Effect of Cu Thickness on the Evolution of the Reaction Products at the Sn-9wt.%Zn Solder/Cu Interface During Reflow

Abstract

Interfacial reactions between Sn-9wt.%Zn solder and Cu substrates at 230A degrees C were investigated. The substrate thickness was found to have noticeable effects on the evolution of the reaction products formed at the solder/Cu interface. The CuZn(5) and Cu(5)Zn(8) phases were formed at the early stage of reflow, regardless of the Cu thickness, while, with increasing reflow time, the two phases displayed different growth behaviors on the Cu substrates with various thicknesses. For the thicker Cu substrates with a thickness of 6 mu m, 10 mu m, and 0.5 mm, CuZn(5) disappeared but Cu(5)Zn(8) kept on growing after a longer reflow time. In contrast, for the thinner Cu substrates with a thickness less than 3 mu m, Cu(5)Zn(8) shrank with increasing reflow time but CuZn(5) grew dominantly. A different evolution of the grain morphology of CuZn(5) was also observed between the thicker and thinner Cu substrates. When the reflow time was increased, the CuZn(5) grains retained a rounded shape on the thinner Cu substrates; however, the grain structure became faceted on the thicker Cu substrates

Three‐dimensional electrically conductive–hydrophobic layer for stable Zn metal anodes

“…As shown in Figure 1B, the surface of CZ@Zn exhibits a uniform 3D structure with numerous protuberances, which are caused by the different diffusion rates of Zn and Cu atoms during the heat treatment. 42 The atomic force microscope images also display the same rough morphology. This 3D rough surface of CZ@Zn contributes to remarkably increased surface roughness (Ra, 5.9-123 nm) and specific surface area (3.83-5.98 m 2 g −1 ) compared with plane Zn (Figure S3).…”

“…The morphology of the as‐prepared CZ@Zn sample was observed by SEM image. As shown in Figure 1B, the surface of CZ@Zn exhibits a uniform 3D structure with numerous protuberances, which are caused by the different diffusion rates of Zn and Cu atoms during the heat treatment 42 . The atomic force microscope images also display the same rough morphology.…”

Effect of electromigration on the tensile strength of Cu/Sn-9Zn/Cu solder interconnects

“…The formation of the two different interfacial IMCs was associated with Cu content [4]. 3 shows the microstructural evolution of the Cu/Sn-9Zn/Cu interconnects during aging at 150 o C without EM for various durations.…”

“…Sn-9Zn alloy is considered as one of the promising leadfree solders because of its lower cost, suitable mechanical properties, and closer melting point (198.5 o C) to that of conventional Sn-37Pb solder (183 o C) [4]. In previous studies [5][6][7], EM was found to have significant effects on the interfacial reaction of Cu/Sn-9Zn/Cu solder joints, and a reverse polarity effect was revealed, i.e, the Cu-Zn intermetallic compound (IMC) layer at the cathode side was thicker than that at the anode side.…”

Intermetallic Compound Formation and Evolution in Solid-State Sn/Immersion-Ag/Cu Trilayer Interfacial Reactions on a Flexible Polymer Board

“…Therefore, studies of Sn/Cu interfacial reactions are of great industrial application value and have been extensively investigated. [1][2][3][4][5][6][7][8] To prevent excess reactions of Cu metallization with Sn-based solders and avoid severe oxidation, an electroless-Ni/immersion-Au bilayer is usually deposited on the Cu metallization to act as a surface finish layer on a printed circuit board (PCB). However, it has been found that Au embrittlement occurs in solder joints employing the Ni/Au bilayer.…”