| Summary: | 碩士 === 國立高雄大學 === 電機工程學系--先進電子構裝技術產業研發碩 === 95 === According to the fast development of portable electronic devices, their characteristics are inclined to miniature outline and lightweight. So we need to develop good reliable package to meet the future trend. The demand of small outlines, lightweight and chip size area has become an essential issue for wafer-level chip scale package (WLCSP) design. When the portable electronic devices are more and more small, the current density of internal components (including solder bump, metal runner and UBM etc.) has increased apparently. So the products will hasten fail and reduce the using life. However, the major fail reasons are caused by the heavy current and large heat, i.e. electromigration.
In this thesis, we investigated three kinds of metal runners of WLCSP and study their reliability of a board-level WLCSP subjected to different fixed current stressing conditions, namely, 0.5 A, 0.6 A and 0.7 A, at a fixed ambient temperature of 125 oC. A correlation between mean-time-to-failure of the WLCSP test vehicle and the average current density carried by a metal runner was sought. Cross-section examinations and SEM/EDX analysis were conducted to identify the failure mode due to electromigration. Finally, we use power-law model equation, which is usually employed in characterizing the electromigration reliability of metal runners. For this experiment discovered metal runner TiAlTi and the TiAl, its expiration position occurs in the electron enters region, namely the metal runner broken at cathode position is large affected of electromigration. In this work, for WLCSP with metal runner TiCuTi possess best ability on electromigration immunity.
Keywords: electromigration, WLCSP, fixed current, metal runner
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