Ni5Zn21 Phase Research Articles

Effects of Composition on the Electromagnetic Wave Shielding/Absorption and Corrosion in Zn-Ni Alloy Thin Film

In the Fourth industrial age, there is increasing use of electronic devices with high frequency (GHz) operating circuits for radio wave transmission/reception. This can lead to electromagnetic noise, and malfunctions in nearby devices. Electromagnetic shielding technology has emerged as an important way of preventing device malfunctions due to noise, and interest in shielding materials for electromagnetic waves has also increased. To allow compact integration and light weight electronic devices, highly efficient, thin and multifunctional film materials are required. This study selected the Zn-Ni alloy, which has adequate corrosion resistance, to protect the metal parent material of electronic components. Various compositions of the alloy were deposited using magnetron sputtering. Phase formation and composition were confirmed through XRD and SEM and EDS. The surface resistance of the thin films was measured using the 4point probe method, to calculate the shielding rate of the thin films. The electromagnetic wave shielding/absorption rate then measured according to frequency and the results compared with the calculated values. Corrosion resistance was evaluated with a polarization test. The far field electromagnetic shielding/absorption rate increased as the Zn content increased, up to 52 dB in a film with 70 at% of Zn. Corrosion resistivity behavior was the opposite. However, the Ni5Zn21 phase formation, which occurred in films with lower Zn composition, helped to improve electromagnetic absorption in the near field as well as corrosion resistivity. Therefore, the optimum composition of the Zn-Ni films was provisionally determined to be around Ni: Zn = 43:57 for electronic devices using electromagnetic waves in the near field range.

Interfacial Reactions Between Lead-Free Solders and Ni-Pd-Co Alloys

The liquid/solid interfacial reactions of Sn, Sn-(3.0 wt.% to 0.5 wt.%)Cu (SAC), and Sn-9.0 wt.%Zn (SZ) solders with Ni-xPd-yCo substrates at 240°C, 270°C, and 300°C for 0.5 h to 5 h have been investigated. The Ni-xPd-yCo alloys were prepared with x = 0.5 wt.% and 1.5 wt.% and y = 0.5 wt.%, 1.5 wt.%, and 3.0 wt.%. The intermetallic compound (IMC) Ni3Sn4 formed in the Sn/Ni-xPd-yCo reaction couples at 240°C, 270°C, and 300°C. Although (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 phases appeared at the interface of the SAC/Ni-xPd-yCo couples after 0.5 h to 2 h at 240°C, only (Ni,Cu)3Sn4 phase formed after 5 h at 240°C or 0.5 h to 5 h at 270°C or 300°C in the SAC/Ni-xPd-yCo systems. The SZ/Ni-xPd-yCo interfacial reactions at three different temperatures formed the Ni5Zn21 phase, but when the reaction time was extended to 5 h, Ni5Zn21, Sn, and δ phases were also observed. The thickness of the IMCs was measured and used to calculate the reaction rate constant and activation energy. The interfacial reactions between the lead-free solders (Sn, SAC, and SZ) and Ni-xPd-yCo substrates were determined to be diffusion controlled.

Effect of Doping of Nanoparticles on the Properties of Zn-Ni Composite Coatings

The purpose of this paper was to investigate the effect of Al2O3 and TiO2 nanoparticles contents on structural proporties, microhardness and corrosion resistance of Zn-Ni alloy coationg. Zn-Ni, Zn-Ni-Al2O3 and Zn-Ni-TiO2 composite coatings were electrodeposited on steel substrate by direct current in sulphate bath.The structure of the coatings was studied by X-ray diffration and by scaning electron miroscopy. The results showed the appearance of Ni5Zn21 phases and that the incrorporation of Al2O3 and TiO2 in the Zn-Ni coating refined the crystal grain size.The corrosion performance of coating in the 0.6M NaCl as a corrisive solution was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy EIS methods. It was found that the incorporation of nanoparticules in Zn-Ni alloy coating have better corrosion resistance and the values of Rct and Zw increase, while the values of Cdl decrease with increasing of nanoparticules.

Wetting of Sn-Zn-Ga and Sn-Zn-Na Alloys on Al and Ni Substrate

Wetting of Al and Ni substrate by Sn-Zn eutectic-based alloys with 0.5 (wt.%) of Ga and 0.2 (wt.%) of Na was studied using the sessile drop method in the presence of ALU33® flux. Spreading tests were performed for 60 s, 180 s, and 480 s of contact, at temperatures of 503 K, 523 K and 553 K (230°C, 250°C, and 280°C). After cleaning the flux residue from solidified samples, the spreading areas of Sn-Zn0.5Ga and Sn-Zn0.2Na on Al and Ni substrate were determined. Selected, solidified solder-pad couples were cross-sectioned and subjected to scanning electron microscopy with energy dispersive spectroscopy, x-ray diffraction study and synchrotron measurements of the interfacial microstructure and identification of the phases. The growth of the intermetallic Ni5Zn21 phase layer was studied at the solder/Ni substrate interface, and the kinetics of the formation and growth of the intermetallic layer were determined. The formation of interlayers was not observed on the Al pads. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed.

Interfacial Reactions in the Ni/Sn-xZn/Cu Sandwich Couples

The interfacial reactions in Ni/Sn-xZn/Cu sandwich couples which were reflowed at 270°C for 1 h and then aged at 160°C for 1–1000 h were investigated. When the 1000-μm-thick Sn-Zn alloy reacted with Ni and Cu in this couple, the results indicated that the (Ni, Cu)3Sn4, (Ni, Cu)5Zn21, and Ni5Zn21 phases were formed at Sn-1Zn/Ni, Sn-5Zn/Ni, and Sn-9Zn/Ni interfaces for 1 h reflowing, respectively. After 1000 h aging, each intermetallic compound (IMC) was converted to (Cu, Ni, Zn)6Sn5, (Ni, Cu, Sn)5Zn21/Ni5Zn21, and Ni5Zn21 (two layers) phases in the related couples. On the Cu side, the Cu6Sn5 phase in the Sn-1Zn/Cu interface and the Cu5Zn8 phase in the Sn-5Zn/Cu and Sn-9Zn/Cu interfaces were observed when the couple was reflowed at 270°C for 1 h. After 100 h aging, the (Cu, Ni, Zn)6Sn5, Cu5Zn8/(Cu, Zn)6Sn5, and Cu5Zn8 phases were formed at the Sn-1Zn/Cu, Sn-5Zn/Cu and Sn-9Zn/Cu interfaces. When the Sn-Zn alloy thickness was decreased to 500 μm, the (Cu, Ni, Zn)6Sn5 phase at the Sn-1Zn/Ni interface and the (Ni, Cu, Sn)5Zn21 phase at the Sn-5Zn/Ni and Sn-9Zn/Ni interfaces were observed after 1 h reflowing. When the couple was aged at 160°C for 1000 h, each IMC was converted to (Cu, Ni, Zn)6Sn5 and Cu5Zn8/(Cu, Ni, Sn)Zn/Ni5Zn21 phases at the Sn-1Zn/Ni and Sn-(5, 9)Zn/Ni interfaces. (Cu, Ni, Zn)6Sn5 and Cu5Zn8 were, respectively, formed at the Sn-1Zn/Cu and Sn-(5, 9)Zn/Cu interfaces for 1 h reflowing. After 100 h aging, the IMCs were converted to (Cu, Ni, Zn)6Sn5 and Cu5Zn8/(Cu, Zn)6Sn5 phases. This current study reveals that the IMC formation in Ni/(Sn-xZn)/Cu sandwich couples are very sensitive to the Zn concentration and thickness in Sn-xZn alloys.

Solid-state reactions between Sn-20.0 wt.%In-x wt.%Zn solders and Ag and Ni substrates

The Sn-20 wt.%In (Sn–20In) alloy is a promising base material for low-temperature Pb-free solders. Zn is usually added in solders to reduce the extent of undercooling during reflow, while Ag and Ni are commonly seen under bump metallurgy in contact with solder in electronic products. In this study, solid-state reactions at 150 °C between Zn-doped Sn–20In solders and Ag and Ni substrates are investigated. In Sn–20In–xZn/Ag couples, when the Zn-doping level is low (x ≤ 1.0), the reaction path is γ-InSn4/ζ-AgZn/ζ-(Ag,In)/ζ-AgZn/Ag, that the ζ-AgZn layer near the solder has non-uniform composition, the ζ-(Ag,In) layer has a porous microstructure, and the ζ-AgZn phase near the substrate is composed of small grains. When the Zn doping level is high (x ≥ 2.0), the reaction path becomes γ-InSn4/ε-AgZn3/γ-Ag5Zn8/ζ-AgZn/Ag, that all intermetallic compounds (IMCs) are planar and neither Sn nor In participate in the reactions. Although the reactions are very sensitive to Zn contents, the overall thicknesses of IMCs do not vary much with different Zn-doping levels. In Sn–20In–xZn/Ni couples, the planar Ni5Zn21 phase is the only reaction product with a very slow growth rate. The interfacial liquation in Sn–20In/Ni contacts can be fully mitigated with a minor Zn addition of 0.5 wt.%.

Cruciform Pattern of Ni5Zn21 Formed in Interfacial Reactions Between Ni and Sn–Zn Solders

A unique cruciform pattern was observed for the Ni5Zn21 phase formed in both liquid-state and solid-state interfacial reactions between rectangular Ni substrate and both Sn–9 wt.%Zn and Sn–80 wt.%Zn. In these reactions, the Ni5Zn21 layers were uniformly formed at the interfaces. However, the Ni5Zn21 layer ruptured near the edges of the rectangular Ni substrate and the reaction layers were discontinuous. The cruciform pattern was closely correlated with linear growth of the Ni5Zn21 phase and the tensile stress generated because of the edge geometry. The liquid-state reaction between Sn–9 wt.%Zn and Ni resulted in a crescent shape at the edges because Ni5Zn21 growth was enhanced, owing to its linear growth. Most importantly, cruciform pattern formation also occurred in the solid-state reactions between Sn–Zn and Ni. In the liquid-state reaction between Sn–80 wt.%Zn and Ni, a porous structure and unusually fast growth at the acute-angled corner were observed. The reactions between Cu and Sn–9 wt.%Zn and Sn–80 wt.%Zn were also studied. For these, in contrast, parabolic growth was observed. The reaction layer was uniformly formed at the corners of the Cu substrate, leading to complete coverage.

Study of the Effects of Zn Content on the Interfacial Reactions Between Sn-Zn Solders and Ni Substrates at 250°C

The interfacial reactions of Ni with Sn-Zn alloys with 1 wt.% to 9 wt.% Zn at 250°C were examined. The Zn content greatly affected the intermetallic compounds formed and microstructural evolution. A continuous Ni5Zn21 layer was formed for the Sn-Zn/Ni couples with a Zn content higher than 5 wt.%. A stable reaction layer existed at the interface and grew thicker with time. When decreasing to 3 wt.% Zn, two thin reaction layers of Ni5Zn21 and (Ni,Zn)3Sn4 were simultaneously observed initially, and then an extremely large faceted Ni5Zn21 phase was formed near the boundary between the Ni5Zn21 layer and the solder. Furthermore, when the Zn content was lower than 2 wt.%, the dominant phase changed to (Ni,Zn)3Sn4. The Zn concentration of the solder gradually decreased with reaction, and thus the interfacial stability was reduced. Subsequently, a large amount of (Ni,Zn)3Sn4 grains were dispersed into the molten solder, and finally the reaction product at the interface changed to Ni3Sn4.

Interfacial Reactions of Sn-58Bi and Sn-9Zn Lead-Free Solders with Au/Ni/SUS304 Multilayer Substrate

The liquid/solid interfacial reactions of Sn-58Bi (SB) and Sn-9Zn (SZ) lead-free solders with Au/Ni/SUS304 multilayer substrates have been investigated in this study. In the SB/Au/Ni/SUS304 couple, only the Ni3Sn4 phase with needle-like grains was formed at the SB/Au/Ni/SUS304 interface. The Ni5Zn21 phase with a column structure was formed at the SZ/Au/Ni/SUS304 interface. The thickness of both intermetallic compounds (IMCs) increased with increasing reaction temperature and time. Meanwhile, the growth mechanism of these two IMCs is seen to follow a parabolic law and is diffusion controlled.

Zn-TiO<sub>2</sub> and ZnNi-TiO<sub>2</sub> Nanocomposite Coatings: Corrosion Behaviour

This work presents the corrosion behaviour of the as-prepared of Zn-TiO2 and ZnNi-TiO2 films in neutral Na2SO4 solution and a first attempt to correlate with their composition, morphology and structure. The films were prepared by galvanostatic pulse method onto steel electrodes, at room temperature. The X-ray diffraction study revealed that the ZnNi alloy consists of a homogenous Ni5Zn21 phase and that the preferred crystallographic orientation of Zn deposits changes in the presence of TiO2. The SEM results show that the morphology of the metallic coating is function of the metal phase composition and become more porous in the presence of 1.5 wt% TiO2.The corrosion parameters for the nanocomposite coatings were compared with those of pure Zn and ZnNi electrodeposits, and the ZnNi-TiO2 nanocomposite coating shows the less cathodic corrosion potential.

Effects of Electromigration on Interfacial Reactions in the Ni/Sn-Zn/Cu Solder Interconnect

Electromigration in the Ni/Sn-Zn/Cu solder interconnect was studied with an average current density of 3.51 × 104 A/cm2 for 168.5 h at 150°C. When the electrons flowed from the Ni side to the Cu side, uniform layers of Ni5Zn21 and Cu5Zn8 were formed at the Ni/Sn-Zn and Cu/Sn-Zn interfaces. However, upon reversing the current direction, where electron flow was from the Cu side to the Ni side, a thicker Cu6Sn5 phase replaced the Ni5Zn21 phase at the Ni/Sn-Zn interface, whereas at the Cu/Sn-Zn interface, a thicker β-CuZn phase replaced the Cu5Zn8 phase.

Interfacial reactions in the Sn–9Zn–(xCu)/Cu and Sn–9Zn–(xCu)/Ni couples

Sn–Zn-based alloys are promising low melting-point Pb-free solders, and it has been reported that their wetting properties and oxidation resistance can be improved with the addition of Cu. The interfacial reactions in the Sn–9 wt% Zn–xCu/Cu couples at 250 °C and Sn–9 wt% Zn–xCu/Ni at 280 °C were examined in this study. A thick γ–Cu5Zn8 phase layer and a very thin β′–CuZn phase layer were formed in both the Sn–9 wt% Zn/Cu and the Sn–9 wt% Zn–1 wt% Cu/Cu couples. The γ–Ni5Zn21 phase layer was formed in both the Sn–9 wt% Zn/Ni and Sn–9 wt% Zn–1 wt% Cu/Ni couples. With longer reaction time, the δ–Ni3Sn4 phase were formed in the Sn–9 wt% Zn/Ni couple as well. In both the Cu and Ni couples, the Zn-containing γ phases were uniform and planar and were the dominant reaction products. However, when the Cu content of the Sn–9 wt% Zn–xCu solders was 10 wt%, the interfacial reaction product becomes the η–Cu6Sn5 phase in both the Cu and Ni couples.

Influence of interfacial reaction layer on reliability of chip-scale package joint from using Sn-37Pb and Sn-8Zn-3Bi solder

The microstructure of Sn-37Pb and Sn-8Zn-3Bi solders and the full strength of these solders with an Au/Ni/Cu pad under isothermal aging conditions were investigated. The full strengths tended to decrease as the aging temperature and time increased, regardless of the properties of the solders. The Sn-8Zn-3Bi had higher full strength than Sn-37Pb. In the Sn-37Pb solder, Ni3Sn4 compounds and irregular-shaped Pb-rich phase were embedded in a β-Sn matrix. The Ni3Sn4 compounds were observed at the interface between the solder and pad. The microstructure of the as-reflowed Sn-8Zn-3Bi solder mainly consists of the β-Sn matrix scattered with Zn-rich phase. Zinc first reacted with Au and then was transformed to the AuZn compound. With aging, Ni5Zn21 compounds were formed at the Ni layer. Finally, a Ni5Zn21 phase, divided into three layers, was formed with column-shaped grains, and the thicknesses of the layers were changed.

Analysis on interfacial reactions between Sn–Zn solders and the Au/Ni electrolytic-plated Cu pad

Interface reactions between Sn–Zn lead-free solders and the Au/Ni electrolytic-plated Cu pad after isothermal aging were investigated. The intermetallic compounds at the interface between solder and the Au/Ni electrolytic-plated Cu pad were examined by field-emission scanning electron microscopy and transmission electron microscopy. During the reflow, Zn firstly reacted with Au and then was transformed to the β-AuZn (cubic phase, JCPDS 30-0608) compound in the bottom side of the solder. As aging time increased, γ-Ni5Zn21 (cubic phase, JCPDS 06-0653) compounds were formed on the Ni layer. Finally, the Ni5Zn21 phase divided by three layer was formed with grains of columnar shape, and the thickness of the layers was changed by aging time.