An observation and explanation of interior cracking at the interface of solder by electromigration. (June 2019)

• Record Type: Journal Article
• Authors: Wang, Qizhi; Liu, Qingyi; Zhang, Zheng; Miao, Min; Su, Yehao; Su, Fei
• Is Part Of: Microelectronics and reliability. Volume 97(2019)
• Page Start: 79
• Page End: 84
• Publication Date: 2019-06
• Subjects: Electromigration (EM) -- Interfacial crack -- Solder -- Reliability; Electronic apparatus and appliances -- Reliability -- Periodicals; Miniature electronic equipment -- Periodicals; Appareils électroniques -- Fiabilité -- Périodiques; Équipement électronique miniaturisé -- Périodiques; Electronic apparatus and appliances -- Reliability; Miniature electronic equipment; Periodicals; 621.3815
• DOI: 10.1016/j.microrel.2019.04.013
• Languages: English
• ISSNs: 0026-2714

Abstract

Abstract: The electromigration (EM) of a solder joint under high-current stressing causes damage and reduces its service life. Previous studies have suggested that EM-induced cracks typically initiate at the cathode corner where the electron current enters, and propagate across the intermetallic compound and solder interface. Herein, however, another type of propagation is experimentally demonstrated whereby cracks initiate from voids located in the middle of the interface and propagate in two directions. This phenomenon was investigated further with finite element simulations. These simulations showed that, when the solder corners become rounded via the wetting phenomenon that occurs during solder reflow, the current density around the voids is greater than that at the solder corner. Under these conditions, cracking will initiate from the side of an existing void, instead of the corner from where electron current flows into the solder ball, when tensile stress is present at the void and compressive stress at the electron current entrance. Highlights: Experimentally, a void at the interface of a solder ball and the IMC expands throughout the entire interface, ultimately leading to the failure of the ball. The current density, stress and the vacancy concentration at the void are greater than that at the corner of the solder joint.