The effect of pH on synthesizing Ni-decorated MWCNTs and its application for Sn-58Bi solder

Nickel-decorated multi-walled carbon nanotubes (Ni-MWCNTs) were synthesized using a colloidal method and an electroless plating method to form Ni nanoparticles on the surface of MWCNTs. The Ni electroless plating process was optimized with solutions at various pH (5, 6, 7, and 8) levels. The Ni-MWCNTs fabricated at pH 7 show the most stable Ni nanoparticles on the surface of the MWNCTs. After optimization of the Ni plating process, the Ni-MWCNTs/Sn-58Bi composite solder were fabricated with varying contents of (0, 0.05, 0.1 and 0.2 wt%) Ni-MWCNTs. The experimental results show that Ni-MWCNTs enhance the mechanical properties of Sn-58Bi solder. The shear strength of Sn-58Bi solder improves by about 14% with 0.1 wt% Ni-MWCNTs. Furthermore, the microstructure evolution after a high temperature storage test shows that Ni-MWCNTs have an effect on grain refining and interrupt growth of the Intermetallic compound layer. The distribution of Ni-MWCNTs could be recognized with the results of EPMA.     

Model of electroless Ni deposition on SiCp/Al composites and study of the interfacial interaction of coatings with substrate surface

Metallization techniques based on electroless plating are used to coat SiC_p/Al composite materials. The directly palladium chloride (PdCl₂) solutions in HCl is used to render the surface of such non-conductive substrates catalytically active towards metal deposition in the electroless plating solution. The microstructures of Ni-coated composites provided by scanning electron microscope (SEM) bring light into the palladium activation and electroless coating process. Also, X-ray photoelectron spectroscopy (XPS) and Line-scan have allowed to monitor the chemical and compositional surface modifications of activated and coated SiC_p/Al composites, as well as to understand the mechanisms of the catalyst (palladium species) chemisorption on the composites surface and the interaction mechanisms of Ni layer with the SiC_p/Al composites. The experimental results show that a nickel-substrate bonding action takes place during plating. Ni atom existing on the surface of the composites can partially obtain electrons from metals Al of the SiC_p/Al composites when the substrate is embedded in the Ni layers, that is, the orbital interaction through the mutual overlap of the electronic orbits does exist in the interfacial regions between the coated Ni atoms and composites substrate instead of the mechanical-interlocked form. On the basis of the evidence, a model of electroless Ni deposition on SiC_p/Al composites is submitted including Pd activation and Ni deposition processes to describe the formation of catalytic centers and the growth of deposited layer. The deposition model reveals that metal-substrate bond plays an important role in the high adhesion strength between the Ni coatings and the composites.     

Selective electroless nickel deposition on copper as a final barrier/bonding layer material for microelectronics applications

A low cost, selective electroless metallisation of integrated circuit (IC) copper bond pads with nickel and gold is demonstrated. This metallurgy can function as a barrier layer/bondable material when deposited as a thin layer or as the chip bump for flip chip applications when deposited to greater heights. Four alternative activation steps for selective electroless nickel deposition on bond pad copper are demonstrated. Selective low cost deposition has been achieved with a proprietary electroless plating bath developed at NMRC and three commercial baths on both sputtered copper substrates and electrolessly deposited copper on titanium nitride barrier layer material.     

An investigation of smooth nano-sized copper seed layers on TiN and TaSiN by new non-toxic electroless plating

The purpose of this research is to explore the properties of a copper seed layer grown by electroless plating on TiN. We have developed a displacement layer made of amorphous silicon (a-Si) and copper contact displacement process to improve the island structure of copper activated layer which can then be grown directly on the surface of TiN. Furthermore, this research proposes glyoxylic acid as replacements to formaldehyde, which is commonly used at present as a reductant but regarded as a carcinogen, and is of high volatility. The copper seed layer has been grown by electroless plating on an activated surface of TiN, at the set temperature of 60 °C with the plating bath consisting of the copper source, complexing agent, stabilizer and surfactant. The existence of a copper seed layer provides not only the conduction layer, but also the copper nucleation layer, to help the growth of electroplated copper on the surface of TiN. Moreover, based on the results of the studies can lead us to grow a smooth nano-sized Cu seed layer on the top of a TaSiN layer.     

Preparation of Sn films deposited on carbon nanotubes

In this work carbon nanotubes were first grown on copper substrate by chemical vapor deposition method. The Sn deposits were then deposited on the surface of as-grown carbon nanotubes by three different methods: electroplating, electroless plating and displacing methods. The Sn deposits on CNTs surface were characterized by both scanning electron microscope and field emission scanning electron microscope. The compositions of Sn deposits were analyzed by energy dispersive X-ray spectroscope. The results showed that both electroless plating and displacing deposits can but the electroplating deposits cannot cover on the surface of CNTs. Besides C, Sn, Ni and Pd, the electroless deposits also contain element of oxygen and the displacing deposits also contain elements of copper and oxygen.     

Optimization of microvia-technology using excimer laser for build-up layer application in microelectronics

In interconnection microelectronics microvias play a key role in the manufacture of high-density circuitry for use in electronic systems such as portable, smart sensors and computing applications. In the current work an excimer laser is used and microvias in the dielectric of the build-up layer are generated with the mask imaging method. Different laser parameters (demagnification factor, energy transmission percentage, fluence) are optimised in order to obtain microvias with different diameters, taper angle and aspect ratio. With electrochemical Cu-deposition interconnections between the upper and the underlying circuitry are realised. A nearly uniform thickness of the plated copper is obtained, and quality of the plating is assessed by means of the degree of delamination of the electrochemically deposited copper.     

Electroless plating of copper on surface-modified glass substrate

This work focuses on developing a novel convenient method for electroless copper deposition on glass material. This method is relied on the formation of amino (NH₂)-terminated film on the surface of glass substrate, by coating polyethylenimine (PEI) on glass matrix and using epichlorohydrin (ECH) as cross-linking agent. The introduced amino groups can effectively adsorb the palladium, the catalysts which could initiate the subsequent Cu electroless plating, onto the glass substrate surface. Finally, a copper film is formed on the palladium-activated glass substrate through copper electroless plating and the surface-coppered glass material is therefore acquired. X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscopy (SEM) images combined with energy diffraction X-ray (EDX) analysis demonstrate the successful copper deposition on the surface of glass substrate.     

Multiple activation of ion track etched polycarbonate for the electroless synthesis of metal nanotubes

In our study, we examined the formation of thin films of silver nanoparticles on polycarbonate and the influence of the silver loading on the electroless synthesis of metal nanotubes. Control of the silver film thickness occurred by consecutive dipping of the polymer template in tin(II) and silver(I) solutions. The deposition progress was studied using UV-Vis spectroscopy. The reaction mechanism relies on the adsorption of reactive ions on the polymer template as well as on the silver nanoparticles. The initial catalytic activity of silver-covered ion track etched polycarbonate is an important governing factor for the electroless synthesis of metal nanotubes with desired thickness and shape. Therefore, the presented method allows specific template preparation according to given synthetic demands. High aspect ratio copper, gold, and platinum nanotubes were produced by the combination of sufficiently activated templates with optimized electroless plating procedures.     

X-ray fluorescence method for determining the mass absorption coefficient in two-layer thin-film Ti/Ge and Ni/Ge systems

We propose a new method for determining the mass absorption coefficient in x-ray fluorescence analysis of two-layer thin-film Ti/Ge and Ni/Ge systems using easily made standardized film layers obtained by deposition of titanium or nickel on a polymer film substrate. We calculate correction factors taking into account absorption of primary emission from the x-ray tube and absorption of the analytical line for an element of the bottom layer in the top layer.     

Fabrication of microelectrodes deeply embedded in LiNbO3 using a femtosecond laser

We present a novel technique to fabricate deeply embedded microelectrodes in LiNbO₃ using femtosecond pulsed laser ablation and selective electroless plating. The fabrication process mainly consists of four steps, which are (1) micromachining of microgrooves on the surface of LiNbO₃ by femtosecond laser ablation; (2) formation of AgNO₃ films on substrates; (3) scanning the femtosecond laser beam in the fabricated microgrooves for modification of the inner surfaces; and (4) electroless copper plating. The void-free electroless copper plating is obtained with appropriate cross section of microgrooves and uniform initiation of the autocatalytic deposition on the inner surface of grooves. The dimension and shape of the microelectrodes could be accurately controlled by changing the conditions of femtosecond laser ablation, which in turn can control the distribution of electric field inside LiNbO₃ crystal for various applications, opening up a new approach to fabricate three-dimensional integrated electro-optic devices.     

Comparative study of electroless copper deposition based on the seed layers of Pd, PtPd and AuPd

The article reports on electroless deposition of copper films onto p-silicon (1 0 0) using different seed (co-seed) layers of Pd, PtPd and AuPd. The dependence of the compositions and morphologies of different seed layers on resultant Cu films were comparatively studied in detail by atomic force microscopy (AFM), field emission scanning electron microscope (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The activities of electroless copper deposition on the p-silicon (1 0 0) with different seed (co-seed) layers were evaluated by polarization curve. It is concluded that the bimetallic AuPd seed displayed the highest catalytic activity for electroless copper deposition, and followed by the order of PtPd > Pd.     

Preparation and magnetic properties of polymer magnetic composites based on acrylate resin filled with nickel plating graphite nanosheets

Nickel plating graphite nanosheets (Ni/GNs) were prepared by electroless plating method using graphite nanosheets (GNs). Then a novel polymer magnetic composites based on acrylate pressure-sensitive adhesive (acrylate PSA) filled with Ni/GNs were fabricated by solution blend method. The Ni/GNs and acrylate PSA/Ni/GNs composites were characterized by scanning electron microscope (SEM)/energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and transmission electron microscope (TEM). All results showed that relatively uniform and compact Ni layer is successfully coated onto GNs under the given conditions, furthermore, Ni/GNs are homogeneously dispersed in acrylate PSA. The VSM results showed that the saturation magnetization of acrylate PSA/Ni/GNs composites increases with an increasing content of Ni/GNs while the coercivity decreases with an increasing content of Ni/GNs. When the content of GNs is 20 wt%, acrylate PSA/Ni/GNs composites exhibites good mechanical properties.     

A plating method for metal coating of fiber Bragg grating

We present a method for metal coating optical fiber and in-fiber Bragg grating. The technology process which is based on electroless plating and electroplating method is described in detail. The fiber is firstly coated with a thin copper or nickel plate with electroless plating method. Then, a thicker nickel plate is coated on the surface of the conductive layer. Under the optimum conditions, the surfaces of chemical plating and electroplating coatings are all smooth and compact. There is no visible defect found in the cross-section. Using this two-step metallization method, the in-fiber Bragg grating can be well protected and its thermal sensitivity can be enhanced. After the metallization process, the fiber sensor is successfully embedded in the 42CrMo steel by brazing method. Thus a smart metal structure is achieved. The embedding results show that the plating method for metallization protection of in-fiber Bragg grating is effective.     

Improvement of copper plating adhesion on silane modified PET film by ultrasonic-assisted electroless deposition

Copper thin film on silane modified poly(ethylene terephthalate) (PET) substrate was fabricated by ultrasonic-assisted electroless deposition. The composition and topography of copper plating PET films were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. Peel adhesion strength, as high as 16.7 N/cm, was achieved for the planting copper layer to the modified PET substrate with ultrasonic-assisted deposition; however, a relative low value as 11.9 N/cm was obtained for the sample without ultrasonic vibration by the same measurement. The electrical conductivity of Cu film was changed from 7.9 × 10⁴ to 2.1 × 10⁵ S/cm by using ultrasonic technique. Ultrasonic operation has the significant merits of fast deposition and formation of good membranes for electroless deposition of Cu on PET film.     

Solder with discontinuous melting point in semiconductor laser arrays and stacks

High power semiconductor laser arrays must be mounted in the epitaxy-side down configuration for good heat transfer and so require a well-controlled solder. Selection of solder is very important in semiconductor laser arrays and stacks. Usually, the solder consists of two layers. The outer layer prevents In from oxidation. A new type of solder with several layers of Au between the two layers of In was made, which constitutes of multi-layer of W/Ni/Au/In/Cu. In packaging, the Au layer in the solder does not melt. Quick temperature decrease can avoid expansion of the solder. The solder cannot oxidize during packaging.     

Fabrication of 3D metal/polymer microstructures by site-selective metal coating

Three-dimensional silver/polymer conjugated microstructures were fabricated by site-selective metal deposition on photopolymer structures in the sub-micrometer scale. Photopolymerizable resins with and without an amide group were independently prepared, and a three-dimensional polymer structure was fabricated with those resins by means of the two-photon-induced photopolymerization technique to confine the photopolymerization to a sub-micrometer volume. Silver was selectively deposited on the surface of the amide-containing polymer parts by electroless plating. This method can provide 3D arbitrary silver/polymer composite microstructures with sub-micrometer resolution. PACS 81.07-b; 81.16-c; 81.07.Pr     

Investigation of the structure and the physical properties of nickel-phosphorus ultra-black surfaces

Ultra-black materials with low reflectivity can be applied in many fields of science and technology. We deposited nickel-phosphorus alloys (Ni-P) on copper substrate with the electroless plating method and etched the electroless plating with nitric acid in order to build ultra-black surface. On the one hand, the components of the Ni-P ultra-black surface layer were investigated by XRF and XPS. SEM represented that there are innumerable conical holes with the different diameters on the surface. XRD showed that the whole surface has become amorphous. On the other hand, compared to electroless blackening film by oxidation and black chromium plating materials, the Ni-P ultra-black surface showed lower wavelength dependence and lower reflectance in the range of 380–780 nm. In addition, the temperature of the sample with the Ni-P ultra-black surface increased more highly and quickly compared to the black chromium plating film after exposure in an IR laser for about half an hour. PACS 68.55.-a; 82.80.Kq; 78.68.+m     

Highly adhesive metal plating on Zylon fiber via iodine pretreatment

Highly adhesive metal plating was performed on poly(p-phenylene-2,6-benzobisoxazole) fiber named Zylon^® via iodine pretreatment followed by electroless plating. First, iodine components were selectively doped into the inner part of the fiber near the surface through iodine vapor exposure. The doped iodine was converted to palladium iodide particles by treating with palladium chloride solution. After the reduction of the iodide to metal palladium particles, electroless copper plating was conducted on the fiber. A uniform copper layer was deposited on the fiber surface and exhibited high durability in durability tests such as ultrasonic exposure, tape peeling-off, and corrosion in NaCl solution. This durability was attributed to the palladium particles formed at the fiber surface that served as an anchor for the plated layer as well as an electroless plating catalyst. The plated fibers also possessed electrical conductivity. Although the tensile strength of the Zylon^® fiber decreased from 5.8 to 4.9 GPa after undergoing the pretreatment and plating processes, the light shielding effect improved the light resistance of the plated fibers in terms of tensile properties. After 18 days of xenon lamp exposure, the plated fibers retained 74% of its initial strength, whereas that of untreated fibers decreased to 43%.     

Stress reduction in planar waveguide using polymer top layer

Planar optical waveguides consisting of layers from different materials created at elevated temperatures usually exhibit substantial stresses. By controlling the layer thickness of polymeric top layer on planar waveguide structures, it is possible to use very thin layers for stress compensation, significantly reducing required deposition times. It is possible to reduce birefringence within planar device by controlling top polymer layer thickness with thermal expansion coefficient greater than silica or PMMA.     

Micropatterning of fluoropolymers

Fluoropolymer (PTFE and FEP) substrates have been patterned through micro-contact printing of an aminosilane. The silane pattern was activated with a palladium catalyst that allowed the electroless deposition of copper which was used to form micropatterned copper electrodes. Conducting polymer micropatterns were then fabricated by electrodeposition of polypyrrole (PPy) onto the copper. The resulting patterns of 80 μm and 10 μm grids and 2 μm and 5 μm checkerboards were characterized using imaging XPS, TOF-SIMS, AFM and SEM. The size and resolution of the smallest copper patterns were limited by the copper grain size created during electroless deposition. The polypyrrole patterns were also limited by the roughness of the electrolytically deposited polymer film.