Crystallographic Characteristic Effect of Cu Substrate on Serrated Cathode Dissolution in Cu/Sn-3.0Ag-0.5Cu/Cu Solder Joints during Electromigration.

Wu Yue,Chenggong Gong,Chao Ding,Junxi Zhang,Hongbo Qin

doi:10.3390/ma14102486

Abstract

The crystallographic characteristic effect of Cu substrate on cathode dissolution behavior in line-type Cu/Sn–3.0Ag–0.5Cu (SAC305)/Cu solder joints during electromigration (EM) was investigated by scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and first-principles calculations. The SEM and EBSD results show that the crystallographic characteristic of Cu substrate is crucial to cathode dissolution behavior under a direct current of 1.5 × 104 A/cm2 at 125 °C ± 2 °C. When the (001) plane of copper grain adjacent to the Cu3Sn/Cu interface is perpendicular or nearly perpendicular to the current direction, local cathode dissolution tips are easily formed, whereas the (111) plane remains mostly undissolved, which finally leads to the inhomogeneous cathode serrated dissolution in the substrate. The first-principles calculation results reveal that the different surface energies and energy barriers of the different crystallographic planes of Cu grains in the substrate are responsible for the local cathode dissolution tips. Adjusting the copper grain in a substrate to a crystal plane or direction that is difficult to dissolve during EM is a promising method for improving the reliability of solder joints in the future.

Highlights

The increasing demand for miniaturized, multifunctional portable electronic products and devices has led to a continuous scaling-down of the dimensions of solder joints in microelectronic packaging
Such downscaling dramatically increases the current density in the solder joints, causing electromigration (EM), that is, the directional migration of atoms under a high-density electric current [1,2,3,4]
The failure mechanisms of solder joints induced by EM are extensively studied and many results have been obtained [14,15,16,17], and one of the most well-known results is that when the c-axis of β-Sn grains, which usually refers to the Sn grain orientation, is aligned or nearly aligned along the current direction, the Cu atoms diffuse quickly and the EM deterioration is more serious [18,19]

Summary

Introduction

The increasing demand for miniaturized, multifunctional portable electronic products and devices has led to a continuous scaling-down of the dimensions of solder joints in microelectronic packaging. Such downscaling dramatically increases the current density in the solder joints, causing electromigration (EM), that is, the directional migration of atoms under a high-density electric current [1,2,3,4]. The failure mechanisms of solder joints induced by EM are extensively studied and many results have been obtained [14,15,16,17], and one of the most well-known results is that when the c-axis of β-Sn grains, which usually refers to the Sn grain orientation, is aligned or nearly aligned along the current direction, the Cu atoms diffuse quickly and the EM deterioration is more serious [18,19]

Methods

Results

Conclusion