Work

Enhancing Electromigration Lifetime Through Controlled Reduction of Bismuth Content in Sn-Bi-Ag Solder Interconnects

Year: 2025

Type: article

Abstract: This study systematically investigates the influence of Bi content on the electromigration (EM) lifetime of low-temperature Cu/Sn-xBi-1Ag (600 μm)/Cu interconnects, where x = 57, 47 and 40 wt.%. The intrinsically higher product of diffusivity and effective charge number (DZ*) for Bi compared to Sn drives pronounced preferential migration of Bi atoms towards the anode, resulting in progressive β-Sn/Bi phase separation and linear thickening of a Bi-rich layer at the anode. Reducing the Bi content suppresses the EM-induced atomic flux (JEM) through three principal mechanisms: (i) a decrease in the atomic concentration of mobile Bi atoms; (ii) a reduction in electrical resistivity that weakens the electron wind force; and (iii) an increase in lattice diffusion distance that lowers the effective diffusion coefficient (Deff). The suppression of JEM directly governs the thickening kinetics of anodic Bi layer, as evidenced by the close agreement between the calculated (1:0.40:0.23) and measured (1:0.45:0.26) anodic Bi layer growth rate ratios. Consequently, the EM lifetime is significantly extended from 62.3 h (Sn-57Bi-1Ag) to 164.9 h (Sn-47Bi-1Ag) and 414.1 h (Sn-40Bi-1Ag), representing 2.6-fold and 6.6-fold improvements, respectively. This study highlights that reducing the Bi content is an effective strategy for enhancing the EM reliability of Sn-Bi-Ag solder interconnects.

Source: Materials

DOI: 10.3390/ma18245672

Authors: Shengbo Wang, Shuai Meng, Houlin Liu, Mingliang Huang

Institution: Dalian University of Technology

Language: English

Topic: Electronic Packaging and Soldering Technologies

Subfield: Electrical and Electronic Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,137

Funder: National Natural Science Foundation of China