Effect of high current pulses on solder interfacial reaction and interconnect reliability. (July 2021)

• Record Type: Journal Article
• Authors: Mei, J.; Haug, R.; Grözinger, T.; Zimmermann, A.
• Is Part Of: Microelectronics and reliability. Volume 122(2021)
• Publication Date: 2021-07
• Subjects: Power cycling -- Reliability -- Solder joint -- Electromigration -- FEM simulation -- Intermetallic compound; 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.2021.114151
• Languages: English
• ISSNs: 0026-2714

Abstract

Abstract: The trend of electrification and miniaturization brings the reliability of interconnects to the forefront. The solder joints are subjected to thermo-mechanical mismatch due to the Joule heating and electromigration (EM)-induced degradation under high current stressing conditions. However, most of the studies are limited to lab test samples or lab test conditions, which lack transferability in engineering applications. In this paper, automotive electronic components are studied subjected to field-like current pulse conditions. The work aims to understand the field-relevant failure modes of solder joints exposed to high current stressing via experimental and numerical investigations. Shunt components with and without Ni plating are analyzed in power cycling tests. A polarity effect is observed in the growth of intermetallic compounds (IMCs). The thickness of IMC at the anode exhibits an approximately linear growth with current stressing time, whereas the thickness of IMC at the cathode remains almost unchanged or slightly decreased. Ni, as diffusion barrier, serves to restrain Cu consumption from the terminals of shunts and also reduces Cu mass transport into and within the solder. The net Cu flux at the interface and in the solder is discussed to analyze the IMC growth kinetics. The shunts with Ni plating undergo less EM of Cu and yield longer lifetime. Voids and crack formation are detected in computer tomography (CT) scans and cross-sectional analysis by scanning electron microscopy (SEM). Finite element method (FEM) is implemented to simulate thermo-electro-mechanical fields of the assembly under power cycling test conditions. The distribution of divergence of material flux density corresponds well with the location of voids formation and provides good estimation for the lifetime. Highlights: Field-relevant failure mode of solder joints under high current loads is reproduced and investigated. A polarity effect is observed in the growth of intermetallic compounds and shunts with Ni plating yield a longer lifetime. Simulation is performed to characterize electromigration and thermo-mechanical fatigue of the solder joint. Lifetime of the solder is proportional to the inverse value of divergence of material flux density. With longer stressing time, the strain in solder joint will be increased owing to voids formation and coalescence of voids.