Interfacial reaction of Sn-Ag-Cu solder with magnetron sputtered Cu-Cr alloy film during aging treatment

doi:10.13251/j.issn.0254-6051.2021.11.016

Abstract

Abstract: Cu-Cr alloy films with different content of Cr was deposited by magnetron sputtering. The solder joint structure was formed by reflow soldering with Sn-Ag-Cu (SAC) solder at 240 ℃, and then the specimens were vacuum aged at 180 ℃. The soldering reliability of the Cu-Cr alloy as under bump metallization layer (UBM layer) forming solder joint with SAC was studied. The morphology of interfacial intermetallic compound (IMC) and the shear strength of solder joint were analyzed by field emission scanning electron microscope equipped with energy dispersive X-ray spectrometer and multifunctional thrust tester. The results show that needle-like IMC, which is different from the traditional SAC/Cu interface scallop-like IMC, is formed in the SAC/Cu-Cr solder joint after reflow soldering. After aging, the segregation of Cr at the grain boundary forms a chromium rich layer, which acts as a diffusion barrier to prevent the diffusion of Cu into IMC, so that the growth of Cu₃Sn and Kirkendal void is inhibited. The shear strength test results show that the SAC/Cu-Cr specimen after reflow soldering has higher shear strength than that of the SAC/Cu specimen. The solder joint structure formed by the Cu-Cr alloy UBM layer with a Cr target current of 1.5 A has smaller IMC thickness and the highest solder joint shear strength. It is confirmed that the Cu-Cr alloy UBM layer is beneficial to improve soldering reliability.

Key words: unbalanced magnetron sputtering, Cu-Cr alloy UBM layer, Sn-Ag-Cu solder, aging treatment, interfacial reaction

CLC Number:

TB43

Wang Yupeng, Wu Hongjun, Bao Mingdong, Yang Wenhao, Zhao Guohua, Zhou Bing. Interfacial reaction of Sn-Ag-Cu solder with magnetron sputtered Cu-Cr alloy film during aging treatment[J]. Heat Treatment of Metals, 2021, 46(11): 103-109.

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