Ni-P Layer Research Articles

Effects of phosphorus content on the reaction of electroless Ni-P with Sn and crystallization of Ni-P

The reaction between electroless Ni-P and Sn and the crystallization behavior of Ni-P were investigated to better understand the effect of P content on the Ni-P layer. Electroless Ni-P specimens with three different P contents, 4.6 wt.%, 9 wt.%, and 13 wt.%, were used to study the effect of the P content and the microstructure of Ni-P on the subsequent crystallization and intermetallic compound (IMC) formation during the reaction between Ni-P and electroplated Sn. Ni3Sn4 was the major phase formed in all samples heated up to 300°C, which totally transformed into Ni3Sn2 when samples were heated up to 450°C and the Sn layer was 0.5-µm thick. The IMC formed on the nanocrystalline Ni-P showed stronger texture compared to that formed on the amorphous Ni-P. Both the IMC thickness and density decreased with P content in the Ni-P layer, and Ni3Sn4 morphologies varied with P content. Dissolution of Ni into Sn increased with P content, which made IMC size in the bulk Sn increase with P content.

Recording Performance of the Perpendicular Recording Media With an Electroless-Plated Ni–P Soft Magnetic Underlayer

An electroless-plated ferromagnetic Ni-P layer, which is suitable for mass production, was employed as a soft magnetic underlayer (SUL) for a double-layered perpendicular recording media. A Ni-P SUL with a thickness range from 1.5 to 3.0 /spl mu/m was plated on the Al substrate, then the surface of the Ni-P SUL was polished about 1 /spl mu/m to obtain a smooth surface with a roughness Ra of less than 0.3 nm. The saturation flux density B/sub s/ and the in-plane coercivity H/sub c/ for the Ni-P SUL were about 0.5 T and 15/spl sim/20 Oe, respectively. Media with a Ni-P SUL at a thickness of more than 0.5 /spl mu/m showed almost the same magnetic properties and recording performances as a medium with a 200-nm thick sputtered CoZrNb SUL. Furthermore, the spike noise commonly observed from an SUL was not found for the media with the Ni-P SUL in this study, indicating great potential for the electroless-plated ferromagnetic Ni-P layer as the SUL of the perpendicular recording media.

Intermetallic compound formation between Sn–3.5Ag solder and Ni-based metallization during liquid state reaction

Ni and its alloys possess a lower reaction rate with Sn than Cu and Cu alloys. Ni-based under bump metallization (UBM) therefore receives considerable attention from the microelectronic packaging industry for the popular flipchip applications. In this work, we study the interfacial reaction of electroless Ni–P (EN) alloy and Ni UBMs with Sn–3.5Ag solder. Morphology and growth kinetics of the formed Ni 3Sn 4 intermetallic compound (IMC) in both systems are investigated under different reflow durations. With the Ni–P alloy as the UBM, needle-type, boomerang-type and chunk-type IMC grains coexist at short reflow time, but only chunk-type grains remain after prolonged reflow. With pure Ni as UBM, only scallop grains with faceted surfaces are found under both short and long reflow durations. The thickness of the intermetallic compound in both UBM systems is measured under different reflow conditions, from which the growth kinetics parameters are obtained. It is found that the IMC growth rate is higher with the Ni–P UBM than with pure Ni UBM. Another difference between the two UBMs is the existence of Kirkendall voids at the interface: the voids are found inside the Ni 3P layer in the Ni–P UBM system after long-time reflow. However, such voids are not observed in the pure Ni UBM system.

Abrasive Wear of DLC/PVD Multilayer Coatings: AFM Studies

AbstractThe tribological behaviour of multilayered coatings deposited on plain carbon steel was investigated by microscale abrasion tests (MSATs). The multilayered coatings consisted of an outer diamond‐like carbon (DLC) layer, a physical vapour deposition (PVD) nitride‐based interlayer, and an inner electroless Ni‐P layer. PVD TiN‐ and Ti(C,N)‐coated samples with and without the DLC outer layer were studied in order to evaluate the influence of each layer on the tribological behaviour of the multilayer‐coated system.The MSATs were carried out using a device based on ball‐cratering geometry: a hard steel sphere was rotated against the coated specimen in the presence of an aqueous suspension of SiC particles. The wear coefficients of the multilayers were calculated from the diameter of the wear craters. The morphology of the wear scars produced by the MSATs was studied by atomic force microscopy (AFM). The wear damage was described by measuring the r.m.s. roughness (Sq) on the sides of the wear craters. Roughness values were related to the wear coefficients (kc) for the different multilayers on the basis of mathematical elaboration typical of the ‘design of experiment’ (DOE) statistical technique. The presence of the DLC outer layer reduced the roughness of the crater sides and significantly increased the wear resistance of the multilayer only in the case of the PVD TiN sublayer.

Growth kinetics of Ni 3Sn 4 and Ni 3P layer between Sn–3.5Ag solder and electroless Ni–P substrate

Interfacial reactions and growth kinetics of intermetallic compound (IMC) layers formed between Sn–3.5Ag solder and electroless Ni–P substrate were investigated at temperature between 100 and 170 °C for up to 60 days. The IMC formed at the interface was mainly Ni 3Sn 4. Also, a P-rich Ni (Ni 3P) layer was observed as a by-product of the Ni–Sn reaction. The Ni 3P layer was between the Ni 3Sn 4 IMC and the electroless Ni–P deposit layer. The thickness results fitted a power-law relationship with exponent of 0.4 for the Ni 3Sn 4 layer. The interface between electroless Ni–P and Ni 3P was planar and the thickness of the Ni 3P layer also was found to increase linearly with the square root of aging time. The thickness of the Ni 3Sn 4 and Ni 3P layer reached about 3 and 2 μm after 60 days of aging at 170 °C, respectively. The activation energy for the growth of the Ni 3Sn 4 IMC equals 49 kJ/mol.

Solid state interfacial reaction of Sn–37Pb and Sn–3.5Ag solders with Ni–P under bump metallization

Thermal aging is one of the accelerated tests for IC package reliability during manufacturing processes and under actual usage conditions. During the process of thermal aging, intermetallic compounds (IMC) grow continuously due to element diffusion, resulting in their morphology change and thickness increase. In this work, the solid state reaction between electroless Ni–P and two types of Sn-based solders (Sn–3.5Ag and Sn–37Pb) has been investigated. Three distinctive layers, Ni 3Sn 4, NiSnP and Ni 3P, were found between the Sn-containing solders and Ni–P under bump metallization. The growth rates of Ni 3Sn 4 IMC at different temperatures were obtained from the aged samples and the activation energy of Ni 3Sn 4 growth was estimated. The kinetic data obtained show that the Ni 3Sn 4 in the Sn–3.5Ag/Ni–P joints grows much faster than with the Sn–37Pb solder under the same condition. Kirkendall voids are found inside the Ni 3P layer after thermal aging. The void formation mechanism is due to net Ni out-flux into the solder area.

Influence of the Interfacial Reaction Layer on Reliability of CSP Joints Using Sn-8Zn-3Bi Solder and Ni/Au Plating

In this study, we used a solder paste of Sn-8Zn-3Bi. The structure and specification of the CSP used in this study are shown in Fig. 1. The composition of the solder ball of the CSP is Sn-3.0Ag-0.5Cu. The CSPs were reflow-soldered on the Cu pad of the FR-4 PCB using Sn-8Zn-3Bi solder paste in air. The surface finish on the Cu pad was Ni-P(5 mm)/ Au(0.05 mm), Ni-P(5 mm)/Au(0.5 mm), or heat-resistant preflux (Fig. 2). The Ni-P layer was formed by electroless plating and the Au layer was formed by substitution plating. Figure 3 schematically illustrates thermal process for reflowsoldering. The reflow profile was composed of preheat at 403423 K for 60 s, followed by 20 s at a temperature above

モデル電極を用いたＡｌへの無電解Ｎｉめっき初期過程の解析

In order to reproduce the initial process of the electroless plating of Ni on Al prepared with a double zincate pretreatment, a model electrode was prepared in which a small Zn tip was pressed to an Al plate. The immersion potential of the model electrode during plating was around-1 V for the first few seconds, which corresponds to the period of Zn dissolution, and then shifted to about-0.6 V which corresponds to electroless Ni plating on the Ni-P layer. By applying pressure to the Zn tip, it became possible to plate the Al specimen without zincate pretreatment. However, an anomalous deposition of Ni was sometimes observed around the Zn tip. This anomalous deposition was found to be formed at damaged areas such as the area to which the Zn tip was applied and the edges of the specimen. When these areas were coated, the time at which Ni deposition began was delayed and the distribution of Ni on the surface became uniform. Based on these results, the function of zincate pretreatment in electroelss Ni plating was considered.

SIMS and XPS Analysis on Displacement Au Layers Formed on Electroless Plated Ni-P Layer

SIMS and XPS Analysis on Displacement Au Layers Formed on Electroless Plated Ni-P Layer

Ａｌ／ＮｉＰディスク上に作製しためっき軟磁性裏打ち層の磁気特性と単磁区化

We propose a noble stacked soft magnetic underlayer (SUL) with the so-called top-type pinning structure, which consists of a soft magnetic layer (SM layer) fabricated by plating and an antiferromagnetic layer (AFM layer) deposited by sputtering, on an Al/NiP disk. Through investigation of the structure and magnetic properties of this stacked SUL, we clarified the following points: (1) the thermal stability of NiFeP plated on an Al/NiP disk is 280°C, which is the crystallization temperature of the amorphous NiP layer; (2) to induce large unidirectial magnetic anisotropy in the SUL, it is necessary to introduce a soft magnetic buffer layer and apply dry etching to the NiFeP surface; (3) a unidirectional magnetic anisotropy field can be induced in an SM layer fabricated by plating as well as in one fabricated by sputtering, which results in the whole disk having a single-domain structure.

Growth of an intermetallic compound layer with Sn-3.5Ag-5Bi on Cu and Ni-P/Cu during aging treatment

Growth kinetics of intermetallic compound (IMC) layers formed between the Sn-3.5Ag-5Bi solder and the Cu and electroless Ni-P substrates were investigated at temperatures ranging from 70°C to 200°C for 0–60 days. With the solder joints between the Sn-Ag-Bi solder and Cu substrates, the IMC layer consisted of two phases: the Cu6Sn5 (η phase) adjacent to the solder and the Cu3Sn (e phase) adjacent to the Cu substrate. In the case of the electroless Ni-P substrate, the IMC formed at the interface was mainly Ni3Sn4, and a P-rich Ni (Ni3P) layer was also observed as a by-product of the Ni-Sn reaction, which was between the Ni3Sn4 IMC and the electroless Ni-P deposit layer. With all the intermetallic layers, time exponent (n) was approximately 0.5, suggesting a diffusion-controlled mechanism over the temperature range studied. The interface between electroless Ni-P and Ni3P was planar, and the time exponent for the Ni3P layer growth was also 0.5. The Ni3P layer thickness reached about 2.5 µm after 60 days of aging at 170°C. The activation energies for the growth of the total Cu-Sn compound layer (Cu6Sn5 + Cu3Sn) and the Ni3Sn4 IMC were 88.6 kJ/mol and 52.85 kJ/mol, respectively.

Retarding growth of Ni 3P crystalline layer in Ni(P) substrate by reacting with Cu-bearing Sn(Cu) solders

The formation of Ni 3P layers in Sn(Cu)/Ni(P) reaction couples were limited compared to Sn/Ni(P). The sluggish growth of the Ni 3P layer was attributed to a Cu–Sn compound layer formed on the Ni(P) substrate, and it depended on the Ni diffusion in the Cu–Sn compound.

Comparative study of the dissolution kinetics of electrolytic Ni and electroless Ni–P by the molten Sn3.5Ag0.5Cu solder alloy

Lead-free solders have high Sn content and high melting temperature, which often cause excessive interfacial reactions at the interface. Sn3.5Ag0.5Cu lead-free solder alloy has been used to identify its interfacial reactions with two-metal layer flexible substrates. In this paper we investigate the dissolution kinetics of Sn3.5Ag0.5Cu solder on electrolytic Ni/electroless NiP layer. It is found that during 1 min of reflow electroless NiP layer dissolves slightly lower than the electrolytic Ni due to the barrier layer formation between the intermetallic compounds (IMCs) and electroless NiP layer. Faster nucleation of IMCs on the electrolytic Ni layer is proposed as the main reason for higher initial dissolution. The appearance of P-rich Ni layer acts as a diffusion barrier layer between the solder and electroless NiP layer, which decreases the dissolution rate and IMCs growth rate than that of the electrolytic Ni layer, but weaken the interface and reduces the ball shear strength and reliability. After acquiring certain thickness P-rich Ni layer breaks and increases the diffusion rate of Sn and as a consequence both the IMCs growth rate and dissolution rate also increases. It is found that 3 μm thick electroless NiP layer cannot protect the Cu layer for more than 120 min at 250 °C. In electrolytic Ni shear strength does not change significantly and lower dissolution rate and more protective for Cu layer during long time molten reaction.

Direct Plating of Electroless Ni-P Layers on Sputter-Deposited Al-Ni Alloy Films

Direct plating of electroless Ni-P layers on Al-Ni alloy films formed on glass substrates was performed using magnetron-sputtered deposition and ion beam-assisted deposition methods. Dissolution of Al from the alloy films occurred in the initial stage of the plating process and resulted in enrichment of Ni on the surface. Since Ni acts as a catalyst for the Ni-P deposition reaction, Ni-P deposition occurs on the alloy surface without zincate pretreatment. In the case of an Al-10Ni alloy film, however, Ni clusters dropped from the Al-Ni alloy surface, and Ni-P particles grew in the plating bath, causing dissipation of chemicals in the bath. Such particles also readhered to the surface, resulting in a nonuniform plating layer. A lower concentration of Ni in an alloy such as an Al-3Ni or Al-1Ni alloy resulted in a rather smooth plating surface. In the case of a neutral plating bath containing a low concentration of P, cone structures were formed in the plating layer. Such structures seem to form at the nucleation sites of Ni deposition in the initial stage of the plating process. © 2003 The Electrochemical Society. All rights reserved.

Interfacial reaction of Pb-Sn solder and Sn-Ag solder with electroless Ni deposit during reflow

The interfaces between electroless Ni-P deposit and Pb-Sn solder and Sn-Ag solder were formed by reflowing for different time periods to examine their microstructures and microchemistry. It was found that the Pb-Sn solder interface is more stable than the Sn-Ag solder interface. Sn-Ag solder reacts quickly with the electroless Ni-P deposit and forms nonadherent Ni-Sn intermetallic compounds (IMCs). Pb-Sn solder reacts slowly and forms adherent Ni-Sn IMC. A P-rich Ni layer, revealed as a dark layer under scanning electron microscopy (SEM), is formed on the electroless Ni-P deposit due to the solder reaction. For short reflow times, this P-rich Ni layer consists of only Ni3P compound, but during prolonged reflow, new crystals of Ni2P, Ni5P4, and NiP2 are also found to be formed from the amorphous electroless Ni-P layer.

Electrochemical impedance measurements on Ni–P coated magnesium alloy, chromated magnesium alloy, and anodised aluminium alloys in aqueous salt solutions

Both electroless nickel coated and chromated surfaces of magnesium alloy AZ 31 and hydrothermally sealed anodised surfaces of unalloyed aluminium Al-2S and aluminium alloy 6061 have been prepared and the corrosion behaviour of these surfaces in aqueous K Cl and K2SO4 solutions has been studied using electrochemical impedance spectroscopy (EIS). The effect of the concentration of hypophosphite in the plating bath used for electroless plating on the Ni-P layers formed and their corrosion behaviour has also been studied. The EIS studies have shown that the diffusion of ionic species is less for yellow chromated surfaces of magnesium alloy than for black chromated ones. In the case of anodised aluminium surfaces, impedance values are much higher in KCl than in K2SO4 solutions. The effect of anodising time on pore resistance R po and barrier capacitance Cb has also been studied. Data from EIS indicate that the pore resistance of aluminium alloys A1-2S and AA 6061 attains a saturation value after anodisation for ~45 min.

The Influence of Phosphorus Concentration of Electroless Plated Ni-P Film on Interfacial Structures in the Joints between Sn-Ag Solder and Ni-P Alloy Film

The interface structure between Sn-3Ag solder and electroless plated Ni film and the structure near that interface were examined. Plated electroless Ni films contained 3.7 mass% phosphorus or 8.5 mass% phosphorus. A P-enriched layer is formed at the joining interface between plated electroless Ni film and Sn-3Ag solder, in each sample with 3.7 mass%P and 8.5 mass%P. P-enriched layers of both P concentration samples contained double the P concentration than the original plated Ni films. Also, the P-enriched layer of the Ni-8.5 mass%P sample was much thicker than that of the Ni-3.7 mass%P sample. Both P-enriched layers have been composed of Ni-Sn-P layer and P enriched Ni-P layer. Kirkendall voids were formed between the 1st Ni-Sn-P layer and 2nd Ni-P layer. The number of voids observed in Ni-8.5 mass%P sample was much greater than those in the Ni-3.7 mass%P sample. Intermetallic compounds, mixtures of Ni 3 Sn 2 and Ni 3 Sn 4 , were formed by the interfacial reaction. In the case of the Ni-3.7 mass%P sample, Ni-Sn intermetallic compounds continuously crystallized on the P-enriched layer, while in the case of the Ni-8.5 mass%P sample, Ni-Sn intermetallic compound crystallized dispersively in the solder.

The effects of NiP seed layer in Co-alloy perpendicular thin film media

The effect of NiP seed layer on CoCrPt perpendicular recording media has been studied. It was observed that the well isolated, small cluster of amorphous NiP layer helped to reduce the grain size, and the grain size distribution of the CoCrPt magnetic layer. The improvement in grain size and distribution also lead to better magnetic and recording properties.

Effects of nitrogenated NiP seedlayer on Co-alloy thin film media

In this study, nitrogen gas was introduced during deposition of NiP seedlayer for Co-alloy thin film media. Thermal stability and magnetic switching volume for thin film media with different nitrogen content in NiP seedlayer and NiP-N seedlayer thickness were studied using dynamic coercivity measurements. It was found that nitrogenated NiP seedlayer could further enhance the effects of magnetic decoupling and magnetic switching volume reduction that has been demonstrated by NiP before. Delta-M peak and domain size for Co-alloy thin film media were significantly decreased when nitrogenated NiP is used as a seedlayer. Surface roughness of NiP layer was also reduced when nitrogen gas is introduced.

Characterization of nano-wear mechanisms of hard disk coatings

The wear mechanisms of carbon coated computer hard disks with laser-textured (LT) and mechanically-textured (MT) surfaces were characterized after contact start/stop (CSS) cyclic tests. Various analytical and mechanical testing techniques were employed to study the changes in topography, roughness, chemical elements, mechanical properties, and friction characteristics of the coating and lubricant. These techniques include: the atomic force microscopy (AFM), continuous nano-indentation test, nano-scratch test, time-of-flight secondary ion mass spectroscopy (TOF-SIMS), and Auger electron spectroscopy (AES). The CSS test at 15 k cycles resulted in tangible reductions of surface roughness of approximately 3.0 nm and 5.8 nm, respectively, for the LT bump and MT zone. The elastic modulus and hardness values increased after the CSS test, indicating strain hardening of the top coating layer. A critical load was identified for adhesion failure between the magnetic layer and the Ni-P layer. The TOF-SIMS analysis also revealed reductions in the intensities of all lubricant elements, indicating wear of the lubricant applied on the disk surface. All foregoing results confirm the usefulness of the characterization techniques employed to detect the subtle changes in disk surface characteristics.