Copper Electroplating Research Articles

Effect of Current Density on Crystallographic Orientation, and Oxidation Behavior of Copper Plated on Aluminum Substrate

In this work, the electroplating of copper on an aluminum substrate without electrochemical surface treatment was investigated. Electroplating of copper on aluminum substrate was prepared from copper sulfate electrolyte bath with various current densities 1 mA/cm², 3 mA/cm², 10 mA/cm², and 40 mA/cm². The effects of current density on the samples properties were characterized using a different technique. The surface morphology, crystallographic orientation, and corrosion resistance of the Copper film were analyzed using a scanning electron microscope, energy dispersive spectroscopy (SEM-EDS), X-ray diffractometer (XRD), and potentiostat. The samples' surface morphology is changed with different current densities because nucleation is driven by transferring the copper ion rate onto the aluminum substrate. The Cu-10 sample exhibits (111) peak higher and the best corrosion resistance than other samples. Moreover, Cu-1 samples have shifted to positive corrosion voltage (Ecorr) than the other samples.

Effect of Preheat Treatment on Wear and Corrosion Rates of Copper Electrodeposition on Medium-Carbon Steel

The work investigated the effects of pre-surface treatment on wear and corrosion rates of copper electrodeposition on medium-carbon steel. Medium-carbon steel samples were subjected to heat treatment (annealing, normalizing and quenching) in a muffle furnace. The samples were prepared and subjected to nickel striking and copper electroplating using standard bath composition. Electroplated samples were taken for weight test, optical microscopy, wear test and corrosion test. Result showed that the heat-treated copper-electrodeposited substrate had homogenous distribution of fine copper deposition, while the tempered heat-treated substrate was observed with the lowest wear rate of 3.5 × 10−3 g/mm3/min and lowest corrosion rate of 0.01833 mmpy in seawater environment of 0.5 M NaCl, thus having a low resistance to wear and corrosion in saline environment. This research has established that un-electroplated medium-carbon steel is highly corrosive in saline environment due to its higher corrosion penetration rates, while the tempered heat-treated copper-electrodeposited steels are lowly corrosion resistant and therefore suitable for use as a good material of choice in saline environments.

Overcoming the potential drop in conducting polymer artificial muscles through metallization of electrospun nanofibers by electroplating process

Electrochemical actuators made of conducting polymers are one of the major types of artificial muscles that have attracted much attention in recent years. However, these artificial muscles suffer from potential drop along the length, which undermines their performance in applications requiring longer muscles. This study is aimed at enhancing the performance of this type of artificial muscles through overcoming the potential drop along the length. This is implemented using copper electroplating and creating a full-length highly conductive nanofibrous layer. Polyurethane/copper/polypyrrole (PU/Cu/PPy) nanofibrous artificial muscles were fabricated by combining electrospinning, electroplating and electrochemical polymerization. The copper electroplating affected many features of the PU nanofibrous layer including surface morphology of nanofibers, thermal, mechanical and electrical properties. Average diameter of the PU nanofibers was measured as 306 ± 48 nm, which increased significantly by increasing the duration of copper electroplating. By copper electroplating for 20 s, the onset temperature of nanofibers thermal decomposition was increased from 249 to 302 °C. Additionally, using this process, the sample Young’s modulus was increased from 2.20 ± 0.21 to 62.32 ± 5.42 MPa while its elongation at break was decreased from 173.84 ± 14.22 to 94.81 ± 10.96. After copper electroplating for duration as low as 20 s, the electrical conductivity of nanofibers was increased by more than 200 times from 48.90 ± 1.10 to 10 103.06 ± 14.28 S cm−1. Electrochemical polymerization of pyrrole on the surface of metalized nanofibers increased the average diameter of produced nanofibers to 1030 ± 102 nm. Providing an electrical connection along the entire length of artificial muscle resulted in enhanced electroactive property and hence final bending actuation of 88° for a cycle potential between −0.8 V and 0.5 V at a scan rate of 5 mV s−1 was observed. The nanofibrous artificial muscle fabricated by the proposed method has immense potential for use in practical applications.

Development of electro-copper plating with nanodiamonds for electronic interconnects in advanced packaging

In order to advance a technology suitable for fabrication of fine pitch interconnects using copper electro plating, we developed the composite of copper (Cu) and nanodiamonds (NDs). Electro-Cu plating coatings obtained by adding NDs to the electro-Cu plating bath were demonstrated to maintain a smaller crystallite size compared to the plating coatings that NDs were not added. Moreover, in case of the electro-Cu plating coatings obtained by adding NDs, smoothness of the plating coating surface and hardness of the plating coating with time course have been improved, and the electro conductivity has been improved by up to 16%. The composite material of electro-Cu plating and NDs which we developed showed the potential that it could be expected for application to fine pitch interconnects in an advanced packaging technology.

Investigations of the electrochemical performance and filling effects of additives on electroplating process of TSV

Through silicon via (TSV) is one of the most important technologies used in three dimension (3D) packaging. The void-free filling of TSV can be achieved by adding additives into the electrolyte bath during the electrodeposition process. This paper focuses on the effects of three types of commercial additives (the suppressor, the leveler and the accelerator) and analyses additives’ interaction on electroplating through experimental investigations. The results showed that the suppressor, the leveler and the accelerator all have chemical behaviour of inhibition in different degrees to the copper electroplating. The interaction experiments of additives in pairs indicated that the suppressor absorbed on the cathode surface was gradually displaced by the accelerator as the concentration of the accelerator increased; the accelerator and the leveler presented a competitive adsorption relationship; the suppressor and the leveler had a synergistic effect for electroplating inhibition especially under high potential and low suppressor concentration. Experiments of micro via filling by electrodeposition have been conducted to investigated the effects of singular additive and multiple additives on the filling process of the micro vias.

Electroplating of Copper on Low Carbon Steel from Alkaline Citrate Complex Baths

Electroplating of Copper on Low Carbon Steel from Alkaline Citrate Complex Baths

Relationship between Concentration of Alcian Blue and Mechanical Properties on High Current Density Copper Electroplating

The current density in copper electroplating is directly related with the productivity; then, to increase the productivity, an increase in current density is required. This study is based on an analysis of changes in surface characteristics and mechanical properties by applying the addition of Alcian Blue (AB, C56H68Cl4CuN16S4). The amount of Alcian Blue in the electrolytes is changed from 0 to 100 ppm. When Alcian Blue is added at 20 ppm, a seed layer is formed homogeneously on the surface at the initial stage of nucleation. However, crystals electroplated in electrolytes with more than 40 ppm of Alcian Blue are observed to have growth in the vertical direction on the surface and the shapes are like pyramids. This tendency of initial nucleation formation causes protrusions when the thickness of copper foil is 12 μm. Thereafter, a lot of extrusions are observed on the group of 100 ppm Alcian Blue. Tensile strength of groups with added Alcian Blue increased by more than 140% compare to no-addition group, but elongation is reduced. These results are due to the decrease of crystal size and changes of prior crystal growth plane from (111) and (200) to (220) due to Alcian Blue.

Copolymer of Pyrrole and 1,4-Butanediol Diglycidyl as an Efficient Additive Leveler for Through-Hole Copper Electroplating.

A copolymer comprising of pyrrole and 1,4-butanediol diglycidyl ether (PBDGE) was designed and synthesized as a leveler to improve the throwing power for printed circuit board (PCB) through-hole electroplating. The results of linear sweep voltammetry (LSV), galvanostatic measurements (GMs), and cyclic voltammetry (CV) reveal the strong coordination effect of PBDGE with other additives and confirm the advantageous performance of PBDGE to effectively assist the electroplating of through-hole. An increment of 35.5% in the throwing power was achieved under the addition of PBDGE in through-hole plating. Additionally, the reaction mechanism was studied by quantum chemical calculations and molecular dynamics (MD) simulations, indicating that the pyrrole rings of the PBDGE molecule are adsorbed on the copper surface as the adsorption sites to balance the copper plating regardless of the through-hole position differences.

Bis-(sodium sulfoethyl)-disulfide: A Promising Accelerator for Super-conformal Copper Electrodeposition with Wide Operating Concentration Ranges

Accelerators are indispensable additives for super-conformal copper electrodeposition, which has been widely applied in the fabrication of integrated circuits (ICs), printed circuit boards (PCBs), and advanced semiconductor packaging substrates. Currently, bis-(sodium sulfopropyl)-disulfide (SPS) and sodium 3-mercapto-1-propanesulfonate (MPS) are the most widely used accelerators for super-conformal electroplating. However, owing to the limited operating concentration range, frequent measurements of the SPS (or MPS) concentration during the electroplating process are needed to manage the accelerator concentration in a suitable range, which makes the application of SPS (or MPS) tedious and unreliable. In our previous study, bis-(sodium sulfoethyl)-disulfide (SES), which has a molecular structure that is similar to that of SPS but with shorter alkyl chains, was determined to be a weaker depolarizer than SPS. The weaker antagonistic effect against suppressor and leveler imply that the higher concentration of SES maybe applicable to achieve the super-conformal electroplating. In this study, SES was investigated in detail, and it was found that in combination with Cl−, PEG, and JGB, the SES-containing electrolytes can provide the positive potential difference Δη, excellent microvia filling performance, and good copper deposition physical properties in a wide operating concentration range. SES is a promising accelerator for the super-conformal copper electroplating.

Study on Physical Properties of Ultrasonic-Assisted Copper Electrodeposition in Through Silicon Via

Through silicon via (TSV) connection plays a significant role in 3D packaging technology. In this paper, copper electroplating in TSVs under different ultrasonic powers was realized through an ultrasonic electroplating system. The physical properties (surface roughness, Young’s modulus and hardness) of ultrasonic-assisted copper electrodeposition in TSV were analyzed. Copper grain size inside the via was also measured and compared. Based on the analysis of experimental results, a conclusion could be reached that the increase of ultrasonic power has an effect on the physical properties of copper plating in TSV. It can effectively reduce the surface roughness of the copper plating surface. Besides, the increase of ultrasonic power can increase the values of Young’s modulus and hardness. It is also found that the decrease in copper grain size results in a tight connection between copper crystal grains. Explanations on the changes of physical properties under different ultrasonic power have been provided.

3D-Printed UHF-RFID Tag for Embedded Applications

This paper presents the design, manufacture and characterization of a novel 3D passive UHF-RFID tag for embedded applications. The prototype is fabricated using additive manufacturing techniques: 3D printing and copper electroplating. The design, manufacturing process and measurement set-up are presented and discussed in detail. We propose a biconical antenna design with spiral strips embedded in the cones to provide compactness without breaking the symmetry of the component and to improve bandwidth. The antenna is matched to a commercial UHF-RFID integrated circuit. We incorporate a packaging design that consists of a dielectric coating, to provide proper operation in different media or surrounding environments with changing electromagnetic properties. The good agreement between experimental results and Finite Element Method simulations allows us to validate the whole process. Finally, a compact capsule-type RFID tag is proposed and its performance in different media is reported.

Copper electroplating of 3D printed composite electrodes

The manufacture of electrodes by 3D printing approaches has recently been recognized as a fast, inexpensive and environmentally friendly alternative to traditional preparation techniques based on subtractive manufacturing tools. However, as-prepared 3D printed electrodes typically show a considerable intrinsic kinetic barrier for the electron transfer. In this work we employ fused deposition modelling 3D printing to fabricate electrodes from a polylactic acid/copper composite filament and subject them to the surface functionalization by the copper electroplating aiming at eliminating this kinetic barrier. Cyclic voltammetry employing [Ru(NH3)6]3+/2+ couple as the electroactive probe was employed to inspect electron transfer properties of the manufactured electrodes. We demonstrate that electrodes modified by an optimized electroplating procedure show virtually no kinetic barrier and generate faradaic response with the magnitude comparable to that obtained at conventional metallic and carbon-based electrodes. The obtained faradaic peak separation value (70–75 mV) is superior to all values reported for 3D printed electrodes in the literature.

Fully 3-D-Printed Frequency-Scanning Slotted Waveguide Array With Wideband Power-Divider

We report the design, fabrication, and measurement results of a fully three-dimensional (3-D) printed frequency-scanning slotted waveguide array (SWA). The antenna system is composed of an 18 × 4 nonresonant (traveling wave) array operating at 12–18 GHz (Ku-band), a wideband 1 × 4 power divider, and four 50 Ω matched loads all fabricated using a 3-D printer and wet metallization steps. The antenna system is designed to be impedance-matched with S 11 less than −10 dB across the entire band. Inductive walls are added to the power divider to improve the impedance matching of closely packed waveguides. Complex yet smooth waveguides are fabricated using the PolyJet technology. Conformal in-house metallization processes consisting of nickel electroless plating and copper electroplating are established. Measurement results show beam-scanning ranges from −17° at 12 GHz to +15° at 18 GHz. The maximum measured gain is 21.4 dBi with sidelobe level of −13.4 dB at 15.8 GHz and scanning angle of 7°. Furthermore, the array maintains minimum gain of 10 dBi for most of the band ranging from 13.4 to 17.8 GHz. Our measurement results are in an agreement with the simulations. This letter demonstrates a scanning array, together with a wideband power divider, and termination loads all fabricated using a 3-D printing technology.

A 3-D Printed $E$ -Plane Waveguide Magic-T Using Air-Filled Coax-to-Waveguide Transitions

This article reports on a new class of broadband and fully 3-D printed $E$ -plane coax-to-waveguide transition and a monolithically 3-D printed waveguide magic-T based on the transition. The transition is constructed by a section of air-filled rectangular coaxial transmission line (TL) that is placed between two broadband coax-to-waveguide probe transitions. It is used to interconnect the magic-T’s sum port and the waveguide T-junction. The incorporation of the transition reorients all the waveguide arms of the magic-T into the $E$ -plane. Some $X$ -band prototypes of the proposed transition and the magic-T are designed and implemented. Polymer-based additive manufacturing and copper electroplating techniques are employed to monolithically fabricate each prototype. The transition and the magic-T exhibit broadband and low-loss characteristics from 8.2 to 12.4 GHz with the measured performance well matched with the simulations. In addition, the power handling capability (PHC), including the peak PHC (PPHC) and the average PHC (APHC), of the magic-T is evaluated by simulations, showing that the proposed magic-T could handle 100 W of APHC.

Design, fabrication, and testing of a helical antenna using 3D printing technology

AbstractWe report the design, fabrication, and measurements of a circularly polarized 3D‐printed helical antenna operating at 5 GHz. Several commercially‐available dielectric printers and materials (eg, PLA, ABS, PC) were evaluated for the fabrication process. Metallization was performed with nickel electroless plating followed by copper electroplating. Fabrication and metallization process completed within 24 hours. Maximum gain of the antenna is measured as 13.9 dBic at broadside (RHCP). Measured efficiency of the antenna is 89.1% which shows the effectiveness of our metallization process. The results demonstrate the feasibility of rapid fabrication of lightweight and high efficient antennas using 3D printer technology.

Development of High-Temperature-Resistant Seed Layer for Electrodeposition of Copper for Microelectronic Applications

Copper is the most commonly used material for interconnects within microelectronics. However, electromigration and high resistance within the material limit the use of copper in nanoscale applications. New, two-dimensional (2D) materials such as graphene, carbon nanotubes (CNTs), and transition-metal dichalcogenide (TMDs) are being developed for the next generation of interconnects. A composite consisting of a forest of vertically aligned carbon nanotubes within a matrix of copper is a proposed solution to the issues which present themselves in nanoscale copper interconnects. The fabrication of CNTs and graphene often requires high temperatures that exceed the material limitations of copper in microelectronic processing. If these 2D materials are used in conjunction with copper, it is desirable to delay copper deposition to late stages of microfabrication in order to avoid exposing copper to high temperatures. It is proposed that a seed layer be deposited before deposition/growth of CNTs/graphene or other TMD materials, such that later deposition of copper via electroplating is feasible. A conductive seed layer must be introduced underneath the forest of CNTs in order to allow for electroplating to take place. Copper itself may not be used as a seed layer since it migrates at elevated temperatures, which prevents growth of carbon nanotubes. Thus, the seed layer must be able to withstand high temperatures, must not migrate or diffuse into silicon or barrier layers, and must also be a suitable seed layer for copper electroplating. This research focuses on evaluating different metals as potential seed layers for copper electroplating for nanoscale applications. Layers of various metals of 100 A, 275 A, and 1000 A thickness were deposited onto silicon wafers via physical vapor deposition. They were then electroplated with copper and examined visually for quality and consistency. A digital microscope was used for microscopic examination, then a scanning electron microscope was used to examine the development of copper over the seed layers and for elemental mapping to verify copper deposition. Seeds consisting of 1000 A platinum, 1000 A nichrome, and 100 A silver showed strong promise for use as seed layers for nanoscale applications. Platinum and nichrome were found to develop uniform copper coatings and strongly adhere to the silicon wafer. To protect platinum and nichrome from diffusion into silicon during chemical vapor deposition (CVD) CNT growth, a barrier layer may be required. Copper developed uniformly over the 100-A silver seed. Silver is unlikely to diffuse into silicon at the temperatures required during CVD CNT growth. Due to poor adhesion between the silver seed and silicon wafer, an adhesion layer may be used to improve reliability.

Study the impact of CuSO4 and H2SO4 concentrations on lateral growth of hydrogen evolution assisted copper electroplating

Hydrogen evolution assisted (HEA) electroplating has shown some potentials to be used for rapid lateral copper electrodeposition. A lateral electric field was established between the two cathodes while the voltage between the anode and one cathode was set to be high enough for water electrolysis and hydrogen evolution. In this work, the effect of concentrations of cupric sulfate (CuSO4) and sulfuric acid (H2SO4) in the electrolyte on the lateral deposition rate and the deposited layer morphology was studied. We have found that incrementing the acid concentration in the aqueous acidic solution to 1.0 M (H2SO4) and 1.5 M (H2SO4) accelerates the deposition rate to 15.38 and 15.6 μm s−1, respectively, by the interaction of hydrogen bubbles with the surface of the electrode being plated. Scanning electron microscopy (SEM) technique was employed to analyze the morphology of the deposited copper after the completion of the procedure. The technique was also tested for soldering electronic components which demonstrated the potential of using the method for soldering at low temperatures suitable for wearable electronics.

Fabrication and Measurement of Microtip Electrode Array Integrated With Self-Aligned Hemispherical Cell Trapping PDMS Template

This paper presents a novel microtip electrode array integrated with a self-aligned cell trapping polydimethylsiloxane (PDMS) template. Cells can be captured in the hemispherical PDMS template using the ultrasonic assembly technique, and their electrochemical responses can be measured using the microtip electrode positioned at the center of the template. The hemispherical PDMS template can be integrated with the microtip electrode through a sequential process of copper electroplating in a spherical form at the tip end, PDMS coating, and etching of PDMS and electroplated copper, in which an additional photolithography process is not required. The fabricated microtip electrode array integrated with the PDMS template was examined using cyclic voltammetry measurements and applied to the measurements of oxygen reduction current from the photosynthetic reaction of captured chlorella cells in the PDMS template.

Extreme biomimetics: Preservation of molecular detail in centimeter-scale samples of biological meshes laid down by sponges.

Fabrication of biomimetic materials and scaffolds is usually a micro- or even nanoscale process; however, most testing and all manufacturing require larger-scale synthesis of nanoscale features. Here, we propose the utilization of naturally prefabricated three-dimensional (3D) spongin scaffolds that preserve molecular detail across centimeter-scale samples. The fine-scale structure of this collagenous resource is stable at temperatures of up to 1200°C and can produce up to 4 × 10-cm-large 3D microfibrous and nanoporous turbostratic graphite. Our findings highlight the fact that this turbostratic graphite is exceptional at preserving the nanostructural features typical for triple-helix collagen. The resulting carbon sponge resembles the shape and unique microarchitecture of the original spongin scaffold. Copper electroplating of the obtained composite leads to a hybrid material with excellent catalytic performance with respect to the reduction of p-nitrophenol in both freshwater and marine environments.

On the Mitigation of Corrosion Under Insulation (CUI) of Mild Steel Using Local Cathodic Protection

A strategy based on cathodic protection (CP) could be a practically feasible means to protect steel piping from corrosion under insulation. However, experimental studies investigating CP of steel through moist insulation are scarce. Herein, CP was explored to protect insulated steel specimens using sacrificial zinc anodes. The conditions to effectively impart CP through the moist insulation have been discussed. The “throwing power” or protection achieved using sacrificial zinc anodes coupled with mild steel specimens in moist insulation was also estimated using copper electroplating. It was validated that the efficacy of CP depends upon the ionic resistivity of the moist insulation and the moisture content (by volume) must be >25% for efficient ionic conductivity through the insulation. The maximum throwing power of CP through the insulation was achieved when zinc was in direct physical contact with mild steel, with zinc to mild steel area ratio being 1:10.