<PAGE>

                                                                    EXHIBIT 10.4

                      SECOND AMENDMENT TO CREDIT AGREEMENT

                This Amendment, dated as of March 1, 2002, is made by and among
ENTEGRIS, INC., a Minnesota corporation (the "Borrower"), each of the banks
appearing on the signature pages hereof, together with such other banks as may
from time to time become a party to the Credit Agreement (defined below)
pursuant to the terms and conditions of Article VIII of the Credit Agreement
(herein collectively called the "Banks" and individually each called a "Bank"),
and WELLS FARGO BANK, NATIONAL ASSOCIATION, a national banking association,
assignee of Wells Fargo Bank Minnesota, National Association, formerly known as
Norwest Bank Minnesota, National Association, in its separate capacity as
administrative agent for itself and all other Banks (in such capacity, the
"Agent").

                                    Recitals

                A.      The Borrower, the Banks and the Agent have entered into
a Credit Agreement dated as of November 30, 1999, as amended by a First
Amendment to Credit Agreement dated as of October 17, 2000 (as the same may
hereafter be amended or restated from time to time, the "Credit Agreement").

                B.      The Borrower has requested that the Banks and the Agent,
among other things, (i) extend the Maturity Date, and (ii) amend certain other
provisions of the Credit Agreement.

                C.      The Banks and the Agent are willing to grant the
Borrower's requests subject to the terms and conditions set forth below.

                ACCORDINGLY, in consideration of the premises and for other good
and valuable consideration, the Borrower, the Banks and the Agent agree as
follows:

                1.      All capitalized terms used in this Amendment and not
otherwise specifically defined in this Amendment shall have the meanings given
such terms in the Credit Agreement.

                2.      Section 1.1 of the Credit Agreement is hereby amended by
adding the following new definitions in the appropriate alphabetical locations
in Section 1.1 of the Credit Agreement:

                "'Capital Expenditure' means any expenditure of money for the
        purchase or construction of fixed assets or for the purchase or
        construction of any other assets, or for improvements or additions
        thereto, which are capitalized on the Borrower's balance sheet, whether
        payable currently or in the future, excluding, however, any expenditure
        of cash in connection with an acquisition of stock or assets of another
        Person permitted under Section 6.4(g) of this Agreement."

<PAGE>

                "'Harris Bank' means Harris Trust and Savings Bank."

                "'Long Term Debt' of a Person means, as of any date of
        determination, Funded Debt of such Person (excluding Revolving
        Advances)."

                "'Operating Lease Liabilities' of any Person means, with respect
        to the applicable Covenant Computation Period, all monetary obligations
        of such Person under any leasing or similar arrangement which, in
        accordance with GAAP, would be classified as operating leases."

                "'Permitted Restricted Payments' means payments of dividends,
        distributions or otherwise, if any, made by the Borrower pursuant to
        Section 6.5 of this Agreement."

                "'Rent Expense' means Capitalized Lease Liabilities, Operating
        Lease Liabilities and any other monetary obligation of the Borrower for
        rent with respect to the applicable Covenant Computation Period."

                "'Revolving Commitment Period' means a 364-day period commencing
        on March 1, 2002 and ending on the Maturity Date, unless the Revolving
        Commitments are earlier terminated pursuant to Section 7.2 or are
        earlier reduced to zero pursuant to Section 2.14(a)."

                "'Second Amendment' means the Second Amendment to Credit
        Agreement, dated as of March 1, 2002, by and among the Borrower, the
        Banks and the Agent."

                "'Second Amendment Effective Date' means the date on which all
        of the conditions precedent set forth in paragraph 25 of the Second
        Amendment to the effectiveness of the Second Amendment have been
        satisfied."

                "'Tangible Net Worth' of a Person means, as of the applicable
        Covenant Computation Date, the difference between (a) the tangible
        assets of such Person, calculated in accordance with GAAP, after
        deducting adequate reserves in each case where, in accordance with GAAP,
        a reserve is proper and (b) all Debt of such Person; provided, that in
        no event shall there be included as tangible assets, patents,
        trademarks, tradenames, copyrights, licenses, goodwill, receivables from
        Affiliates of such Person, prepaid expenses, deposits, deferred charges
        or treasury stock or any securities or Debt of such Person, or any other
        securities unless such securities are readily marketable on a public
        exchange in the United States of America, income tax liabilities, and
        any other assets designated from time to time by the Bank, in its
        reasonable discretion, as intangible assets."

                                       -2-

<PAGE>

                "'Unused Commitment Fee Percentage' means, as of the date of
        determination, the percentage set forth in the table below opposite the
        applicable range of the ratio of Total Funded Debt to EBITDA of the
        Borrower and its Subsidiaries as of such date of determination;
        provided, however, notwithstanding the foregoing, the Unused Commitment
        Fee Percentage shall be 0.200% so long as (i) the Borrower maintains the
        sum of its cash and cash equivalents in an aggregate amount of more than
        $50,000,000, and (ii) there are no outstanding Revolving Advances under
        the Revolving Facility. Reductions and increases in the Unused
        Commitment Fee Percentage will be verified by the Agent upon receipt of
        the financial statements of the Borrower and its Subsidiaries and
        related compliance certificate as required under Section 5.1(b) of this
        Agreement. The ratio will be determined on the basis of a rolling four
        quarter calculation of the ratio of Total Funded Debt to EBITDA as of
        the last day of the most recent quarter-end reflected in the most recent
        financial statements delivered by the Borrower for the Borrower and its
        Subsidiaries under Section 5.1(b). Any reduction or increase in the
        Unused Commitment Fee Percentage will become effective on the first day
        of the first month following the applicable Quarterly Financial
        Statement Due Date. If the Borrower fails to deliver the financial
        statements of the Borrower and its Subsidiaries and/or related
        compliance certificate required under Section 5.1(b) on or before the
        applicable Quarterly Financial Statement Due Date, the Borrower and its
        Subsidiaries shall be deemed to have a ratio of Total Funded Debt to
        EBITDA for such quarter of more than 2.00 to 1.00, and the Unused
        Commitment Fee Percentage will be 0.350% beginning on the first day of
        the first month following such Quarterly Financial Statement Due Date
        and will continue as such until the Borrower delivers the financial
        statements of the Borrower and its Subsidiaries for the next fiscal
        quarter in accordance with Section 5.1(b).

               Ratio of Total Funded     Unused Commitment Fee
                  Debt to EBITDA              Percentage
          ----------------------------------------------------
                    * 2.00/1.00                 0.350%
          ----------------------------------------------------
             * 1.50/1.00 to 2.00/1.00           0.300%
          ----------------------------------------------------
              1.00/1.00 to 1.50/1.00            0.250%
          ----------------------------------------------------
                   ** 1.00/1.00                 0.200%
          ----------------------------------------------------
* - less than
** - greater than
                "'Wells Fargo' means Wells Fargo Bank, National Association, a
        national banking association."

                3.      Section 1.1 of the Credit Agreement is hereby amended by
amending the following definitions in their entirety to read as follows:

                                       -3-

<PAGE>

                "'EBITDA' means, with respect to the applicable Covenant
        Computation Period, Pre-Tax Earnings (excluding non-cash income) plus
        Interest Expense and Non-Cash Charges, in each case excluding
        extraordinary items, determined with respect to the Borrower during such
        Covenant Computation Period."

                "'Eurodollar Rate Margin' means, as of the date of
        determination, the percentage set forth in the table below opposite the
        applicable range of the ratio of Total Funded Debt to EBITDA of the
        Borrower and its Subsidiaries as of such date of determination.
        Reductions and increases in the Eurodollar Rate Margin will be verified
        by the Agent upon receipt of the financial statements of the Borrower
        and its Subsidiaries and related compliance certificate as required
        under Section 5.1(b) of this Agreement. The ratio will be determined on
        the basis of a rolling four quarter calculation of the ratio of Total
        Funded Debt to EBITDA as of the last day of the most recent quarter-end
        reflected in the most recent financial statements delivered by the
        Borrower for the Borrower and its Subsidiaries under Section 5.1(b). Any
        reduction or increase in the Eurodollar Rate Margin will become
        effective on the first day of the first month following the applicable
        Quarterly Financial Statement Due Date. If the Borrower fails to deliver
        the financial statements of the Borrower and its Subsidiaries and/or
        related compliance certificate required under Section 5.1(b) on or
        before the applicable Quarterly Financial Statement Due Date, the
        Borrower and its Subsidiaries shall be deemed to have a ratio of Total
        Funded Debt to EBITDA for such quarter of more than 2.00 to 1.00, and
        the Eurodollar Rate Margin will be 2.000% beginning on the first day of
        the first month following such Quarterly Financial Statement Due Date
        and will continue as such until the Borrower delivers the financial
        statements for the Borrower and its Subsidiaries for the next fiscal
        quarter in accordance with Section 5.1(b).

              Ratio of Total Funded        Eurodollar Rate Spread for
                  Debt to EBITDA               Revolving Advances
          --------------------------------------------------------------
                   * 2.00/1.00                      2.000%
          --------------------------------------------------------------
             * 1.50/1.00 to 2.00/1.00               1.750%
          --------------------------------------------------------------
              1.00/1.00 to 1.50/1.00                1.500%
          --------------------------------------------------------------
                  ** 1.00/1.00                      1.375%
          --------------------------------------------------------------
* - less than
** - greater than

                                       -4-

<PAGE>

                "'Fixed Charge Coverage Ratio' means, with respect to the
        applicable Covenant Computation Date, the ratio of (a) EBITDA, plus Rent
        Expense, less Capital Expenditures, less cash taxes (but, with respect
        to cash taxes, only to the extent included in the calculation of
        EBITDA), less Permitted Restricted Payments, to (b) Interest Expense,
        plus Rent Expense, plus current maturities of the Borrower's Long Term
        Debt."

                "'Floating Rate Margin' means, as of the date of determination,
        the percentage set forth below in the table opposite the applicable
        range of the ratio of Total Funded Debt to EBITDA of the Borrower and
        its Subsidiaries as of such determination. Reductions and increases in
        the Floating Rate Margin will be verified by the Agent upon receipt of
        the financial statements of the Borrower and its Subsidiaries and
        related compliance certificate as required under Section 5.1(b) of this
        Agreement. The ratio will be determined on the basis of a rolling four
        quarter calculation of the ratio of Total Funded Debt to EBITDA as of
        the last day of the most recent quarter-end reflected in the most recent
        financial statements delivered by the Borrower for the Borrower and its
        Subsidiaries under Section 5.1(b). Any reduction or increase in the
        Floating Rate Margin will become effective on the first day of the first
        month following the applicable Quarterly Financial Statement Due Date.
        If the Borrower fails to deliver the financial statements of the
        Borrower and its Subsidiaries and/or related compliance certificate
        required under Section 5.1(b) on or before the applicable Quarterly
        Financial Statement Due Date, the Borrower and its Subsidiaries shall be
        deemed to have a ratio of Total Funded Debt to EBITDA for such quarter
        of more than 2.00 to 1.00, and the Floating Rate Margin will be 0.125%,
        beginning on the first day of the first month following such Quarterly
        Financial Statement Due Date and will continue as such until the
        Borrower delivers the financial statements for the Borrower and its
        Subsidiaries for the next fiscal quarter in accordance with Section
        5.1(b).

              Ratio of Total Funded
                  Debt to EBITDA           Floating Rate Margin
          --------------------------------------------------------
                   * 2.00/1.00                     .125%
          --------------------------------------------------------
             * 1.50/1.00 to 2.00/1.00             0.000%
          --------------------------------------------------------
              1.00/1.00 to 1.50/1.00              0.000%
          --------------------------------------------------------
                  ** 1.00/1.00                    0.000%
          --------------------------------------------------------
* - less than
** - greater than

                "'Guarantor' means any Person which may now or hereafter
        guaranty any of the Obligations of the Borrower to the Bank."

                                       -5-

<PAGE>

                "'Interest Expense' means, with respect to the applicable
        Covenant Computation Period, the total gross interest expense on all of
        the Borrower's Debt during such period, and shall in any event include,
        without limitation and without duplication, (a) accrued interest
        (whether or not paid) on all Debt, (b) the amortization of Debt
        discounts, (c) the amortization of all fees payable in connection with
        the incurrence of Debt to the extent included in interest expense, and
        (d) the interest portion of any capitalized lease expenditure, all
        determined in accordance with GAAP."

                "'Non-Cash Charges' means, with respect to the applicable
        Covenant Computation Period, the Borrower's depreciation and
        amortization determined in accordance with GAAP."

                "'Maturity Date' means February 28, 2003 with respect to the
        Revolving Facility."

                "'Revolving Commitment' means, with respect to each Bank, the
        amount of the Revolving Commitment set forth opposite such Bank's name
        on the execution pages of the Second Amendment, or below such Bank's
        signature on an Assignment Certificate executed by such Bank, unless
        such amount is reduced pursuant to Section 2.14(a) hereof, in which
        event it means the amount to which said amount is reduced pursuant
        thereto, or as the context may require, the obligation of such Bank to
        make Revolving Advances, as contemplated in Section 2.1."

                "'Revolving Commitment Amount' shall mean Twenty Million Dollars
        ($20,000,000), being the maximum amount of the Revolving Commitments of
        all Banks, in the aggregate, to make Revolving Advances to the Borrower
        pursuant to Section 2.1, subject to reduction in accordance with Section
        2.14(a)."

                "'Revolving Note' means a promissory note of the Borrower
         payable to a Bank in the amount of such Bank's Revolving Commitment, in
         substantially the form of Exhibit A attached to the Second Amendment
         (as such promissory note may be amended, extended or otherwise modified
         from time to time), evidencing the aggregate indebtedness of the
         Borrower to such Bank resulting from such Bank's Percentage of each
         Borrowing under the Revolving Facility, and also means each promissory
         note accepted by such Bank from time to time in substitution therefor
         or in renewal thereof."

                4.      Section 1.1 of the Credit Agreement is hereby deleting
the definitions of "Cash Flow Available for Fixed Charges", "Fixed Charge
Requirements", "Commitment Fee Percentage", "Norwest", "Net Worth", and "Year
2000 Compliant".

                5.      Section 2.1 of the Credit Agreement is hereby amended in
its entirety to read as follows:

                                       -6-

<PAGE>

                "Section 2.1 Commitment as to Revolving Facility. Each Bank
        hereby agrees, on the terms and subject to the conditions herein set
        forth, to make Revolving Advances to the Borrower from time to time
        during the Revolving Commitment Period, in an aggregate amount at any
        time outstanding not to exceed such Bank's Percentage of each Borrowing
        from time to time requested by the Borrower under the Revolving
        Facility; provided, however, that (a) the Revolving Facility Outstanding
        Amount shall at no time exceed the Revolving Commitment Amount and (b)
        no Bank's Percentage of the Revolving Facility Outstanding Amount shall
        at any time exceed such Bank's Revolving Commitment. Within the above
        limits, the Borrower may obtain Revolving Advances, prepay Revolving
        Advances in accordance with the terms hereof and reborrow Revolving
        Advances in accordance with the applicable terms and conditions of this
        Article II."

                6.      The first sentence of Section 2.6 of the Credit
Agreement is hereby amended to read as follows:

        "The Letter of Credit Bank agrees, during the period from the Closing
        Date to the date which is thirty (30) days prior to the Revolving
        Commitment Termination Date, to issue one or more standby letters of
        credit for the account of the Borrower, and the Banks agree to
        participate in the risk of such letters of credit issued for the account
        of the Borrower hereunder, on the terms and subject to the conditions
        set forth below:"

                7.      Section 2.12(b) of the Credit Agreement is hereby
amended to read as follows:

                "(b)    Unused Commitment Fee. The Borrower agrees to pay to the
        Agent, for the pro rata account of the Banks, an unused commitment fee
        (the "Unused Commitment Fee") computed at the rate of the applicable
        Unused Commitment Fee Percentage per annum on the daily average amount
        by which the Revolving Commitment Amount exceeds the Revolving Facility
        Outstanding Amount, from the Closing Date to and including the Revolving
        Commitment Termination Date, payable quarterly in arrears on the last
        day of each August, November, February and May. Any such Unused
        Commitment Fee remaining unpaid on the Revolving Commitment Termination
        Date shall be due and payable on such date. The Unused Commitment Fee
        shall be shared by the Banks on the basis of their respective
        Percentages."

                8.      Section 3.2 of the Credit Agreement is hereby amended to
read as follows:

                "Section 3.2 Conditions Precedent to All Borrowings. The
        obligation of the Banks to fund each request for a Borrowing or to issue
        each Letter of Credit shall be subject to the further conditions
        precedent that on such date:

                                       -7-

<PAGE>

                        (a) the representations and warranties contained in
                Article IV hereof are correct in all material respects on and as
                of the date of such Advance as though made on and as of such
                date;

                        (b) no event has occurred and is continuing, or would
                result from such Advance, which constitutes a Default or an
                Event of Default; and

                        (c) as of the Covenant Computation Date most recently
                preceding such date, the Borrower's Fixed Charge Coverage Ratio
                was not less than 1.50 to 1.00."

                9.      Section 4.4 of the Credit Agreement is hereby amended to
read as follows:

                "Section 4.4 Subsidiaries. Schedule 4.4 attached to the Second
        Amendment is a complete and correct list of all Subsidiaries and
        Affiliates of the Borrower and the percentage of the ownership of the
        Borrower or any Subsidiary in each such Subsidiary or Affiliate as of
        the date of the Second Amendment Effective Date. All shares of each
        Subsidiary and Affiliate owned by the Borrower or any Subsidiary are
        validly issued and fully paid and non-assessable."

                10.     Section 4.15 of the Credit Agreement is hereby amended
to read as follows:

                "Section 4.15 Reserved."

                11.     Section 5.1(a) of the Credit Agreement is hereby amended
to read as follows:

                "(a)    as soon as available, and in any event within 120 days
        after the end of each fiscal year of the Borrower, the annual audit
        report of the Borrower and its Subsidiaries with the unqualified opinion
        of independent certified public accountants selected by the Borrower and
        acceptable to the Agent, which annual report shall include the balance
        sheets of the Borrower and its Subsidiaries as at the end of such fiscal
        year and the related statements of income, retained earnings and cash
        flows of the Borrower and its Subsidiaries for the fiscal year then
        ended, prepared on a consolidated and consolidating basis, all in
        reasonable detail and prepared in accordance with GAAP, together with a
        certificate of the chief financial officer of the Borrower,
        substantially in the form of Exhibit B to the Second Amendment, stating
        that such annual audit report has been prepared in accordance with GAAP
        and whether or not such officer has knowledge of the occurrence of any
        Default or Event of Default hereunder and, if so, stating in reasonable
        detail the facts with respect thereto;"

                                       -8-

<PAGE>

                12.     Section 5.1(b) of the Credit Agreement is hereby amended
to read as follows:

                "(b)    as soon as available and in any event on or before the
        applicable Quarterly Financial Statement Due Date after the end of each
        fiscal quarter of the Borrower, an unaudited/internal balance sheet and
        statement of income, cash flow and retained earnings of the Borrower and
        its Subsidiaries as at the end of and for such quarter and for the
        year-to-date period then ended, prepared on a consolidated and
        consolidating basis, in reasonable detail and the figures for the
        corresponding date and periods in the previous year, all prepared in
        accordance with GAAP hereof, subject to year-end audit adjustments; and
        accompanied by a certificate of the chief financial officer of the
        Borrower, substantially in the form of Exhibit C to the Second
        Amendment, stating (i) that such financial statements have been prepared
        in accordance with GAAP, subject to year-end audit adjustments, (ii)
        whether or not such officer has knowledge of the occurrence of any
        Default or Event of Default hereunder not theretofore reported and
        remedied and, if so, stating in reasonable detail the facts with respect
        thereto, and (iii) all relevant facts in reasonable detail to evidence,
        and the computations as to (A) the status of the Borrower and its
        Subsidiaries for purposes of establishing the appropriate Eurodollar
        Rate Margin, Floating Rate Margin and Unused Commitment Fee Percentage
        and (B) whether or not the Borrower and its Subsidiaries are in
        compliance with the requirements set forth in Sections 5.8 through
        5.10;"

                13.     Section 5.8 of the Credit Agreement is hereby amended to
read as follows:

                "Section 5.8 Fixed Charge Coverage Ratio. As of each Covenant
        Computation Date, the Borrower and its Subsidiaries, on a consolidated
        basis, will maintain a Fixed Charge Coverage Ratio of not less than 1.50
        to 1.00; provided, however, although the Borrower shall report its Fixed
        Charged Coverage Ratio as of each Covenant Computation Date, the
        Borrower shall be required to comply with the ratio required by this
        Section 5.8 only if, as of the applicable Covenant Computation Date, (i)
        the Borrower has outstanding Revolving Advances under the Revolving
        Facility of $1 or more, or (ii) the aggregate amount of cash and cash
        equivalents of the Borrower are less than $50,000,000."

                14.     Section 5.9 of the Credit Agreement is hereby amended to
read as follows:

                "Section 5.9 Leverage Ratio. As of each Covenant Computation
        Date, the Borrower and its Subsidiaries, on a consolidated basis, will
        maintain a Leverage Ratio of not more than (i) 2.50 to 1.00 as of each
        Covenant Computation Date which occurs during the period from the Second
        Amendment Effective Date to and including February 23, 2002, (ii) 3.00
        to 1.00 as of each Covenant Computation Date which

                                       -9-

<PAGE>

        occurs during the period from February 24, 2002 to and including May 25,
        2002, and (iii) 2.50 to 1.00 as of each Covenant Computation Date which
        occurs from and after May 26, 2002."

                15.     Section 5.10 of the Credit Agreement is hereby amended
in its entirety to read as follows:

                "Section 5.10 Minimum Tangible Net Worth. As of each Covenant
        Computation Date, the Borrower and its Subsidiaries, on a consolidated
        basis, will maintain a Tangible Net Worth in an amount not less than the
        amount set forth below opposite the applicable Covenant Computation Date
        set forth below:

             Applicable Covenant              Minimum Tangible Net
               Computation Date                   Worth Amount
         --------------------------        ---------------------------
         August 25, 2001                          $235,000,000

         November 24, 2001 and each        Required Tangible Net Worth
         subsequent Covenant                         Amount
         Computation Date

                As used in this Section 5.10, the "Required Tangible Net Worth
        Amount" for any given Covenant Computation Date is an amount equal to
        the sum of the minimum Tangible Net Worth required as of the immediately
        preceding Covenant Computation Date, plus fifty percent (50%) of the Net
        Income realized by the Borrower and its Subsidiaries, on a consolidated
        basis, since such immediately preceding Covenant Computation Date (with
        any net loss counting as zero in such calculation), plus fifty percent
        (50%) of the net cash proceeds received by the Borrower and/or its
        Subsidiaries from any equity offering made by the Borrower and/or its
        Subsidiaries since such immediately preceding Covenant Computation
        Date."

                16.     Section 5.11 of the Credit Agreement is hereby amended
to read as follows:

                "Section 5.11 Reserved."

                17.     Section 5.12 of the Credit Agreement is hereby amended
to read as follows:

                "Section 5.12 Reserved."

                18.     Section 6.1(a) of the Credit Agreement is hereby amended
to read as follows:

                                      -10-

<PAGE>

                "(a)    mortgages, deeds of trust, pledges, liens, security
        interests and assignments in existence on the Second Amendment Effective
        Date and listed in Schedule 6.1 attached to the Second Amendment (other
        than those described in subsection (f) securing indebtedness for
        borrowed money on the Second Amendment Effective Date);"

                19.     Section 6.1(f) of the Credit Agreement is hereby amended
to read as follows:

                "(f)    purchase money mortgages, liens or security interests,
        including conditional sale agreements or other title retention
        agreements and leases which are in the nature of title retention
        agreements, upon or in property of the Borrower or any of its
        Subsidiaries, or mortgages, liens or security interests existing in such
        property at the time of the acquisition thereof; provided that no such
        mortgage, lien or security interest extends or shall extend to or cover
        any property of the Borrower or any of its Subsidiaries other than the
        property then being acquired and fixed improvements then or thereafter
        erected thereon."

                20.     Section 6.2 of the Credit Agreement is hereby amended to
read as follows:

                "Section 6.2. Indebtedness. The Borrower will not, and will not
        permit any Subsidiary to, incur, create, assume, permit or suffer to
        exist, any indebtedness or liability on account of deposits or advances
        or any indebtedness for borrowed money, or any other indebtedness or
        liability evidenced by notes, bonds, debentures or similar obligations,
        except:

                        (a)     Obligations arising hereunder;

                        (b)     Capitalized Lease Liabilities and indebtedness
                of the Borrower or its Subsidiaries secured by security
                interests permitted by Section 6.1(f) in an aggregate amount not
                to exceed $5,000,000 at any time;

                        (c)     indebtedness of Borrower in connection with the
                IDRB Financing, including, without limitation, the indebtedness
                or reimbursement obligations of Borrower with respect to the
                IDRB Letter of Credit;

                        (d)     indebtedness or reimbursement obligations of the
                Borrower and/or any of its Subsidiaries with respect to any
                documentary letter of credit facility in an amount not to exceed
                $250,000 now or hereafter established by Wells Fargo for the
                Borrower and/or any such Subsidiary, including any present or
                future extension, renewal or modification thereof permitted by
                Wells Fargo;

                                      -11-

<PAGE>

                        (e)     Subordinated Debt, or renewals thereof, provided
                that (a) it is subordinated to the prior payment of all
                indebtedness, reimbursement obligations and guaranties of the
                Borrower and its Subsidiaries in favor of the Banks on terms and
                conditions approved in writing by the Banks and (b) the
                aggregate amount of Subordinated Debt at any one time
                outstanding does not exceed $5,000,000 (Subordinated Debt as of
                the Second Amendment Effective Date as reflected in Schedule 6.2
                attached to the Second Amendment);

                        (f)     an unsecured irrevocable standby letter of
                credit issued in the original amount of $1,669,918 by Wells
                Fargo in favor of Firstar Bank of Minnesota, National
                Association, for the account of Fluoroware PEI, Inc., as the
                same is now and may hereafter be amended from time to time;

                        (g)     Rate Hedging Obligations covering national
                amounts not exceeding $10,000,000 in the aggregate at any one
                time;

                        (h)     Indebtedness for borrowed money in foreign
                currencies in an aggregate principal amount not to exceed at any
                time $30,000,000 (outstanding indebtedness for borrowed money in
                foreign currencies as of the Second Amendment Effective Date is
                reflected in Schedule 6.2 attached to the Second Amendment); and

                        (i)     Indebtedness for borrowed money not permitted by
                any other subsection of this Section 6.2 in an aggregate
                principal amount not to exceed at any time $10,000,000.

                21.     Section 6.3(d) of the Credit Agreement is hereby amended
to read as follows:

                "(c)    guaranties, endorsements and other direct or contingent
        liabilities in connection with the obligations of other Persons in
        existence on the Second Amendment Effective Date and listed in Schedule
        6.3 attached to the Second Amendment;"

                22.     Section 6.3(d) of the Credit Agreement is hereby amended
to read as follows:

                "(d)    a guaranty given in favor of Wells Fargo in connection
        with the letter of credit permitted by Section 6.2(d)."

                23.     Section 6.4(g)(ii)(C) of the Credit Agreement is hereby
amended to read as follows:

                                      -12-

<PAGE>

                "(c)    all consideration (whether in the form of cash paid,
                        indebtedness assumed or otherwise) given by the Borrower
                        and its Subsidiaries for acquisitions permitted under
                        this Section 6.4(g) shall not exceed an aggregate amount
                        of $25,000,000 during the fiscal year in which such
                        acquisition occurs, and"

                24.     Section 6.12 of the Credit Agreement is hereby amended
to read as follows:

                "Section 6.12 Prohibition of Entering into Negative Pledge
        Arrangements. The Borrower will not, and will not permit any of its
        Subsidiaries to, enter into any agreement or covenant with any Person
        (other than with the Banks or Wells Fargo), that prohibits the Borrower
        or any of its Subsidiaries from creating, incurring, assuming or
        suffering to exist mortgages, deeds of trust or other encumbrances on
        any of its assets."

                25.     Section 9.3 of the Credit Agreement is hereby amended to
read as follows:

                "Section 9.3 Addresses for Notices, Etc. Except as otherwise
        expressly provided herein, all notices, requests, demands and other
        communications provided for under the Loan Documents shall be in writing
        and mailed or delivered to the applicable parties at their respective
        addresses set forth on the execution pages of the Second Amendment, or,
        as to each party, at such other address as shall be designated by such
        party in a written notice to the other party complying as to delivery
        with the terms of this Section 9.3. All such notices, requests, demands
        and other communications, when delivered, shall be effective upon actual
        delivery and when mailed, shall be effective when sent by nationally
        recognized overnight mail courier or delivery service, addressed as
        aforesaid, except that notices or requests to the Agent or any Bank
        pursuant to any of the provisions of Article II shall not be effective
        until received by the Agent or such Bank."

                                      -13-

<PAGE>

The parties hereby agree that all references to the address of the Agent or
Wells Fargo in any of the Exhibits to the Credit Agreement or in any other Loan
Document are hereby amended to refer to the address specified for the Agent and
Wells Fargo on the signature page of this Amendment.

                26.     This Amendment shall become effective when the Agent
shall have received the following, each in form and content acceptable to the
Agent in its sole discretion:

                (a)     This Amendment duly executed on behalf of the Borrower,
        the Banks and the Agent, with all schedules completed and attached
        thereto;

                (b)     A certified copy of the resolutions of the board of
        directors of the Borrower, evidencing approval of this Amendment;

                (c)     A signed copy of a certificate of the Secretary or an
        Assistant Secretary of the Borrower, which shall certify the names of
        the officers of such Borrower authorized to sign this Amendment and the
        other documents or certificates to be delivered pursuant to this
        Agreement, including requests for Advances and Eurodollar Rate Fundings,
        together with the true signatures of such officers. The Agent and each
        Bank may conclusively rely on such certificates until they shall receive
        a further certificate of the Secretary or an Assistant Secretary of the
        Borrower canceling or amending the prior certificate and submitting the
        signatures of the officers named in such further certificate;

                (d)     A Certificate of good standing of the Borrower, dated
        not more than thirty (30) days prior to the date hereof, and evidence
        satisfactory to the Agent that the Borrower is qualified to conduct its
        businesses in each state where it presently conducts such business;

                (e)     Certified Articles of Merger from all appropriate
        jurisdictions which establish that Fluoroware, Inc. and Empak, Inc. have
        been merged into the Borrower, with the Borrower as the surviving
        entity.

                (f)     Current searches of appropriate filing offices showing
        that no state or federal tax liens have been filed and remain in effect
        against the Borrower (or Fluoroware, Inc. or Empak, Inc.), and that no
        financing statements or other notifications or filings have been filed
        and remain in effect against the Borrower (or Fluoroware, Inc. or Empak,
        Inc.), other than those for which the Agent has received an appropriate
        release, termination or satisfaction or those permitted in accordance
        with Section 6.1 of the Credit Agreement, as amended by this Amendment;

                (g)     A signed copy of an opinion of counsel for the Borrower,
        addressed to the Agent and the Banks;

                                      -14-

<PAGE>

                (h)     Copies of all promissory notes evidencing Subordinated
        Debt in existence on the date of this Amendment, together with
        subordination agreements executed on behalf of all of such subordinated
        creditors in favor of the Agent and the Banks in form and content
        acceptable to the Agent in its sole discretion.

                27.     Except as amended by this Amendment, all of the terms
and conditions of the Credit Agreement and the other Loan Documents shall remain
in all other respects in full force and effect.

                28.     This Amendment may be executed in any number of
counterparts, each of which shall be deemed to be an original and all of which
counterparts taken together shall constitute but one and the same instrument.

                29.     The Borrower hereby absolutely and unconditionally
releases and forever discharges the Agent and each of the Banks, and any and all
participants, parent corporations, subsidiary corporations, affiliated
corporations, insurers, indemnitors, successors and assigns thereof, together
with all of the present and former directors, officers, agents and employees of
any of the foregoing (the "Released Parties"), from any and all claims, demands
or causes of action of any kind, nature or description, whether arising in law
or equity or upon contract or tort or under any state or federal law or
otherwise, which the Borrower has had, now has or has made claim to have against
such Released Party for or by reason of any act, omission, matter, cause or
thing whatsoever arising from the beginning of time to and including the date of
this Amendment in connection with or related to the transactions evidenced by
the Loan Documents, whether such claims, demands and causes of action are mature
or unmatured or known or unknown.

                30.     The execution of this Amendment shall not be deemed to
be a waiver of any Default or Event of Default under the Credit Agreement,
whether or not known to the Agent and/or the Banks and whether or not existing
on the date of this Amendment.

                31.     The Borrower hereby represents and warrants to the Agent
and the Banks as follows:

                (a)     The Borrower has all requisite power and authority to
        execute this Amendment and to perform all of its obligations under the
        Credit Agreement, as amended by this Amendment, and the Credit
        Agreement, as amended by this Amendment, and the other Loan Documents
        executed on behalf of the Borrower have been duly executed and delivered
        by the Borrower and constitute the legal, valid and binding obligations
        of the Borrower, enforceable in accordance with their respective terms.

                (b)     The execution, delivery and performance by the Borrower
        of the Credit Agreement, as amended by this Amendment, and the other
        Loan Documents executed

                                      -15-

<PAGE>

        on behalf of the Borrower have been duly authorized by all necessary
        corporate action and do not (i) require any authorization, consent or
        approval by any governmental department, commission, board, bureau,
        agency or instrumentality, domestic or foreign, (ii) violate any
        provision of any law, rule or regulation or of any order, writ,
        injunction or decree presently in effect, having applicability to the
        Borrower, or the Articles of Incorporation or By-laws of the Borrower,
        or (iii) result in a breach of or constitute a default under any
        indenture or loan or credit agreement or any other agreement, lease or
        instrument to which the Borrower is a party or by which it or its
        properties may be bound or affected.

                (c)     All of the representations and warranties contained in
        Article IV of the Credit Agreement are correct on and as of the date
        hereof as though made on and as of such date, except to the extent that
        such representations and warranties relate solely to an earlier date.

                32.     References. All references in the Credit Agreement to
"this Agreement" shall be deemed to refer to the Credit Agreement as amended by
this Amendment; and any and all references in any of the other Loan Documents to
the "Credit Agreement" shall be deemed to refer to the Credit Agreement as
amended by this Amendment. All references in the Credit Agreement to "Norwest"
are hereby amended to be references to "Wells Fargo" as defined in this
Amendment. All references in the Credit Agreement to "Commitment Fee Percentage"
are hereby amended to be references to "Unused Commitment Fee Percentage" as
defined in this Amendment. All references in the Credit Agreement to "Schedule
4.4" are hereby amended to be references to Schedule 4.4 attached to this
Amendment. All references in the Credit Agreement to "Schedule 6.1" are hereby
amended to be references to Schedule 6.1 attached to this Amendment.

                                      -16-

<PAGE>

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

Address:                               ENTEGRIS, INC.
3500 Lyman Boulevard
Chaska, Minnesota 55318
Attn: John Villas                      By  /s/ John Villas
Telecopy No. (612) 556-8644               --------------------------------------
                                           Its  Chief Financial Officer
                                               ---------------------------------
                                       And

                                       By  /s/ James Dauwalter
                                          --------------------------------------
                                           Its  Chief Executive Officer
                                               ---------------------------------


Address:                                   WELLS FARGO BANK, NATIONAL
7900 Xerxes Avenue South                    ASSOCIATION, , as Bank and as Agent
MAC N9307-013
Bloomington, Minnesota  55431
Attn: Richard G. Trembley
Telecopy No. (612) 316-1621

Revolving Commitment: $10,000,000      By  /s/ Richard G. Trembley
Percentage: 50%                           --------------------------------------
                                           Its  Vice President
                                               ---------------------------------


Address:                                   HARRIS TRUST AND SAVINGS BANK, as
111 West Monroe                             Bank
P.O. Box 755
Chicago, Illinois  60690
Attn: John P. Quigley
Telecopy No. (312) 293-5040

Revolving Commitment: $10,000,000      By  /s/ John P. Quigley
Percentage: 50%                           --------------------------------------
                                           Its  Vice President
                                               ---------------------------------

             Signature Page to Second Amendment to Credit Agreement