Dual-Gradient Impedance/Insulation Structured Polyimide Nonwoven Fabric for Multi-Band Compatible Stealth

In this study, we use the standard TSMC 0.35 μm 2P4M process to design CMOS-MEMS probe chip. MEMS technology involves the following steps such as lithography process, electroless nickel (EN) plating process, grinding process and dry etching process. The probe chip has through silicon via (TSV) package structure, and the combination of CMOS process within the multi-layer interconnections, which could assist the connection between the probes head the external devices, and reduce the difficulty of wiring layout. In addition, passive components or circuits could be integrated with the CMOS chip to improve the frequency bandwidth and measuring quality. So far, MEMS probe exist a shortcomings that are not able to be integrated with the CMOS process, and the testing cost. The finite element method was adapted to design of probe shapes and sizes. The LIGA-like thick photoresist process and EN plating technique was used in this study, Ni-P alloy to increase the thickness of the cantilever probe to strengthen its support strength were also applied. When the probe cantilever through the EN plating of deposition time, the uneven surface was appeared, each layer structure is used by polishing process to achieve the surface coplanarity. Finally, the probes structure were suspended by the dry etching process (RIE, ICP-RIE), and this study successfully fabricated chips forming one of the probe.

This study investigates the application of electroless nickel deposition on additively manufactured stainless steel samples. Current additive manufacturing (AM) technologies produce metal components with a rough surface. Rough surfaces generally exhibit fatigue characteristics, increasing the probability of initiating a crack or fracture to the printed part. For this reason, the direct use of as-produced parts in a finished product cannot be actualized, which presents a challenge. Post-processing of the AM parts is therefore required to smoothen the surface. This study analyzes chempolish (CP) and electropolish (EP) surface finishing techniques for post-processing AM stainless steel components CP has a great advantage in creating uniform, smooth surfaces regardless of size or part geometry EP creates an extremely smooth surface, which reduces the surface roughness to the sub-micrometer level. In this study, we also investigate nickel deposition on EP, CP, and as-built AM components using electroless nickel solutions. Electroless nickel plating is a method of alloy treatment designed to increase manufactured component’s hardness and surface resistance to the unrelenting environment. The electroless nickel plating process is more straightforward than its counterpart electroplating. We use low-phosphorus (2–5% P), medium-phosphorus (6–9% P), and high-phosphorus (10–13% P). These Ni deposition experiments were optimized using the L9 Taguchi design of experiments (TDOE), which compromises the prosperous content in the solution, surface finish, plane of the geometry, and bath temperature. The pre- and post-processed surface of the AM parts was characterized by KEYENCE Digital MicroscopeVHX-7000 and Phenom XL Desktop SEM. The experimental results show that electroless nickel deposition produces uniform Ni coating on the additively manufactured components up to 20 μm per hour. Mechanical properties of as-built and Ni coated AM samples were analyzed by applying a standard 10 N scratch test. Nickel coated AM samples were up to two times scratch resistant compared to the as-built samples. This study suggests electroless nickel plating is a robust viable option for surface hardening and finishing AM components for various applications and operating conditions.

Effect of bath pH and stabilizer on electroless nickel plating of magnesium alloys

Effects of fluoride ions as electrolyte additives for a PEO/Ni-P composite coating onto Mg alloy AZ31B

Bi3+‐complex ion is presented here as a less toxic stabilizer for use in electroless nickel plating (ENP) to replace the existing Pb2+ ion stabilizer. The asymmetric derivatives of EDTA are identified to be a type of coordination ligands that can combine with Bi3+ ions to form soluble complexes in the acidic ENP solution. In the ENP system studied the Bi3+‐complex ion displays a critical stabilizer concentration of about 10−5 mol/L, that is, the percolation concentration over which the ENP rate drops sharply. Besides the experimental measurement, deposition rates of both Ni and P are also simulated by using a kinetic model that has been derived from the double electric layer theory. The Bi3+‐complex ion, behaving like conventional Pb2+ ion, stabilizes ENP bath through the chemical replacement reaction at the surface of Ni deposition layer and results in a passive plating surface. This investigation also verifies the properties of the EN deposit, which are insignificantly affected by the length of service time of the plating solution by employing Bi3+‐complex ion stabilizer. © 2009 American Institute of Chemical Engineers AIChE J, 2009

Electroless nickel plating has been extensively applied on copper circuits as an under-layer deposition for solder joints, since it is possible to deposit on the isolated patterns without an outer electrode. A palladium catalyst is generally used for the electroless nickel plating reaction on the copper patterns, because copper has a lack of catalytic activity for initiation of the deposition reaction. The electroless nickel plating is applied on the condensed copper patterns by using the palladium catalyst ; however, nickel deposits tend to occur on the resin surface due to the adsorption of palladium ions on it.Dimethylamine-borane (DMAB) has a feature of catalytic activation power on the copper. Therefore we applied dilute nickel plating solution containing DMAB as an initiator for electroless nickel deposition on the copper surface instead of applying the palladium catalyst. Selective nickel plating on the copper patterns without deposition on the resin substrate was achieved using a dilute nickel plating bath containing DMAB. In addition, the strength of solder joints was improved by introducing this process. In this way, nodules on the nickel surface were greatly suppressed, and strong joints between the solder and deposited nickel were achieved.

The process of electroless nickel plating (EN) on magnesium alloys is investigated. The concentration of complexing agent, the concentration of reductant and the pH value of the EN bath for magnesium alloys influence the deposition rate. The results show that the deposition rate increases as the concentration of complexing agent decreases, the concentration of reductant and pH increase. Additionally, deposits with different phosphorus content can be obtained on magnesium alloys by varying the concentration of complexing agent and reductant, and the pH value of the bath. DSC curves of deposits reveal that the microstructure changes from crystalline to amorphous with the increment of the phosphorus content.

Studies were conducted on several fundamental aspects of electroless nickel/solder metallization for silicon solar cells. A process proposed by Motorola, which precedes the electroless nickel plating with several steps of palladium plating and heat treatment, was compared directly with single step electroless nickel plating. Work has directed toward answering specific questions concerning the effect of silicon surface oxide on nickel plating, effects of thermal stresses on the metallization, sintering of nickel plated on silicon, and effects of exposure to the plating solution on solar cell characteristics. The Motorola process was compared with simple electroless nickel plating in a series of parallel experiments. Results are presented. (WHK)

An experimental investigation was made of the effects of optical radiation on the autocatalytic process of electroless nickel plating at an interface betweeen a solid and a liquid. Local optical heating gave rise to special features in the reaction. The rate of reduction of the metal was 20?30 times higher than in traditional methods and there was also some ordering of the structure of the deposit.

In this paper, electroless nickel plating is explored for the protection of binder-jetting-based additively manufactured (AM) composite materials. Electroless nickel plating was attempted on binder-jetted composites composed of stainless steel and bronze, resulting in differences in the physicochemical properties. We investigated the impact of surface finishing, plating solution chemistry, and plating parameters to attain a wide range of surface morphologies and roughness levels. We employed the Keyence microscope to quantitatively evaluate dramatically different surface properties before and after the coating of AM composites. Scanning electron microscopy revealed a wide range of microstructural properties in relation to each combination of surface finishing and coating parameters. We studied chempolishing, plasma cleaning, and organic cleaning as the surface preparation methods prior to coating. We found that surface preparation dictated the surface roughness. Taguchi statistical analysis was performed to investigate the relative strength of experimental factors and interconnectedness among process parameters to attain optimum coating qualities. The quantitative impacts of phosphorous level, temperature, surface preparation, and time factor on the roughness of the nickel-plated surface were 17.95%, 8.2%, 50.02%, and 13.21%, respectively. On the other hand, the quantitative impacts of phosphorous level, temperature, surface preparation, and time factor on the thickness of nickel plating were 35.12%, 41.40%, 3.87%, and 18.24%, respectively. The optimum combination of the factors’ level projected the lowest roughness of Ra at 7.76 µm. The optimum combination of the factors’ level projected the maximum achievable thickness of ~149 µm. This paper provides insights into coating process for overcoming the sensitivity of AM composites in hazardous application spaces via robust coating.

Improvement of thermal-hydraulic performance of plate heat exchanger by electroless nickel, copper and silver plating

We observed the effects of nickel plating temperatures for controlling the surface morphologies of the deposited nickel layers on the alumina nano-pores. The alumina nano-channels were filled with nickel at various processing temperatures of 60-90 degrees C. The electrical properties of the alumina film capacitors were changed with processing temperatures. The electroless nickel plating (ENP) at 60 degrees C improved the nickel penetration into the alumina nano-channels due to the reduced reaction rate. Nickel layers are uniformly formed on the high aspect ratio alumina pores. Due to the uniform nickel electrode, the capacitance density of the alumina film capacitors is improved by the low leakage current, dissipation factor and equivalent series resistance. Alumina film capacitors made by ENP at 60 degrees C had a high capacitance density of 160 nF/cm2.

Flexible metalized polyimide nonwoven fabrics for efficient electromagnetic interference shielding

Skeleton designable SGP/EA resin composites with integrated thermal conductivity, electromagnetic interference shielding, and mechanical performances

Nanocrystalline iron oxide powders were prepared by an inert gas condensation technique under various oxygen partial pressures. The as-prepared nanocrystalline iron oxide powders were further modified by electroless nickel plating. The as-prepared and modified nanocrystalline powders were characterized by X-ray diffraction, transmission electron microscopy, and synchrotron X-ray absorption techniques. In addition, magnetic properties of the iron oxide nanoparticles before and after electroless nickel plating were evaluated by vibrating sample magnetometer. The experimental results show that the as-prepared nanocrystalline iron oxide powders exhibited a mixture of iron and γ-Fe2O3 phases. TEM observations revealed that oxidation started from the surface of the gas-condensed iron nanoparticles. The amount of iron oxide increased with increasing oxygen partial pressure and was confirmed by synchrotron x-ray absorption examination. A decrease in saturated magnetization and coercivity of the nanocrystalline iron oxide powders was observed after electroless nickel plating.