Physics of failure of die-attach joints in IGBTs under accelerated aging: Evolution of micro-defects in lead-free solder alloys. (June 2020)

• Record Type: Journal Article
• Authors: Yongle, Huang; Yifei, Luo; Fei, Xiao; Binli, Liu; Xin, Tang
• Is Part Of: Microelectronics and reliability. Volume 109(2020)
• Publication Date: 2020-06
• Subjects: Physic of failure -- Die-attach solder -- Micro-defects -- Pulsed high current cycling -- Power cycling; 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.2020.113637
• Languages: English
• ISSNs: 0026-2714

Abstract

Abstract: Fatigue of die-attach solder joints is quite critical to reliability of IGBT modules. In the present work, physics of failure of die-attach joints in IGBTs was discussed based on the evolution of micro-defects in materials under accelerated aging through experiments and Finite element (FE) simulations. It shows that voids, cracks of Sn-Ag-Cu (SAC) alloys and detachment of Si/SAC interfaces are three major micro-defects in the die-attach solder. Voids could accelerate evolution of other two micro-defects. Cracking of SAC alloys is the major failure mode of die-attach solder under power cycling and detachment of Si/SAC interfaces turns to be the dominant failure mode under transient electrical/thermal shocks. FE simulations indicate that the shear thermal stress τ shear at Si/SAC interfaces is the decisive factor for switching between the two failure modes. When Δ T j > 105 °C, the average shear stress τ shear_ave at Si/SAC interfaces exceeds the bonding strength and detachment of Si/SAC interfaces plays a major role in failure of die-attach solder. Based on physics of failure, two physical life models for die-attach joints under various accelerated aging conditions were proposed. Highlights: Failure mechanism of die-attach solders were studied by experiments and FE simulations. Cracking of solder is the major failure mode for die-attach solders under power cycling. the chip/solder interface detachment becomes the root cause under electrical/thermal shocks. Voids in the solder layer could accelerate the above two failure modes. Life models for die-attach solder in IGBTs were proposed based on the physics of failure.