<PAGE>
                                                                    EXHIBIT 4.12

PAGES WHERE CONFIDENTIAL TREATMENT HAS BEEN REQUESTED ARE STAMPED 'CONFIDENTIAL
TREATMENT REQUESTED AND THE REDACTED MATERIAL HAS BEEN SEPARATELY FILED WITH THE
     COMMISSION' AND THE CONFIDENTIAL SECTION HAS BEEN MARKED IN THE MARGIN
                                WITH A STAR (*)


    Amendment renewing the IMMUNITY AGREEMENT entered into October 18, 1996
         between Motorola, Inc. and ST Assembly Test Services Pte. Ltd.



Motorola, Inc. and ST Assembly Test Services Ltd. agree to amend the
above-identified IMMUNITY AGREEMENT as follows:

     1.   In Section 1, after Section 1.7 add new Section 1.8 below:

          1.8  ASSEMBLY HOUSE SALES shall mean the total consolidated gross
               sales revenues of ST ASSEMBLY TEST SERVICES PTE. LTD., and any of
               its subsidiaries as reported by ST ASSEMBLY TEST SERVICES PTE.
               LTD., or its parent company, if any, to the relevant Singapore
               government authorities or to the public, as the case may be.

     2.   In Section 1.4, line 6, replace "integrated circuit device" with
          "INTEGRATED CIRCUIT STRUCTURE or STRUCTURES".

     3.   In Section 1.7, replace "the date of the last signature hereto." with
          "January 1, 2003."

     4.   Replace Old Section 4.1 with New Section 4.1 below:

          4.1  In partial consideration of the rights granted by MOTOROLA under
               Section 3 for the period beginning on the EFFECTIVE DATE and
               extending to December 31, 2010, ASSEMBLY HOUSE agrees to pay
               MOTOROLA royalty payments amounting to XXXXXXXXXX of ASSEMBLY  *
               HOUSE SALES.                                                   *

     5.   Delete Section 4.1.1.

     6.   Delete Section 4.1.2.

     7.   Delete Section 4.2.

     8.   Delete Section 4.5.

     9.   Delete Section 4.6.

     10.  In Section 5.1, line 2, replace "2002" with "2010".

     11.  In Section 5.6, lines 3-7, remove ", except to a successor in
          ownership of all or substantially all of the assets of the assigning
          party. Such successor, before such assignment or transfer is
          effective, shall expressly assume in writing to the other party the
          performance of all of the terms and conditions of this Agreement to be
          performed by the assigning party".

     12.  Renumber Section "6.9" to "6.10".

      CONFIDENTIAL TREATMENT REQUESTED AND THE REDACTED MATERIAL HAS BEEN
                      SEPARATELY FILED WITH THE COMMISSION
<PAGE>
 Amendment renewing the IMMUNITY AGREEMENT entered into October 18 1996 between
             Motorola, Inc. and ST Assembly Test Services Pte. Ltd.

13.  Renumber Section "6.9.1" to "6.10.1".

14.  Renumber Section "6.9.2" to "6.10.2".

15.  Renumber Section "6.9.3" to "6.10.3".

16.  After Section 6.8, add new Sections 6.9 and 6.9.1-6.9.6 as indicated below:

     6.9 The parties shall have the right to disclose the existence of this
     Agreement. The parties hereto, however, shall keep the terms of the
     Agreement confidential and shall not now or hereafter divulge any part
     thereof to any third party except:

         6.9.1 with the prior written consent of the other party; or

         6.9.2 to any governmental body having jurisdiction to request and to
         read the same; or

         6.9.3 as otherwise may be required by law or legal processes; or

         6.9.4 to legal counsel representing either party.

         6.9.5 Notwithstanding the above, no disclosure of this Agreement shall
         be made pursuant to Section 6.9.2 or 6.9.3 without the disclosing party
         first giving the other party reasonable prior notice of such intended
         disclosure so as to allow the other party sufficient time to seek a
         protective order or otherwise assure the confidentiality of this
         Agreement as that other party shall deem appropriate.

         6.9.6 Notwithstanding anything to the contrary herein, the provisions
         of this Section 6.9 shall survive termination of this Agreement and
         continue in perpetuity.

All other terms and conditions of the above-identified IMMUNITY AGREEMENT remain
the same.

Indicating their agreement to the foregoing, the parties have hereto executed
this Agreement in duplicate.

Motorola, Inc.                               ST Assembly Test Services Ltd.

By: /s/ Paul Reidy                           By: /s/ Han Byung Joon
    -------------------------                    ------------------------

Title: Director, IP Licensing                Title: CTO
       ----------------------                       ---------------------

Date: 4/18/03                                Date: 4/22/03
      -----------------------                      ----------------------
<PAGE>
                               IMMUNITY AGREEMENT

THIS AGREEMENT is effective as of the 18th day of OCTOBER, 1996, by and between
MOTOROLA, INC., a Delaware corporation having an office at 3102 North 56th
Street, Phoenix, Arizona 85018, (hereinafter called "MOTOROLA"), and ST ASSEMBLY
TEST SERVICES PTE. LTD., having its principal office at 33 Marsiling Industrial
Estate Road 3, #03-01, Singapore 739256, (hereinafter called "ASSEMBLY HOUSE").

WHEREAS, MOTOROLA owns and has, or may have patents issued, and applications for
patents pending, in various countries of the world which relate to ball grid
array (BGA) PACKAGEs (as hereinafter defined), and

WHEREAS, ASSEMBLY HOUSE owns and has, or may have, rights in various patents
issued, and applications for patents pending, in various countries of the world
which may relate to BGA PACKAGEs and

WHEREAS, ASSEMBLY HOUSE and MOTOROLA are engaged in continuing research,
development and engineering in regard to BGA PACKAGES and have programs for the
patenting of inventions resulting therefrom; and

WHEREAS, MOTOROLA is interested in proliferating BGA PACKAGEs as a standard in
semiconductor industry; and

WHEREAS, ASSEMBLY HOUSE is interested in providing the service of making BGA
PACKAGEs for semiconductor manufacturers including those who are competitors of
MOTOROLA;

NOW THEREFORE, in consideration of the mutual covenants and conditions
hereinafter set forth, it is agreed as follows:


Section 1 -- DEFINITIONS

1.1  SUBSIDIARY(IES) means a corporation, company, or other entity more than
     fifty percent (50%) of whose outstanding shares or securities (representing
     the right to vote for the election of directors or other managing
     authority) are, now or hereafter, owned or controlled, directly or
     indirectly by a party hereto, but such corporation, company, or other
     entity shall be deemed to be a SUBSIDIARY only so long as such ownership or
     control exists.

1.2  SEMICONDUCTIVE MATERIAL means any material whose conductivity is
     intermediate to that of metals and insulators at room temperature and whose
     conductivity, over some temperature range, increases with increases in
     temperature. Such material shall include but not be limited to refined
     products, reaction products, reduced products, mixtures and compounds.

1.3  INTEGRATED CIRCUIT STRUCTURE means an integral unit consisting primarily of
     a plurality of active and/or passive circuit elements associated on, or in,
     a unitary body of SEMICONDUCTIVE MATERIAL for performing electrical or
     electronic functions.

                                     Page 1
<PAGE>
1.4  BGA PACKAGE means a housing for an INTEGRATED CIRCUIT STRUCTURE or
     STRUCTUREs in which the INTEGRATED CIRCUIT STRUCTURE or STRUCTUREs are
     mounted on one side of a substrate of printed circuit board material or the
     like and are wire bonded to the substrate, plastic overlies the INTEGRATED
     CIRCUIT STRUCTURE or STRUCTUREs, and pads for receiving solder balls or the
     like and providing electrical contacts to the integrated circuit device are
     mounted on the substrate on the side opposite to that on which the
     INTEGRATED CIRCUIT STRUCTURE or STRUCTUREs are mounted. Some BGA packages
     may have some pads which are not electrically connected to the INTEGRATED
     CIRCUIT STRUCTURE or STRUCTUREs.

1.5  MOTOROLA PATENTS means all classes or types of patents, utility models,
     design patents and applications for the aforementioned of all countries of
     the world relating to BGA PACKAGEs and enhancements thereto which, prior to
     the date of expiration or termination of this Agreement, are:

     (i)  issued, published or filed, and which arises out of inventions made
          solely by one or more employees of MOTOROLA or a SUBSIDIARY thereof,
          or

     (ii) acquired by MOTOROLA or a SUBSIDIARY thereof.

     and under which and to the extent to which and subject to the conditions
     under which MOTOROLA or a SUBSIDIARY thereof may have, as of the EFFECTIVE
     DATE of this Agreement, or may thereafter during the term of this Agreement
     acquire, the right to grant licenses or rights of the scope granted herein
     without the payment of royalties or other consideration to third persons,
     except for payments to third persons (a) for inventions made by said third
     persons while engaged by MOTOROLA or a SUBSIDIARY thereof, and (b) as
     consideration for the acquisition of such patents, utility models, design
     patents and applications.

1.6  ASSEMBLY HOUSE PATENTS means all classes or types of patents, utility
     models, design patents and applications for the aforementioned of all
     countries of the world relating to BGA PACKAGEs and enhancements thereto
     which, prior to the date of expiration or termination of this Agreement,
     are:

     (i)  issued, published or filed, and which arise out of inventions made
          solely by one or more employees of ASSEMBLY HOUSE or a SUBSIDIARY
          thereof, or

     (ii) acquired by ASSEMBLY HOUSE or a SUBSIDIARY thereof,

     and under which and to the extent to which and subject to the conditions
     under which ASSEMBLY HOUSE or a SUBSIDIARY thereof may have, as of the
     EFFECTIVE DATE of this Agreement, or may thereafter during the term of this
     Agreement acquire, the right to grant licenses or rights of the scope
     granted herein without the payment of royalties or other consideration to
     third persons, except for payments to third persons (a) for inventions made
     by said third persons while engaged by ASSEMBLY HOUSE or a SUBSIDIARY
     thereof and (b) as consideration for the acquisition of such patents,
     utility models, design patents and applications.

                                     Page 2

<PAGE>
           CONFIDENTIAL TREATMENT REQUESTED AND THE REDACTED MATERIAL
                 HAS BEEN SEPARATELY FILED WITH THE COMMISSION

1.7  EFFECTIVE DATE means the date of the last signature hereto.


Section 2 - MUTUAL RELEASES

2.1  MOTOROLA hereby releases, acquits and forever discharges ASSEMBLY HOUSE and
     its SUBSIDIARIES for any time prior to the EFFECTIVE DATE, from any and all
     claims or liability for infringement or alleged infringement of any
     MOTOROLA PATENTS for which immunity from suit is herein granted by
     MOTOROLA.

2.2  ASSEMBLY HOUSE and its SUBSIDIARIES hereby releases, acquits and forever
     discharges MOTOROLA and its SUBSIDIARIES for any time prior to the
     EFFECTIVE DATE, from any and all claims or liability for infringement or
     alleged infringement of any ASSEMBLY HOUSE PATENTS for which immunity from
     suit is herein granted by ASSEMBLY HOUSE to MOTOROLA.


Section 3 - IMMUNITY FROM SUIT

3.1  MOTOROLA hereby grants to ASSEMBLY HOUSE and its SUBSIDIARIES, for the term
     of this Agreement, immunity from suit under MOTOROLA PATENTS for making BGA
     PACKAGES, with or without solder balls or the like, for another and for
     ASSEMBLY HOUSE internal use. In no event shall the immunity from suit apply
     to MOTOROLA PATENTS which are infringed by the INTEGRATED CIRCUIT STRUCTURE
     or STRUCTUREs independent of being packaged in BGA PACKAGES.

3.2  ASSEMBLY HOUSE and its SUBSIDIARIES hereby grant to MOTOROLA and its
     SUBSIDIARIES, for the term of this Agreement, immunity from suit under
     ASSEMBLY HOUSE PATENTS for making and/or having made BGA PACKAGES, with or
     without solder balls or the like, and for the subsequent sale and use
     thereof. In no event shall the immunity from suit apply to ASSEMBLY HOUSE
     PATENTS which are infringed by the INTEGRATED CIRCUIT STRUCTURE or
     STRUCTUREs independent of being packaged in BGA PACKAGEs.

3.3  No licenses under any copyrights or mask work rights of either MOTOROLA or
     ASSEMBLY HOUSE or a SUBSIDIARY thereof, are granted under this Agreement.


Section 4 - PAYMENTS

4.1  In partial consideration of the rights granted by MOTOROLA under Section 3,
     for the period beginning on the EFFECTIVE DATE and extending to December
     31, 2002. ASSEMBLY HOUSE agrees to pay MOTOROLA a royalty based on the
     total number of pads on BGA PACKAGEs made by ASSEMBLY HOUSE and its
     SUBSIDIARIES, and shipped and invoiced to customers of ASSEMBLY HOUSE or
     its SUBSIDIARIES, excluding those made for MOTOROLA and excluding returns.

     4.1.1  The royalty shall be XXXXXX per X until a royalty of XXXXXX has    *
            been accrued.                                                      *

                                     Page 3




<PAGE>
           CONFIDENTIAL TREATMENT REQUESTED AND THE REDACTED MATERIAL
                 HAS BEEN SEPARATELY FILED WITH THE COMMISSION

*    4.12 After a royalty of XXXXX has been accrued, the royalty shall be      *
          XXXXX per pad.                                                       *

4.2. Royalty payments shall be determined by the total number of pads on BGA
     PACKAGEs subject to the immunity from suit of section 3.1 shipped during a
     payment period to customers of ASSEMBLY HOUSE or its SUBSIDIARIES
     excluding those shipped to MOTOROLA and excluding returns.

4.3  Payment periods shall be on a quarterly basis. Within forty-five (45) days
     after each calender quarter ending March 31, June 30, September 30, and
     December 31. ASSEMBLY HOUSE shall pay to MOTOROLA the royalties payable
     hereunder for the respective calender quarter ending on such date as
     determined above.

4.4  Any payment hereunder which shall be delayed for more than thirty (30)
     days beyond the due date shall be subject to an interest charge of one (1)
     percent per month on the unpaid balance payable in United States currency
     until paid. The foregoing payment of interest shall not affect MOTOROLA's
     right to terminate in accordance with Section 5.

4.5  ASSEMBLY HOUSE shall keep full, clear and accurate records with respect to
     BGA PACKAGEs. MOTOROLA shall have the right through a mutually agreed upon
     independent auditor to examine and audit no more than once a year at a
     mutually agreeable time all such records and such other records and
     accounts as may under recognized accounting practices contain information
     bearing upon the amount of royalty payable to MOTOROLA under this
     Agreement. Prompt adjustment shall be made to compensate for any errors or
     omissions disclosed by such examination or audit. Neither such right to
     examine and audit nor the right to receive such adjustment shall be
     affected by any statement to the contrary appearing on a check or
     otherwise, MOTOROLA shall be responsible for the compensation of the
     auditor.

4.6  Within forty-five (45) days after each calender quarter ending March 31,
     June 30, September 30, December 31 and continuing thereafter until all
     royalties payable hereunder shall have been reported and paid, ASSEMBLY
     HOUSE shall furnish to MOTOROLA a detailed and complete written statement,
     certified by a responsible officer of ASSEMBLY HOUSE as showing all BGA
     PACKAGEs which were either manufactured, sold, leased, put into use, or
     otherwise disposed of during such periods, and the amount payable thereon.
     If no such BGA PACKAGEs have been manufactured, sold, leased, put into
     use, or otherwise disposed of, that fact shall be shown on such statement.

4.7  Payments hereunder are to be made to MOTOROLA's New York City account at
     CITIBANK 38491386, 1 Citicorp Center, 399 Park Avenue, New York, New York
     10043. Notice of payments shall be sent by ASSEMBLY HOUSE to MOTOROLA's
     address in Section 6.9.

Section 5 - TERM AND TERMINATION AND ASSIGNABILITY

5.1  The term of this Agreement shall be from the EFFECTIVE DATE until December
     31, 2002 unless earlier terminated as elsewhere provided in this Agreement.

                                     Page 4
<PAGE>
5.2  In the event of any breach of this Agreement by either party hereto
     (including ASSEMBLY HOUSE's obligation to make payments under Section 4),
     if such breach is not corrected within forty-five (45) days after written
     notice describing such breach, this Agreement may be terminated forthwith
     by further written notice to that effect from the party noticing the
     breach.

5.3  Either party hereto shall also have the right to terminate this Agreement
     forthwith by giving written notice of termination to the other party at any
     time, upon or after:

     5.3.1  the filing by such other party of a petition in bankruptcy or
            insolvency; or

     5.3.2  any adjudication that such other party is bankrupt or insolvent; or

     5.3.3  the filing by such other party of any legal action or document
            seeking reorganization, readjustment or arrangement of its business
            under any law relating to bankruptcy or insolvency; or

     5.3.4  the appointment of a receiver for all or substantially all of the
            property of such other party; or

     5.3.5  the making by such other party of any assignment for the benefit of
            creditors; or

     5.3.6  the institution of any proceedings for the liquidation or winding up
            of such other party's business or for the termination of its
            corporate charter.

5.4  In the event of termination of this Agreement by one party pursuant to
     Section 5.2, the immunity and rights granted to or for the benefit of that
     one party hereto and its SUBSIDIARIES under MOTOROLA PATENTS or ASSEMBLY
     HOUSE PATENTS, as the case may be, depending upon who is the party doing
     the terminating, shall survive such termination and shall extend for the
     full term of this Agreement, but the immunity and rights granted to or for
     the benefit of the other party shall terminate as of the date termination
     takes effect.

5.5  At such time as is mutually agreeable, at the written request of either
     party hereto to the other party hereto, but in no event less than six (6)
     months prior to the expiration of this Agreement, the parties hereto shall
     discuss the possible extension of or the renewal of the term of this
     Agreement, including the possible amendment of the provisions thereof.

5.6  The rights or privileges provided for in this Agreement may be assigned or
     transferred by either party only with the prior written consent of the
     other party and with the authorization or approval of any governmental
     authority as then may be required, except to a successor in ownership of
     all or substantially all of the assets of the assigning party. Such
     successor, before such assignment or transfer is effective, shall expressly
     assume in writing to the other party the performance of all of the terms
     and conditions of this Agreement to be performed by the assigning party.

                                     Page 5

<PAGE>
Section 6 - MISCELLANEOUS PROVISIONS

6.1  Each of the parties hereto represents and warrants that it has the right to
     grant to or for the benefit of the other the immunity and rights granted
     hereunder in Sections 2 and 3.

6.2  Nothing contained in this Agreement shall be construed as:

     6.2.1  restricting the right of MOTOROLA or any of its SUBSIDIARIES to
            make, use, sell, lease or otherwise dispose of any particular
            product or products not herein licensed;

     6.2.2  restricting the right of ASSEMBLY HOUSE or any of its SUBSIDIARIES
            to make, use, sell, lease or otherwise dispose of any particular
            product or products not herein licensed;

     6.2.3  an admission by ASSEMBLY HOUSE of, or a warranty or representation
            by MOTOROLA as to, the validity and/or scope of the MOTOROLA
            PATENTS, or a limitation on ASSEMBLY HOUSE to contest, in any
            proceeding, the validity and/or scope thereof;

     6.2.4  an admission by MOTOROLA of, or a warranty or representation by
            ASSEMBLY HOUSE as to, the validity and/or scope of the ASSEMBLY
            HOUSE PATENTS, or a limitation on MOTOROLA to contest, in any
            proceeding, the validity and/or scope thereof;

     6.2.5  conferring any license or other right, by implication, estoppel or
            otherwise, under any patent application, patent or patent right,
            except as herein expressly granted under the MOTOROLA PATENTS, and
            the ASSEMBLY HOUSE PATENTS;

     6.2.6  conferring any license or right with respect to any trademark, trade
            or brand name, a corporate name of either party or any of their
            respective SUBSIDIARIES, or any other name or mark or contraction,
            abbreviation or simulation thereof;

     6.2.7  imposing on MOTOROLA any obligation to institute any suit or action
            for infringement of any MOTOROLA PATENTS, or to defend any suit or
            action brought by a third party which challenges or concerns the
            validity of any MOTOROLA PATENTS;

     6.2.8  imposing upon ASSEMBLY HOUSE any obligation to institute any suit or
            action for infringement of any ASSEMBLY HOUSE PATENTS, or to defend
            any suit or action brought by a third party which challenges or
            concerns the validity of any ASSEMBLY HOUSE PATENTS;

     6.2.9  imposing on either party any obligation to the file any patent
            application or to secure any patent or maintain any patent in force;
            or

                                     Page 6

<PAGE>
     6.2.10  an obligation on either party to furnish any manufacturing or
             technical information under this Agreement except as the same is
             specifically provided for herein.

6.3  No express or implied waiver by either of the parties to this Agreement of
     any breach of any term, condition or obligation of this Agreement by the
     other party shall be construed as a waiver of any subsequent breach of that
     term, condition or obligation or of any other term, condition or obligation
     of this Agreement of the same or of a different nature.

6.4  Anything contained in this Agreement to the contrary notwithstanding, the
     obligations of the parties hereto shall be subject to all laws, both
     present and future, of any Government having jurisdiction over either party
     hereto, and to orders or regulations of any such Government, or any
     department, agency, or court thereof, and acts of war, acts of public
     enemies, strikes, or other labor disturbances, fires, floods, acts of God,
     or any causes of like or different kind beyond the control of the parties,
     and the parties hereto shall be excused from any failure to perform any
     obligation hereunder to the extent such failure is caused by any such law,
     order, regulation, or contingency but only so long as said law, order,
     regulation or contingency continues.

6.5  The captions used in this Agreement are for convenience only, and are not
     to be used in interpreting the obligations of the parties under this
     Agreement.

6.6  This Agreement and the performance of the parties hereunder shall be
     construed in accordance with and governed by the laws of the State of
     Illinois.

6.7  If any term, clause, or provision of this Agreement shall be judged to be
     invalid, the validity of any other term, clause or provision shall not be
     affected; and such invalid term, clause, or provision shall be deemed
     deleted from this Agreement.

6.8  This Agreement sets forth the entire Agreement and understanding between
     the parties as to the subject matter hereof and merges all prior
     discussions between them, and neither of the parties shall be bound by any
     conditions, definitions, warranties, understandings or representations with
     respect to such subject matter other than as expressly provided herein or
     as duly set forth on or subsequent to the date hereof in writing and signed
     by a proper and duly authorized officer or representative of the party to
     be bound thereby.

6.9  All notices required or permitted to be given hereunder shall be in writing
     and shall be valid and sufficient if dispatched by registered airmail,
     postage prepaid, in any post office in the United States, addressed as
     follows:

                                     Page 7
<PAGE>
       6.9.1  If to MOTOROLA:

              Motorola Inc.
              1303 East Algonquin Road
              Schaumburg, Illinois 60196

              Attention: Vice President for Patents, Trademarks & Licensing

       6.9.2  If to ASSEMBLY HOUSE:

              ST Assembly Test Services Pte. Ltd.
              33 Marsiling Industrial Estate Road 3
              #03-01
              Singapore 739256

              Attention: Mr. Lee Joon Chung, General Manager

6.9.3  The date of receipt of such a notice shall be the date for the
       commencement of the running of the period provided for in such notice, or
       the date at which such notice takes effect, as the case may be.

IN WITNESS WHEREOF, the parties hereto have executed this Agreement in
duplicate.


MOTOROLA, INC.                              ST ASSEMBLY TEST SERVICES PTE. LTD.



/s/ George Turner                           /s/ Lee Joon Chung
-----------------------------------         ---------------------------------
George Turner                               Mr. Lee Joon Chung
Vice President & General Manager            General Manager
Logic and Analog Technologies Group         ST Assembly Test Services Pte. Ltd.
Semiconductor Products Sector
Motorola, Inc.

Date: 9/30/96                               Date: 9/11/96
      -----------------------------               ---------------------------



/s/ James W. Gillman                        /s/ Tan Bock Seng
-----------------------------------         ---------------------------------
James W. Gillman                            Mr. Tan Bock Seng
Corporate Vice President, Patents,          Board Director
Trademarks, and Licensing                   ST Assembly Test Services Pte. Ltd.
Motorola, Inc.

Date: 10/18/96                              Date: 9/11/96
      -----------------------------               ---------------------------

                                     Page 8