Copper Electroplating Research Articles

Pentaerythritol-Based Compound as a Novel Leveler for Super-Conformal Copper Electroplating

Leveler is one of the most important organic additives in copper electroplating for microvia filling. To enhance the microvia filling efficiency and reduce the bath control difficulty, novel levelers with high filling performance and wide application concentration range has long been pursued. Herein, a novel leveler named L1 with four pyrrolidine rings linked by a pentaerythritol backbone is designed and synthesized. Compared with the previously reported leveler TPM-1, L1 shares the same nitrogen-containing group but has an additional pyrrolidine ring. The structure-property relationship of L1 is thoroughly characterized by electrochemical measurements, theoretical calculations, and electroplating experiments. Results show that with one more positively charged ammonium groups, L1 exhibits stronger interactions with Cl− and the accelerator SPS compared to TPM-1. However, due to the variation of the connecting group, its interaction with the suppressor PEG is much weaker. With L1 as the leveler, both good microvia filling performance and high-quality copper deposition was obtained within a wide concentration range. The findings indicate that L1 is a very promising leveler for microvia filling copper electroplating, and both nitrogen-containing groups and linking groups in a leveler significantly influence its properties and performances.

Evaluating copper plating process for filling micro vias with thin surface Cu by the 1-(4-carboxyphenyl)-5-mercapto-1H-tetrazole additive

The 1-(4-carboxyphenyl)-5-mercapto-1 h-tetrazole (CMHT) as a novel leveler for the overfilling of micro-blind vias was investigated in acidic copper electroplating. The synergistic effect between CMHT and other additives were confirmed through chronoamperometry, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed a convection-dependent interaction between the CMHT and suppressor (propyleneoxide (PO)-ethylene oxide (EO)-propylene oxide (PO), named PEP). Metallographic section testing demonstrated that the CMHT not only have excellent microvia filling performances, but also only have 19.1 μm thin surface Cu for micro blind vias with a diameter of 150 µm and a depth of 80 µm by the electrodepositing 60 min of 2 A/dm2. The quantum chemical calculations experiments revealed also that the CMHT parallel orientation of the benzene ring and tetrazole heterocycle can enhance the effective adsorption area. The obtained results from electrochemical test and quantum chemical calculations were in reasonably good agreement.

Copper‐graphene coatings for improving thermal shielding of CFRPs through electrodeposition techniques

AbstractToday, carbon fiber reinforced plastics (CFRPs) are materials of interest several industrial sectors because of their mechanical properties and low weight. However, applications in high‐temperature areas are limited because of thermal degradation. Thus, thin coatings acting as thermal shielding and ensuring the upkeep of CFRP structural stiffness are of high interest. This work presents an innovative approach to produce copper/graphene bilayer coatings through electrodeposition and electrophoretic deposition; it consists of laser pre‐treatment of the composite surface to remove the matrix layer exposing the carbon fibers, enabling the subsequent deposition. Bi‐layer graphene/copper coatings exhibit an enhancement in copper electrodeposition efficiency of more than 59% resulting in a 97% stiffness improvement compared to the single layer copper electroplating. All the obtained coatings were able to act as a thermal shield of the CFRPs, reducing the maximum temperature of the composite by more than 60%. In particular, due to the synergistic effect of copper and graphene, the GNPs‐Cu coating achieved the highest maximum temperature reduction (81%). Cross‐sectional analysis indicates severe delamination in uncoated CFRPs, whereas double‐layer coatings maintain structural integrity and prevent delamination even under high‐energy exposure. In addition, the coated composites exhibit a higher electrical conductivity compared to the laser cleaned CFRP, with the GNPs‐Cu coating that obtained a 90% enhancement because of the outstanding electrical properties of copper and graphene.Highlights The laser cleaning pretreatment allows the electrodepositions on CFRPs. The GNP‐Cu scenario achieves the highest deposition efficiency. A 97% stiffness improvement was achieved by GNPs‐Cu scenario. GNPs‐Cu coatings exhibit the utmost reduction in resistivity (98%). The GNPs‐Cu coating achieves the highest thermal shielding performance (81%).

Enhanced adhesion strength of copper metallization on silicon heterojunction solar cell due to improved electrochemical reduction uniformity of ITO

Copper electroplating is an ideal technique for the metallization of highly efficient silicon heterojunction (SHJ) solar cells due to the unique advantage in the low cost, strong adhesion, and low contact resistance. Achieving these characteristics depends strongly on the seed layer before Cu electroplating. This work reports a potential economical and effective route for electrochemically reducing ITO to assist electroplating of Ni seed layer and increase the adhesion of the metallization grids. Good wettability of electrolyte solution to ITO and the low temperature account for the reduction uniformity. A uniform In,Sn/SnO mixed metal layer is formed on ITO surface after electrochemical reduction. With the assistance of the uniform reduction the adhesion strength of the metallization grid reaches to 9.9 N mm⁻1. Although it is conducted on a small-size ITO-coating Si plate, the present plating is convenient and low-cost for the metallization, which is expected to be suitable for the large-scale commercialization of SHJ solar cells.

Numerical and experimental investigation of 2-thiazoline-2-thiol and nitrotetrazolium blue chloride compound as levelers for through-hole copper electroplating

Leveler is essential in the electroplating process of the through-hole (TH), the adsorption characteristics of which are strongly influenced by the aspect ratios of the THs. However, only a single kind of leveler usually appears in the most frequently performed THs’ filling electrolyte, which is highly possible to limit the electrolyte's capability to fill THs and improve the copper film properties. In this paper, two levelers, 2-Thiazoline-2-Thiol (T1) and Nitrotetrazolium Blue chloride (NBT), with significant molecular weight differences, were combined to fill THs with multiple ARs. The interactions among the leveler compounds and other additives become the primary factor controlling the THs electroplating process, which was systematically investigated through a combination of flow field numerical simulation and electrochemical measurements. T1 presents a weaker inhibition effect and is more sensitive to convection than NBT, which also exhibits a convection-enhanced inhibition effect with other additives. The convection of the electrolyte in the THs center continuously decreases with the ARs, guiding to the increasing electroplating rate at the THs center, high throwing power (TP) of 141%, and flawless filling of the THs with ARs of 4.75:1∼1.9:1 in 2.5 h. The copper film on the surface maintains extremely high flatness and low thickness.

Studies on the quantitative analysis of an electrochemical solution via the Schlieren method

A quantitative schlieren technique has been applied to measure the change of copper sulfate concentration in an electrochemical cell during the copper electroplating process. We constructed a mathematical model that correlates the grayscale values of schlieren images with the concentration of copper sulfate and analyzed the impact of refraction, reflection, and absorption of light during its passage through the solution on the precision of a schlieren quantitative analysis. Ultimately, by examining the temporal and spatial changes in the distribution of the copper sulfate concentration, we ascertained the impacts of convection, diffusion, and electromigration on the concentration distribution. The impact of the current studies would be greatly expanded in important electrochemical practices such as renewable energy conversions and rechargeable batteries.

Simultaneously performing interlayer copper interconnecting and TSV filling in stacked chips at room temperature based on copper electroplating

Simultaneously performing interlayer copper interconnecting and TSV filling in stacked chips at room temperature based on copper electroplating

Antenna array of waveguide horns with an E-plane aperture, as well as horns with an aperture in the E- and H-planes

Background. Currently, in connection with the conduct of a special military operation, the issue of the availability of inexpensive mobile terminals for high-speed satellite communications of domestic production is very relevant, as well as due to the large extent of the territories of our country, there are a number of areas where cellular communication is absent, for example, the Taiga, the Arctic, the territory of the Arctic Ocean, etc. Therefore, the only possible connection in these territories is satellite communication. Aim. Development of a linear equidistant antenna array with equal amplitude and common-mode excitation for a mobile satellite communication terminal. Methods. The antenna array was designed from the open ends of waveguides with a cross section of 19 × 11 mm with air filling. Adjacent pairs of radiating waveguides are powered by an E-planar divider: the waveguide is divided in half in height by a thin metal diaphragm, wave reflections from which are insignificant; further, in each half of the power divider, height-separated right and left turns and smooth transitions in the E-plane are implemented – an extension from 5,25 mm to 11 mm. Results. An antenna array with a period of 19,5 mm has been developed. Overall dimensions: opening width – 624 mm, height – 12 mm, depth – 118 mm. A feature of the antenna array design is the use of smooth asymmetric transitions in the E-plane according to the exponential law; in the opening of the headlights, waveguide asymmetric horns alternate, with a period equal to 4 values of the width of the waveguides, taking into account the width of their narrow walls, expanding in the upper (2 adjacent radiators) and lower (next 2 radiators) directions. Conclusion. The advantage of using an approach to the construction of linear antenna arrays powered by multichannel power dividers is the ability to minimize the depth of the antenna system. The main disadvantages are the constructive and technological complexity of power dividers and significant power losses with a large number of channels. Possible manufacturing technologies of the developed phased array: 1. Stamping of polystyrene of the inner part of the power divider and emitters. Next, polishing, copper spraying and electroplating with a layer of copper. 2. Printing on a 3D polystyrene printer, polishing, copper spraying and copper electroplating. 3. Manufacture of a power divider using SIW technology based on standard microwave laminates. The use of metallized through holes for matching power dividers. Antenna elements and coaxial waveguide junctions are made by stamping from polystyrene, or printing on a 3D printer from polystyrene, then polishing, spraying a layer of copper and electroplating with a layer of copper. 4. Metal stamping of the power divider, emitters and coaxial waveguide junctions (2 parts). The dielectric insert can be printed on a 3D printer made of polystyrene.

A Novel Model for Copper Electroplating Process Simulation Minimizing Chemical Additives

A Novel Model for Copper Electroplating Process Simulation Minimizing Chemical Additives

Preparation and application method of CNTs dispersion solution for direct electroplating on circuit board holes

Abstract The utilization of carbon black dispersion solutions for the black hole method is common in the electronics industry due to their cost-effectiveness and stable performance. However, the slow electroplating speed caused by carbon black’s poor conductivity can impact industrial processes and time. This paper introduces a water-based dispersion solution of carbon nanotubes (CNTs) for the direct copper electroplating process on circuit board holes and its application method. The dispersion solution comprises “shortened” CNTs with a small aspect ratio, a dispersant, a pH adjuster, and other optimization agents. This black hole liquid functions as a conductive fluid with “shortened” CNTs as the conductive medium, exhibiting high dispersibility, strong through-hole capability, low resistance, and excellent adhesion. Its performance surpasses that of black hole liquids using single-carbon black as the conductive medium. The key advantage lies in avoiding the entanglement associated with conventional long aspect ratio CNTs, thereby enhancing the conductivity of the water-based dispersion solution. This facilitates the formation of a uniform conductive film through the electrostatic self-adsorption method, which is suitable for preparing a conductive film on circuit board hole walls before copper electroplating.

Tributyl(hexyl)phosphonium chloride as a new leveler for microvia copper superconformal electronic plating

A phosphorus-containing new compound of tributyl(hexyl)phosphonium chloride (TBHP), but not the commonly used nitrogen-containing heterocycles and quaternary ammonium salts, is successfully applied for the superconformal copper filling of microvia in acid sulfate electroplating bath for the application of electronic industry. The molecular interaction mechanisms of TBHP combined with suppressor (polyethylene glycol, PEG) and accelerator (bis-(sodium sulfopropyl)-disulfide, SPS) are investigated in detail. Galvanostatic measurements at platinum rotation disk electrode indicate that the leveler of TBHP among with the suppressor and accelerator behaves the key characters of inhibition and convection-dependent adsorption during copper ions electroreduction for the bottom-up filling of microvia. Cyclic voltammetry measurements and in-situ FTIR spectroscopy further reveal that TBHP synergistically interacts with the suppressor to inhibit copper ions electroreduction at the mouth of microvia; while TBHP competes for adsorption with the accelerator, behaving as TBHP gradually replaced by the accelerator at the bottom. Based on the sufficient theoretical supports, the practical copper electroplating is conducted for the verification of microvia void free filling. In the developed novel copper plating formula containing TBHP, PEG and SPS, the void free filling is successfully achieved and the filling percentage (FP) is high in 95.5%.

Electroplated Copper Additives for Advanced Packaging: A Review.

Acid copper electroplating stands as a core technology in advanced packaging processes, facilitating the realization of metal interconnects, bumps, vias, and substrate wiring between transistors. The deposition quality of copper interconnect materials has a crucial impact on the final performance of chips, directly influencing their yield, reliability, and stability. In this intricate process, additives play a pivotal role in regulating the deposition quality and behavior of metal copper. This mini-review comprehensively summarizes the recent research progress in the field of electroplating copper additives for advanced packaging, both domestically and internationally, delving into the types and mechanisms of various additive molecules, including accelerators, inhibitors, and leveling agents. Through in-depth research on these additives, we gain a profound understanding of their specific roles in the electroplating process and the intricate interaction mechanisms among them, providing theoretical support for optimizing the electroplating process. Furthermore, this mini-review also delves into a thorough analysis of the current issues and challenges facing acid copper electroplating, exploring the key factors that constrain the further development of electroplating copper technology. Based on this analysis, we propose several potential solutions and research directions, offering crucial references for the development and application of electroplating copper additives in advanced packaging. In conclusion, this mini-review aims to provide a comprehensive perspective and profound understanding of the development and application of electroplating copper additives through a review and analysis of recent research progress, ultimately aiming to promote the further advancement of advanced packaging technology.

Alkyl-terminated PEG suppressors for copper electroplating and their hydrophilic and hydrophobic properties

This study explores the structure-activity relationship of copper electroplating suppressors, with a focus on alkyl-terminated polyethylene glycols (PEGs), to better understand their efficacy in electronic interconnect fabrication. Electrochemical analysis demonstrated that an increase in the molecular weight of PEG suppressors significantly raises the electrochemical polarization overpotential during copper electrodeposition. Additionally, alkyl terminal capping was observed to amplify this polarization effect, with the extent of overpotential increase directly correlating with the alkyl chain length. However, the advantageous impact of molecular weight on overpotential diminishes at higher molecular weights. In contrast to the electrochemical results, through-hole electroplating experiments revealed that a suppressor with a molecular weight of 1 k and butyl termination exhibits superior through-hole throwing power. Further analysis indicated that a greater proportion of alkyl functional groups within the suppressor's molecular chain enhances uniform electroplating capabilities. The study also suggests that measuring contact angles, as an expression of hydrophobicity, could provide a more efficient and precise method for evaluating suppressor performance.

Quantifying thiolated chemical additives for copper electroplating process

BackgroundCopper foil, a thin layer of high-purity metallic copper, having excellent conductivity, ductility, and corrosion resistance, is extensively applied in various electronic applications. Thiolated (SH-containing) chemical additives (i.e., accelerator and inhibitor) in copper electroplating solution are known to be critical for optimizing the copper foil manufacturing processes. Due to the high ionic strength and acidity of copper electroplating solution, proper and accurate characterization of the thiolated chemical additives is a critical concern. ResultsIn this study, a facile, accurate approach is developed for quantitative characterization of thiolated additives in the copper electroplating solution. Firstly, gold nanoparticles (AuNPs) were employed as an adsorbent for separating the thiolated chemical additives, namely, poly(ethylene glycol) methyl ether thiol (PEG-SH) as inhibitor, and 3-mercaptopropionic acid (MPA) as accelerator from other interfering chemicals present in the copper electroplating solution. Subsequently, quantitative analysis of the AuNPs in the form of thin particle film was performed using attenuated total reflection-Fourier transform infrared spectroscopy. Electrospray-differential mobility analyzer was employed orthogonally for the quantitative analysis of the amount of thiolated additives adsorbed on AuNP. Interestingly, the results indicated that the detection concentration ranges of 5 μM–100 μM for PEG-SH and 10 μM–200 μM for MPA, respectively. SignificanceOverall, this work demonstrates a successful separation and analysis methodology for the thiolated chemical additives in copper electroplating solution which enables the precise control over the copper foil manufacturing process.

Copper-Plated Nanoporous Anodized Aluminum Oxide for Solar Desalination: An Experimental Study

Currently, there is a shortage of potable water in several regions. Various alternative methods exist for producing purified water; however, one particular technology known as solar desalination is gaining prominence as a sustainable and environmentally friendly solution. Solar desalination harnesses solar energy to produce fresh water in regions with abundant sunlight. This study involved the fabrication of a nanostructured porous material composed of copper using anodization, followed by copper electroplating. In order to create three distinct nanoporous structures, we utilized three anodization periods of 40 min, 60 min, and 80 min. Subsequently, these structures underwent a copper deposition process for 30 min using the copper electroplating technique. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDAX), and X-ray diffraction (XRD) techniques were utilized to analyze the characteristics of the copper-plated nanoporous structure. Three distinct samples were utilized in solar desalination experiments, employing solar stills over a span of three consecutive days, with each sample being tested on a separate day. All three samples underwent desalination, unlike the standard solar still, which did not include any sample. Our observation revealed that the sample, which underwent 60 min of anodization followed by copper electroplating, had a significantly greater evaporation rate of 22.22% compared to the conventional still.

Enhancing Electrical and Mechanical Properties of Conductive Textile for Wearable Embedded Systems Through Copper Electroplating

Wearable electronics, particularly electronic textiles, hold promise for significant advancements, yet their limited electrical conductivity hinders widespread application. This study examines the application of copper electrodeposition to enhance the electromechanical attributes of textronics. The conductive fabric undergoes copper electroplating for varying durations, assessing the increase in electrical conductivity relative to copper thickness. Experimental conditions span current densities from 0.2 to 20 A dm−2. Additionally, the research evaluates the mechanical resistance of the resulting interconnection with conventional electronic components. Voltammetric measurements, sheet resistance, and microscope observations establish optimal copper deposition conditions. As hypothesized, an inverse proportionality between the sheet resistance of the electrodeposited fabric and the thickness of the copper layer has been observed. This improvement raises a query: does the electromechanical reliability of e‐textiles improve with the addition of only a few micrometers of copper? The study reveals the significant enhancement of the mechanical resistance of soldered interconnections with rigid components after a few seconds of electrodeposition as well as an improvement of the quality factor of a textile antenna. In conclusion, electroplating significantly improves the electromechanical properties of textronics without compromising their wearability. This discovery paves the way for novel applications such as wireless fast charging with textile antennas.

Enhancing Electrical and Physical Contacts of Copper‐Electroplated Silicon Heterojunction Solar Cells through Chemical Pretreated Seed Layers

Copper electroplating offering the potential to replace low‐temperature sintered silver pastes holds significant promise as a metallization process for silicon heterojunction (SHJ) solar cells (SCs). To unlock the full potential of copper electroplating, it is crucial to enhance the contact properties between the electroplated grids and the indium tin oxide (ITO) films, addressing both contact resistivity and physical adhesion. Herein, a zinc‐assisted Fe2+ system to modify the ITO film is used, leading to the formation of an In/Sn/SnO mixed‐metal transition layer. This transition layer serves as a seed layer for metal electroplating, reducing contact resistivity and enhancing the mechanical connection between the electroplated metals and the ITO films. Following the ITO pretreatment process, the contact resistivity is significantly reduced from 1.4 to 0.2 mΩ cm2, and the peel force value of the pretreated sample reaches 14.2 N mm−1, which is 75.3% higher than that of the untreated sample. The proof‐of‐concept SHJ SC with copper electroplating after ITO pretreatment achieves a remarkable power conversion efficiency of 22.6%. These results clearly demonstrate that ITO pretreatment using the zinc‐assisted Fe2+ system is an effective approach for enhancing contact properties and improving the performance of copper‐electroplated SHJ SCs, showcasing significant potential for industry applications.

Application of Electrochemical Impedance Spectroscopy (EIS) to Study the Effect of Temperature and Ion Concentration During Electroplating of Copper from an Acidic Bath

Application of Electrochemical Impedance Spectroscopy (EIS) to Study the Effect of Temperature and Ion Concentration During Electroplating of Copper from an Acidic Bath

Formation of Sn seeds on indium-free TCO for plating metallization of silicon heterojunction solar cells

The cost-prohibitive ITO and low-temperature silver paste pose significant challenges in the manufacture of SHJ solar cells. The SnO2-based TCO (indium-free) and Cu electroplating are promising solutions to address these issues. The key point of Cu electroplating is the seed layer for achieving good adhesion and low contact resistivity to the TCO. In this study, we report the electrochemical reduction method for the Sn seeds on FTO films, offering an alternative to the costly vacuum deposition process. We reveal that the electrochemical reduction process is dominated by the breaking of lower-energy bonds during electrons injection, resulting in the formation of tin nanoparticles which serve as the excellent seeds for the subsequent electroplating of a nickel metal layer on the FTO film. A tightly binding interface without any pores between the FTO film and Ni was observed, confirming its effectiveness. Our calculation results using the DFT method manifest that the binding energies of Sn/Ni interface are significantly lower than SnO2/Ni, indicating that Sn seeds present a lower energy barrier for deposition, which promotes Ni deposition kinetics. The integration of indium-free TCO, seeds preparation of electrochemical reduction, and copper electroplating is expected to boost SHJ solar cells in near future.

The Effect of electrolyte concentration and temperature at electroplating with copper on the plate thickness and corrosion rate of plated gray cast iron

This study aims to determine the effect of variations in electrolyte solution concentration and copper electroplating temperature on gray cast iron to achieve the desired copper layer thickness and reduce the corrosion rate of gray cast iron impeller pumps. A total of 30 test specimens made from gray cast iron were used, with dimensions conforming to the ASTM G31-72 standard for corrosion rate testing. The specimens were coated with copper electroplating using three different solutions: solution 1 (195 g/L copper sulfate, 45 g/L sulfuric acid), solution 2 (205 g/L copper sulfate, 50 g/L sulfuric acid), and solution 3 (215 g/L copper sulfate, 55 g/L sulfuric acid). Each solution was used with dipping temperatures of 30 – 34 °C, 40 – 44 °C, and 50 – 54 °C. After being coated with copper, the layer thickness was measured using a digital coating thickness gauge (F&NF type). The corrosion rate was then tested using the weight loss method, following the ASTM G31-72 standard, by immersing the specimens in seawater for 240 hours. The test results showed that the highest average thickness was achieved with solution 3 and a plating temperature of 50 – 54 °C, measuring 27.46 μm. The lowest average thickness was with solution 1 and a plating temperature of 30 – 34 °C, measuring 26.23 μm. The lowest corrosion rate was observed with solution 3 and a plating temperature of 50 – 54 °C, at 0.0041 mmpy, whereas the highest corrosion rate was found with solution 1 and a plating temperature of 30 – 34 °C, at 0.0079 mmpy. For comparison, the average corrosion rate of uncoated specimens was 2.2947 mmpy.