Document:

<PAGE>

                                                                    EXHIBIT 4.20

                                                                  EXECUTION COPY

THIS YANGDO TAMBO AGREEMENT (the "Agreement") is entered as of this 26th day of
December 2003, by and between:

     (i) SIMMTECH CO. LTD, a company duly incorporated and existing under the
     laws of Korea and having its principal place of of business at 70-5
     Songjung-Dong, Heungduk-ku, Choungju, Chungchongbuk-do, Korea 361-290 (the
     "Transferor"); and

     (ii) ST ASSEMBLY TEST SERVICES LTD., a company duly incorporated and
     existing under the law of Singapore and having a place of business at 5
     Yishun Street 23, Singapore 768442 (the "Transferee").

                                    RECITALS

WHEREAS:

A.   By the Loan Agreement dated as of December 26, 2003 (the "Loan Agreement")
     made by and between the Transferor, the Transferee and Mr. Se-Ho Chun, the
     Transferee has agreed, subject to and upon the terms and conditions
     contained therein, to provide a loan to the Transferor in the amount of USD
     15 million (USD 15,000,000);

B.   The Transferor will be, upon acquisition, the legal and beneficial owner of
     the Property To Be Owned (as defined below); and

C.   For the purposes of securing the Secured Obligations (as defined below),
     the Transferor desires to transfer to the Transferee, among other things,
     all its rights, title and interests in and to the Property To Be Owned
     pursuant to terms and conditions herein.

NOW, THEREFORE, it is agreed as follows:

SECTION 1. INTERPRETATION

Words and expressions defined in the Loan Agreement shall, unless otherwise
defined herein or the context otherwise requires, have the same meaning when
used in this Agreement. References to any agreement or document shall be
construed as references to such agreement or document as varied, amended,
novated or supplemented from time to time. In addition thereto, as used in this
Agreement:

<PAGE>

1.1  "Property to Be Owned" shall mean any and all Equipment (as defined in the
     Loan Agreement) to be purchased by the Transferor using the Loan monies, as
     described in Schedule I hereto (as amended from time to time pursuant to
     this Agreement).

1.2. "Secured Obligations" shall mean (i) any and all obligations, liabilities
     and indebtedness of the Transferor owing to the Transferee, presently
     existing or to be incurred hereinafter under or with respect to the Loan
     Agreement, (ii) moneys, obligations and liabilities owing and payable by
     the Major Shareholder (defined in the Loan Agreement) to the Transferee
     under the Share Pledge Agreement dated December 26, 2003 made between the
     Major Shareholder and the Transferee, (iii) moneys, obligations and
     liabilities owing and payable by the Company to the Pledgee under the
     Factory Kun-Mortgage Agreement dated December 26, 2003 between the
     Transferor and Transferee and (iv) moneys, obligations and liabilities
     owing and payable by the Transferor to the Transferee under this Agreement.

SECTION 2. YANGDO TAMBO AGREEMENT

2.1  Immediately upon the Transferor obtaining legal title to the Property To Be
     Owned, the Transferor shall transfer and assign to the Transferee the
     Property To Be Owned as security for the punctual payment, performance and
     discharge in full of the Secured Obligations; provided, that unless and
     until an Event of Default occurs under the Loan Agreement the Transferee
     shall hold the title to the Property To Be Owned for the purpose of
     security only and shall not use, seize or dispose of the Property To Be
     Owned. The Transferor hereby agrees that any Property to Be Owned shall be
     subject to Yangdo Tambo on such property for the benefit of the Transferee
     pursuant to this Agreement and that if such property may not be subject to
     such Yangdo Tambo, the Transferor shall transfer and assign to the
     Transferee the Property to Be Owned as security for the punctual payment,
     performance and discharge in full of the Secured Obligations in the manner
     applicable to the nature of it and perform any and all actions necessary
     for the establishment and effectuation of such collateral arrangement under
     the laws of Korea.

2.2  At each time the Transferor obtaining legal title to the Property To Be
     Owned, but no later than 2 days after obtaining such legal title, the
     Transferor shall send to the Transferee a written notice which shall
     include a statement that that the Transferor has obtained legal title to
     the concerned Property To Be Owned and a detailed description of the
     concerned Property To Be Owned (to the reasonable satisfaction of the
     Transferee).

SECTION 3. REPRESENTATIONS AND WARRANTIES

3.1  The Transferor hereby represents, warrants and covenants to the Transferee
     that:

     (a)  the execution, delivery and performance by the Transferor of this
          Agreement have been duly authorized by the Transferor, and are not in
          conflict with any provision of any applicable laws or regulations or
          the articles of incorporation of the Transferor;

                                       2

<PAGE>

     (b)  the execution, delivery and performance by the Transferor of this
          Agreement does not violate or cause any default under any indenture,
          agreement or undertaking by which the Transferor is bound;

     (c)  all authorizations required from any government or governmental agency
          in connection with this Agreement have been obtained and are in full
          force and effect;

     (d)  this Agreement constitutes valid obligations of the Transferor,
          legally binding upon it and enforceable in accordance with its terms,
          subject, as to enforceability, to laws relating to bankruptcy,
          insolvency, liquidation, reorganization, court schemes, moratoria,
          administration and other laws generally affecting the rights of
          creditors;

     (e)  all property forming part of the Property To Be Owned, prior to the
          transfer and assignment by the Transferor to the Transferee to be made
          hereby, shall be owned legally by the Transferor by good and
          marketable title free from all security, interest, lien or other
          encumbrance, and such title shall, by the transfer and assignment
          contained herein, be automatically transferred and assigned to the
          Transferee to provide for payment when due of the Secured Obligations
          and shall at all times be and remain free from any security, interest,
          lien or other encumbrance, except for the transfer and assignment of
          title made hereunder;

     (f)  the Transferor has not agreed, and will not agree to sell, assign,
          transfer or create any security, interest, lien or other encumbrance
          in or over all or any part of the Property To Be Owned other than in
          favor of the Transferee hereunder;

     (g)  to the knowledge of the Transferor, there are no circumstances that
          may or will diminish the value of the Property To Be Owned; and

     (h)  the Transferor has not taken any corporate action nor have any other
          steps been taken or legal proceedings been started by it or any third
          party for its winding up, dissolution, reorganization or bankruptcy or
          for the appointment of a receiver, trustee or similar officer over the
          Transferor or its assets or revenues, and there occurs or continues no
          cause/event that may lead to such action or steps.

3.2  Each of the warranties and representations contained in the preceding
     sub-clause shall survive and continue to have full force and effect until
     the termination of this Agreement.

SECTION 4. COVENANTS OF THE TRANSFEROR

The Transferor covenants and undertakes the following with the Transferee:

                                       3

<PAGE>

     (a)  duly and punctually to observe and perform all the conditions and
          obligations imposed on it by the Loan Agreement and this Agreement;

     (b)  not, without the prior written consent of the Transferee, to attempt
          to sell, assign, transfer or create any security, interest or lien
          over the Property To Be Owned to or in favor of any person other than
          the Transferee or otherwise dispose of or encumber any of the Property
          To Be Owned, and shall not remove the Property To Be Owned from the
          Transferor's premise unless it is replaced with the substitute
          property as provided in paragraph (f) below;

     (c)  at any time following the occurrence of an Event of Default, to do or
          permit to be done each and every act or thing the Transferee may from
          time to time require to be done for the purpose of enforcing the
          Transferee's rights under this Agreement or in respect of any of the
          Property To Be Owned and to allow its name to be used as and when
          required by the Transferee for such purpose;

     (d)  to possess and use the Property To Be Owned in accordance with its
          customary usage and preserve the value of the Property To Be Owned
          with such care as is required of a good manager;

     (e)  to make all registrations, filings and recordings, and take all other
          actions as are necessary or determined by the Transferee to be
          advisable to ensure the continued legality, validity, enforceability,
          priority and admissibility in evidence of this Agreement;

     (f)  to promptly notify the Transferee of any theft, loss or destruction of
          and damage to any of the Property To Be Owned or any other accident or
          reduction in price that has occurred or is expected to occur with
          respect to the Property To Be Owned (including but not limited to
          reduction in value due to depreciation), and in connection therewith,
          the Transferor agrees not to claim against the Transferee for any
          damages or loss incurred in connection with any such theft, loss
          destruction or damage unless attributable to any wilful misconduct of
          the Transferee. In case the value of the Property To Be Owned is
          materially affected due to theft, loss, destruction, damage,
          depreciation, etc., and the Transferor notifies the Transferee of such
          as provided in this paragraph (f), the Transferee may request the
          Transferee to replace the concerned the Property To Be Owned with
          other property that is acceptable to the Transferee, and the Parties
          hereto shall take all necessary steps to ensure that the terms of this
          Agreement shall apply to such replacement property, including but not
          limited to execution of an amendment to this Agreement which
          identifies the replacement property as the Property To Be Owned that
          is subject to this Agreement;

     (g)  to be responsible for the resolution of any disputes with a third
          party in connection with the Property To Be Owned, including any
          disputes involving claims against the Property To Be Owned , and in
          connection therewith, the Transferor agrees not to take any action
          which might adversely affect the enforcement of the Transferee's
          rights or Transferee'

                                       4

<PAGE>

          interests in the Property To Be Owned and to affirmatively protect and
          defend such rights and interests in accordance with the instructions
          of the Transferee;

     (i)  to conduct its business in accordance with any applicable laws and
          regulations;

     (j)  to pay all taxes, assessments and other governmental charges of any
          kind imposed on or in respect of its income or any of its business
          when due;

     (k)  immediately upon the acquisition of the Property To Be Owned , and
          until all Secured Obligations have been fully discharged, to affix a
          clearly visible sign or plaque on each Property To Be Owned (to the
          satisfaction of the Transferee) providing to the effect that the legal
          title to the Property To Be Owned belongs to the Transferee and that
          the Property To Be Owned may not be transferred, sold or offered as
          collateral (the exact content of which shall be approved in advance by
          the Transferee); and

     (l)  throughout the term of this Agreement, to procure and maintain
          insurance on the Property To Be Owned in such an amount and such a
          form as approved by the Transferee and from such an insurance company
          as may be selected or approved by the Transferee; and

     (m)  Each time when the Transferor obtains title to any Property to Be
          Owned, the Transferor shall immediately notify the Transferee together
          with a certified copy of amended Schedule I to add such property in
          the list thereto. Upon confirmation by the Transferee, such amended
          Schedule shall be deemed as the Schedule hereunder.

SECTION 5. ATTORNEY-IN-FACT

The Transferor hereby irrevocably appoints the Transferee as its true and lawful
attorney-in-fact with full power to require, demand and receive any and all
moneys and claims for money due and to become due under or with respect to the
Property To Be Owned to the extent transferred hereunder and to take any action
or execute any instrument which the Transferee may deem necessary or appropriate
to accomplish the purpose hereof.

SECTION 6. TERMINATION AND REASSIGNMENT

The term of this Agreement shall begin on the date of this Agreement and end on
the date on which all Secured Obligations shall have been unconditionally and
irrevocably paid and discharged. Upon termination of this Agreement, the
Transferee shall, at the request and cost of the Transferor, promptly
re-transfer to the Transferor all right, title, interest and benefit transferred
hereunder and the security constituted hereby to the Transferee, and take such
other actions as may be reasonably requested to effectuate such reassignment.

                                       5

<PAGE>

SECTION 7. PRESERVATION OF TRANSFERRED PROPERTY

The Transferor shall hold the Property To Be Owned, as custodian for the
Transferee. The Transferor hereby agrees that it will, from time to time at its
own expense, promptly execute and deliver all further instruments, and take all
further actions, as may be necessary or desirable in the opinion of the
Transferee, or as the Transferee may request, in order to effect or protect the
assignment of title to the Property To Be Owned by the Transferor to the
Transferee granted hereunder and to enable the Transferee's rights and remedies
hereunder with respect to the Property To Be Owned.

SECTION 8. ADDITION TO TRANSFERRED PROPERTY

Any structure, mechanical components, wires, parts, fuels and attached machinery
and tools, which are united with or attached to the Property To Be Owned and
goods to be attached to or united with the Property To Be Owned by extension,
reconstruction, repair or rebuilding shall be deemed to have been transferred
and delivered to the Transferee under this Agreement.

SECTION 9. ENFORCEMENT BY TRANSFEREE

9.1  If any of the Secured Obligations becomes due and payable, the Transferee
     shall be entitled to enforce its rights under this Agreement.

9.2  If any of the Secured Obligations becomes due and payable, the Transferee
     shall in its sole discretion have the authority to sell, transfer or
     otherwise dispose of the Property To Be Owned at such times and at such
     prices as are generally recognized as appropriate in custom and practice,
     without the necessity of any legal process or procedure. Upon such sale,
     transfer or disposal, the Transferee shall apply the Proceeds, after
     deducting the costs of such sale, transfer or disposal, against the Secured
     Obligations. Any excess amount shall be paid to the Transferor and any
     Secured Obligations not fully covered by the Proceeds shall remain due and
     owing and shall promptly be paid by the Transferor. Alternatively, the
     Transferee may, at its sole discretion, choose to maintain possession and
     ownership over the Property To Be Owned, in which case, the Transferee
     shall value the Property To Be Owned based on commercially reasonable
     standards and return any excess amount (net of any and all costs and taxes
     involving transfer of the ownership of the Property To Be Owned y) to the
     Transferor and any Secured Obligations not fully covered by the value of
     the Property To Be Owned shall remain due and owing and shall promptly be
     paid by the Transferor.

9.3  If any of the Secured Obligations becomes due and payable, the Transferee
     shall at any time have the right to enter upon any premises where the
     Property To Be Owned is located, take possession of all or any part thereof
     and remove the same from such premises and the Transferor shall not
     interfere with such taking of possession and removal.

9.4  The Transferor hereby consents to the procedures set out in Section 9.2 and
     9.3 above and waives any and all objections it may have thereto.

                                       6

<PAGE>

9.5  The Transferee shall incur no liability as a result of the sale,
     maintenance of ownership or any other disposition of the Property To Be
     Owned or any part thereof pursuant to Section 9.2 hereof conducted in a
     commercially reasonable manner. The Transferor hereby waives any claims
     against the Transferee arising by reason of the fact that the price at
     which the Property To Be Owned has been sold at such private sale may be
     less than the price at which it could have been sold if the Transferee had
     not accepted the first offer received or had offered the Property To Be
     Owned to more than one offeree.

9.6  The application of the Proceeds shall be determined by the Transferee in
     its absolute discretion, subject only to any other agreements between the
     Transferee and the Transferor relating thereto and to the requirements of
     any applicable law.

          As used in this Section 9, "Proceeds" of the Property To Be Owned
          shall mean cash, securities and other property realized in respect of,
          and distributions in kind of, the Property To Be Owned , including any
          thereof received under any reorganization, liquidation or adjustment
          of debt of the Transferor.

9.7  In case where the Transferor or a third party provides collateral (other
     than the Property To Be Owned) to the Transferee to secure all or any part
     of the Secured Obligations, the Transferee shall in its sole discretion
     have the authority to determine the priority and extent of enforcement
     between/among its rights under this Agreement and such other collateral
     arrangements, without the necessity of any legal process or consultation
     with the Transferor.

SECTION 10. ASSIGNMENT

This Agreement and the yangdo tambo created hereunder shall be binding upon and
inure to the benefit of the Transferor and the Transferee and their respective
successors and assigns. The Transferee may, in accordance with the Loan
Agreement and applicable laws, at any time assign all or any part of its rights
or obligations hereunder to any party (each an "Assignee"). The parties hereto
agree that to the extent of any transfer, the Assignee shall be deemed to have
the same rights and benefits under this Agreement as it would have had if it
were a Transferee signatory hereunder. The Transferor may not assign any of its
rights or obligations hereunder without the prior written consent of the
Transferee.

SECTION 11. FURTHER ASSURANCE

The Transferor shall do all such acts as may be necessary or appropriate in the
opinion of the Transferor including, but not limited to, the execution and
delivery of all further instruments, notices and documents and all further
action (whilst acting in a commercially reasonable manner) that may be necessary
or appropriate in the opinion of the Transferee in order to perfect and/or
protect any lien granted or purported to be granted hereby or to enable the
Transferee to exercise and enforce its rights and remedies hereunder with
respect to the Property To Be Owned.

                                       7

<PAGE>

SECTION 12. EXPENSES, TAXES AND INDEMNIFICATION

The Transferor shall be liable for and shall indemnify the Transferee on demand
against, and shall pay, (a) the reasonable costs, expenses, taxes and other
liabilities (including legal fees on a full indemnity basis) incurred by the
Transferee to protect or enforce the Transferee's title to and interest in the
Property To Be Owned and the Transferee's rights against the Transferor under
this Agreement (including, without limitation, the transfer and assignment by
the Transferor to the Transferee of the Property To Be Owned and the re-transfer
and re-assignment by the Transferee to the Transferor of the Property To Be
Owned), provided that any such enforcement shall be in a commercially reasonable
manner; (b) all withholding, excise, stamp, registration and other taxes, fees
and duties payable in connection with the entry into, performance, enforcement
or admissibility in evidence of this Agreement, and all reasonable costs,
expenses and other liabilities, incurred by the Transferee in connection with,
or otherwise attributable to, receipt by the Transferees of, or payment by
Transferor of, any reasonable costs, expenses and other liabilities and
indemnities provided for in this Section or any other provision of this
Agreement, other than taxes imposed on overall net income of the Transferee.

SECTION 13. MISCELLANEOUS

13.1 Notices. All notices, requests and demands to or upon the respective
     parties hereto to be effective, shall be in writing and shall be personally
     delivered or sent by facsimile (with subsequent written confirmation) or by
     registered or certified first class mail, postage prepaid, return receipt
     requested, or by overnight (or next business day) courier service shall be
     deemed to have been duly given or made when delivered by hand, on the day
     that such facsimile is transmitted, or, if by first class mail, five days
     following the date on which such writing is deposited with the postal
     service, or the day after the date when deposited with an overnight (or
     next business day) courier service, addressed as follows, or to such other
     address as either party hereto may hereafter specify in writing to the
     other party:

     To:          ST Assembly Test Services Ltd
                  5 Yishun Street 23
                  Singapore 768442
     Attention:   Director, Legal
     DID:         65 6824 1948
     Fax:         65 822 7837

     To:          SimmTech Co., Ltd.
                  70-5 Songjung-dong
                  Huengduk-ku
                  Choungju, Chungchongbuk-Do
                  Korea
     Attention:   Chief Marketing Officer
     DID:         82-43-269 9280
     Fax:         82-43-269 9048

13.2 Severability. If any of the provisions of this Agreement shall contravene
     any law or regulation or be held invalid, this Agreement shall be construed
     as if not containing

                                       8

<PAGE>

      those provisions, and the rights and obligations of the parties hereto
      shall be construed and enforced accordingly.

13.3  Amendments, Changes and Modifications. This Agreement shall not be
      amended, changed, modified, altered or terminated, unless the prior
      written approval of each of the Transferor and the Transferee is obtained.
      This Agreement shall not be amended by an oral agreement.

13.4  Counterparts. This Agreement may be executed in multiple counterparts,
      each of which, when executed, shall constitute an original but all of
      which together shall constitute one and the same instrument.

13.5  Heading. Headings and titles herein are for convenience only and shall not
      affect the construction or interpretation of this Agreement.

13.6  Entire Agreement. This Agreement is intended by the parties as the written
      final expression of each party's obligations and rights in connection with
      the Transferred Property and supersedes all prior and contemporaneous
      understandings or agreements concerning the subject matter hereof.

13.7  Conflict. In the case of a conflict between the provisions of this
      Agreement and the provisions of the Loan Agreement, the Loan Agreement
      shall prevail.

13.8  No Waiver. The Transferee shall not, by any act, delay, indulgence,
      omission or otherwise, except by an express written instrument clearly
      indicating an intention to waive, be deemed to have waived any right or
      remedy hereunder or to have acquiesced in any Event of Default. No failure
      to exercise, nor any delay in exercising on the part of the Transferee,
      any right, power or privilege hereunder shall operate as a waiver thereof.
      No single or partial exercise of any right, power, privilege hereunder
      shall preclude any other or further exercise thereof or the exercise of
      any other right, power or privilege.

13.9  Remedies Cumulative. The rights and remedies provided herein are
      cumulative and may be exercised individually or concurrently, and are not
      exclusive of any other rights or remedies provided by law.

13.10 Currencies. All Secured Obligations under this Agreement are payable in
      United States dollars (the "Required Currency"). If the Transferee
      receives or recovers any moneys in any other currency, whether upon
      enforcement of its rights under this Agreement or otherwise, the
      Transferor shall indemnify the Transferee against the difference (if any)
      between the amount received by the Transferee when it converts amounts
      received in currencies other than the Required Currency to the Required
      Currency and the amount due in the Required Currency. The Transferor shall
      assist the Transferee at all times to obtain any exchange conversion
      approval required by the Transferee in connection with this Agreement or
      the Secured Obligations.

13.11 Governing Law and Jurisdiction. This Agreement and the security created
      pursuant hereto shall be governed by the laws of Korea in all respects,
      including matters of construction, validity and performance. The parties
      hereto agree to submit to the non-exclusive jurisdiction of the Seoul
      District Court for the purpose of this Agreement.

                            SIGNATURE PAGE TO FOLLOW

                                       9

<PAGE>
IN WITNESS WHEREOF, the parties hereto have caused this Yangdo Tambo Agreement
to be duly executed as of the day and year first above written.

                  TRANSFEROR:     SIMMTECH CO. LTD

                                  By: /s/ Se-Ho Chun
                                      ------------------------------------------
                                  Name: Se-Ho Chun
                                  Title: Representative Director

                                  In the presence of: /s/ Young Goo Kim
                                                      --------------------------

                  TRANSFEREE:     ST ASSEMBLY TEST SERVICES LTD

                                  By: /s/ Suh Tae Suk
                                      ------------------------------------------
                                  Name: Mr. Tan Lay Koon
                                  Title: President and CEO

                                  In the presence of : /s/ Juliana Ho
                                                       -------------------------

                                       10

<PAGE>

                                   SCHEDULE I

<TABLE>
<CAPTION>
---------------------------------------------------------------------------------------
              EQUIPMENT                 UNIT PRICE (US$)     QUANTITY      PRICE (KUS$)
---------------------------------------------------------------------------------------
<S>                                     <C>                  <C>           <C>
DESMEAR+PTH+PNL LINE                        4,275,000              1             4,275
---------------------------------------------------------------------------------------
DEBURRING (CHEMICAL)                          380,000              1               380
---------------------------------------------------------------------------------------
EXPOSURE                                      598,500              1               599
---------------------------------------------------------------------------------------
SCAN                                          304,000              3               912
---------------------------------------------------------------------------------------
VRS                                           114,000              5               570
---------------------------------------------------------------------------------------
SEMI AUTO PRINTER                              47,500              2                95
---------------------------------------------------------------------------------------
ROLL COATER WITH TUNNEL OVEN                  532,000              1               532
---------------------------------------------------------------------------------------
AUTO PRINTING SYSTEM                          182,000              2               364
---------------------------------------------------------------------------------------
TUNNEL OVEN FOR PRECURE                       228,000              2               456
---------------------------------------------------------------------------------------
AUTO EXPOSURE SYSTEM                          349,600              1               350
---------------------------------------------------------------------------------------
TUNNEL OVEN FOR FINAL CURE                    199,500              1               200
---------------------------------------------------------------------------------------
JET SCRUBBING FOR PRETREATMENT                277,400              1               277
---------------------------------------------------------------------------------------
SOFT AU PLATING LINE                          748,885              1               749
---------------------------------------------------------------------------------------
BBT (FOR PBGA)                                190,000              1               190
---------------------------------------------------------------------------------------
BBT (FOR CSP)                                 475,000              1               475
---------------------------------------------------------------------------------------
AVI                                           211,660              3               635
---------------------------------------------------------------------------------------
VRS                                            28,500              3                86
---------------------------------------------------------------------------------------
ROUTING RINSING                               190,000              1               190
---------------------------------------------------------------------------------------
EXPOSURE SYSTEM                                19,000              1                19
---------------------------------------------------------------------------------------
DEVELOP                                       152,000              1               152
---------------------------------------------------------------------------------------
ALKALINE ETCHING WITH R/STRIPPING             228,000              1               228
---------------------------------------------------------------------------------------
S/W         GENESIS LICEN.                     46,474              5               232
            ---------------------------------------------------------------------------
            GENESIS GRAHP.                     12,350              8                99
            ---------------------------------------------------------------------------
            WORKSTATION                        19,627             13               255
            ---------------------------------------------------------------------------
            STELLAR                            95,000              1                95
---------------------------------------------------------------------------------------
MACHINE     LASER PLOTTER                     250,000              3               750
            ---------------------------------------------------------------------------
            DEVELOPER                          30,970              3                93
            ---------------------------------------------------------------------------
            FILM AOI                          213,300              2               427
---------------------------------------------------------------------------------------
HAST                                           45,108              1                45
---------------------------------------------------------------------------------------
IR REFLOW                                      42,505              1                43
---------------------------------------------------------------------------------------
  TC                                           73,733              1                74
---------------------------------------------------------------------------------------
MEASURING SCOPE                                30,000              1                30
---------------------------------------------------------------------------------------
VACUUM LAMINATOR                              562,500              1               563
---------------------------------------------------------------------------------------
YAG LASER                                     562,500              1               563
---------------------------------------------------------------------------------------
TOTAL                                                                           15,000
=======================================================================================
</TABLE>

                                       11<PAGE>
                                                                    Exhibit 4.21

                                                                  EXECUTION COPY

THIS SHARE PLEDGE AGREEMENT (the "Agreement") is entered as of this 26th day of
December, 2003 by and among:

          (i) MR. SE-HO CHUN, a shareholder of Simmtech Co. Ltd (the "Company")
          holding 39.9% of the issued and outstanding shares of the Company,
          with resident card number 560515-1005415 (the "Pledgor"); and

          (ii) ST ASSEMBLY TEST SERVICES LTD., a company duly incorporated and
          existing under the law of Singapore and having a place of business at
          5 Yishun Street 23, Singapore 768442 (the "Pledgee").

                                    RECITALS

WHEREAS:

A.   By the Loan Agreement dated as of December 26, 2003 (the "Loan Agreement")
     made by and between the Company, the Pledgor and the Pledgee, the Pledgee
     has agreed, subject to and upon the terms and conditions contained therein,
     to provide a loan to the Company in the amount of USD 15 million (USD
     15,000,000);

B.   The Pledgor is the legal and beneficial owner of the Securities (as defined
     below); and

C.   For the purposes of securing the Secured Obligations (as defined below),
     the Pledgor hereby agrees to, inter alia, deposit with and pledge to the
     Pledgee the Securities (as defined below) pursuant to terms and conditions
     herein.

NOW, THEREFORE, it is agreed as follows:

SECTION 1. INTERPRETATION

Words and expressions defined in the Loan Agreement shall, unless otherwise
defined herein or the context otherwise requires, have the same meaning when
used in this Agreement. References to any agreement or document shall be
construed as references to such agreement or document as varied, amended,
novated or supplemented from time to time. In addition thereto, as used in this
Agreement:

1.1  "Securities" shall mean the securities described in Schedule I hereto.

1.2. "Secured Obligations" shall mean (i) any and all obligations, liabilities
     and indebtedness of the Company owing to the Pledgee, presently existing or
     to be incurred hereinafter under or with respect to the Loan Agreement,
     (ii) moneys,

<PAGE>
     obligations and liabilities owing and payable by the Company to the Pledgee
     under the Yangdo Tambo Agreement dated December 26, 2003 between the
     Company and the Pledgee, (iii) moneys, obligations and liabilities owing
     and payable by the Company to the Pledgee under the Factory Kun-Mortgage
     Agreement dated December 26, 2003 between the Company and the Pledgee and
     (iv) moneys, obligations and liabilities owing and payable by the Pledgor
     to the Pledgee under this Agreement.

1.3. "Proceeds" means all proceeds of, and all other profits, income or
     receipts, in whatever form and whatever currency, arising from the
     ownership, collection, sale, exchange, assignment or other disposition of,
     or realization of any of the Securities, and all interest, dividends (cash,
     stock or otherwise) and other payments and distributions on or with respect
     to such Securities or in exchange for such Securities.

SECTION 2. PLEDGE

2.1. The Pledgor hereby agrees to pledge the Securities to the Pledgee and
     hereby agrees to grant in favor of the Pledgee a first priority security
     interest (jilkwon) in the Securities and the Pledgee shall accept the
     security interest in the Securities for the due and punctual payment,
     performance and discharge of the Secured Obligations. The Pledgor hereby
     agrees that any Proceeds of any Securities on which a pledge under this
     Agreement has been established and perfected shall be subject to the pledge
     (jilkwon) on such Securities pursuant to this Agreement and that if any
     such Proceeds may not be subject to such pledge, the Pledgor shall pledge
     the Proceeds for the benefit of the Pledgee in the manner applicable to the
     nature of it and perform any and all actions necessary or appropriate in
     the opinion of the Pledgee for the establishment and effectuation of such
     pledge under the laws of Korea.

2.2  Simultaneous with, or prior to the provision of the Loan on the Loan Date,
     the Pledgor shall have the Pledgee's name and address recorded in the
     shareholders' registry of the Company (maintained with the Korea Securities
     Depository) as a holder of the security interest (jilkwon) in the
     Securities and have the Pledgee's name recorded on the share certificates
     representing the Securities.

2.3  Immediately upon performance of Section 2.2 hereof and at least [one (1)]
     business day prior to the provision of the Loan on the Loan Date, the
     Pledgor shall deliver or cause to be delivered the share certificates
     representing the Securities in physical form to the Pledgee or to the agent
     of the Pledgee, as requested by the Pledgee together with a certified copy
     of the shareholders' registry of the Company and any documents necessary or
     appropriate in the opinion of the Pledgee to constitute a legally valid
     delivery of the certificates.

<PAGE>
SECTION 3. REPRESENTATIONS AND WARRANTIES

3.1  The Pledgor hereby represents, warrants and covenants to the Pledgee that:

     (a)  the execution, delivery and performance by the Pledgor of this
          Agreement are not in conflict with any provision of any applicable
          laws or regulations or the articles of incorporation of the Company;

     (b)  the execution, delivery and performance by the Pledgor of this
          Agreement does not violate or cause any default under any indenture,
          agreement or undertaking by which the Pledgor is bound;

     (c)  all authorizations required from any government or governmental agency
          in connection with this Agreement have been obtained and are in full
          force and effect;

     (d)  this Agreement constitutes valid obligations of the Pledgor, legally
          binding upon it and enforceable in accordance with its terms, subject,
          as to enforceability, to laws relating to bankruptcy, insolvency,
          liquidation, reorganization, court schemes, moratoria, administration
          and other laws generally affecting the rights of creditors;

     (e)  the Pledgor has full right, title and interest over the Securities;

     (f)  the Pledgor has not agreed to sell, assign, transfer, pledge or create
          any security, interest, lien or other encumbrance in or over all or
          any part of the Securities other than in favor of the Pledgee
          hereunder;

     (g)  no person (other than the Pledgor and the Pledgee) is exercising, has
          exercised or attempted to exercise any ownership interest or other
          lien over any of the Securities;

     (h)  to the knowledge of the Pledgor, there are no circumstances that may
          diminish the value of the Securities;

     (i)  the Pledgor has not taken any action nor have any other steps been
          taken or legal proceedings been started by him or any third party for
          bankruptcy, workout, or similar proceedings over the Pledgor or his
          assets, and there occurs or continues no cause/event that may lead to
          such action or steps; and

     (j)  the Pledgor has acquired the Securities in accordance with any
          provision of any applicable laws or the articles of incorporation of
          the Company and has been, and during the term of the Loan Agreement
          will be, permitted to have right, title and interest over the
          Securities under such laws and articles of incorporation.

3.2  Each of the warranties and representations contained in the preceding
     sub-clause shall survive and continue to have full force and effect until
     the termination of this Agreement.

SECTION 4. COVENANTS OF THE PLEDGOR

The Pledgor covenants and undertakes the following with the Pledgee:

<PAGE>
     (a)  duly and punctually to observe and perform all the conditions and
          obligations imposed on it by this Agreement;

     (b)  not, without the prior written consent of the Pledgee, to attempt to
          sell, assign, transfer, create any security, interest or lien over, or
          otherwise dispose of or encumber any of the Securities to or in favor
          of any person other than the Pledgee;

     (c)  to do or permit to be done each and every act or thing the Pledgee may
          from time to time require to be done for the purpose of enforcing the
          Pledgee's rights under this Agreement or in respect of any of the
          Securities and to allow its name to be used as and when required by
          the Pledgee for such purpose;

     (d)  to make all registrations, filings and recordings, and take all other
          actions as are necessary or determined by the Pledgee to be advisable
          to ensure the continued legality, validity, enforceability, priority
          and admissibility in evidence of this Agreement;

     (e)  to be responsible for the resolution of any disputes with a third
          party in connection with the Securities, including any disputes
          involving claims against the Securities, and in connection therewith,
          the Pledgor agrees not to take any action which might adversely affect
          the enforcement of the Pledgee's rights or Pledgee's interests in the
          Securities and to affirmatively protect and defend such rights and
          interests in accordance with the instructions of the Pledgee;

     (f)  to pay all taxes, assessments and other governmental charges of any
          kind imposed on or in respect of his income or any of his assets when
          due;

     (g)  to immediately notify the Pledgee of any and all notices that the
          Pledgor has received from the Company in his capacity as a shareholder
          upon the receipt of such notice;

     (h)  if and when it is required to or entitled to vote, give any consent or
          exercise any other rights with respect to the Securities, to first
          notify such situation to the Pledgee immediately and act in accordance
          with the instruction of the Pledgee;

     (i)  not to make or cause to make any action, procedure or event that may
          diminish the value of the Securities; and

     (j)  to notify the Pledgee of any event that would result in or lead to a
          breach of any representation and warranty provided under Section 3
          immediately upon becoming aware of such event.

<PAGE>
SECTION 5. ADMINISTRATION OF SECURITIES

5.1  Until there shall have occurred an Event of Default or a Potential Event of
     Default, the Pledgor shall be entitled to vote, give any consent or
     exercise any other rights with respect to the Securities in any manner not
     inconsistent with this Agreement and subject to applicable law.

5.2  Unless an Event of Default or a Potential Event of Default has occurred,
     and without prejudice to Section 2 hereof, the Pledgor shall receive or
     shall become entitled to receive, any dividend, interest or any other
     distribution whether in securities or property (including cash) with
     respect to the Securities by way of stock-split, spin-off, split-up or
     reclassification, combination of shares or the like. For the avoidance of
     doubt, any distributions (whether in cash or in shares or other property)
     received by the Pledgor shall be deemed to be the Proceeds and subject to
     the pledge created under this Agreement, and if any such Proceeds may not
     be subject to such pledge, the Pledgor shall pledge the Proceeds for the
     benefit of the Pledgee in the appropriate manner and perform any and all
     actions necessary or appropriate in the opinion of the Pledgee for the
     establishment and effectuation of such pledge under the laws of Korea.

SECTION 6. ATTORNEY-IN-FACT

The Pledgor shall be deemed to irrevocably appoint the Pledgee as its true and
lawful attorney-in-fact with full power to require, demand and receive any and
all moneys and claims for money due and to become due under or with respect to
the Securities to the extent pledged hereunder and to take any action or execute
any instrument which the Pledgee may deem necessary or appropriate to accomplish
the purpose hereof.

SECTION 7. TERMINATION AND REASSIGNMENT

The term of this Agreement shall begin on the date of this Agreement and end on
the date on which all Secured Obligations shall have been unconditionally and
irrevocably paid and discharged. Upon termination of this Agreement, the Pledgee
shall release the security interest in the Securities held by the Pledgee,
return the share certificates representing the Securities to the Pledgor at the
cost of the Pledgor and take any actions as may be reasonably requested by the
Pledgor to effectuate such release.

SECTION 8. ENFORCEMENT BY PLEDGEE

8.1  If any of the Secured Obligations becomes due and payable, the Pledgee
     shall be entitled, as and when it may see fit, to put into force and to
     exercise all or any of the rights and power possessed by it as pledgee of
     the Securities under the applicable laws and this Agreement in or towards
     satisfaction of the Secured Obligations, including without limitation, the
     right and power to:

<PAGE>
     (a)  sell, transfer or otherwise dispose of the Securities at such times
          and at such prices as are generally recognized as appropriate in
          custom and practice, without the necessity of any legal process or
          procedure;

     (b)  acquire title to the Securities in lieu of foreclosure of the
          Securities in any manner in its discretion without notice to the
          Pledgor; and

     (c)  demand, sue for, collect or receive, in the name of the Pledgor, any
          money or property at any time payable or receivable on account of or
          in exchange for any of the Securities, but shall be under no
          obligation to do so.

8.2  Upon the exercise of its rights pursuant to Section 8.1. hereof, the
     Pledgee shall apply the Proceeds, after deducting the costs of such
     exercise of rights, against the Secured Obligations. Any excess amount
     shall be paid to the Pledgor and any Secured Obligations not fully covered
     by the Proceeds shall remain due and owing and shall promptly be paid by
     the Pledgor. In the case of acquisition of the title to the Securities
     pursuant to Section 8.1.(b) hereof, the Pledgee shall value the Securities
     based on commercially reasonable standards and return any excess amount
     (net of any and all costs and taxes involving transfer of the ownership of
     the Securities) to the Pledgor and any Secured Obligations not fully
     covered by the value of the Securities shall remain due and owing and shall
     promptly be paid by the Pledgor.

8.3  The Pledgor hereby consents to the procedures set out in Sections 8.1 and
     8.2 above and waives any and all objections it may have thereto.

8.4  The Pledgee shall incur no liability as a result of the sale, acquisition
     or any other disposition of the Securities or any part thereof by the
     Pledgee pursuant to Section 8.1 hereof conducted in a commercially
     reasonable manner. The Pledgor hereby waives any claims against the Pledgee
     arising by reason of the fact that the price at which the Securities has
     been sold at any private sale by the Pledgee may be less than the price at
     which it could have been sold if the Pledgee had not accepted the first
     offer received or had offered the Securities to more than one offeree.

8.5  The application of the Proceeds shall be determined by the Pledgee in its
     absolute discretion, subject only to any other agreements between the
     Pledgee and the Pledgor relating thereto and to the requirements of any
     applicable law.

8.6  In case where the Pledgor or a third party provides collateral (other than
     the Securities) to the Pledgee to secure all or any part of the Secured
     Obligations, the Pledgee shall in its sole discretion have the authority to
     determine the priority and extent of enforcement between/among its rights
     under this Agreement and such other collateral arrangements, without the
     necessity of any legal process or consultation with the Pledgor.

SECTION 9. ASSIGNMENT

This Agreement and the security interest created hereunder shall be binding upon
and inure to the benefit of the Pledgor and the Pledgee and their respective
successors and assigns. The Pledgee may, in accordance with the Loan Agreement
and applicable laws, at any time

<PAGE>
assign all or any part of its rights or obligations hereunder to any party (each
an "Assignee"). The parties hereto agree that to the extent of any transfer, the
Assignee shall be deemed to have the same rights and benefits under this
Agreement as it would have had if it were a Pledgee signatory hereunder. The
Pledgor may not assign any of its rights or obligations hereunder without the
prior written consent of the Pledgee.

SECTION 10. FURTHER ASSURANCE

The Pledgor shall do all such acts as may be necessary or appropriate in the
opinion of the Pledgee including, but not limited to, the execution and delivery
of all further instruments, notices and documents and all further action (whilst
acting in a commercially reasonable manner) that may be necessary or appropriate
in the opinion of the Pledgee in order to perfect and/or protect any lien
granted or purported to be granted hereby or to enable the Pledgee to exercise
and enforce its rights and remedies hereunder with respect to the Securities and
the Proceeds.

SECTION 11. EXPENSES, TAXES AND INDEMNIFICATION

The Pledgor shall be liable for and shall indemnify the Pledgee on demand
against, and shall pay, (a) the reasonable costs, expenses, taxes and other
liabilities (including legal fees on a full indemnity basis) incurred by the
Pledgee to protect or enforce the Pledgee's interest in the Securities and the
Pledgee's rights against the Pledgor under this Agreement, provided that any
such enforcement shall be in a commercially reasonable manner; (b) all
withholding, excise, stamp, registration and other taxes, fees and duties
payable in connection with the entry into, performance, enforcement or
admissibility in evidence of this Agreement, and all reasonable costs, expenses
and other liabilities, incurred by the Pledgee in connection with, or otherwise
attributable to, receipt by the Pledgee of, or payment by Pledgor of, any
reasonable costs, expenses and other liabilities and indemnities provided for in
this Section or any other provision of this Agreement, other than taxes imposed
on overall net income of the Pledgee.

SECTION 12. MISCELLANEOUS

12.1 Notices. All notices, requests and demands to or upon the respective
     parties hereto to be effective, shall be in writing and shall be personally
     delivered or sent by facsimile (with subsequent written confirmation) or by
     registered or certified first class mail, postage prepaid, return receipt
     requested, or by overnight (or next business day) courier service shall be
     deemed to have been duly given or made when delivered by hand, on the day
     that such facsimile is transmitted, or, if by first class mail, five days
     following the date on which such writing is deposited with the postal
     service, or the day after the date when deposited with an overnight (or
     next business day) courier service, addressed as follows, or to such other
     address as either party hereto may hereafter specify in writing to the
     other party:

<PAGE>
     To:               ST Assembly Test Services Ltd
                       5 Yishun Street 23
                       Singapore 768442
     Attention:        Director, Legal
     DID:              65 6824 1948
     Fax:              65 822 7837

     To:               Mr. S.H. Chun
                       SimmTech Co. Ltd.
                       70-5 Songjung-dong
                       Huengduk-ku
                       Choungju, Chungchongbuk-Do
                       Korea
     Attention:        Chief Marketing Officer
     DID:              82-43-269 9280
     Fax:              82-43-269 9048

12.2 Severability. If any of the provisions of this Agreement shall contravene
     any law or regulation or be held invalid, this Agreement shall be construed
     as if not containing those provisions, and the rights and obligations of
     the parties hereto shall be construed and enforced accordingly.

12.3 Amendments, Changes and Modifications. This Agreement shall not be amended,
     changed, modified, altered or terminated, unless the prior written approval
     of each of the Pledgor and the Pledgee is obtained. This Agreement shall
     not be amended by an oral agreement.

12.4 Counterparts. This Agreement may be executed in multiple counterparts, each
     of which, when executed, shall constitute an original but all of which
     together shall constitute one and the same instrument.

12.5 Heading. Headings and titles herein are for convenience only and shall not
     affect the construction or interpretation of this Agreement.

12.6 Entire Agreement. This Agreement is intended by the parties as the written
     final expression of each party's obligations and rights in connection with
     the Securities and supersedes all prior and contemporaneous understandings
     or agreements concerning the subject matter hereof.

12.7 Conflict. In the case of a conflict between the provisions of this
     Agreement and the provisions of the Loan Agreement, the Loan Agreement
     shall prevail.

12.8 No Waiver. The Pledgee shall not, by any act, delay, indulgence, omission
     or otherwise, except by an express written instrument clearly indicating an
     intention to waive, be deemed to have waived any right or remedy hereunder
     or to have acquiesced in any Event of Default. No failure to exercise, nor
     any delay in exercising on the part of the Pledgee, any right, power or
     privilege hereunder shall operate as a waiver thereof. No single or partial
     exercise of any right, power, privilege hereunder shall preclude any other
     or further exercise thereof or the exercise of any other right, power or
     privilege.

<PAGE>
12.9  Remedies Cumulative. The rights and remedies provided herein are
      cumulative and may be exercised individually or concurrently, and are not
      exclusive of any other rights or remedies provided by law.

12.10 Currencies. All Secured Obligations under this Agreement are payable in
      United States dollars ("the Required Currency"). If the Pledgee receives
      or recovers any moneys in any other currency, whether upon enforcement of
      its rights under this Agreement or otherwise, the Pledgor shall indemnify
      the Pledgee against the difference (if any) between the amount received by
      the Pledgee when it converts amounts received in currencies other than the
      Required Currency to the Required Currency and the amount due in the
      Required Currency. The Pledgor shall assist the Pledgee at all times to
      obtain any exchange conversion approval required by the Pledgee in
      connection with this Agreement or the Secured Obligations.

12.11 Governing Law and Jurisdiction. This Agreement and the security created
      pursuant hereto shall be governed by the laws of Korea in all respects,
      including matters of construction, validity and performance. The parties
      hereto agree to submit to the non-exclusive jurisdiction of the Seoul
      District Court for the purpose of this Agreement.

                            SIGNATURE PAGE TO FOLLOW

<PAGE>
IN WITNESS WHEREOF, the parties hereto have caused this Pledge Agreement to be
duly executed as of the day and year first above written.

                  PLEDGOR: /s/ Se-Ho Chun
                           -----------------------------

                           In the presence of: /s/ Young Goo Kim
                                               -----------------------------

                  PLEDGEE: ST ASSEMBLY TEST SERVICES LTD

                           By  /s/ Suh Tae Suk
                              --------------------------
                              Name:  Mr. Tan Lay Koon
                              Title: President and CEO

                           In the presence of: /s/ Juliana Ho
                                               ----------------------
<PAGE>
                                   SCHEDULE I

Description of Securities

2,400,000 shares of common stock of the Company in denominations as the
following:

<TABLE>
<CAPTION>
Serial Number           Denomination              Number of share certificate(s)
-------------           ------------              ------------------------------
<S>                     <C>                       <C>
2601~2636               10,000 shares                           36
2397~2446               10,000 shares                           50
2447~2496               10,000 shares                           50
2497~2546               10,000 shares                           50
2547~2596               10,000 shares                           50
2597~2600               10,000 shares                           4
</TABLE>

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00063-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00063-of-00352.parquet"}]]