loans to federal government agencies in accordance with
applicable banking laws and regulations. Lender may also from time to time
assign its rights and delegate its obligations, including its obligation to make
part or all of the Loans or grant part or all of any other financial
accommodation under this Agreement, in which event Borrower shall only have
recourse to the assignee for the performance of Lender's obligations that have
been so delegated. For these purposes Lender may disclose to an intended or
actual participant or assignee all or any information supplied to Lender by or
on behalf of Borrower.

        8.5.    GOVERNING LAW. This Agreement, the Notes and other Loan
Documents shall be governed by, and construed and interpreted in accordance
with, the laws of the Commonwealth of Massachusetts.



                                      -23-


<PAGE>   27

        8.6.    SUBMISSION TO JURISDICTION; WAIVER OF TRIAL BY JURY.

                (a) For purposes of any action or proceeding involving the Loan
Documents or any other agreement or document referred to therein, Borrower
hereby submits to the jurisdiction of all federal and state courts located in
the Commonwealth of Massachusetts and consents that any order, process, notice
of motion or other application to or by any of said courts or a judge thereof
may be served within or without such court's jurisdiction by registered mail or
by Personal service, PROVIDED a reasonable time for appearance is allowed (but
not less than the time otherwise afforded by any law or rule).

                (b) THE BORROWER AND LENDER HEREBY KNOWINGLY, VOLUNTARILY AND
INTENTIONALLY WAIVE (TO THE EXTENT PERMITTED BY APPLICABLE LAW) (i) ANY RIGHT IT
MAY HAVE TO A TRIAL BY JURY OF ANY DISPUTE ARISING UNDER OR RELATING TO THIS
AGREEMENT, ANY NOTE, ANY OTHER LOAN DOCUMENT OR ANY OTHER AGREEMENT OR DOCUMENT
REFERRED TO HEREIN OR THEREIN AND AGREES THAT ANY SUCH DISPUTE SHALL BE TRIED
BEFORE A JUDGE SITTING WITHOUT A JURY; and (ii) ANY RIGHT TO CONTEST THE
APPROPRIATENESS OF ANY ACTION BROUGHT WITHIN THE JURISDICTION MENTIONED IN
PARAGRAPH (a) OF THIS SECTION BASED ON LACK OF PERSONAL JURISDICTION, IMPROPER
VENUE, OR FORUM NON CONVENIENS.

        8.7.    COMPLETE AGREEMENT, AMENDMENTS. This Agreement, together with
the Notes and other Loan Documents contains the entire agreement between the
parties with respect to the transactions contemplated hereby, and supersede all
negotiations, presentations, warranties, commitments, offers, contracts and
writings prior to the date hereof relating to the subject matter. This Agreement
may only be amended, modified, waived, discharged or terminated by a writing
signed by the party to be charged with such amendment, modification, waiver,
discharge or termination.

        8.8.    EXPENSES. The Borrower shall pay on demand, regardless of
whether any Default or Event of Default has occurred or whether any proceeding
to enforce any Loan Document has been commenced, all out-of-pocket expenses
(including, without limitation, the reasonable fees and disbursements of counsel
to Lender) incurred by Lender in connection with (a) the negotiation,
preparation, administration, filing or recording of the Loan Documents, and any
future requests for amendments or waivers of the Loan Documents (whether or not
the transactions contemplated thereby shall be consummated), (b) the collection
of the Loans and any and all other obligations of Borrower to Lender whether now
existing or hereafter arising, or with the preservation, exercise or enforcement
of Lender's rights and remedies under or in connection with the Loan Documents,
including, without limitation, any and all expenses incurred by Lender in or in
connection with any case commenced by or against Borrower under the Bankruptcy
Code, and (c) any claim or liability for any stamp, excise or other similar
taxes and any penalties or interest with respect thereto that may be levied,
collected, withheld or assessed by any jurisdiction in connection with the
execution and delivery of the Loan Documents or any modification thereof. This
covenant shall survive payment of the Loans and termination of this 


                                      -24-


<PAGE>   28

Agreement. Borrower hereby authorizes Lender to make Loans to pay any amount
owed by Borrower under this Section if Borrower fails to pay such amount
promptly after demand.

        8.9.    INDEMNIFICATION. Borrower agrees to indemnify and hold Lender
harmless from and against any and all loss, liability, obligations, damages,
penalties, judgments, actions, claims, costs and expenses (including, without
limitation, attorneys' fees and disbursements) now or in the future incurred by
or asserted against Lender by any Person arising out of or in connection with
any past, present, or future action or inaction by Lender or Borrower in
connection with any Loan Document, or any transaction contemplated thereby,
except any action or inaction arising out of Lender's gross negligence or
willful misconduct.

        8.10.   CHANGE IN LAWS. If while any Loan is outstanding, any law,
executive order or regulation is enforced, adopted or interpreted which is
applicable generally to national bank associations in the United States of
America so as to affect any of Borrower's obligations or the compensation to
Lender in respect of any Eurodollar Loan or the cost to Lender of making any
Eurodollar Loan, Lender shall notify Borrower thereof in writing and Borrower
shall, promptly upon Lender's request, reimburse or indemnify Lender, with
respect thereto so that Lender shall be in the same position as if there had
been no such enforcement, adoption or interpretation. The foregoing agreement of
Borrower to reimburse or indemnify Lender shall apply in (but shall not be
limited to) the case of an imposition of or change in reserve, capital
maintenance or other similar requirements or in United States interest
equalization taxes or other excise or similar taxes or monetary restraints,
except a change in tax on the net income of Lender.

        8.11.   SURVIVAL OF AGREEMENTS. All covenants, agreements,
representations and warranties made herein and in the certificates delivered
pursuant hereto shall survive the making of Loans and the execution and delivery
to Lender of the Notes and shall continue in full force and effect so long as
the Notes is outstanding and unpaid or this Agreement remains in effect. All
agreements, obligations and liabilities of Borrower under this Agreement
concerning the payment of money to Lender, other than the obligation to pay
principal of and interest on Loans, shall survive the payment in full of Loans,
the Revolving Credit Note and Letters of Credit and termination of this
Agreement.

        8.12.   SEVERABILITY. Any provision hereof that is prohibited or
unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective
to the extent of such prohibition or unenforceability without invalidating the
remaining provisions hereof, and any such prohibition or unenforceability in any
jurisdiction shall not invalidate or render unenforceable such provision in any
other jurisdiction.

        8.13.   DESCRIPTIVE HEADINGS. The Table of Contents and the captions in
this Agreement are for convenience of reference only and shall not define or
limit the provisions hereof.

        8.14.   COUNTERPARTS. This Agreement may be executed by one or more of
the parties on any number of separate counterparts, and all of said counterparts
taken together shall be deemed to constitute one and the same instrument.


                                      -25-



<PAGE>   29

        IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed under seal by their respective duly authorized officers as of the date
first written above.

WITNESS:                                      BTU INTERNATIONAL, INC.


____________________________                  By: ____________________________
                                                     Name:
                                                     Title:


                                              USTRUST


_____________________________                 By: ____________________________
                                                     Name:
                                                     Title:



                                      -26-


<PAGE>   30



                                   SCHEDULE I

                                   DEFINITIONS


        "AFFILIATE" - as to any Person (a) any other Person which, directly or
indirectly, is in control of, is controlled by, or is under common control with
such Person, or (b) any other Person who is an officer or director of such
Person, or (c) any Person described in clause (a) above (other than any
Subsidiary all of the capital stock of which is owned by Borrower).

        "AUTHORIZED ACQUISITION" - has the meaning given such term in Section
4.8 hereof.

        "BANKRUPTCY CODE" - The Bankruptcy Reform Act of 1978, as heretofore and
hereafter amended, and codified as 11 U.S.C. ss.ss.101, ET SEQ.

        "BASE RATE" - for any day the rate on such day announced by Lender as
its Base Rate. The Base Rate is a reference rate and does not necessarily
represent the lowest or best rate charged to any customer.

        "BASE RATE REVOLVING CREDIT LOAN" - a Revolving Credit Loan bearing
interest at the Base Rate.

        "BORROWING DATE" - the Business Day on which any Loan is made.

        "BUSINESS DAY" - any day on which commercial banks are open for domestic
and international business, including dealing in dollar deposits in Boston,
Massachusetts, and if the applicable Business Day relates to a Eurodollar Loan,
any London Banking Day.

        "CAPITAL EQUIPMENT" - equipment that in accordance with GAAP is required
or permitted to be depreciated or amortized on Borrower's balance sheet.

        "CAPITAL EXPENDITURES" - for any period, the sum of (i) all expenditures
that, in accordance with GAAP, are required to be included in land, property,
plant or equipment or similar fixed asset account (whether involving real or
personal property) and (ii) Capital Lease Obligations incurred during such
period (excluding renewals of Capital Leases).

        "CAPITAL LEASE" - any capital lease, conditional sales contract or other
title retention agreement relating to the acquisition of Capital Equipment.

        "CAPITAL LEASE OBLIGATIONS" - the aggregate capitalized amount of the
obligations of Borrower under all Capital Leases.

        "CASH EQUIVALENTS" - (a) securities with maturities of 180 days or less
from the date of acquisition issued or fully guaranteed or insured as to payment
of principal and interest by the United States or any agency thereof, (b)
certificates of deposit with maturities of 365 days or less 


                                      -1-


<PAGE>   31

from the date of acquisition issued by Lender or any domestic commercial bank
having capital and surplus reasonably acceptable to Lender and (c) commercial
paper of a domestic issuer rated at least either A-2 by Standard & Poor's or B-2
by Moody's Investors Service with maturities of 180 days or less from the date
of acquisition.

        "COBRA" - the Consolidated Omnibus Budget Reconciliatory Act of 1985, as
amended, including the sections of the IRC affected by it and all regulations
promulgated under such Act or the IRC.

        "COLLATERAL" - has the meaning given such term in the Security
Agreement.

        "COMMITMENT PERIOD" - the period from and including the Initial
Borrowing Date to and including the Termination Date.

        "COMMONLY CONTROLLED ENTITY" - an entity, whether or not incorporated,
which is under common control with Borrower within the meaning of Section 414(b)
or (c) of the IRC.

        "COMPLIANCE CERTIFICATE" - a compliance certificate in the form of
EXHIBIT B, duly completed and executed by the President or chief financial
officer of Borrower, certifying, as of any date, that the conditions set forth
in Section 6.2 to the making of Revolving Credit Loans and the issuance of
Letters of Credit have been satisfied.

        "CONTINGENT LIABILITY" - any obligation of Borrower guaranteeing or in
effect guaranteeing any Indebtedness, leases, dividends or other obligations
("primary obligations") of any other Person (the "primary obligor") in any
manner, whether directly or indirectly; PROVIDED, HOWEVER, that the term
Contingent Liability shall not include endorsements of negotiable instruments in
the ordinary course of business, product warranties issued in ordinary course of
business, and Borrower's guaranties of its wholly owned Subsidiaries'
obligations for leases and equipment purchases incurred in the ordinary course
of business.

        "CREDIT COMMITMENTS" - the Revolving Credit Commitment and Letter of
Credit Commitment.

        "CURRENT ASSETS" - current assets, as determined in accordance with
GAAP.

        "CURRENT LIABILITIES" - current liabilities, as determined in accordance
with GAAP.

        "CURRENT MATURITIES OF LONG TERM DEBT" - the current maturity of long
term Indebtedness paid during the applicable period including, but not limited
to, amounts required to be paid during such period under Capital Leases.

        "DEFAULT" - any event specified in Article 7, whether or not any
requirement for the giving of notice or lapse of time or any other condition has
been satisfied.



                                      -2-


<PAGE>   32

        "DIVIDENDS" means, for any applicable period, the aggregate of all
amounts paid or payable (without duplication) as dividends (exclusive of
dividends payable solely in capital stock of Borrower), distributions or owner
withdrawals with respect to Borrower's shares of capital stock, whether now or
hereafter outstanding and includes any purchase, redemption or other retirement
of any shares of the Borrower's stock, directly or indirectly.

        "DOLLARS" and "$" - lawful money of the United States. Any reference to
payment means payment in immediately available Dollar funds.

        "EBITDA" - for any period, Borrower's Earnings before the payment of
interest and income tax plus depreciation and amortization, all as determined in
accordance with GAAP provided that any one time charges and write-offs resulting
from an Authorized Acquisition shall be excluded from such calculation.

        "ERISA" - the Employee Retirement Income Security Act of 1974, as
amended from time to time, including all regulations promulgated under such Act.

        "EARNINGS" - for any period, the net income from continuing operations
(or deficit) of the Borrower determined in accordance with GAAP excluding all
extraordinary and nonrecurring gains. Any gain realized by Borrower from the
sale or other disposition of BTI or Borrower's Investment in BTI shall not be
included in the calculation of Earnings.

        "EURODOLLAR LOAN NOTICE" - Borrower's notice given pursuant to Section
2.3 that Borrower elects to borrow a Revolving Credit Loan and pay interest at
the applicable Eurodollar Rate thereon or convert an outstanding Revolving
Credit Loan to a Eurodollar Loan and specifying the applicable Interest Period
therefor.

        "EURODOLLAR LOANS" - Revolving Credit Loans bearing interest at the
Eurodollar Rate.

        "EURODOLLAR RATE" - the LIBOR Rate plus 125 basis points.

        "EVENT OF DEFAULT" - any event specified in Article 7, PROVIDED that any
requirement for the giving of notice or lapse of time or any other condition has
been satisfied.

        "FINANCIAL STATEMENTS" - financial statements of Borrower and its
Subsidiaries, on a consolidated basis, prepared on a consistent basis in
accordance with GAAP (except for changes in GAAP with which such accountants
concur) and containing balance sheets, statements of income and retained
earnings and statements of cash flow. Financial Statements for a fiscal year
shall contain an audit report without qualification (except for nonmaterial
qualifications) by independent certified public accountants selected by Borrower
and acceptable to Lender. Financial Statements for a quarter shall be certified
by the chief financial officer of Borrower as prepared in accordance with GAAP
except for year-end adjustments and except that such interim statements need not
contain footnotes.



                                      -3-


<PAGE>   33

        "GAAP" - those generally accepted accounting principles set forth in
Statements of the Financial Accounting Standards Board and in Opinions of the
Accounting Principles Board of the American Institute of Certified Public
Accountants or which have other substantial authoritative support in the United
States and are applicable in the circumstances, as applied on a consistent
basis. As used in the preceding sentence "consistent basis" shall mean that the
accounting principles observed in the current period are comparable in all
material respects to those applied in the preceding period.

        "HANCOCK MORTGAGE DOCUMENTS - the Promissory Note, Loan Agreement,
Mortgage and other agreements and instruments between Borrower and John Hancock
Mutual Life Insurance Company ("Hancock") in respect of the mortgage loan
furnished by Hancock to Borrower which mortgage loan was in the outstanding
principal amount of [$6,297,531.31] on [September 30, 1994] as such may be
amended, supplemented, or otherwise modified, from time to time.

        "HAZARDOUS MATERIAL" - any hazardous waste, toxic substance hazardous
chemical, radioactive material, hazardous material, oil or gasoline, under any
applicable federal or state statute, county or municipal law or ordinance,
including (without limitation) any substance defined as a "hazardous substance"
or "toxic substance" (or comparable term) in the Comprehensive Environmental
Response, Compensation and Liability Act, as amended (42 U.S.C. 9601, ET SEQ.),
the Hazardous Materials Transportation Act (49 U.S.C. 1802), or the Resource
Conservation and Recovery Act (42 U.S.C. 6901, ET SEQ.).

        "INDEBTEDNESS" - with respect to any Person, any item that would
properly be included as a liability on the liability side of a balance sheet of
such Person as of any date as of which Indebtedness is to be determined and
includes (but is not limited to) (a) all obligations for borrowed money
including all Loans, (b) all obligations evidenced by bonds, debentures, notes
or other similar instruments, (c) all obligations to pay the deferred purchase
price of property or services, (d) all Capital Lease Obligations and (e) all
obligations in respect of advances made or to be made under Letters of Credit
issued for such Person's account and in respect of acceptances of drafts drawn
by such Person.

        "INITIAL BORROWING DATE" - the first to occur of the date that the first
Loan is made or first Letter of Credit is issued under this Agreement.

        "INTELLECTUAL PROPERTY" - shall mean "Intellectual Property," as defined
in Section 101(60) of the Bankruptcy Code, now or hereafter owned by Borrower,
together with all of the following property now or hereafter owned by Borrower:
all domestic and foreign patents and patent applications; inventions,
discoveries and improvements, whether or not patentable; trademarks, trademark
applications and registrations; service marks, service mark applications and
registrations; copyrights, copyright applications and registrations; all
licenses therefor; trade secrets and all other proprietary information.

        "INTEREST PERIOD" - (a) with respect to Eurodollar Loans, a one (1), two
(2), three (3), six (6) or twelve (12) calendar month period as selected by
Borrower pursuant to this Agreement. Each Interest Period shall commence on the
date such Loan is made or the date of a subsequent interest 



                                      -4-

<PAGE>   34

rate election, as the case may be, and shall end on the corresponding date one
(1), two (2), three (3), six (6) or twelve (12) calendar months later, as
selected by the Borrower, provided, that:

                (i) any Interest Period which would otherwise end on a day which
is not a Business Day shall end on the next preceding or succeeding Business Day
as is the Lender's custom in the inter-bank Eurodollar market to which such Loan
relates;

                (ii) each Interest Period which commences before and would
otherwise end after April 30, 2002, shall end on April 30, 2002; and

                (iii) any Interest Period which begins on a day for which there
is no numerically corresponding day in the calendar month during which such
Interest Period is to end, shall (subject to clause (i) above) end on the last
day of such calendar month.

        (b)     with respect to Revolving Credit Loans bearing interest at the
Base Rate, successive periods of one day each.

        "INVESTMENT" - any transfers of property to, contribution to capital of,
acquisition of stock, other securities or evidences of indebtedness of,
acquisition of businesses or acquisition of property of any Person, other than
in the ordinary course of business.

        "IRC" - the Internal Revenue Code of 1986, as amended from time to time
and including all regulations promulgated thereunder.

        "LETTER OF CREDIT" - a letter of credit issued by Lender pursuant to
Section 2.8 for the account of Borrower.

        "LETTER OF CREDIT COMMITMENT" - the commitment of the Lender to issue
Letters of Credit pursuant to Section 2.8 hereof.

        "LIBOR RATE" - the rate quoted by the Lender two (2) Business Days prior
to an Interest Period for the offering by prime commercial banks to other prime
commercial banks in the interbank Eurodollar market of dollar deposit for a
period equal to the Interest Period and in an amount equal to the requested
advance. The LIBOR Rate shall be increased by the marginal reserve percentages
as prescribed by the Board of Governors of the Federal Reserve System for
determining the reserve requirements for the Lender for Eurodollar deposits
having a maturity equal to the Interest Period.

        "LIABILITY" - any liability which the Lender could incur for obligations
for the term of a Fixed Rate Equipment Loan selected in an amount equal to such
portion or all of the principal amount of the Equipment Loan for which the Fixed
Rate is offered and selected. The choice of which Liabilities to use in
determining the Fixed Rate shall be made by Lender in its sole and absolute
discretion. Lender shall not be obligated to incur the particular Liability on
which the Fixed Rate is based, but may do so in its sole and absolute
discretion.



                                      -5-

<PAGE>   35

        "LIEN" - any mortgage, deed of trust, pledge, hypothecation, assignment,
deposit arrangement, encumbrance (including, without limitation, any easement,
right-of-way, zoning or similar restriction or title defect), lien (statutory or
other) or preference, priority or other security agreement or preferential
arrangement of any kind or nature whatsoever (including, without limitation, any
conditional sale or other title retention agreement, any financing lease having
substantially the same economic effect as any of the foregoing and the filing of
any financing statement under the UCC or comparable law of any jurisdiction).

        "LOAN" - any Revolving Credit Loan.

        "LOAN DOCUMENTS" - this Agreement, the Revolving Credit Note, any
application for a Letter of Credit and all other instruments and documents
executed in connection with the indebtedness covered hereby and thereby.

        "LONDON BANKING DAY" shall mean any day in which dealings in deposits in
Dollars are transacted in the London interbank market.

        "MATERIAL ADVERSE CHANGE" means a material adverse change, as reasonably
determined by the Lender, in the property, business, operations, or financial
condition, of Borrower and its Subsidiaries (taken as a whole).

        "MATERIAL ADVERSE EFFECT" - means a material adverse effect, as
reasonably determined by the Lender, on (a) the property, business, operations,
or financial condition, of Borrower and its Subsidiaries (taken as a whole); or
(b) the validity or enforceability of any of the Loan Documents.

        "MULTIEMPLOYER PLAN" - a Plan which is a multiemployer plan as defined
in Section 3(37)(A) of ERISA or Section 414(f) of the IRC.

        "NET WORTH" - at any date, in accordance with GAAP (except as otherwise
provided below), the (a)(i) shareholders equity of Borrower, plus (ii)
additional paid-in-capital, plus or minus (iii) Borrower's cumulative
translation adjustment, plus or minus (iv) Borrower's retained Earnings, and
less (b) Borrower's treasury stock.

        "PBGC" - the Pension Benefit Guaranty Corporation established pursuant
to Subtitle A of Title IV of ERISA.

        "PERSON" - an individual, partnership, corporation, business trust,
joint stock company, trust, unincorporated association, joint venture,
governmental authority or other entity of whatever nature.

        "PLAN" - any pension plan, as defined in Section 3(2) of ERISA and any
welfare plan, as defined in Section 3(1) of ERISA, which is sponsored,
maintained or contributed to by Borrower or any Commonly Controlled Entity, or
in respect of which Borrower or a Commonly Controlled Entity is an "employer" as
defined in Section 3(5) of ERISA.



                                      -6-


<PAGE>   36

        "PERMITTED ACQUISITION INDEBTEDNESS" - has the meaning given such term
in Section 5.1(h) hereof.

        "REPORTABLE EVENT" - any of the events set forth in Section 4043(b) of
ERISA.

        "REVOLVING CREDIT COMMITMENT" - the commitment by the Lender to make
Revolving Credit Loans pursuant to Section 2.1.

        "REVOLVING CREDIT LIMIT" - as of any date, the amount of Fourteen
Million Dollars ($14,000,000.00).

        "REVOLVING CREDIT LOAN" - any loan made pursuant to Section 2.1.

        "REVOLVING CREDIT NOTE" - a promissory note of Borrower made to evidence
the Revolving Credit Loans, in the form of EXHIBIT A, as it may be amended,
supplemented or otherwise modified, from time to time.

        "SENIOR INDEBTEDNESS" - means all Indebtedness for borrowed money
including obligations under Letters of Credit of the Borrower and its
Subsidiaries excluding the Indebtedness arising under the Hancock Mortgage
Documents, Capital Lease Obligations and Permitted Acquisition Indebtedness.

        "SOLVENT" - as to any Person, such Person (i) owns Property the fair
market value of which is greater than the amount required to pay all such
Liabilities, (ii) owns Property the present fair salable value of which is
greater than the amount that will be required to pay the probable liability of
such Person on its existing Indebtedness as such becomes absolute and matured,
(iii) is able to pay all its Indebtedness as such Indebtedness matures and (iv)
has capital sufficient to carry on its business and transactions and all
business and transactions in which it is about to engage.

        "SUBSIDIARY" - with respect to any Person, any corporation, partnership,
trust or other organization, whether or not incorporated, the majority of the
voting stock or voting rights of which is owned or controlled, directly or
indirectly, by such Person.


        "TERMINATION DATE" - the earlier of (a) April 30, 2002, and (b) the date
the Lender's commitment to make Loans is terminated pursuant to Section 7.2 of
Article 7.

        "TOTAL LIABILITIES" - with respect to the Borrower shall mean all
Indebtedness of the Borrower.

        "TREASURY RATE" - as of the date of any calculation or determination,
the latest published rate for United States Treasury Notes or Bills (but the
rate on Bills issued on a discounted basis shall be converted to a bond
equivalent) as published weekly in the Federal Reserve Statistical Release
H.15(519) of Selected Interest Rates in an amount which approximates (as
determined by Lender) 



                                      -7-

<PAGE>   37

in the case of a prepayment the amount prepaid and with a maturity closest to
the original maturity of the Equipment Loan which is prepaid in whole or in
part.

        "TITLE IV PLAN" - any Plan that is covered by Title IV of ERISA.

        "UCC" - the Uniform Commercial Code as it may from time to time be in
effect in the Commonwealth of Massachusetts.



                                       -8-


<PAGE>   38



                                    EXHIBIT A

                              REVOLVING CREDIT NOTE

$14,000,000.00                                             Boston, Massachusetts
                                                               September 5, 1997

FOR VALUE RECEIVED, the undersigned, BTU International, Inc., a Delaware
corporation, with a principal place of business at 23 Esquire Road, North
Billerica, Massachusetts 01863 (the "Maker"), hereby promises to pay to the
order of USTrust ., a Massachusetts trust company, having an address at 30 Court
Street, Boston, Massachusetts 02108 (the "Lender"), the sum of FOURTEEN MILLION
AND 00/100 DOLLARS ($14,000,000.00), or so much as may have been advanced to the
Maker, as provided under that certain Credit Agreement dated as of September 5,
1997, by and between Maker and Lender, as the same may be amended from time to
time (the "Agreement"), together with interest on the unpaid principal amount
from time to time outstanding at (i) the Base Rate, or (ii) the Eurodollar Rate,
as the Borrower may elect pursuant to the terms of the Agreement. Interest shall
be payable in arrears on the first Business Day of each month commencing on the
first such date to occur after date hereof. The entire balance of principal,
accrued interest, and other fees and charges shall be due and payable on April
30, 2002 except as otherwise provided in the Agreement.

        After maturity (whether by acceleration after default or otherwise),
interest shall be payable on the unpaid principal balance from time to time
outstanding at a rate in excess of the rate that is otherwise payable, that is
two percent (2%) until fully paid. Any payment hereunder not paid within fifteen
(15) days after the date such payment is due shall be subject to a late fee
equal to five percent (5%) of the amount overdue.

        "Base Rate" means for any day the rate on such day announced by Lender
as its Base Rate. Any change in rate resulting from a change in the Base Rate
shall become effective as of the day on which such charge in the Base Rate
becomes effective. "Eurodollar Rate" means the LIBOR Rate (as defined in the
Agreement) plus 125 basis points.

        "Business Day", means any day on which commercial banks are open for
domestic and international business, including dealing on dollar deposits in,
Boston, Massachusetts and, if the applicable Business Day relates to a
Eurodollar Loan, any London Banking Day. If any day on which a payment on a
Revolving Credit Loan is due is not a Business Day, then the payment shall be
due on the next day following which is a Business Day, unless, with respect to
such Revolving Credit Loan, the effect would be to make the payment due in the
next calendar month, in which event such payment shall be due on the next
preceding day which is a Business Day.

        Interest and fees shall be calculated on the basis of a 360-day year for
the actual days elapsed, from and including the date of such Revolving Credit
Loan to but excluding the date of any repayment. Revolving Credit Loans bearing
interest at the Base Rate may be prepaid in whole or in part, without premium or
penalty, at any time. Revolving Credit Loans bearing interest at the 





<PAGE>   39

Eurodollar Rate may be prepaid only upon payment of any amount due under Section
2.4 of the Agreement.

This Note evidences borrowings under the Agreement and, except as provided in
the Agreement, is secured by and entitled to all benefits of the provisions of
the Agreement, and other Loan Documents, as defined therein. All capitalized
terms not specifically defined herein shall have the same meanings as in the
Agreement.

If an Event of Default shall occur, the entire unpaid balance of principal,
accrued interest, and any and all other fees and charges may become, or may be
declared, immediately due and payable in the manner and with the effect provided
in the Credit Agreement.

Maker also agrees to pay all costs and expenses, including, without limitation,
reasonable attorneys' fees and expenses incurred, or which may be incurred, by
the Lender in connection with the negotiation, documentation, administration,
and enforcement of this Note and the Loan Documents.

The Maker and all guarantors and endorsers hereby waive presentment, demand,
notice, protest, and all other demands and notices in connection with the
delivery, acceptance, performance and enforcement of this Note, and assent to
extensions of the time of payment or forbearance or other indulgence without
notice.

This instrument shall be governed by Massachusetts law. For purposes of any
action or proceeding involving this note, Maker hereby expressly submits to the
jurisdiction of all federal and state courts located in the Commonwealth of
Massachusetts and consents that any order, process, notice of motion or other
application to or by any of said courts or a judge thereof may be served within
or without such court's jurisdiction by registered mail or by personal service,
PROVIDED a reasonable time for appearance is allowed (but not less than the time
otherwise afforded by any law or rule), and waives any right to contest the
appropriateness of any action brought in any such court based upon lack of
personal jurisdiction, improper venue or FORUM NON CONVENIENS. MAKER AND LENDER
EACH HEREBY KNOWINGLY, VOLUNTARILY AND INTENTIONALLY WAIVES (TO THE EXTENT
PERMITTED BY APPLICABLE LAW) ANY RIGHT IT MAY HAVE TO A TRIAL BY JURY OF ANY
DISPUTE ARISING UNDER OR RELATING TO THIS NOTE AND AGREES THAT ANY SUCH DISPUTE
SHALL BE TRIED BEFORE A JUDGE SITTING WITHOUT A JURY.

Executed as an instrument under seal as of the date first above written.

WITNESS:                                     BTU INTERNATIONAL


______________________                       By: ___________________________
                                                 Name:
                                                 Title:


                                      -2-
<PAGE>   40




                                    EXHIBIT B

                             COMPLIANCE CERTIFICATE


        The undersigned hereby certifies pursuant to that certain Credit
Agreement (the "Agreement") dated September 5, 1997 between BTU International,
Inc. ("Borrower") and USTrust ("Lender"), as follows as of this date. The
capitalized terms as used herein shall have the meanings given to them in the
Agreement.

        (a). To the best knowledge of the undersigned, the representations and
warranties made by Borrower in the Agreement and other Loan Documents and in
each certificate, document or financial or other written statement furnished at
any time under or in connection therewith, are and remain true and correct in
all material respects.

        (b). No Event of Default described in the Agreement has occurred and is
continuing.

        (c). There has occurred no Material Adverse Change since December 31,
1996 other than as disclosed to Lender.

        (d). The undersigned represents and warrants to the Lender that the
financial covenant calculations shown on the attached Schedule A are true and
accurate as of the date hereof.

        Executed as of _________, 1997.


                                             BTU INTERNATIONAL, INC.


                                             -----------------------------------
                                             Name:
                                             Title: Chief Financial Officer




<PAGE>   41


                                   SCHEDULE A


Section 5.5(a)      Current Ratio                   Actual: __________________
                                                    Minimum: 1.75:1.00

                    Compliance                      Yes _____  No _____


Section 5.5         Ratio of Net Worth              Actual: __________________
                    to Senior Indebtedness          Minimum: 1.50:1.00

                    Compliance                      Yes _____  No _____


Section 5.5(c)      Ratio of Total Liabilities      Actual: __________________
                    to Net Worth                    Maximum: 1.25:1.00

                    Compliance                      Yes _____  No _____


Section 5.5(d)      Debt Service                    Actual: __________________
                    Coverage Ratio                  Minimum: 1.20:1.00

                    Compliance                      Yes _____  No _____








                                       -2-





<PAGE>   42


                              REVOLVING CREDIT NOTE

$14,000,000.00                                             Boston, Massachusetts
                                                               September 5, 1997

FOR VALUE RECEIVED, the undersigned, BTU International, Inc., a Delaware
corporation, with a principal place of business at 23 Esquire Road, North
Billerica, Massachusetts 01863 (the "Maker"), hereby promises to pay to the
order of USTrust ., a Massachusetts trust company, having an address at 30 Court
Street, Boston, Massachusetts 02108 (the "Lender"), the sum of FOURTEEN MILLION
AND 00/100 DOLLARS ($14,000,000.00), or so much as may have been advanced to the
Maker, as provided under that certain Credit Agreement dated as of September 5,
1997, by and between Maker and Lender, as the same may be amended from time to
time (the "Agreement"), together with interest on the unpaid principal amount
from time to time outstanding at (i) the Base Rate, or (ii) the Eurodollar Rate,
as the Borrower may elect pursuant to the terms of the Agreement. Interest shall
be payable in arrears on the first Business Day of each month commencing on the
first such date to occur after date hereof. The entire balance of principal,
accrued interest, and other fees and charges shall be due and payable on April
30, 2002 except as otherwise provided in the Agreement.

     After maturity (whether by acceleration after default or otherwise),
interest shall be payable on the unpaid principal balance from time to time
outstanding at a rate in excess of the rate that is otherwise payable, that is
two percent (2%) until fully paid. Any payment hereunder not paid within fifteen
(15) days after the date such payment is due shall be subject to a late fee
equal to five percent (5%) of the amount overdue.

     "Base Rate" means for any day the rate on such day announced by Lender as
its Base Rate. Any change in rate resulting from a change in the Base Rate shall
become effective as of the day on which such charge in the Base Rate becomes
effective. "Eurodollar Rate" means the LIBOR Rate (as defined in the Agreement)
plus 125 basis points.

     "Business Day", means any day on which commercial banks are open for
domestic and international business, including dealing on dollar deposits in,
Boston, Massachusetts and, if the applicable Business Day relates to a
Eurodollar Loan, any London Banking Day. If any day on which a payment on a
Revolving Credit Loan is due is not a Business Day, then the payment shall be
due on the next day following which is a Business Day, unless, with respect to
such Revolving Credit Loan, the effect would be to make the payment due in the
next calendar month, in which event such payment shall be due on the next
preceding day which is a Business Day.

Interest and fees shall be calculated on the basis of a 360-day year for the
actual days elapsed, from and including the date of such Revolving Credit Loan
to but excluding the date of any repayment. Revolving Credit Loans bearing
interest at the Base Rate may be prepaid in whole or in part, without premium or
penalty, at any time. Revolving Credit Loans bearing interest at the Eurodollar
Rate may be prepaid only upon payment of any amount due under Section 2.4 of the
Agreement.





<PAGE>   43

This Note evidences borrowings under the Agreement and, except as provided in
the Agreement, is secured by and entitled to all benefits of the provisions of
the Agreement, and other Loan Documents, as defined therein. All capitalized
terms not specifically defined herein shall have the same meanings as in the
Agreement.

If an Event of Default shall occur, the entire unpaid balance of principal,
accrued interest, and any and all other fees and charges may become, or may be
declared, immediately due and payable in the manner and with the effect provided
in the Credit Agreement.

Maker also agrees to pay all costs and expenses, including, without limitation,
reasonable attorneys' fees and expenses incurred, or which may be incurred, by
the Lender in connection with the negotiation, documentation, administration,
and enforcement of this Note and the Loan Documents.

The Maker and all guarantors and endorsers hereby waive presentment, demand,
notice, protest, and all other demands and notices in connection with the
delivery, acceptance, performance and enforcement of this Note, and assent to
extensions of the time of payment or forbearance or other indulgence without
notice.

This instrument shall be governed by Massachusetts law. For purposes of any
action or proceeding involving this note, Maker hereby expressly submits to the
jurisdiction of all federal and state courts located in the Commonwealth of
Massachusetts and consents that any order, process, notice of motion or other
application to or by any of said courts or a judge thereof may be served within
or without such court's jurisdiction by registered mail or by personal service,
PROVIDED a reasonable time for appearance is allowed (but not less than the time
otherwise afforded by any law or rule), and waives any right to contest the
appropriateness of any action brought in any such court based upon lack of
personal jurisdiction, improper venue or FORUM NON CONVENIENS. MAKER AND LENDER
EACH HEREBY KNOWINGLY, VOLUNTARILY AND INTENTIONALLY WAIVES (TO THE EXTENT
PERMITTED BY APPLICABLE LAW) ANY RIGHT IT MAY HAVE TO A TRIAL BY JURY OF ANY
DISPUTE ARISING UNDER OR RELATING TO THIS NOTE AND AGREES THAT ANY SUCH DISPUTE
SHALL BE TRIED BEFORE A JUDGE SITTING WITHOUT A JURY.

Executed as an instrument under seal as of the date first above written.

WITNESS:                                BTU INTERNATIONAL


______________________                  By: ___________________________
                                            Name:
                                            Title:





                                      -2-