Electroless Copper Plating Process Research Articles

Fabrication of conductive polyimide/metal composite fibers for high temperature EMI shielding

Surface metallization of high-performance polymer fibers via electroless plating represents a significant advancement in producing lightweight, flexible and durable electromagnetic interference (EMI) shielding fabrics. The conventional process for metallization of polyimide (PI) fibers faces challenges, including complex procedures and insufficient interfacial adhesion between the metal layer and fiber matrix. Herein, carboxylate-containing PI (PIC) fibers were developed to mitigate the mechanical degradation caused by traditional alkaline etching. Conductive composite fibers (PIC/Cu) were successfully produced through a continuous electroless copper plating process. The robust PIC/Cu interfacial bonding achieved based on nanoscale mechanical interlocking through Ni nanoparticles imparts excellent flexibility and durability, evidenced by only a 4 % increase in electrical resistance after 5000 bending cycles. The dense, uniform copper layer provides high conductivity (1.3 × 104 S/cm), resulting in an optimal EMI shielding efficiency of 63.4 dB for the corresponding fabric. Moreover, PIC/Cu-Ni fibers prepared by further electroless plating of nickel layer on the surface of PIC/Cu fibers demonstrate remarkable electrical stability across temperatures ranging from 50 to 350°C, with only a 1.2 % reduction in conductivity after exposure to 350°C for 1 h. These findings advance the development of high-performance conductive PI fibers for applications in aerospace vehicles and high-temperature environments.

Use of sodium trithiocarbonate for remove of chelated copper ions from industrial wastewater originating from the electroless copper plating process

Use of sodium trithiocarbonate for remove of chelated copper ions from industrial wastewater originating from the electroless copper plating process

Properties of an electroless copper process as a function of nickel and cyanide ion concentrations

A cyanide-stabilized electroless copper plating process with nickel as a stress-regulating additive was investigated. Small amounts of nickel or cyanide increase the deposition rate, while large amounts of cyanide decrease the deposition rate. The steady-state mixed potential shifts by – 0.23 V when about 0.05 at.% nickel is co-plated with copper. Cyanide by itself does not change the mixed potential. If nickel is also present, cyanide causes an anodic shift by + 0.09 V. Nickel changes the stress during deposition towards tensile, while cyanide changes it towards compressive. Both nickel and cyanide accelerate the transition to steady-state plating conditions.

Effects of processing parameters on phase, morphology, mechanical and corrosion properties of W–Cu nanocomposite powder prepared by electroless copper plating

Because of excellent physical properties and wide range of applications in electrodes, electrical connections, microelectronic packaging, and heating mineral, Tungsten–copper (W–Cu) composite powders have been significantly remarkable. The substantial differences in the density and lack of fusion of copper and tungsten in both solid and liquid phases, led to occur some problems in W–Cu composite powders. Among the various methods of preparing tungsten–copper composites, the electroless plating process is one of the conventional methods as it is easy to use, efficient, and inexpensive. In this paper, the copper electrolyte solution containing copper sulfate as the main salt, formaldehyde as the reducing agent, sodium ethylene diamine tetra-acetate as the sophisticated agent, has been employed in the electroless copper plating process of tungsten powder. The effects of main parameters of electroless copper plating including NaOH concentration, time and operating temperature, and pre-activation of tungsten powder on the amount of deposited copper layer were investigated. Then, the phase behavior, morphology, mechanical, and corrosion behavior were evaluated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy(EDS), Vickers hardness tester, and electrochemical impedance spectroscopy (EIS), respectively. Results demonstrated an improvement in the morphology and amount of the copper, which was deposited on the surface of the activated tungsten powder. Indeed, the defects formed on the surface of the tungsten powder increased the sites for nucleation and growth of copper particles. In agreement with the Fick's 2nd law, the maximum deposition rate of 7.9 vol% was obtained at 14 g/l NaOH, 100 °C and processing time of 90 min, with a (111) orientation on the activated tungsten powder surface. The higher capacitance and the charge transfer resistance along with the highest ndl at the 14 g/l NaOH concentration demonstrated the homogeneity and integrity of W–Cu composite, the lowest hardness of 149.0 ± 2.8 Hv and a compressive strength of 187 ± 11 MPa.

Solution Chemistry of Alkaline Formaldehyde-Containing Electroless Copper Plating Systems and Kinetics of Electroless Copper Deposition

Electroless copper plating process using solutions containing formaldehyde as reducing agent is known from the middle of this century and are widespread in the practice up to now. However, the investigation of this system remains actual because of its complexity, e. g. alkaline medium, hydrated form of formaldehyde (methanediol), Cu(II) complex compounds with different ligands, additives which improve the properties of the coatings obtained and/or protect from the reduction of copper(II) in the solution bulk. Moreover, various equilibria are possible including deprotonation of methanediol, Cu(II) complex formation, additional interactions between components of the solution.The aims and tasksof this work were to investigate or define more precisely equilibria in conventional alkaline solutions of electroless copper deposition as well as influence of the nature of Cu(II) ligands on the copper deposition process. This research report deals with the results obtained by means of dc-polarography, vis-spectrophotometry, voltammetry, potentiometry, pH-metry, 1H and 13C NMR spectroscopy, scanning electron microscopy, X-ray diffractometry and gravimetry.The composition, stability and the values of the diffusion coefficient of Cu(II) complex compounds with ligands (EDTA, DTPA, pyridine-2,6-dicarboxylic acid and 4-hydroxypyridine-2,6-dicarboxylic acid, Quadrol, L(+)-, D(–)- and DL(-/+)-tartrate, glycerol, saccharose and OH- ions) which are used or usable in alkaline electroless copper deposition solutions were established. Formation of mixed complex compounds between Cu(II) complexonates andK4Fe(CN)6, as well as between Cu(II) tartrate complexes and methanediol was investigated. The interaction of methanediol with L(+)-tartrate alongside with the influence of the ionic strength and cation nature on the deprotonation of methanediol in alkaline solutions were studied.The kinetic data on electroless copper deposition from solutions containing above-mentioned ligands are presented and the influence of the ligand nature on the process of electroless copper deposition is discussed.

Hieratical CuO clusters in-situ grown on copper films coated three-dimensional nickel foams for high-performance supercapacitors

Copper oxides (CuO) are promising pseudocapacitive materials for supercapacitors. However, the intrinsically poor electronic conductivity limits their applications. Herein, an electrode with hieratical CuO clusters based on nickel foams (CuO–Ni) are synthesized via the electroless copper plating and chemical etching process. The specific areal capacitance of CuO–Ni electrode in aqueous 6 M KOH solution reaches up to 1.61 F cm−2 at 3 mA cm−2 (equivalent to 679 F g−1 at 1.27 A g−1), and retains 93.6% after 5000 testing cycles, which is mainly attributed to their perfect hieratical structure and high electrical conductivity. The asymmetric supercapacitor device was assembled with the positive electrode of CuO–Ni and negative electrode of active carbon (AC). The energy density reaches up to 43.12 Wh kg−1 even at a high power density of 2.12 kW kg−1. This work offers a facile and attractive strategy for the rational construction of electrodes for supercapacitors with high-performance.

Electroless Copper Plating Process Applicable to Molded Interconnect Device Using Laser Direct Structuring

Electroless Copper Plating Process Applicable to Molded Interconnect Device Using Laser Direct Structuring

Using Reduce Graphene Oxide (rGO) As a Conducting Layer for a PCB Metallization

Electroless (ELS) copper plating process has been commonly used for PCB metallization. However, the ELS copper process is not environment-friendly because it contains precious metal (i.e., Pd catalyst), formaldehyde and chelating agents. Also, ELS copper plating process gives rise to several problems on the metallization of through holes (THs) and microvias. In this work, ELS copper deposition process was replaced by a reduced graphene oxide (rGO) process to form a conducting layer on the sidewalls of THs and microvias of a PCB for subsequent copper electroplating. rGO has an excellent conductivity and metal barrier capability. Also, the rGO process has more advantages such as environment-friendly, short process steps, no toxic chemicals and organic solvent. A high copper throwing power (> 90 %) in the THs with a high aspect ratio can be obtained using rGO as a conducting layer, even better than ELS copper plating. Moreover, the rGO process could result in good copper filling performance in the microvias without seam or void in the via center. After thermal reliability test, the rGO grafted on the sidewall of the through holes and microvias could pass critical thermal reliability criterion due to its excellent thermal stability. Therefore, brand-new and promising rGO process is hopeful to play a significant role in the future PCB fabrication.

Electroless Copper Deposition Using Complexed Copper(II) Ion As Catalyst for Printed Circuit Board Fabrication

Electroless (ELS) copper plating process has been commonly used for printed circuit board (PCB) metallization. The traditional ELS copper plating process uses tin/palladium colloid or complexed palladium ion as catalysts for ELS copper deposition. But the price of palladium catalyst is much higher than that of gold. Herein, we use complexed copper(II) ion to replace the palladium catalyst in order to greatly reduce the process cost but maintain the performance and the reliability of the complexed copper(II) ion as good as palladium. The synthesis process of the complexed copper ion is simple and its cost, which compared with palladium, is cheap. Especially, they have no oxidation issue because they are not metallic copper nanoparticles but copper(II) ions. Before ELS copper plating, the grafted copper(II) ion that is chemically adsorbed onto the substrate surface is reduced to copper atom, so they can catalyze ELS copper deposition. In this work, we optimize the experimental parameters such as operating temperature, reaction time, copper ion concentration and the pH of the plating solution. After ELS plating process, the backlight test of through holes (THs) of a PCB and the morphology of the ELS copper deposited onto the sidewalls of the THs are evaluated by optical microscope (OM) and scanning electron microscope (SEM), respectively. The thermal reliability of the ELS copper deposition catalyzed by the grafted copper catalyst was examined after copper electroplating using thermal shock in a tin bath at 288℃ for ten seconds and repeated it for 5 times. Results show that it can pass the thermal shock test. Therefore, the application of complexed copper(II) ion as the catalyst of ELS copper plating is expected to replace the expensive palladium for PCB fabrication.

Laser induced selective electroless copper plating on polyurethane using EDTA-Cu as active material

Using EDTA-Cu as the active material and polyurethane as the matrix, flexible cathodes were fabricated by laser-induced electroless copper plating process (LPKF-LDS) and characterized by SEM, X-ray energy spectrum and Auger electron spectroscopy. Flexible cathodes prepared from EDTA-Cu and polyurethane showed good selectivity in copper plating process. Composition and particle morphology of EDTA-Cu, laser power, scanning speed, laser wavelength, laser spot size, pulse frequency etc. are the main factors that affect the fineness of electroless copper plating. By adjusting these parameters, the fineness of the copper plating was improved. X-ray energy spectrum and Auger electron spectroscopy results showed that after the laser scanning, both Cu^0 and Cu^(+1) appeared in the scanning area, revealing thus the mechanism of electroless copper plating for polyurethane-EDTA-Cu flexible cathodes.

Copper Superfilling without a Copper Pad at the Microvia Bottom Due to Reduced Graphene Oxide (rGO) Coating

Reduced graphene oxide(rGO) has outstanding thermal and electrical conductivity. Compared to electroless (ELS)copper plating process, rGO grafting process is more environmentally friendly because ELS copper plating solution contains toxic species (i.e. formaldehyde as a reducer) and precious metal (i.e., Pd as a catalyst). rGO grafting process has less step than ELS deposition process, which makes it has a great prospect. Particularly, if the copper pad at microvia bottom was removed before the rGO grafting process and the sidewall and the bottom of the microvia were coated with rGO, the copper superfilling exhibited more excellent compared with ELS copper deposition process. This special process is related to the physical property of rGO. In other word, the issue of seam formation between the filled copper and the copper pad due to ELS deposition process is solved. Moreover, this approach also can be used to perform copper pillar plating, which exhibits excellent bottom-up deposition in the photoresistant hole. In this work, copper pad at the microvia bottom was removed by piranha solution at first. To enhance the filling performance, the effect of sonication in graphene oxide(GO)solution and plating time were discussed. In addition, the effect of the sidewall roughness of the microvia was evaluated to inference the exact nucleation position of plated copper the mechanism thereof. Result show that, the brand-new copper super-filling process was expected to replace the ELS copper deposition process in the future. Keyword Microvia, Electroplating, reduced Graphene Oxide, Copper superfilling References : Pei, S. F.; Cheng, H. M., The reduction of graphene oxide. Carbon 2012, 50 (9), 3210-3228.Chen, P. Y.; Sodhi, J.; Qiu, Y.; Valentin, T. M.; Steinberg, R. S.; Wang, Z. Y.; Hurt, R. H.; Wong, I. Y., Multiscale Graphene Topographies Programmed by Sequential Mechanical Deformation. Advanced Materials 2016, 28 (18), 3564-+.

Selective Metalization of Non-Conductive Materials By Macropatterning of Catalytic Particles and the Application of a Gradient Magnetic Field

Photolithography is commonly used in various manufacturing sectors to achieve metal patterning of non-conductive materials. However, the high cost and toxicity of reagents used in this process have prompted the investigation of alternative approaches to selective metallisation. The present work shows a novel approach that utilizes a gradient magnetic field to achieve selective metallization on the millimeter scale. The magnetic field is applied during the seeding (catalysation) stage, which is required to initiate electroless copper deposition. Subsequent copper deposition occurs selectively according to the pre-defined pattern of the magnetic field. The modified approach uses a new type of magnetic catalyst i.e. a Fe­3O4-Ag composite material, which was obtained by a wet chemical synthesis method. The Fe component of these particles enables them to be arranged on the substrate in a way that directly corresponds to the pattern of the magnetic field and therefore subsequent electroless copper plating will follow this pattern. The magnetic and catalytic properties of particles for the initiation of electroless copper deposition were characterised by vibrating sample magnetometry and cyclic voltammetry measurements. The Fe3O4-Ag composite colloid solution was optimized by varying the pH, mixing approach and particle concentration. This paper will demonstrate the potential for selective catalysation in a magnetic field to compete with the commonly used photolithography and ink-jet printing approaches for macroscale selective metallisation of non-conductive materials. Figure 1. The schematic representation of standard electroless copper plating process and modified process of selective metalization in a gradient magnetic field. Figure 1

The Effect of Levelers on Plating through Holes of a PCB By Using Reduced Graphene Oxide (rGO) As a Conducting Layer

Electroless (ELS) copper plating process has been commonly used in the metallization process of printed circuit boards (PCBs), because the sidewalls of the through holes (THs) of PCBs are composited of resin and glass fiber, which are not conductive materials. Hence, before plating these THs, their sidewalls have to be metallized by ELS copper plating. The process causes harmful influence to environment because it contains precious metal (i.e., Pd as a catalyst), formaldehyde and chelating agents. However, reduced graphene oxide (rGO) grafting process, proposed in this work, is environment-friendly and can replace the ELS copper plating process to make the sidewall of the TH of a PCB be conductive for copper electroplating. The rGO grafting process has less steps and an environment-friendly formulation. In this work, the rGO is grafted on the sidewalls of THs of a PCB with a high aspect ratio (AR). We observed that the copper nucleation mechanism of electrochemical deposition on a PCB is progressive. In addition, we studied the suppression of various levelers on copper electrodeposition in order to control the copper to be less deposited at the hole opening but much more deposited at the hole center. Finally, the throwing power (TP) of the copper electrodeposition in the TH can be significantly enhanced. In our research, the effects of electroplating baths, operating parameters and electroplating additives, especially levelers, were investigated for obtaining a high TP of THs. On the other hand, the suppression of various levelers was evaluated by electrochemical analysis, such as linear sweep voltammetry (LSV) and galvanostatic measurements. The results indicate that the electroplating bath containing the leveler with stronger suppression can control the copper to be specifically deposited at the hole opening. Hence, a high TP of plating TH was achieved by using the rGO process. Moreover, the plated TH can pass thermal shock test. That means, a brand-new and promising rGO process can replace the ELS copper plating in the future for producing advanced electronic products.

The Study of Complexed Copper(II) Ion and Its Application for Electroless Copper Deposition

Nowadays, sidewall metallization of microvias and through holes of a printed circuit board (PCB) after drilling and desmearing processes mainly utilizes palladium as a catalyst for electroless copper plating process. Although the palladium catalyst has been commonly used in PCB metallization, the palladium catalyst is expensive. In this work, we use complexed copper(II) ion to replace the palladium catalyst in order to greatly reduce the process cost and maintain the same metallization performance and reliability as that of palladium. The synthesis process of the complexed copper ion is simple and its cost is inexpensive compared to palladium. Particularly, they have no oxidation issue because they are not metallic copper nanoparticles but copper(II) ions. In this study, we utilized a PCB with through holes as a substrate. A conditioner with a quaternary ammonium group was employed to graft the complexed copper(II) ions onto the sidewalls of these through holes. Before electroless copper plating, the grafted copper(II) ions were chemically reduced to copper atoms, so that they can catalyze electroless copper deposition. The deposition performance of the electroless copper plating on the sidewall of a through hole catalyzed by the grafted copper catalyst were examined by backlight degree analysis using an optical microscope (OM) and surface morphology analysis using a scanning electron microscope (SEM). The thermal reliability of the electroless copper deposition catalyzed by the grafted copper catalyst was examined after copper electroplating using thermal shock in a tin bath at 288℃ for ten seconds and repeated it for 5 times. Results show that it can pass the thermal shock test.

The effects of ultrasonic vibration on mechanical properties of tungsten particle-reinforced copper-matrix composites

ABSTRACTW-Cu micro-powder mixtures usually have poor sinterability due to the relatively low solubility of W in both solid and liquid Cu. In fabricating W-Cu composites, an electroless copper plating process is often used to coat Cu on the W particle surface prior to the sintering process. Due to their small size W particles tend to agglomerate during the plating process, hence the individual particle may not be properly coated with Cu. In this study, ultrasonic vibration is applied in the electroless plating process to break up the agglomerations and restrain the powders from gathering, ensuring a uniform deposition of the Cu on individual W particle. W-Cu composite samples containing pure Cu and 6, 9 and 12 wt-% of Cu-coated W particles, respectively, are fabricated using a standard powder metallurgy technique. It is shown that the application of ultrasonic vibration in the activation and deposition steps of the electroless copper plating process prevents W powder agglomeration and ensures that each W particle is coated with Cu. As a result, the mechanical properties of the W-Cu composites are significantly improved. It is found that the optimal tensile strength and yield strength are obtained using a W reinforcement phase content of 9 wt-%.

Electroless Copper Plating Process by Applying Alternating One-Side Air Stirring Method for High-Aspect-Ratio Through-Holes

A new electroless copper plating process, namely, an alternating one-side air stirring method, was studied to improve the throwing power of high-aspect-ratio through-holes in multilayer printed wiring boards. The throwing power can even be improved for through-holes of a 40-aspect ratio under an appropriate flow velocity of the solution because the generation of differential-pressure between the front and the back of the board enhances supplying the solution into the through-holes. The necessary flow velocity can be estimated by considering the consumption rate of copper ions in a through-hole and calculating it on the basis of Bernoulli's and Hagen-Poiseuille's equation.

Electroless Copper Plating Process By Applying Alternating One-Side Air Stirring Method for High-Aspect-Ratio through-Holes

A new electroless copper plating process was studied to improve throwing power (ratio of thickness of deposited films at the center of through-hole to that of the films at the surface of the board) of high-aspect-ratio through-holes in multilayer printed circuit boards. An alternating one-side air stirring method was devised to supply adequate plating solution into through-holes. In this method, a board was put between peripheral plates via spacers. Plating solution was stirred through supplying air to one side of a narrow flow channel composed of the board and the plate by air-supplying pipes arranged at the bottom of the flow channel, while the solution in the other channel was kept static. Air was alternately supplied for each channel. This operation was expected to generate differential-pressure between the front and the back of a board, leading to supplying the solution into through-holes. Plating tests were conducted to verify the effect of this method on throwing power of the high-aspect through-holes. A plating test by applying a conventional method (both-side air stirring) was also conducted as a reference. Electroless copper plating solution was used that contained copper sulfate, formaldehyde, sodium hydroxide, ethylenediaminetetraacetic acid, dipyridyl and surfactant. Sodium sulfate, sodium formate, and sodium carbonate were also added into the solution as salts accumulated as plating time increased. The plating rate of the solution was approximately 2 to 3 μm/h. Copper sulfate, formaldehyde, and sodium hydroxide were periodically supplied by using the concentrated solution. Temperature and pH were 73 °C and 12.4. Six-mm-thick printed circuit boards with through-holes of 0.25-, 0.20-, and 0.15-mm diameter (aspect ratio: 24, 30 and 40, respectively) were used as substrates. Flow velocity of the solution was controlled by adjusting the flow rate of supplied air. Studied flow velocity was preliminary calculated by applying the Bernoulli and Hagen-Poiseuille equations on the basis of consideration that the supplying rate of reactants, particularly copper ion, needed to be higher than the consumption rate of the ion in a through-hole to improve throwing power. Plating tests revealed that throwing power indicated approximately 0.4 for the through-holes of a 24 aspect ratio in the conventional method. On the other hand, throwing power indicated nearly 1 even for through-holes of a 40 aspect ratio under the conditions in which flow velocity of the solution was more than 7 cm/s by applying our alternating one-side air stirring method. Throwing power was also found to increase as flow velocity of the solution increased at one side for any through-hole (24, 30, or 40 aspect ratio). Throwing power decreased remarkably as flow velocity of the solution decreased, implying that flow velocity of the solution significantly affected throwing power as the aspect ratio of through-hole increased. Moreover, flow velocity theoretically estimated by fluid equation reflected behavior of throwing power measured in the plating tests. Therefore, it is concluded that the alternating one-side air stirring method efficiently improves throwing power of high-aspect-ratio through-holes.

Electroless copper plating on particulate reinforcements and effects on mechanical properties of SiCp/Fe composite

The electroless copper plating process on the powder of SiC has been investigated. Thickness of the coating was tailored by the amount of copper salt added in the bath with a molar ratio of 4∶1 between reducing agent of sodium hypophosphite and copper salt. It is also found that mixed complexing agent improves the smoothness of the coating surface. Compared with mechanical properties of the SiCp/Fe composites with and without copper coating, it is shown that the copper coating improves the tensile strength by 12·6% and the final elongation by 18·1% with the SiC volume fraction of 20%. Moreover, further investigation shows that the copper coating has a same effect on the tensile strength improvement as a similar nickel coating process but has a significantly better effect on improvement of the final elongation of the composite.

English

This article focuses on the effects and applications of ethylenediamine dithiocarbamate (EDADTC) on coordination and electro chemistry. EDADTC shows stable palladium (II) metal complex in organosulphur chemistry. Since they have soft sulphur donor atoms can make a strong metal binding property, act as the ligand and stable above pH 12. Due to their water soluble tendency, flow of electron from alkyl group to nitrogen, inductive effect and conjugation effect proved the stabilizing property in electroless plating process. EDADTC has improved the physical property and produce the quality deposits in electroless copper plating process. The palladium (II) metal complex was characterized by Rapid Elemental Analysis. The structure of the stable complex was confirmed with Electronic and I.R Spectral Analysis. The surface morphologies of copper deposits were characterized by AFM studies. The crystallite sizes of the copper deposits were measured by XRD studies and the quality of the copper deposits was investigated by cyclic voltammetry studies

Fabrication of conductive copper-coated glass fibers through electroless plating process

A simple electroless copper plating process was employed to prepare copper-coated glass fibers with excellent conductivity. The glass fibers were pretreated by etching, sensitizing, and activating procedures. Disodium ethylenediamine tetra acetate (EDTA-2Na) and hydrazine hydrate (N2H4·H2O) were employed as complex reagent and reductant, respectively. It was found that the copper deposition was greatly influenced by dosage of EDTA-2Na, concentration of sodium hydroxide (NaOH), temperature, and volume of N2H4·H2O. The optimal temperature for electroless copper plating ranged from 40 to 60 °C. The composites were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy techniques. The result showed that the minimum volume resistivity of 0.0010 Ω cm was obtained for the sample with perfect copper coatings on the surface of glass fibers. This method is simple, low-cost, and large production, and can be extended to fabricate other metal-coated glass fibers with distinct conductivity.