Ni-P Layer Research Articles

Effect of gamma radiation on oxidation of electroless Ni-P deposited on stainless steel st. 304

The given work deals with the effect of gamma-irradiation on the oxidation process of the Ni-P che-mical deposition on the surface of the stainless steel marked 304. The methods used are scanning electron microscopy and X-ray analysis. As a result, it has been found out that after gamma-irradiation the surface of the Ni-P layer is completely covered with cracks, and on the surface of this layer a high content of oxygen and phosphor has been detected because of formation of the P2O5 oxide.

Improving the grain structure and adhesion of Ni-P coating to 3004 aluminum substrate by nanostructured anodic film interlayer

Two different types of interlayers were produced on aluminum alloy specimens prior to electroless nickel coating in an attempt to improve the structure and adhesion of such coatings to aluminum substrates. The amorphous Ni-P layer of medium phosphorous content was deposited on 3004 aluminum alloy sheet either without interlayer or over an interlayer of a zinc coating (zincate process) or an oxide coating (anodizing process). Formation of the nickel electroless coating and the effect of heat treatment were evaluated by x-ray diffraction (XRD) and microanalysis (EDS). The surface morphology and topography of the coatings were characterized by scanning electron microscope (SEM) and atomic force microscope (AFM). Adhesion of the coatings to aluminum substrate was qualitatively evaluated by the bend test. It was observed that application of a nano-porous aluminum anodic oxide as an interlayer caused a much finer morphology of Ni-P electroless coating. In addition, this interlayer effectively increased the adhesion of coating to aluminum surface; the crack density calculated after the bend test was about four times that obtained in the specimen with zincate interlayer and six times more than without interlayer.

Replacement Deposition of Ni-S Films on Cu and Their Catalytic Activity for Electroless Nickel Plating

A Ni-S film was prepared on Cu substrate via the replacement reaction due to the quite negative electrode potential of Cu in high concentrated thiourea solution. A lower pH environment was facilitated to form more uniform Ni-S film. The sulfur content in the Ni-S film increased with the increase of deposition time and the rise of pH in solution. Relative to pure Ni, the existence of sulfur in the Ni-S film was found to result in different electrochemical properties. More importantly, constant current discharge curve and anodic polarization curve measurements indicated that the Ni-S film with higher sulfur content was more prone to be passivated, with negative influences on its catalytic activity. Polarization curve, electrochemical impedance spectroscopy and open circuit potential measurements were employed to investigate the catalytic activity of the Ni-S film for hypophosphite oxidation and electroless nickel (EN) plating. With the optimization of sulfur content by plating conditions, we could significantly improve the catalytic activity of the Ni-S film for hypophosphite oxidation and consequently for EN plating. Compared with the traditional Pd film, the Ni-S film exhibited a comparable catalytic activity, with a uniform electroless Ni-P layer obtained during the EN plating.

An X-ray Radiography Study of the Effect of Thermal Cycling on Damage Evolution in Large-Area Sn-3.5Ag Solder Joints

There is a need for next-generation, high-performance power electronic packages and systems utilizing wide-band-gap devices to operate at high temperatures in automotive and electricity transmission applications. Sn-3.5Ag solder is a candidate for use in such packages with potential maximum operating temperatures of about 200°C. However, there is a need to understand the thermal cycling reliability of Sn-3.5Ag solders subject to such high-temperature operating conditions. The results of a study on the damage evolution occurring in large-area Sn-3.5Ag solder joints between silicon dies and direct bonded copper substrates with Au/Ni-P metallization subject to thermal cycling between 200°C and 5°C are presented in this paper. Interface structure evolution and damage accumulation were followed using high-resolution X-ray radiography, cross-sectional optical and scanning electron microscopies, and X-ray microanalysis in these joints for up to 3000 thermal cycles. Optical and scanning electron microscopy results showed that the stresses introduced by the thermal cycling result in cracking and delamination at the copper–intermetallic compound interface. X-ray microanalysis showed that stresses due to thermal cycling resulted in physical cracking and breakdown of the Ni-P barrier layer, facilitating Cu-Sn interdiffusion. This interdiffusion resulted in the formation of Cu-Sn intermetallic compounds underneath the Ni-P layer, subsequently leading to delamination between the Ni-rich layer and Cu-Sn intermetallic compounds.

Electromigration Study on Sn(Cu) Solder/Ni(P) Joint Interfaces

This study investigates the electromigration (EM) effect under a high current density (104 A/cm2) on the different interfacial compound phases at Sn(Cu) solder/electroless nickel immersion gold (ENIG) interfaces. The interfacial Ni3Sn4 phase at the Sn-0.7 wt.%Cu/ENIG joint interface was quickly depleted after a short period (50 h) of current stressing. The inference drawn is that the Ni atoms in the Ni3Sn4 phase at the joint interface are likely forced out under current stressing; however, the ternary (Cu,Ni)6Sn5 compound effectively reduces the EM-driven Ni flux into the Sn bump; thus, a significantly lower Ni(P) consumption was observed at the Sn-1 wt.%Cu/ENIG interface. The EM-induced Ni(P) dissolution rates in the Sn-0.2 wt.%Cu/ENIG and Sn-1 wt.%Cu/ENIG cases were calculated to be 0.028 μm/h and 0.018 μm/h, respectively. In addition, significant EM-assisted Ni3P formation was observed for the current-stressed Sn-0.2 wt.%Cu/ENIG and Sn-0.7 wt.%Cu/ENIG cases; however, for the Sn-1 wt.%Cu/ENIG case, formation of a Ni3P layer was scarcely observed. Moreover, the initial (Cu,Ni)6Sn5 that formed at the interface appeared compact with a layer-type structure, which reduced the EM-driven Ni diffusion.

Ni-Px/C 다층 도금층의 내식성과 표면 전기저항 평가

Research Center, Jiodeco Co. Ltd.(Received August 14, 2012 ; revised August 29, 2012 ; accepted August 30, 2012)Abstract Ni-P/C multi-layer was synthesized by electroless plating and paste coating for better corrosion and surfaceconductance as a metallic bipolar plate. The Ni-P layer could be synthesized with the range of 2.6~22.4at.% P contents and it's surface morphology and corrosion resistance depend on content of P. Corrosion resis-tance of the Ni-P layer in sulfuric acid by electrochemical test is similar with pure Ni. Surface resistanceof pure Ni after corrosion was increased about 8% compared to pure Ni. On the other hand, that of theNi-P/C composite with 20% carbon content was increased only 1%.

Effect of Alloying Elements on the Microstructure and IMC Formation of SnAgCu Solder on Ni (P) Substrate

When the use of lead was banned, the development of lead-free solders began to rise and was greatly explored. Presently, majority of the eutectic Pb-free solders are Sn-based and the most promising is ternary SnAgCu (SAC) solder. However, SnAgCu solder tends to become brittle in nature and excessive solder interfacial reactions. An attractive approach is by introducing alloying elements such as Ce, Fe and Zn into the SnAgCu solder, which allows for an increase of the mechanical properties and refine the solder microstructure as well as improve the wetting properties. The present work focuses on the effects of a series of elemental additions of 0.5% Ce, Fe and Zn into the basic Sn3.0Ag0.5Cu solder, in attempt to reduce the intermetallic compound (IMC) growth as well as joint reliability and reflow properties of the solder on Ni-P surface finish. The intermetallic compound Cu6Sn5, containing a small amount of dissolved Ni, was found to form preferentially on the Ni coating. This compound layer served as a barrier for direct reaction of Sn with the Ni-P coating. The P-rich Ni layer acts as a good diffusion barrier layer, which decreases the dissolution rate of the Ni-P layer hence decreases the growth of IMC thickness layer. It is also expected that with the addition of alloying elements, the wetting properties will be further enhanced.

Improvement of Adhesion Strength of Electroless Nickel Coating on AZ91D by Anodized Oxide Interlayer

Nickel-oxide duplex coatings were successfully deposited on magnesium alloy (AZ91D) by anodizing and electroless nickel-phosphorus plating processes. The anodizing interlayer was used to increase the adhesion strength of Ni-P layer. The electroless Ni-P coating enhances the corrosion resistance of the anodic oxide layer. Specimen of AZ91D magnesium alloy was polished firstly. The anodizing process was preceded in alkaline anodizing solution at 24 °C, and the bath voltage maintained at 70 volts for 2 hours. Successive electroless Ni-P plating was used to achieve the sandwich structure. The surface morphologies of the coatings were observed by field-emission scanning electron microscopy (FE-SEM). The adhesion strength was measured by pull-off tester. The electrochemical behavior of coatings with corrosion resistance in 3.5 wt.% NaCl solution was evaluated by potential polarization curve. The experimental results showed that the adhesion strength of directly deposited coating and duplex coating were 115.4 kgf/cm2 and 142.2 kgf/cm2, respectively. The adhesion strength of coatings on AZ91D magnesium alloy was improved by the synergistic effect between anodized magnesium oxide and Ni-P layer in duplex coating.

A novel high-speed shear test for lead-free flip chip packages

Despite the importance of lead-free solders in modern environmentally friendly packaging, few studies have been conducted on their mechanical reliability at the wafer level. In the present study, high-speed die shear tests were conducted to investigate the effects of strain rate on the shearing resistance and fracture mode of Sn-3wt%Ag-0.5wt%Cu solder joints on electroless Ni-P/immersion Au surface finish pads. The results indicated that the solder joints underwent ductile and mixed ductile-brittle fracture at low ( 25,385 s−1) strain rates, respectively. Thus, the overall shear stress-strain curve can be divided into three areas according to Hollomon’s law, starting from low strain rates: area I, 100% ductile fracture of the solder itself; area II, mixed ductile-brittle fracture resulting in a ductile-brittle transition region; and area III, 100% brittle fracture at the interface between the intermetallic compound and the Ni-P layer.

Deposition of a Ni3P nano-scale layer on B4C nanoparticles by simple electroless plating in an acidic bath

In this study, deposition of a Ni3P nano-scale layer on B4C nanoparticles via simple electroless plating in an acidic bath was investigated. B4C nanoparticles were produced by mechanical milling with the average size of about 95 nm. Electroless nickel plating was carried out at temperature and pH of 85°C and 5.5, respectively. The uncoated and composite powders were characterized by transition electron microscope and the phases present were revealed by X-ray diffraction. Also, nickel and phosphorous contents of the coating were measured by inductively coupled plasma analysis. The results confirmed deposition of a Ni3P layer with the average thickness of about 25 nm on B4C nanoparticles.

Improved Anode Performance of Ni-P-Coated Si Thick-Film Electrodes for Li-Ion Battery

To improve the deviation of cycling performances as Li-ion battery anode, we controlled the morphology of Ni-P layers deposited on Si particles in thick-film electrodes prepared by a gas-deposition method. The spotty Ni-P layers were uniformly coated on Si particles by an electroless deposition in a neutral bath. The resulting electrodes using Ni-P-coated Si exhibited excellent cycling performances and their good reproducibility. The reason for the improvement of performances is probably that the Ni-P layers can effectively release a stress generated by alloying/dealloying reactions of Li with Si.

Effect of electromigration on interfacial reaction in Ni/Sn3.0Ag0.5Cu/Au/Pd/Ni-P flip chip solder joints

The effect of electromigration (EM) on the interfacial reaction in the Ni/Sn3.0Ag0.5Cu/Au/Pd/Ni-P flip chip solder joint is investigated under a current density of 1.0× 104 A/cm2 at 150℃. The (Cu,Ni)6Sn5 intermetallic compounds (IMCs) form at both solder/Ni and solder/Ni-P interfaces in the as-reflowed state. During aging at 150℃, the (Cu,Ni)6Sn5 interfacial IMCs grow thicker and transform into (Ni,Cu)3Sn4 type after 200 h at solder/Ni interface and 600 h at solder/Ni-P interface, respectively. During EM, the current direction plays an important role in Ni-P layer consumption. When electrons flow from Ni-P to Ni, EM enhances the consumption of Ni-P, i.e., the Ni-P s completely consumed and transforms into Ni2SnP after EM for 600 h. There is no Cu-Sn-Ni ternary IMC at the solder/Ni-P interface (cathode). Crack forms at the Ni2SnP/Cu interface due to the weak bonding force between Ni2SnP and Cu. When electrons flow from Ni to Ni-P, no obvious consumption of Ni-P is observed during EM; the current crowding effect induces a rapid and localized dissolution of Ni UBM and Cu pad at the chip side (cathode). The dissolved Ni and Cu atoms are driven along the flowing direction of electrons and form a large number of IMC particles in the solder matrix. During EM, the (Au,Pd,Ni)Sn4 phase prefers to be redistributed only at the anode interface, regardless of the direction of electron flow.

Current-induced interfacial reactions in Ni/Sn–3Ag–0.5Cu/Au/Pd(P)/Ni–P flip chip interconnect

Abstract

Suppressing Ni 3Sn 4 formation in the Sn–Ag–Cu solder joints with Ni–P/Pd/Au surface finish

The interfacial reactions of Sn–3.0Ag–0.5Cu solder jointed with electroless Ni–P/immersion Au (ENIG) and electroless Ni–P/electroless Pd/immersion Au (ENEPIG) were investigated. Cu 6Sn 5 grew rather slower in ENEPIG samples among all aging conditions as compared with ENIG. Furthermore, the second phase, Ni 3Sn 4, started to form in the ENIG aged joints, but not in the ENEPIG aged joints. It was demonstrated that ENEPIG could inhibit the formation of Ni 3Sn 4, which further decreased the growth of columnar Kirkendall voids inside the Ni 3P layer. With less voids formed in the Ni 3P layer, it is expected that the reliability of ENEPIG joints would be superior to that of ENIG joints. Detailed mechanisms of Ni 3Sn 4 suppression and void formation were discussed and proposed.

Effect of Laser Power on the Microstructure of Ni-P Layer Deposited on Aluminum Substrate

Laser processing of Ni-P layer electroless deposited on aluminum substrate was carried out by Nd-YAG pulsed laser. Different laser processing parameters were selected. When lower laser power density was employed, the modified Ni-P layer was obtained, however, when employed laser power density increased, laser alloying of Ni-P layer with aluminum substrate occurred. The characteristic dendritic or lamellar microstructures were observed in the alloyed layer. The phase constituents of the alloyed zones determined by X-ray diffraction are consisted of nickel-aluminum intermetallic compounds NiAl, Al3Ni and Al3Ni2, as well as some non-equilibrium phases, depending on the employed laser power density.

Investigation of Interfacial Reactions and Sn Whisker Formation in the Matte Sn Layer With NiP/Ni/Cu and Ni/Cu Multilayer Systems

This paper investigates the relationship between the interfacial reactions and Sn whisker formation in the matte Sn layer in NiP/Ni/Cu and Ni/Cu multilayer systems. All specimens were first reflowed at 250°C for 10 min and then aged at 150°C for 500 h. Sn whiskers were found only in the Sn/Ni/Cu multilayer specimen. Ni from the NiP layer was consumed to form the Ni3Sn4 phase in the Sn/NiP/Ni/Cu specimen. Thus, the phosphorous (P) atoms segregated at the interface and reacted with Ni and Sn atoms to form the Ni-P-Sn ternary phase between the phase and NiP layer. This Ni-P-Sn ternary phase acted as a diffusion barrier and decreased the diffusion rate and diffusion flux of the Ni atoms. The compressive stress induced by the flux of the Ni atoms was the driving force resulting in Sn whisker growth. The Ni-P-Sn ternary can inhibit this compressive stress. That is why no Sn whiskers were found in the Sn/NiP/Ni/Cu multilayer specimen.

Interfacial Reaction of Ni (P)-Sn Coating on Magnesium

Hot dip tin coating was obtained on AZ91D magnesium alloy surface, and interfacial reactions between Sn coating and electroless Ni-P plating was studied. The results show: after 220±5°C, 2h diffusion, the intermetallic compounds possessed corresponding thickness, and Ni3P layer along the interface acted as a good diffusion barrier between Sn and Ni. When Ni3Sn4 spread to the surface, microcracks were observed on the surface. Corrosion resistance of Ni(P)-Sn coating before and after diffusion was investigated with polarization curves. The results show: Ni(P)-Sn coating significantly enhance the corrosion potential of base material, but after the Ni3Sn4 growth to the surface, it caused electrochemical corrosion and decreased the corrosion resistance.

Interdependent Intermetallic Compound Growth in an Electroless Ni-P/Sn-3.5Ag Reaction Couple

The interfacial microstructure of electroless Ni-P/Sn-3.5Ag solder joints was investigated after reflow and high-temperature solid-state aging to understand its interdependent growth mechanism and related kinetics of intermetallic compounds (IMCs) at the interface. The reflow and aging results showed that mainly three IMC layers, Ni3Sn4 ,N i 2SnP, and Ni3P, formed during the soldering reaction. It was found that the Ni3Sn4 and Ni3P layers grow predominantly as long as the electroless Ni-P layer is present; however, once the Ni-P layer is fully consumed, the Ni2SnP layer grows rapidly at the expense of the Ni3P layer. A transition in the Ni3Sn4 morphology from needle and chunky shape to scallop shape was observed after the solid-state aging of reflowed samples. The kinetics data obtained from the growth of compound layers in the aged samples revealed that initially the growth of the Ni2SnP layer is controlled by diffusion, and subsequently by the rate of reaction after the Ni-P metallization is fully consumed. It was found that complete transformation of the electroless Ni-P layer into a Ni3P layer results in the rapid growth of the Ni2SnP layer due to the dominating reaction of Sn with Ni3P. The apparent activation energies for the growth of Ni3Sn4 ,N i 2SnP, and Ni3P compound layers were found to be 98.9 kJ/mol, 42.2 kJ/mol, and 94.3 kJ/mol, respectively.

The High Thickness Ni Layer on Single-Walled Carbon Nanotubes Prepared by an Electroless Coating Process

The Single-walled carbon nanotubes were coated with Ni-P layers by an electroless plating technique. A Ni-P layers are thick and smooth and on individual nanotube with thickness of 20 nm can be obtained after the deposition process. The Single-walled carbon nanotubes were obtained in the suspension of purification solution. The samples have been characterized by X-ray diffraction, selected area electron diffraction, transmission electron microscopy and energy dispersive spectrometry.The coating layers after heat-treatment convert the amorphous Ni-P coated layers into the nanocrystalline Ni-P layers.

The pH effect on black spots in surface finish: Electroless nickel immersion gold

In order to understand the black spot generation after electroless nickel immersion gold (ENIG) plating, we investigated the pH effect with a combined approach of experiments and computer aided engineering (CAE). As the pH is increased in IG plating solution, the deprotonation of citric acid as chelating agent is enhanced to stabilize the solution by producing Ni–citrate complex ion. For the substitution reaction between nickel and gold, excess citrate ions (deprotonated citric acids) are adsorbed along nodal boundaries of Ni-P layer to decrease the surface reactivity. Since the low reactivity decreases the overall growth rate, the resulting homogeneous Au layer growth avoids the unfavorable galvanic cell corrosion to control black spot. Based on molecular orbital method and kinetic Monte Carlo calculation, our computational approach well explained the capability of citric acid as chelating agent and the Au growth rate along the nodal boundaries of Ni-P layer depending on the surface reactivity.