<PAGE>   1
                                                                   Exhibit 10.45

                             BTU INTERNATIONAL, INC.

                1998 STOCK OPTION PLAN FOR NON-EMPLOYEE DIRECTORS



     1.   PURPOSE

     The purpose of this 1998 Stock Option Plan for Non-Employee Directors (the
"Plan") is to advance the interests of BTU International, Inc. (the "Company")
by enhancing the ability of the Company to attract and retain non-employee
directors who are in a position to make significant contributions to the success
of the Company and to reward directors for such contributions through the
awarding of options ("Options") to purchase shares of the Company's common stock
(the "Stock").

     2.   ADMINISTRATION

     The Plan shall be administered by a committee (the "Committee") of the
Board of Directors (the "Board") of the Company designated by the Board for that
purpose. Unless and until a Committee is appointed the Plan shall be
administered by the entire Board, and references in the Plan to the "Committee"
shall be deemed references to the Board. The Committee shall have authority, not
inconsistent with the express provisions of the Plan, (a) to grant Options in
accordance with the Plan to such directors as are eligible to receive Options;
(b) to prescribe the form or forms of instruments evidencing Options and any
other instruments required under the Plan and to change such forms from time to
time; (c) to adopt, amend and rescind rules and regulations for the
administration of the Plan; and (d) to interpret the Plan and to decide any
questions and settle all controversies and disputes that may arise in connection
with the Plan. Such determinations of the Committee shall be conclusive and
shall bind all parties. Subject to Section 7, the Committee shall also have the
authority, both generally and in particular instances, to waive compliance by a
director with any obligation to be performed by him or her under an Option and
to waive any condition or provision of an Option.

     3.   EFFECTIVE DATE AND TERM OF PLAN

     The Plan shall become effective on the date on which the Plan is approved
by the Board of Directors of the Company, subject to approval by the
stockholders of the Company. No Option shall be granted under the Plan after the
completion of ten years from the date on which the Plan was adopted by the
Board, but Options previously granted may extend beyond that date.


<PAGE>   2
     4.   SHARES SUBJECT TO THE PLAN

     (a) Number of Shares. Subject to adjustment as provided in Section 4(c),
the aggregate number of shares of Stock that may be delivered upon the exercise
of Options granted under the Plan shall be 50,000. If any Option granted under
the Plan terminates without having been exercised in full, the number of shares
of Stock as to which such Option was not exercised shall be available for future
grants within the limits set forth in this Section 4(a).

     (b) Shares to be Delivered. Shares delivered under the Plan shall be
authorized but unissued Stock or, if the Board so decides in its sole
discretion, previously issued Stock acquired by the Company and held in
treasury. No fractional shares of Stock shall be delivered under the Plan.

     (c) Changes in Stock. In the event of a stock dividend, stock split or
combination of shares, recapitalization or other change in the Company's capital
stock, after the effective date of the Plan, the number and kind of shares of
stock or securities of the Company subject to Options then outstanding or
subsequently granted under the Plan, the maximum number of shares or securities
that may be delivered under the Plan, the exercise price, and other relevant
provisions shall be appropriately adjusted by the Committee, whose determination
shall be binding on all persons.

     The Committee may also adjust the number of shares subject to outstanding
awards and the exercise price and the terms of outstanding awards to take into
consideration material changes in accounting practices or principles,
extraordinary dividends, consolidations or mergers (except those described in
Section 6(j)), acquisitions or dispositions of stock or property or any other
event if it is determined by the Board that such adjustment is appropriate to
avoid distortion in the operation of the Plan.

     5.   ELIGIBILITY FOR OPTIONS

     A Director eligible to receive Options under the Plan (an "Eligible
Director") shall be any director who is not an employee of the Company or of any
subsidiary of the Company, and (ii) is not a holder of more than 5% of the
outstanding shares of the Stock, or a person who is in control of such holder.

     6.   TERMS AND CONDITIONS OF OPTIONS

     (a) Formula Options. On the date that the Board approves this Plan, each
person who is then an Eligible Director shall be awarded on such date an Option
covering 1,000 shares of Stock, subject to stockholder approval of the Plan.
Each Eligible Director elected for the first time thereafter shall also be
awarded on the date of his or her first election an Option covering 2,000 shares
of Stock. Thereafter, immediately following the annual meeting of stockholders,
each Eligible Director shall be awarded an Option covering 1,000 shares of
Stock. The Options awarded under this paragraph (a) are referred to as "Formula
Options."


<PAGE>   3
     (b) Discretionary Options. The Committee shall also have the authority
under this Plan to award Options to purchase Stock to Eligible Directors in such
amounts and on such terms not inconsistent with this Plan as it shall determine
at the time of the award. The Options awarded under this paragraph (b) are
referred to herein as "Discretionary Options."

     (c) Exercise Price. The exercise price of each Formula Option shall be 100%
of the fair market value per share of the Stock at the time the Option is
granted. The exercise price of each Discretionary Options shall be set by the
Committee. In no event, however, shall the Option price be less, in the case of
an original issue of authorized stock, than par value per share. For purposes of
this paragraph, the fair market value of a share of Stock will be the mean
between the high and low sale prices as reported on the principal market on
which the Stock is traded or, if no sales are reported, the fair market value as
determined in good faith by the Committee.

     (d) Duration of Options. The latest date on which a Option may be exercised
(the "Final Exercise Date") shall be (i) in the case of Formula Options, the
date which is seven years from the date the Option was granted and (ii) in the
case of Discretionary Options, such date as the Committee may determine, but in
no event later than seven years from the date the Option was granted.

     (e) Exercise of Options.

     (1)  Each Formula Option shall become exercisable as to one-fourth of the
          shares covered thereby on each anniversary of the date of the grant.
          Each Discretionary Option shall become exercisable at such time or
          times as the Committee shall determine.

     (2)  Any exercise of an Option shall be in writing, signed by the proper
          person and delivered or mailed to the Company, accompanied by (i) any
          documentation required by the Committee and (ii) payment in full for
          the number of shares for which the Option is exercised.

     (3)  If an Option is exercised by the executor or administrator of a
          deceased director, or by the person or persons to whom the Option has
          been transferred by the director's will or the applicable laws of
          descent and distribution, the Company shall be under no obligation to
          deliver Stock pursuant to such exercise until the Company is satisfied
          as to the authority of the person or persons exercising the Option.

     (f) Payment for and Delivery of Stock. Stock purchased under the Plan shall
be paid for as follows: (i) in cash or by check (acceptable to the Company in
accordance with guidelines established for this purpose), bank draft or money
order payable to the order of the Company or (ii) if so permitted by the
Committee, (A) through the delivery of shares of Stock (which, in the case of
shares of Stock acquired from the Company, have been outstanding for at least
six months) having a fair market value on the last business day preceding the
date of exercise equal to the purchase price or (B) by having the Company hold
back from the shares transferred upon exercise Stock having a fair market value
on the last business day preceding the date of exercise equal to the purchase
price or 


<PAGE>   4
(C) by delivery of a promissory note of the Option holder to the Company, such
note to be payable on such terms as are specified or (D) by delivery of an
unconditional and irrevocable undertaking by a broker to deliver promptly to the
Company sufficient funds to pay the exercise price or (E) by any combination of
the permissible forms of payment; provided, that if the Stock delivered upon
exercise of the Option is an original issue of authorized Stock, at least so
much of the exercise price as represents the par value of such Stock shall be
paid other than with a personal check or promissory note of the Option holder.

     An Option holder shall not have the rights of a shareholder with regard to
awards under the Plan except as to Stock actually received by him or her under
the Plan.

     The Company shall not be obligated to deliver any shares of Stock (a)
until, in the opinion of the Company's counsel, all applicable federal and state
laws and regulations have been complied with, and (b) if the outstanding Stock
is at the time listed on any stock exchange, until the shares to be delivered
have been listed or authorized to be listed on such exchange upon official
notice of issuance, and (c) until all other legal matters in connection with the
issuance and delivery of such shares have been approved by the Company's
counsel. If the sale of Stock has not been registered under the Securities Act
of 1933, as amended, the Company may require, as a condition to exercise of the
Option, such representations or agreements as counsel for the Company may
consider appropriate to avoid violation of such Act and may require that the
certificates evidencing such Stock bear an appropriate legend restricting
transfer.

     (g) Nontransferability of Options. Except as the Committee shall otherwise
provide, no Option may be transferred other than by will or by the laws of
descent and distribution, and during a director's lifetime an Option may be
exercised only by him or her.

     (h) Death. Except as the Committee shall otherwise provide, upon the death
of any director granted Options under this Plan, all Options not then
exercisable shall terminate. All Options held by the director that are
exercisable immediately prior to death may be exercised by his or her executor
or administrator, or by the person or persons to whom the Option is transferred
by will or the applicable laws of descent and distribution, at any time within
six months after the director's death (subject, however, to the limitations of
Section 6(d) regarding the maximum exercise period for such Option). After
completion of that six-month period, such Options shall terminate to the extent
not previously exercised.

     (i) Other Termination of Service. Except as the Committee shall otherwise
provide, if a director's service with the Company terminates for any reason
other than death, all Options held by the director that are not then exercisable
shall terminate. Options that are exercisable on the date of termination shall
continue to be exercisable for a period of three months (subject to Section
6(d)), but shall terminate immediately if the director was removed for cause or
resigned under circumstances which, in the opinion of the Committee, casts such
discredit on him or her as to justify termination of his Options. After
completion of that three-month period, such Options shall terminate to the
extent not previously exercised, expired or terminated.


<PAGE>   5

     (j) Mergers, etc. Subject to the second paragraph of this paragraph 6(j),
in the event of a consolidation or merger in which the Company is not the
surviving corporation (other than a consolidation or merger in which the holders
of Stock of the Company acquire a majority of the voting stock of the surviving
corporation) or which results in the acquisition of substantially all the
Company's outstanding Stock by a single person or entity or by a group of
persons and/or entities acting in concert, or in the event of a sale or transfer
of substantially all of the Company's assets or a dissolution or liquidation of
the Company, all Options hereunder will terminate, but 20 days prior to the
anticipated effective date of any such merger, consolidation, sale, dissolution,
or liquidation, all Options outstanding hereunder that are not otherwise
exercisable shall become immediately exercisable, provided, that if the
transaction is a merger or consolidation that is accounted for as a pooling of
interests the Committee shall arrange to have the successor or surviving
corporation assume all Options outstanding under this Plan, with such
adjustments to the number of shares covered by such Options and the exercise
price thereof as may be necessary to reflect the exchange ratio provided for in
the transaction. Such assumed options shall otherwise be on terms and conditions
substantially equivalent to those set forth in this Plan, shall be immediately
exercisable and, except as to Eligible Directors who become directors of the
acquiring or surviving corporation, shall terminate on the 180th day following
the consummation of the transaction. Options held by Eligible Directors who
become directors of the acquiring or surviving corporation shall be governed,
mutatis mutandis, by the provisions of this Plan and the agreement evidencing
the Option surrendered in substitution.

     Notwithstanding any other provision of this Plan, in the event of a Change
in Control of the Company as defined in Exhibit A hereto each Option held by
each Eligible Director will immediately become fully exercisable.

     7.   EFFECT, DISCONTINUANCE, CANCELLATION, AMENDMENT, TERMINATION AND
          EFFECTIVENESS

     Neither adoption of the Plan nor the grant of Options to a director shall
affect the Company's right to grant to such director Options that are not
subject to the Plan, to issue to such directors Stock as a bonus or otherwise,
or to adopt other plans or arrangements under which Stock may be issued to
directors.

     The Committee may at any time terminate the Plan as to any further grants
of Options. The Committee may at any time or times, amend the Plan for any
purpose which may at the time be permitted by law, but no such amendment shall
adversely affect the rights of any Optionee (without the Optionee's consent)
under any Option previously granted.


<PAGE>   6
                                    EXHIBIT A



     A Change in Control will occur for purposes of this Plan if (i) any
individual, corporation, partnership, company or other entity (a "Person")
becomes the "beneficial owner" (as defined in Rule 13d-3 under the Securities
Exchange Act of 1934, as amended (the "Exchange Act")) of securities of the
Company representing more than 30% of the combined voting power of the Company's
then outstanding securities (other than as a result of acquisitions of such
securities from the Company), (ii) there is a change in control of the Company
of a kind which would be required to be reported under Item 6(e) of Schedule 14A
of Regulation 14A promulgated under the Exchange Act (or a similar item in a
similar schedule or form), whether or not the Company is then subject to such
reporting requirement, (iii) the Company is a party to, or the stockholders
approve, a merger, consolidation, or other reorganization (other than (a) a
merger, consolidation or other reorganization which would result in the voting
securities of the Company outstanding immediately prior thereto continuing to
represent, either by remaining outstanding or by being converted into voting
securities of the surviving entity, more than 50% of the combined voting power
of the voting securities of the Company or such surviving entity outstanding
immediately after such merger, consolidation, or other reorganization, or (b) a
merger, consolidation, or other reorganization effected to implement a
recapitalization of the Company, or similar transaction, in which no Person
acquires more than 20% of the combined voting power of the Company's then
outstanding securities), a sale of all or substantially all assets, or a plan of
liquidation, or (iv) individuals who, at the date hereof, constitute the Board
cease for any reason to constitute a majority thereof, PROVIDED, HOWEVER, that
any director who is not in office at the date hereof but whose election by the
Board or whose nomination for election by the Company's shareholders was
approved by a vote of at least a majority of the directors then still in office
who either were directors at the date hereof or whose election or nomination for
election was previously so approved (other than an election or nomination of an
individual whose initial assumption of office is in connection with an actual or
threatened election contest relating to the election of the Directors of the
Company, as such terms are used in Rule 14a-11 of Regulation 14A promulgated
under the Exchange Act) shall be deemed to have been in office at the date
hereof for purposes of this definition.

     Notwithstanding the foregoing provisions of this Exhibit A, a "Change in
Control" will not be deemed to have occurred solely because of the acquisition
of beneficial ownership of securities of the Company by an employment benefit
plan maintained by the Company for its employees.