[SCHEDULE TO (RULE 14d-100) Tender Offer Statement SILICONWARE PRECISION INDUSTRIES CO., LTD. (Name of Subject Company (Issuer)) ADVANCED SEMICONDUCTOR ENGINEERING, INC. (Offeror) American Depositary Shares, Each Representing Five Common Shares, (Title of Class of Securities) 827084864 (American Depositary Shares) (CUSIP Number of Class of Securities) TW0002325008 (Common Shares) (ISIN Number of Class of Securities) Joseph Tung (Name, Address and Telephone] [Shares, not including those tendered into the U.S. Offer or those represented by ADSs, such that we will acquire at least 5% of the issued and outstanding share capital of SPIL (the "Minimum Condition") and (ii) receipt of antitrust approval from the Taiwan Fair Trade Commission (the "TFTC Condition"). In addition, the U.S. Offer is subject to the conditions set] [QuickLinks -- Click here to rapidly navigate through this document ADS LETTER OF TRANSMITTAL To Tender American Depositary Shares of Siliconware Precision Industries Co., Ltd. by Advanced Semiconductor Engineering, Inc. THE U.S. OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 1:30 A.M., NEW YORK CITY NO GUARANTEED DELIVERY Please deliver this properly completed and duly executed ADS Letter of Transmittal and] [QuickLinks -- Click here to rapidly navigate through this document COMMON SHARE FORM OF ACCEPTANCE To Tender Common Shares of Siliconware Precision Industries Co., Ltd. by Advanced Semiconductor Engineering, Inc. THE U.S. OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 1:30 A.M., NEW YORK CITY TIME, ON FEBRUARY 16, 2016, UNLESS THE U.S. OFFER IS EXTENDED NO GUARANTEED DELIVERY Please deliver] [QuickLinks -- Click here to rapidly navigate through this document of Siliconware Precision Industries Co., Ltd. for by Advanced Semiconductor Engineering, Inc. THE U.S. OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 1:30 A.M., NEW YORK CITY TIME, ON FEBRUARY 16, 2016, UNLESS THE U.S. OFFER IS EXTENDED Please note that The Depository Trust Company and its participants, including the custodians] [QuickLinks -- Click here to rapidly navigate through this document U.S. Offer to Purchase for Cash Outstanding American Depositary Shares and of Siliconware Precision Industries Co., Ltd. for NT$275 Per American Depositary Share (Payable in U.S. Dollars) and by Advanced Semiconductor Engineering, Inc. THE U.S. OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 1:30 A.M., NEW YORK CITY TIME, ON FEBRUARY] [QuickLinks -- Click here to rapidly navigate through this document U.S. Offer to Purchase for Cash of Siliconware Precision Industries Co., Ltd. for NT$275 Per American Depositary Share (Payable in U.S. Dollars) and by Advanced Semiconductor Engineering, Inc. THE U.S. OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 1:30 A.M., NEW YORK CITY TIME, ON FEBRUARY 16, 2016, UNLESS THE U.S.] [QuickLinks -- Click here to rapidly navigate through this document U.S. Offer to Purchase for Cash of Siliconware Precision Industries Co., Ltd. for NT$275 Per American Depositary Share (Payable in U.S. Dollars) and by Advanced Semiconductor Engineering, Inc. THE U.S. OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 1:30 A.M., NEW YORK CITY TIME, ON FEBRUARY 16, 2016, UNLESS THE U.S.] [QuickLinks -- Click here to rapidly navigate through this document This announcement is neither an offer to purchase nor a solicitation of an offer to sell ADSs or Common Shares. The U.S. Offer is made solely by the U.S. Offer to Purchase dated December 29, 2015 and the related ADS Letter of Transmittal and Common Share Form of Acceptance and] [QuickLinks -- Click here to rapidly navigate through this document Fairness Opinion on the Consideration of the 100% Share Acquisition Proposal 1. Content of Appointment Advanced Semiconductor Engineering, Inc. (" ASE ") appoints me as an accountant to issue fairness opinion in relation to the case (" This Case ") by ASE to acquire 100% of the shares of Siliconware] [QuickLinks -- Click here to rapidly navigate through this document Fairness Opinion on the Consideration of Tender Offer 1. Content of Appointment Advanced Semiconductor Engineering, Inc. (" ASE ") appoints me as an accountant to issue fairness opinion in relation to the case (" This Case ") of the tender offer from ASE in acquiring 24.71% of the shares of]