<PAGE>
                                                                    EXHIBIT 10.8

            SUPPLEMENTAL INDENTURE (this "Supplemental Indenture"), dated as of
October 29, 2004 among Unitive Electronics, Inc., a North Carolina corporation
(the "Guaranteeing Subsidiary"), an indirect subsidiary of Amkor Technology,
Inc. (or its permitted successor), a Delaware corporation (the "Company"), the
Company, the other Guarantors (as defined in the Indenture referred to herein)
and Wells Fargo Bank, N.A., as trustee under the indenture referred to below
(the "Trustee").

                               W I T N E S S E T H

            WHEREAS, the Company has heretofore executed and delivered to the
Trustee an indenture (the "Indenture"), dated as of March 12, 2004, providing
for the issuance of an aggregate principal amount of up to $250,000,000 of
7 1/8% Senior Notes due March 15, 2011 (the "Notes");

            WHEREAS, the Indenture provides that under certain circumstances the
Guaranteeing Subsidiary shall execute and deliver to the Trustee a supplemental
indenture pursuant to which the Guaranteeing Subsidiary shall unconditionally
guarantee all of the Company's Obligations under the Notes and the Indenture on
the terms and conditions set forth herein (the "Note Guarantee"); and

            WHEREAS, pursuant to Section 9.01 of the Indenture, the Trustee is
authorized to execute and deliver this Supplemental Indenture.

            NOW THEREFORE, in consideration of the foregoing and for other good
and valuable consideration, the receipt of which is hereby acknowledged, the
Guaranteeing Subsidiary and the Trustee mutually covenant and agree for the
equal and ratable benefit of the Holders of the Notes as follows:

            1. CAPITALIZED TERMS. Capitalized terms used herein without
definition shall have the meanings assigned to them in the Indenture.

            2. AGREEMENT TO GUARANTEE. The Guaranteeing Subsidiary hereby agrees
as follows:

                  (a) Along with all Guarantors named in the Indenture, to
      jointly and severally Guarantee to each Holder of a Note authenticated and
      delivered by the Trustee and to the Trustee and its successors and
      assigns, the Notes or the obligations of the Company hereunder or
      thereunder, that:

                        (i) the principal of and interest on the Notes will be
            promptly paid in full when due, whether at maturity, by
            acceleration, redemption or otherwise, and interest on the overdue
            principal of and interest on the Notes, if any, if lawful, and all
            other obligations of the Company to the Holders or the Trustee
            hereunder or thereunder will be promptly paid in full or performed,
            all in accordance with the terms hereof and thereof; and

                        (ii) in case of any extension of time of payment or
            renewal of any Notes or any of such other obligations, that same
            will be promptly paid in full when due or performed in accordance
            with the terms of the extension or renewal, whether at stated
            maturity, by acceleration or otherwise. Failing payment when due of
            any amount so guaranteed or any performance so guaranteed for
            whatever reason, the Guarantors shall be jointly and severally
            obligated to pay the same immediately.

                  (b) The obligations hereunder shall be unconditional,
      irrespective of the validity, regularity or enforceability of the Notes or
      the Indenture, the absence of any action to enforce the same, any waiver
      or consent by any Holder of the Notes with respect to any provisions
      hereof or thereof, the recovery of any judgment against the Company, any
      action to enforce the same or any

                                                                               1
<PAGE>

      other circumstance which might otherwise constitute a legal or equitable
      discharge or defense of a guarantor.

                  (c) The following is hereby waived: diligence presentment,
      demand of payment, filing of claims with a court in the event of
      insolvency or bankruptcy of the Company, any right to require a proceeding
      first against the Company, protest, notice and all demands whatsoever.

                  (d) This Note Guarantee shall not be discharged except by
      complete performance of the obligations contained in the Notes and the
      Indenture, and the Guaranteeing Subsidiary accepts all obligations of a
      Guarantor under the Indenture.

                  (e) If any Holder or the Trustee is required by any court or
      otherwise to return to the Company, the Guarantors, or any Custodian,
      Trustee, liquidator or other similar official acting in relation to either
      the Company or the Guarantors, any amount paid by either to the Trustee or
      such Holder, this Note Guarantee, to the extent theretofore discharged,
      shall be reinstated in full force and effect.

                  (f) The Guaranteeing Subsidiary shall not be entitled to any
      right of subrogation in relation to the Holders in respect of any
      obligations guaranteed hereby until payment in full of all obligations
      guaranteed hereby.

                  (g) As between the Guarantors, on the one hand, and the
      Holders and the Trustee, on the other hand, (x) the maturity of the
      obligations guaranteed hereby may be accelerated as provided in Article 6
      of the Indenture for the purposes of this Note Guarantee, notwithstanding
      any stay, injunction or other prohibition preventing such acceleration in
      respect of the obligations guaranteed hereby, and (y) in the event of any
      declaration of acceleration of such obligations as provided in Article 6
      of the Indenture, such obligations (whether or not due and payable) shall
      forthwith become due and payable by the Guarantors for the purpose of this
      Note Guarantee.

                  (h) The Guarantors shall have the right to seek contribution
      from any non-paying Guarantor so long as the exercise of such right does
      not impair the rights of the Holders under the Guarantee.

                  (i) Pursuant to Section 10.02 of the Indenture, after giving
      effect to any maximum amount and any other contingent and fixed
      liabilities that are relevant under any applicable Bankruptcy or
      fraudulent conveyance laws, and after giving effect to any collections
      from, rights to receive contribution from or payments made by or on behalf
      of any other Guarantor in respect of the obligations of such other
      Guarantor under Article 10 of the Indenture, this Note Guarantee shall be
      limited to the maximum amount permissible such that the obligations of
      such Guarantor under this Note Guarantee will not constitute a fraudulent
      transfer or conveyance.

            3. EXECUTION AND DELIVERY. Each Guaranteeing Subsidiary agrees that
the Note Guarantees shall remain in full force and effect notwithstanding any
failure to endorse on each Note a notation of such Note Guarantee.

            4. GUARANTEEING SUBSIDIARY MAY CONSOLIDATE, ETC. ON CERTAIN TERMS.

            (a) The Guaranteeing Subsidiary may not consolidate with or merge
with or into (whether or not such Guarantor is the surviving Person) another
corporation, Person or entity whether or not affiliated with such Guarantor
unless:

                                                                               2
<PAGE>

                  (i) subject to Sections 10.04 and 10.05 of the Indenture, the
      Person formed by or surviving any such consolidation or merger (if other
      than a Guarantor or the Company) unconditionally assumes all the
      obligations of such Guarantor, pursuant to a supplemental indenture in
      form and substance reasonably satisfactory to the Trustee, under the
      Notes, the Indenture and the Note Guarantee on the terms set forth herein
      or therein; and

                  (ii) immediately after giving effect to such transaction, no
      Default or Event of Default exists.

            (b) In case of any such consolidation, merger, sale or conveyance
and upon the assumption by the successor corporation, by supplemental indenture,
executed and delivered to the Trustee and satisfactory in form to the Trustee,
of the Note Guarantee endorsed upon the Notes and the due and punctual
performance of all of the covenants and conditions of the Indenture to be
performed by the Guarantor, such successor corporation shall succeed to and be
substituted for the Guarantor with the same effect as if it had been named
herein as a Guarantor. Such successor corporation thereupon may cause to be
signed any or all of the Note Guarantees to be endorsed upon all of the Notes
issuable hereunder which theretofore shall not have been signed by the Company
and delivered to the Trustee. All the Note Guarantees so issued shall in all
respects have the same legal rank and benefit under the Indenture as the Note
Guarantees theretofore and thereafter issued in accordance with the terms of the
Indenture as though all of such Note Guarantees had been issued at the date of
the execution hereof.

            (c) Except as set forth in Articles 4 and 5 and Section 10.05 of
Article 10 of the Indenture, and notwithstanding clauses (a) and (b) above,
nothing contained in the Indenture or in any of the Notes shall prevent any
consolidation or merger of a Guarantor with or into the Company or another
Guarantor, or shall prevent any sale or conveyance of the property of a
Guarantor as an entirety or substantially as an entirety to the Company or
another Guarantor.

            5. RELEASES.

            (a) In the event of a sale or other disposition of all of the assets
of any Guarantor, by way of merger, consolidation or otherwise, or a sale or
other disposition of all to the capital stock of any Guarantor, in each case to
a Person that is not (either before or after giving effect to such transaction)
a Restricted Subsidiary of the Company, then such Guarantor (in the event of a
sale or other disposition, by way of merger, consolidation or otherwise, of all
of the capital stock of such Guarantor) or the corporation acquiring the
property (in the event of a sale or other disposition of all or substantially
all of the assets of such Guarantor) will be released and relieved of any
obligations under its Note Guarantee; provided that the Net Proceeds of such
sale or other disposition are applied in accordance with the applicable
provisions of the Indenture, including without limitation Section 4.10 of the
Indenture. Upon delivery by the Company to the Trustee of an Officers'
Certificate and an Opinion of Counsel to the effect that such sale or other
disposition was made by the Company in accordance with the provisions of the
Indenture, including without limitation Section 4.10 of the Indenture, the
Trustee shall execute any documents reasonably required in order to evidence the
release of any Guarantor from its obligations under its Note Guarantee.

            (b) Any Guarantor not released from its obligations under its Note
Guarantee shall remain liable for the full amount of principal of and interest
on the Notes and for the other obligations of any Guarantor under the Indenture
as provided in Article 10 of the Indenture.

            6. NO RECOURSE AGAINST OTHERS. No past, present or future director,
officer, employee, incorporator, stockholder or agent of the Guaranteeing
Subsidiary, as such, shall have any liability for any obligations of the Company
or any Guaranteeing Subsidiary under the Notes, any Note Guarantees, the

                                                                               3
<PAGE>

Indenture or this Supplemental Indenture or for any claim based on, in respect
of, or by reason of, such obligations or their creation. Each Holder of the
Notes by accepting a Note waives and releases all such liability. The waiver and
release are part of the consideration for issuance of the Notes. Such waiver may
not be effective to waive liabilities under the federal securities laws and it
is the view of the SEC that such a waiver is against public policy.

            7. NEW YORK LAW TO GOVERN. THE INTERNAL LAW OF THE STATE OF NEW YORK
SHALL GOVERN AND BE USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE BUT WITHOUT
GIVING EFFECT TO APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT
THE APPLICATION OF THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

            8. COUNTERPARTS The parties may sign any number of copies of this
Supplemental Indenture. Each signed copy shall be an original, but all of them
together represent the same agreement.

            9. EFFECT OF HEADINGS. The Section headings herein are for
convenience only and shall not affect the construction hereof.

            10. THE TRUSTEE. The Trustee shall not be responsible in any manner
whatsoever for or in respect of the validity or sufficiency of this Supplemental
Indenture or for or in respect of the recitals contained herein, all of which
recitals are made solely by the Guaranteeing Subsidiary and the Company.

                                                                               4
<PAGE>

      IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed and attested, all as of the date first above
written.

Dated: October 29, 2004

                                UNITIVE ELECTRONICS, INC.

                                By: /s/ Arthur Bergens, Jr.
                                    ---------------------------------
                                    Name: Arthur Bergens, Jr.
                                    Title: Chief Financial Officer,
                                           Secretary and Treasurer

                                AMKOR TECHNOLOGY, INC.

                                By: /s/ Kenneth Joyce
                                    ------------------------------------
                                    Name: Kenneth Joyce
                                    Title: Executive Vice President and
                                           Chief Financial Officer

                                WELLS FARGO BANK, N.A.,
                                  as Trustee

                                By: /s/ Jane Schweiger
                                    ------------------------------------
                                    Authorized Signatory

<PAGE>

                                   SCHEDULE I
                             SCHEDULE OF GUARANTORS

      The following schedule lists each Guarantor under the Indenture as of the
date of issuance of the Notes:

None.

<PAGE>

                              NOTATION OF GUARANTEE

      For value received, each Guarantor (which term includes any successor
Person under the Indenture) has, jointly and severally, unconditionally
guaranteed, to the extent set forth in the Indenture and subject to the
provisions in the Indenture dated as of March 12, 2004 (the "Indenture") among
Amkor Technology, Inc., the Guarantors listed on Schedule I thereto from time to
time, and Wells Fargo Bank, N.A., as trustee (the "Trustee"), (a) the due and
punctual payment of the principal of, premium, if any, and interest on the Notes
(as defined in the Indenture), whether at maturity, by acceleration, redemption
or otherwise, the due and punctual payment of interest on overdue principal and
premium, and, to the extent permitted by law, interest, and the due and punctual
performance of all other obligations of the Company to the Holders or the
Trustee all in accordance with the terms of the Indenture and (b) in case of any
extension of time of payment or renewal of any Notes or any of such other
obligations, that the same will be promptly paid in full when due or performed
in accordance with the terms of the extension or renewal, whether at stated
maturity, by acceleration or otherwise. The obligations of the Guarantors to the
Holders of Notes and to the Trustee pursuant to the Note Guarantee and the
Indenture are expressly set forth in Article 10 of the Indenture and reference
is hereby made to the Indenture for the precise terms of the Note Guarantee.
Each Holder of a Note, by accepting the same, agrees to and shall be bound by
such provisions.

Dated: October 29, 2004

                                UNITIVE ELECTRONICS, INC.

                                By: /s/ Arthur Bergens, Jr.
                                    -------------------------------
                                    Name: Arthur Bergens, Jr.
                                    Title: Chief Financial Officer,
                                           Secretary and Treasurer