<PAGE>

                                                                     Exhibit 4.6

                     15% SENIOR SUBORDINATED NOTE DUE 2010


                               SMTC CORPORATION

     THIS SECURITY BEARS ORIGINAL ISSUE DISCOUNT.  UPON WRITTEN REQUEST TO THE
     VICE PRESIDENT, FINANCE AND ADMINISTRATION, SMTC CORPORATION, 635 HOOD
     ROAD, MARKHAM, ONTARIO, CANADA L3R 4N6, INFORMATION REGARDING THE ISSUE
     PRICE, AMOUNT OF ORIGINAL ISSUE DISCOUNT, ISSUE DATE AND YIELD TO MATURITY
     WILL BE MADE AVAILABLE.

     THIS NOTE WAS ISSUED IN A PRIVATE PLACEMENT, WITHOUT REGISTRATION UNDER THE
     SECURITIES ACT OF 1933, AS AMENDED (THE "ACT") AND MAY NOT BE SOLD,
     ASSIGNED, PLEDGED OR OTHERWISE TRANSFERRED IN THE ABSENCE OF AN EFFECTIVE
     REGISTRATION STATEMENT UNDER THE ACT COVERING THE TRANSFER OR AN OPINION OF
     COUNSEL ACCEPTABLE TO THE ISSUER THAT SUCH REGISTRATION UNDER THE ACT IS
     NOT REQUIRED.

     THIS NOTE IS SUBORDINATED TO AND JUNIOR IN RIGHT OF PAYMENT TO PAYMENT IN
     FULL OF ALL SENIOR INDEBTEDNESS AS DEFINED IN THE SENIOR SUBORDINATED LOAN
     AGREEMENT DATED AS OF MAY __, 2000, AS THE SAME MAY BE AMENDED, MODIFIED,
     RESTATED OR SUPPLEMENTED FROM TIME TO TIME (THE "AGREEMENT") TO THE EXTENT,
     AND IN THE MANNER PROVIDED IN THE AGREEMENT.

$1,081,051.79                                                   May 18, 2000

     FOR VALUE RECEIVED, the undersigned SMTC Corporation, a Delaware
corporation (the "Company"), hereby promises to pay to Bain Capital Fund VI,
L.P. or its registered assigns (the "Payee"), at 11:00 a.m. (New York time) on
the Maturity Date (as defined in the Agreement), the principal sum of one
million eighty-one thousand fifty-one and 79/100 United States Dollars (US
$1,081,051.79) or such lesser principal amount thereof as may remain
outstanding, in lawful money of the United States of America in immediately
available funds, and to pay interest from the date hereof on the principal
amount hereof from time to time outstanding at a rate or rates per annum, and
payable on such dates, as determined pursuant to the terms of the Agreement,
through the issuance to the Payee of additional notes substantially in the form
attached hereto as Exhibit A-1 (the "Interest Notes"), each such Interest Note
having a stated principal amount equal to the amount of interest due and payable
to the Payee on such interest payment date and each such Interest Note to be
delivered to the Payee as specified in the Agreement.

     The Company promises to pay interest, on demand, on any overdue principal
and, to the extent permitted by law, overdue interest from their due dates at a
rate or rates determined as set forth in the Agreement.

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     The Company hereby waives diligence, presentment, demand, protest and
notice of any kind whatsoever, other than as expressly required by the
Agreement.  The nonexercise by the holder of any of its rights hereunder in any
particular instance shall not constitute a waiver thereof in that or any
subsequent instance.

     Prior to any transfer of this Note, all payments and prepayments of the
principal hereof shall be endorsed by the holder on the schedule attached hereto
or any continuation thereof; provided, however, that the failure of the holder
hereof to make such a notation or any error in such a notation shall not in any
manner affect the obligations of the Company to make payments of principal and
interest in accordance with the terms of this Note and the Agreement.

     This Note and all obligations of the Company hereunder are subordinated to
and junior in right of payment to the prior payment in full of all Senior
Indebtedness (as defined in the Agreement) on the terms and subject to the
provisions set forth in the Agreement.

     This Note is one of the PIK Notes referred to in the Agreement, which,
among other things, contains provisions for the acceleration of the maturity
hereof upon the happening of certain events, for optional and mandatory
prepayment of the principal hereof prior to the maturity hereof and prepayment
premiums thereon and for the amendment or waiver of certain provisions of the
Agreement, all upon the terms and conditions therein specified.  This Note shall
be construed in accordance with and governed by the laws of the State of
Delaware without giving effect to principles of conflicts of laws.


                         SMTC CORPORATION



                         By: /s/ Richard Smith
                             ------------------------------
                             Name: /s/ Richard Smith
                             Title: Vice President Finance and Administration

                                      -2-
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Lender Schedule to Exhibit 4.6





                                                          NOTE
                                      PRINCIPAL         PURCHASE
     LENDER                            AMOUNT             PRICE
     ------                            ------             -----

Bain Capital Fund VI, L.P.           $1,081,051.79     $1,081.051.79

BCIP Associates II                   $  394,345.75     $  394,345.75

BCIP Associates II-B                 $   66,054.32     $   66,054.32

BCIP Associates II-C                 $   48,330.24     $   48,330.24

Celerity Partners III, L.P.          $  958,520.55     $  958,520.55

Venteura Limited                     $  309,860.77     $  309,860.77

Kilmer Electronics Group Limited     $  909,605.75     $  909,605.75

P.N. Walker Consulting               $  529,190.68     $  529,190.68

Nichal Inc.                          $  529,190.68     $  529,190.68

Philip Woodard                       $  101,694.84     $  101,694.84

General Electric Capital Corporation $   72,154.62     $   72,154.62