Microstructure evolution during electromigration in eutectic SnPb solder bumps

Abstract

A technique has been developed to facilitate analysis of the microstructural evolution of solder bumps after current stressing. Eutectic SnPb solders were connected to under-bump metallization (UBM) of Ti/Cr-Cu/Cu and pad metallization of Cu/Ni/Au. It was found that the Cu6Sn5 compounds on the cathode/chip side dissolved after the current stressing by 5 × 103 A/cm2 at 150 °C for 218 h. However, on the anode/chip side, they were transformed into (Nix,Cu1-x)3Sn4 in the center region of the UBM, and they were converted into (Cuy,Ni1-y)6Sn5 on the periphery of the UBM. For both cathode/substrate and anode/substrate ends, (Cuy,Ni1-y)6Sn5 compounds were transformed into (Nix,Cu1-x)3Sn4. In addition, the bumps failed at cathode/chip end due to serious damage of the UBM and the Al pad. A failure mechanism induced by electromigration is proposed in this paper.

The effect of Cu addition on the electrochemical corrosion and passivation behavior of stainless steels

“…The chemical compositions of the Cu-containing specimens are presented in Table 1. Details of the fabrication (including the heat treatment regimen), microstructure and antibacterial characterization of the Cu-containing specimens are as previously reported [17,18]. Specimens for corrosion tests were wet-polished with SiC paper (up to 1200 grit) and degreased with acetone.…”

“…This work is a continuation of our interest in characterizing the corrosion behavior of some novel Cucontaining antibacterial stainless steels produced in our laboratory [17][18][19]. Earlier reports show that the Cu-containing specimens manifest strong, long term, broad-spectrum antibacterial efficacy in excess of 99% for organisms such as Bacillus coli, Staphylococcus aureus and Candida albicans, whereas 80% efficacy was reported for Bacillus sublis [17,18].…”

“…This work is a continuation of our interest in characterizing the corrosion behavior of some novel Cucontaining antibacterial stainless steels produced in our laboratory [17][18][19]. Earlier reports show that the Cu-containing specimens manifest strong, long term, broad-spectrum antibacterial efficacy in excess of 99% for organisms such as Bacillus coli, Staphylococcus aureus and Candida albicans, whereas 80% efficacy was reported for Bacillus sublis [17,18]. The present study includes determination of the passive regions of the different stainless steel specimens both with and without Cu, evaluation of the impedance responses of the active and passive steel surfaces, and determination of the semiconducting character and dopant levels in the passive films.…”

Effect of UBM Thickness on the Mean Time to Failure of Flip-Chip Solder Joints under Electromigration

“…[1][2][3][4][5][6][7]10,11,13 In order to understand the degree of current crowding, a three-dimensional finite-element simulation was used to calculate the current density distribution of the joint. Figure 6a shows the mesh geometry used in this study.…”

Effect of thermal aging on microstructure, shear and mechanical shock failures for solder ball bonding joint

“…SnPb eutectic solder are extensively used as soldering materials in electronic packaging due to its good wettability and acceptable physical-chemical characteristics. The intermetallic compound (IMC) formation at Sn-37%Pb and Au/Ni/Cu interface has been widely discussed in literatures [1][2][3].…”