Impact of Mechanical Property Degradation and Intermetallic Compound Formation on Electromigration-Oriented Failure of a
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https://doi.org/10.1007/s11664-020-08514-y Ó 2020 The Minerals, Metals & Materials Society
Impact of Mechanical Property Degradation and Intermetallic Compound Formation on Electromigration-Oriented Failure of a Flip-Chip Solder Joint MD. TUSHER AHMED,1 MOHAMMAD MOTALAB and JEFFREY C. SUHLING2
,1,3
1.—Department of Mechanical Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh. 2.—Department of Mechanical Engineering, Auburn University, Auburn, AL 36830, USA. 3.—e-mail: [email protected]
Due to the increased complexity and optimization in microprocessor packaging from 2D to 3D packages, the size of solder joints is being reduced significantly. This trend currently leads to an increased amount of current density across flip-chip solder joints as well as microbumps and causes electromigrationoriented void formation and subsequent failure of the solder joints. It has been observed from literature that solder material undergoes microstructure evolution and subsequent degradation of mechanical properties under isothermal aging conditions. The current study is based on the effects of material property degradation due to thermal aging of flip-chip Sn-Ag-Cu (SAC) solder joints on electromigration-oriented failure. Finite element analysis has been used to analyze the diffusion characteristics of a SAC solder joint under isothermal aging conditions of 100°C for a period of 1–20 days, and electromigration simulation has been performed at two different temperatures of 100°C and 125°C for 100 h at an input current range of 0.01–0.05 A. The effect of intermetallic compound (IMC) layer thickness is analyzed to reveal the impact on electromigration-oriented failure in isothermally 60 days long aged solder bumps. Results have revealed that resistance to electromigration-oriented failure is higher in the case of aged components compared to unaged components along with the increment of time to failure with IMC formation in the SAC solder joint. Key words: Lead-free solder, electromigration, finite element method, isothermal aging, intermetallic compound
INTRODUCTION In spite of size and space constraints, the total number of input/output ports in modern-day electronic packages has been significantly increased for ensuring improved performance. Due to the large area of application of small-sized flip-chip C4 (controlled-collapse chip connection) bumps as electrical
(Received September 25, 2019; accepted September 22, 2020)
connections and mechanical supports in electronic devices, a substantial concern regarding reliability is being observed in the field of semiconductor technology. Progressive shrinking of flip-chip solder joints to a microbump size (characteristic size of only 20 lm) has caused flow of electrical current with a significantly high order of current density (order of 108 A/m2) which has given rise to electromigration-oriented failure.1 The electromigration phenomenon is a diffusion process in which migration of atoms occurs in the direction of applied electron flux w
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