Direct Electroless Nickel Plating Research Articles

Process of environmentally-friendly direct electroless nickel plating on AZ91D magnesium alloy surface

Process of environmentally-friendly direct electroless nickel plating on AZ91D magnesium alloy surface

Effects of pretreatments of magnesium alloys on direct electroless nickel plating

The effects of two different pretreatments on direct electroless nickel plating of magnesium alloys have been studied in order to obtain an environmentally friendly process of pretreatment. The surface morphology, chemical composition and corrosion resistance were characterised using SEM, energy dispersive X-ray and polarisation curves. An environmentally friendly pretreatment has been finally established by the procedure of pickling with nitric acid plus phosphoric acid, twice activating with K4P2O7 and NH4HF2. It is found that a coarse surface was produced on the Mg substrate via the researched pretreatment. The adherence between the coating and the substrate was improved. A compact Ni–P alloy coating with better adhesion and corrosion resistance was fabricated. The phosphorus content in the coating was ∼11·24%.

Deposition Mechanism Study of a Novel Electroless Nickel Plating Technique on AZ91D Magnesium Alloy

A novel direct electroless nickel plating method was developed for the AZ91D magnesium alloy. The electroless nickel initial deposition morphology was analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The initial deposition characteristics of the coating and the deposition mechanism of the nickel layer are discussed. The results show that after activation, an uneven scaly-activated membrane was formed on the AZ91D magnesium alloy surface. The weakest part of the activated membrane dissolved first, where small Ni particles deposited initially. These deposited Ni particles had high catalytic activity and they were involved in the catalytic reduction reaction of hypophosphite, from which P was precipitated. As the plating proceeded, the number of the deposited Ni particles gradually increased in a three-dimensional manner and the surface was gradually covered by the growing cellular particles. A compact pore-free nickel-plated film was finally formed.

Low Temperature and Low Phosphorus Electroless Nickel Plating

Direct electroless nickel plating on n-Si(100) wafers in alkaline solutions was performed without any activation procedure in advance. The effect of pH and temperature on the size of deposited metal particles was examined. Moreover, The phosphorus contents of deposits were also analyzed by the energy disperse spectroscopy. The results indicated that the optimal reaction temperature was 60°C and the optimal pH value was 10.0 with a plating rate of about 3.0 µm/hr and the phosphorus content of about 3.6 wt%.

Process of Ni-P Electroless Deposition on SiCp/Al Composites from Acid Bath

The initial nickel deposition for the direct electroless nickel plating on active SiCp/Al composites is critical. So it is necessary to investigate the process of the electroless Ni-P plating deposition on SiCp/Al composites by means of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). In addition, the mass gain/loss in the initial nickel deposition process was measured by using the electro-balance. The results show that after being treated using phosphoric acid and hydrogen peroxide, the compositions of SiCp/Al composites substrate contains Al, SiC and Al2O3. The Al2O3 film was gradually corroded by the plating solution. And then Ni-P coating was deposited on the substrate without Al2O3 film during the initial electroless plating process, which was mostly growing on the boundary between the SiC particles and the Al crystal of the activation substrate, and then came to two sides. After that, the Ni-P coating growth rate to cover with the SiC particles and Al crystals was prior to the Al2O3 film. The electroless plating was in company with the substrate corrosion, but the electroless plating rate catalyzed by the exchanged nickel was more than the substrate corrosion rate.

Low temperature direct electroless nickel plating on silicon wafer

In the study of electroless nickel (EN) plating on n‐type (100) silicon wafers, a relatively low‐temperature alkaline plating process is developed. Further experiments show that simple ethanol pretreatment of the substrate is practicable for obtaining an EN layer with a good adhesion strength of about 9.8 to 14.7 MPa. Both sodium tungstate and sodium fluoride can be used to decrease the threshold plating temperature from near 80°C to 65°C. The phosphorous content of the as‐plated layer is slightly higher than 7 wt.%.

A Study on the Pretreatment of Direct Electroless Nickel Plating on Magnesium Alloys AZ91D

Magnesium alloys are considered as “difficult to plate” metal. The pretreatment processes play a key role for plating. The pretreatments of alkaline cleaning, chromic acid etching and hydrofluoric acid activating were carried out and the microstructures investigated by SEM and EDAX in detail. The hydrofluoric acid activating time of 8 minutes was determined by Potential-Time curve. The experimental results showed that the alkaline cleaning moved the grease and oils off the substrate surface, but there was no apparent surface morphology change. The chromic acid etching was a very critical step, and the optimum etching time of 1 minute was chosen; the eutectic α was severely etched, and the chromic compounds were mainly formed on the surface. During the hydrofluoric acid activating, the white activating product of magnesium fluoride was preferentially generated on the β–phase, and obvious morphology change has been observed on the alloy substrate surface.

Direct electroless nickel plating on silicon surface

Direct electroless nickel plating onn-Si(100) wafers in alkaline solutions was demonstrated without any activation procedure in advance, the effect of pH and temperature of the solutions on size of metal particles in deposits was examined, and also the element contents of deposits were analyzed by energy disperse spectroscopy (EDS). The results indicated that the size of metal particles increases with increasing temperature or decreasing pH. The possible mechanism of nickel deposition onn-Si(100) was discussed in terms of semiconductor electrochemistry, and the formation of nickel seed crystal on Si was mainly attributed to the generation of atomic hydrogen by electron capture of water molecule from the semiconductor in alkaline solutions.

Direct electroless nickel plating on silicon surface

Direct electroless nickel plating on silicon surface

無電解ニッケルめっきの有孔度の低減と環境を配慮した評価法

An electro-graph test using zinc instead of cadmium was evaluated as a alternative porosity measurement method. This technique was effective in the porosity evaluation of electroless nickel plating on copper substrate.Pinholes of electroless nickel deposits produced on copper substrate by the conventional palladium catalyst process have been compared to direct electroless nickel plating on copper using DMAB as a second reducing agent.Results confirmed that fewer pinholes are produced on electroless nickel films when not using the palladium catalyst process than with films treated using the conventional palladium catalyst process. The direct electroless nickel plating films displayed excellent corrosion resistance.

無電解めっき マグネシウム合金へのダイレクト無電解ニッケルめっきプロセス

無電解めっき マグネシウム合金へのダイレクト無電解ニッケルめっきプロセス

Fabrication of Nickel Microbump on Aluminium Substrate Using Electroless Nickel Plating

Tape automated bonding (TAB) and flip chip bonding technologies have been progressing with the advancement of surface mounting technologies. The formation of metallic microbump is required to connect outer lead with each pad electrically for these mounting technologies. In general, aluminium has been used as a circuit or electrode material for large scale integrated circuits (LSI) fabrication. Recently, bump formation or via-hole filling by electroless nickel deposition was reported. A zincate process is generally used prior to electroless nickel plating on aluminium substrate. However, an organic resist cannot be applied because the zincate bath is strongly alkaline. Accordingly, we investigated electroless nickel plating on aluminium substrates using a nickel displacement process and fabrication of nickel bumps on aluminium electrode by electroless nickel plating. Furthermore, direct electroless nickel plating without nickel displacement on aluminium and nickel bump formation were studied. As major results, catalytic nickel site with a good adhesion on bulk aluminium substrate can be formed by the process of nickel displacement plating. A straight-walled nickel bump about 20 μm in width and 15 μm in height may be formed by optimization of nickel displacement plating bath composition and operating conditions. In addition, more uniform nickel bumps can be fabricated on an aluminium substrate by activation with dimethyl amine borane (DMAB) instead of nickel displacement plating.

アルミニウム合金上メッキ膜の密着力

Many methods of plating on aluminum alloys have been proposed, but most of the adhesion of plated films obtained by these methods still remains unexplained.The authors evaluated the adhesive bond by tension test on the following 5 typical methods, and also investigated the effects of heat-treatment on adhesion.1. Zincate method2. Double zincate method3. Nickel displacement plating method4. Direct electroless nickel plating method5. Vacuum evaporation methodAs the results of these studies, the following conclusions were drawn.(1) The greatest adhesive bond among the five was obtained by double zincate method. The tensile strength in this method was estimated to be equal to that of the mother aluminum alloy. For this reason, the above method was considered to be the most suitable for critical applications such as a cylinder, magnetic disc, and waveguide.(2) The tensile strength in zincate method was 1, 300kg/cm2.(3) The tensile strength in direct electroless nickel plating method was 370kg/cm2 as plated and it was found to be increased to 1, 100kg/cm2 by the effects of heat-treatment at 150°C for 4hr.