<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-12-31</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001108320</issuerCik>
        <issuerName>SMTC CORP</issuerName>
        <issuerTradingSymbol>SMTX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001325533</rptOwnerCik>
            <rptOwnerName>Red Oak Partners, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>654 BROADWAY</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 5</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10012</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001423093</rptOwnerCik>
            <rptOwnerName>Sandberg David</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>654 BROADWAY</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 5</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10012</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-12-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F4"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>625000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.2</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1845392</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By The Red Oak Fund, LP</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-12-31</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F4"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>625000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.2</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2488792</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By David Sandberg</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Red Oak Partners, LLC (the &quot;General Partner&quot;) serves as the general partner of The Red Oak Fund, LP, a Delaware limited partnership (the &quot;Fund&quot;), the direct owner of the subject securities. David Sandberg is the managing member of the General Partner and the Fund's portfolio manager.</footnote>
        <footnote id="F2">Red Oak Partners, LLC (the &quot;General Partner&quot;) serves as a general partner of Pinnacle Fund LLLP, a Colorado limited liability limited partnership (&quot;Pinnacle&quot;), the direct owner of the subject securities. David Sandberg is a limited partner of Pinnacle, the managing member of the General Partner and an investment advisor to Pinnacle.</footnote>
        <footnote id="F3">Each Reporting Person disclaims beneficial ownership of all securities reported herein, except to the extent of their pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of the shares for purposes of Section 16 of the Securities and Exchange Act of 1934 or for any other purpose.</footnote>
        <footnote id="F4">Explanation of transaction code: The partnership transferred securities to a limited partner as an in-kind redemption of partnership interests. The deemed transfer price was the closing price on the transfer date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>David Sandberg</signatureName>
        <signatureDate>2011-01-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
