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.

Influence of PUB2 on the Leveling Effect of Chip Copper Connection Electroplating: Mechanism and Applications.

The copper connectivity technique is essential for achieving electrical interconnection in wafer level packaging (WLP), system in packaging (SiP), and 3D packaging. The essential processing material for copper connectivity is a copper sulfate electroplating solution in which organic additives play a crucial role in the regularity of copper electrodeposition. In this study, electrochemical tests, X-ray diffraction, 3D profiling, and scanning electron microscopy were used to investigate the leveling effect and mechanism of polyquaternary ammonium urea-containing polymer (PUB2) in the process of copper electrodeposition on-chip copper connections. PUB2 has excellent polarization ability on the target surface, remains unaffected by the sulfur additive SPS and poly(ethylene glycol), and displays a strong ability to regulate the copper deposition rate of through-holes and surface wiring. The waviness of the wafer surface wiring was reduced from 130 to approximately 70 nm after optimizing the PUB2 concentration, and the surface roughness was reduced from 10 to approximately 7 nm. The coating was dispersed evenly, and the rate of through-hole filling was improved by 57%. This study not only examined PUB2 leveling performance and mechanisms but also devised a research method and system for electroplating additives to facilitate the development and application of new electroplating additives.

A portable magnetic electrochemical sensor for highly efficient Pb(II) detection based on bimetal composites from Fe-on-Co-MOF.

The practical, sensitive, and real-time detection of heavy metal ions is an essential and difficult problem. This study presents the design of a unique magnetic electrochemical detection system that can achieve real-time field detection. To enhance the electrochemical performance of the sensor, Fe2O3@C-800, Co/CoO@/C-600, and CoFe2O4@C-600 magnetic composites were synthesized using three MOFs precursors by the solvothermal method. And the morphology structure and electrochemical properties of as-prepared magnetic composites were researched by X-ray diffraction (XRD), Scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), specific surface area and porosity analyzer (BET) and differential pulse voltammetry (DPV). The results shown that these composites improve conductivity and stability while preserving the MOFs basic frame structure. Compared with the monometallic MOFs-derived composites, the synergistic effect of the bimetallic composite CoFe2O4@C-600 can significantly enhance the electrochemical performance of the sensor. The linear range for the detection of lead ions was 0.001-60 µM, and the detection limit was 0.0043 µM with a sensitivity of 22.22 µA µM·cm-2 by differential pulse voltammetry. The sensor has good selectivity, stability, reproducibility and can be used for actual sample testing.

Recyclable and Efficient Recovery of Ca and S from Phosphogypsum by Using Multistep Precipitation.

The resource utilization of phosphogypsum (PG) is the key to promote the green development of the phosphorus chemical industry. The natural environment and public safety are significantly threatened by the enormous volume of PG storage. In this study, Ca and S were successfully recovered from the PG via a multistep precipitation in the NaOH-BaCO3 system. The alkali solution can be recycled five times, with a first recovery ratio of about 97.9%, and the decomposition ratio of PG remained above 70% after five cycles. In addition, the recovery ratios of Ca and S in PG are 99.9 and 82.5%, respectively. The product of BaSO4 can be used as a weighting agent for oil and natural gas drilling mud. The BaSO4 can also be used as wave-absorbing materials, and its reflection loss value reaches 97.8% of the analytical purity BaSO4. This work provides a new idea for the efficient recycling of Ca and S in PG with an outstanding application prospect.

Prediction and Effect Verification of Thiamine as a Leveling Agent in Chip Wafer Electroplating.

Thiamine, a nitrogen-containing heterocyclic compound, is explored for the first time as a novel leveling agent in this study. Based on the density functional theory (DFT) calculations and molecular dynamics (MD) simulations of the adsorption process of thiamine and the commonly used leveling agent JGB, the average values of the binding energies after equilibrium of thiamine and JGB are similar, which indicates that the thiamine molecules have strong bonding ability with the surface of copper and can be adsorbed tightly on the surface of copper. By cyclic voltammetry (CV) curve, thiamine was found to inhibit copper deposition and the inhibition effect was stronger than JGB. The chrono potential curve (CP) test found that the potential difference △η = 87 > 50 mV at high and low speeds of thiamine, which indicates that thiamine has the potential to be used as a leveling agent. Electrochemical impedance spectroscopy (EIS) testing found that thiamine inhibited copper precipitation by inhibiting the reactions of Cu2+ → Cu+ and Cu+ → Cu. According to electroplating experiments, thiamine has a leveling effect on wafer electroplating and can be used as a leveling agent because the copper layer on the wafer obtained by adding it has a smoother surface compared to the copper layer obtained without adding it. It was found that wafer electroplating does not require PEG, and only adding 55 mg/L Cl-, 6 mg/L SPS, and 4 mg/L thiamine as additives can achieve a good filling effect.

Role of Additives: Modified Hemihydrate Phosphogypsum Morphology and Enhanced Filtration Performance of Wet-Process Phosphoric Acid.

The morphology of hemihydrate phosphogypsum crystals is of vital importance in the hemihydrate-dihydrate (HH-DH) wet-process phosphoric acid production for high filtration strength. The morphology of hemihydrate phosphogypsum is commonly needlelike due to the strong acidic crystallization environment, which is unfavorable to the following filtration process. In this study, the crystal habit of hemihydrate phosphogypsum with a large aspect ratio was skillfully modified by additives to achieve a higher filtration strength. d-Glucitol (DG) reduces the theoretical aspect ratio of hemihydrate phosphogypsum crystals from 2.076 to 1.583 by interacting with the (002) face of CaSO4·0.5H2O preferentially, and poly(vinyl alcohol) (PVA) facilitates the aggregation of small grains to gather into a clusterlike structure. The modified morphologies of hemihydrate phosphogypsum have a lower bulk density and a larger porosity of the formed filter cake, which increases the filtration strength up to 45.9% when DG is added. Our work provides an in-depth explanation of the evolution mechanism of hemihydrate phosphogypsum morphology with the additives and its influence on the filtration performance. The improved filtration strength would reduce the water content of hemihydrate phosphogypsum and relieve the storage pressure of the phosphogypsum slag dump, which is meaningful to the clean production and process emission reduction of the phosphorus chemical industry.

Microwave Reactor with Combined Rigid and Flexible Stirring Paddles for Improving Fluid Heating Uniformity in Soft Manganese Ore Leaching Processes.

In order to overcome the apparent limitations of the inhomogeneous nature of large-scale microwave heating of fluids, a microwave reactor with a rigid-flexible combined stirring paddle is used to heat fluids, destabilizing the hot spots present in the microwave heating of fluids process. An integrated multiphysics field simulation model for calculating the microwave heating process with fluid was created for the purpose of clarifying the temperature field dispersion and fluid flow patterns in the reactor. By using the proposed model, the rigid-flexible combined stirring paddle is compared with the conventional single- and double-layer stirring paddle to highlight the benefits of the rigid-flexible combined stirring paddle in improving fluid heating uniformity. It was found experimentally that the leaching rate of soft manganese ore was increased by 7.08 and 5.22% compared to conventional single and double stirred paddles, respectively. In addition, the optimal stirrer parameters were investigated by the response surface method.

Leaching of phosphate ores with lower dissolution of metallic impurities: the dual role of sodium oleate.

In this work, we report the use of surfactants to improve the performance of phosphate ore leaching while reducing the concentration of metallic impurities in the leaching solution. Based on the zeta potential analysis, sodium oleate (SOL) is determined as a suitable surfactant because it can change interfacial properties and improve ionic diffusion. This is experimentally demonstrated by the high leaching performance. After that, the reaction conditions on the leaching performance are systematically investigated. Under the optimal experimental conditions (SOL concentration of 10 mg L-1, sulfuric acid concentration of 1.72 mol L-1, leaching temperature of 75 °C, and leaching time of 180 min), a high phosphorus leaching efficiency of 99.51% is achieved. Meanwhile, the leaching solution presents a lower content of metallic impurities. Further measurements performed on the leaching residues indicate that the additive SOL can promote the growth of platy crystals and facilitate PO leaching. Overall, this work demonstrates that the SOL-assisted leaching method allows for highly-efficient utilization of PO and high-purity phosphoric acid production.

Enhanced removal of Pb from electrolytic manganese anode slime and preparation of chemical MnO2.

Electrolytic manganese anode slime (EMAS) is produced during the production of electrolytic manganese metal. In this study, a method based on vacuum carbothermal reduction was used for Pb removal in EMAS. A Pb-removal efficiency of 99.85% and MnO purity in EMAS of 97.34 wt.% were obtained for a reduction temperature of 950°C and a carbon mass ratio of 10% for a holding time of 100 min. The dense structure of the EMAS was destroyed, a large number of multidimensional pores and cracks were formed, and the Pb-containing compound was reduced to elemental Pb by the vacuum carbothermal reduction. A recovery efficiency for chemical MnO2 of 36.6% was obtained via preparation from Pb-removed EMAS through the 'roasting-pickling disproportionation' process, with an acid washing time of 100 min, acid washing temperature of 70°C, H2SO4 concentration of 0.8 mol·L-1, liquid-solid mass ratio of 7 mL·g-1, calcination temperature of 60°C and calcination time of 2.5 h. Moreover, the crystal form of the prepared chemical MnO2 was found to be basically the same as that of electrolytic MnO2, and its specific surface area, micropore volume and discharge capacity were all higher than that of electrolytic MnO2. This study provides a new method for Pb removal and recycling for EMAS.HighlightsVacuum carbothermal reduction method was used for Pb removal in EMAS.The removal efficiency of Pb was 99.85%.Chemical MnO2 with excellent discharge performance was prepared using treated EMAS.This study provides a new method for EMAS resource utilization.

A Universal and Simple Method to Obtain Hydrogels with Combined Extreme Mechanical Properties and Their Application as Tendon Substitutes.

With the development of biomedical engineering, the preparation of hydrogels with combined extreme mechanical properties similar to those of some biological hydrogels becomes an important research topic for scientists. In this work, a single-network hydrogel with combined extreme mechanical properties is prepared through a simple and universal method, wherein the strength, elongation at break, toughness, and fracture energy of the hydrogel WPU-3PAAm-6PAN are achieved at 24.7 MPa, 544.0%, 68.9 MJ m-3, and 37.2 kJ m-2, respectively. Herein, a series of photosensitive resins in emulsion form are synthesized, and due to the water-oil diphasic characteristic, hydrophobic monomers and high-efficient hydrophobic photo-initiators are adopted into the resins, which can significantly improve the mechanical properties of the hydrogels due to the hydrophobic association effect and solve the biggest barrier of low curing rate in digital light processing (DLP) fabrication of hydrogels, respectively. Moreover, the simple and facile method to obtain robust and tough hydrogels can be universally applied to other polymer systems. Combined with the excellent mechanical properties and printing ability, the hydrogels with optimized structures are fabricated through DLP printing technology and applied as tendon substitutes. The tendon substitutes exhibit superior performance for mechanical connection and regeneration of collagen fibers. Although further clinical research is required, the hydrogels have great potential applications in various biological areas.

Microwave-enhanced reduction of manganese from a low-grade pyrolusite ore using pyrite: process optimization and kinetic studies.

The inefficient leaching of manganese is the main factor hindering the commercialization of the reduction process during manganese recovery using pyrite as the reducing agent. Hence, a new method for improving recovery efficiency and reducing the cost is required. This study uses microwave heating as a strengthening method to extract Mn2+ from pyrolusite and the leaching conditions are optimized. It was found that the extraction rate of Mn2+ could reach 95.07% under microwave heating through the conditions of H2SO4 is 1.2 mol/L, m(pyrolusite)/m(pyrite) equals to 10:2, leaching temperature is 90 ℃, and a liquid-solid (L/S) ratio of 10:1. The achieved extraction rate was higher than that of 75.08% under the conventional heating achieved at the same conditions. Besides, experimental studies have found that microwave heating can change the process and direction of chemical reactions, shorten the reaction time, and reduce sulfuric acid. Finally, the kinetic study indicates that the leaching process under microwave heating is controlled by surface chemical reactions. The equation of leaching kinetics is 1 - (1 - x)1/3 = 3425.32/r0·[H2SO4]1.316·[FeS2/MnO2]0.907·exp(- 45.03/(RT)·t. The activation energy is 45.03 kJ/mol. Meanwhile, through a scanning electron microscope and particle size analyzer, microwave heating has a significant influence on reducing the ore diameter and increasing the specific surface area of the sample. This study aims to provide an experimental trial case for studying the mechanism of microwave-enhanced leaching process during manganese recovery using pyrite as the reducing agent. The reported kinetics research may guide the development of the industrial application for Mn recovery.

Rigid-Flexible Combined Impeller Enhancement in Leaching of Phosphate Rock: a Kinetics Study.

Conventional rigid impellers are frequently used in the leaching process of phosphate rock, which often form a symmetrical flow field in the reactor, leading to a reduction in the leaching efficiency. In this work, a rigid-flexible combined impeller was applied to the leaching process of phosphate rock to increase the leaching efficiency. The effects of the reaction temperature (T), sulfuric acid excess coefficient (ε), liquid-solid ratio (L/S), agitation speed (N), and leaching time (t) on the leaching of phosphate rock were investigated, and based on this, the leaching kinetics was studied. The results indicated that under the optimum parameters of a reaction temperature of 353 K, a sulfuric acid excess coefficient of 1.15, a liquid-solid ratio of 4.0 mL/g, an agitation speed of 280 rpm, and a leaching time of 120 min, the leaching rate of phosphate rock using the rigid-flexible combined impeller reached 89.1%, which was 7.1% higher than that of the conventional rigid impeller under the same electric energy consumption. The leaching process complied with the unreacted core shrinking model, and the reaction rate was controlled by product layer diffusion. The apparent rate equation of the leaching process was 1 - 2X/3 - (1 - X)2/3 = 2.06 × 10-3[ε]1.375[L/S]1.273[N]0.748 exp(-19.03 × 103/RT)·t, and the apparent activation energy was 19.03 kJ/mol. The numerical simulation and analysis of the leaching residue showed that the system temperature in the rigid-flexible combined impeller system was homogenized, and the mixing effect of reactants was enhanced through the multiposition movement of the flexible connection piece in the axial direction, so that the reactants participated in the chemical reaction more efficiently.

A critical review on approaches for electrolytic manganese residue treatment and disposal technology: Reduction, pretreatment, and reuse.

Electrolytic manganese residue (EMR) has become a barrier to the sustainable development of the electrolytic metallic manganese (EMM) industry. EMR has a great potential to harm local ecosystems and human health, due to it contains high concentrations of soluble pollutant, especially NH4+ and Mn2+, and also the possible dam break risk because of its huge storage. There seems to be not a mature and stable industrial solution for EMR, though a lot of researches have been done in this area. Hence, by fully considering the EMM ecosystem, we analyzed the characteristics and eco-environmental impact of EMR, highlighted state-of-the-art technologies for EMR reduction, pretreatment, and reuse; indicated the factors that block EMR treatment and disposal; and proposed plausible and feasible suggestions to solve this problem. We hope that the results of this review could help solve the problem of EMR and thus promote the sustainable development of EMM industry.

Enhanced leaching of manganese from low-grade pyrolusite using ball milling and electric field.

In this study, electric field and ball milling were used to leach Mn2+ from low-grade pyrolusite (LGP). The effects of current density, reaction time, reaction temperature, ball-to-powder weight ratio, and ball milling time on the leaching efficiency of Mn2+ from LGP as well as the leaching mechanism were systematically studied. The results showed that the combined use of electric field and ball milling enhanced the leaching of Mn2+ from LGP. The leaching efficiency of Mn2+ reached 97.79% under the optimum conditions of LGP-to-pyrite mass ratio of 1:0.18, current density of 30 mA/cm2, LGP-to-H2SO4 mass ratio of 1:0.4, liquid-to-solid ratio of 5:1, ball-to-powder weight ratio of 1:1, ball milling time of 2 h, temperature of 80 °C, and leaching duration of 120 min. This value was 25.95% higher than that attained without ball milling and 41.45% higher than that attained when neither ball milling nor electric field was employed. Pyrite was fully oxidized to generate additional SO42- and Fe3+, and was further hydrolyzed to form jarosite (KFe3(SO4)2(OH)6) and hydronium jarosite (Fe3(SO4)2(OH)5·2H2O) via ball milling and electric field application. Moreover, the electric field changed the surface charge distribution of the mineral particles and promoted collisions between them as well as the collapse of the crystal lattice, further improving the leaching efficiency of Mn2+ from LGP. This study provided a new method for leaching Mn from LGP.

Metal mobility and toxicity of reclaimed copper smelting fly ash and smelting slag.

Copper is a nonferrous metal closely connected to humans. Approximately 40% of copper is produced by reclaimed copper smelting (RCS). Reclaimed copper smelting fly ash and smelting slag are generated during the RCS process, posing a serious threat to the ecosystem and environment as they contain many heavy metals, such as Cu and Zn. In this study, the metal mobility and toxicity of RCS fly ash and smelting slag were analyzed using standard leaching toxicity procedures, sequential extraction procedures, and bioavailability tests. The results showed that the main phases of RCS fly ash were Cu2(OH)3Cl, FeCl2·2H2O, CuS2, C, CuO, Cu, Ca2SiO4, ZnClO42, Zn(OH)2·0.5H2O, and KFeCl3, and those for smelting slag were SiO2, CaCO3, SiS2, CaAl2Si2O8·4H2O, Cu4O3, CuO, ZnO, NiSO4·6H2O, AlPO4, and Na3Mn(PO4)(CO)3. These two slags contain high contents of Cu, Zn and Fe and trace amounts of heavy metals, such as Ba, Be, Cd, Cr, Ni, As, Pb, Au, Se and Sb. RCS fly ash is classified as hazardous waste in both China and the USA as the toxic leaching concentrations of Pb and Cd exceed the thresholds of 5 and 1 mg L-1. Cu and Zn contained in these two slags can easily be released into the environment, although the residual fraction of Cu and Zn was found to be higher than 65%. Additionally, RCS fly ash and smelting slag also show significant biohazardous potential as the EDTA- and DTPA-extractable Zn, Cu and Se of these two residues are considerably high. The results described above could provide reclaimed copper smelting companies and governments with a better understanding of the risk of RCS fly ash and smelting slag, urging them to stop the slag from harming ecosystems and humans.

Chloride ion inhibition of electrochemical oscillations on the anode of an electrolytic manganese metal cell.

In industrial electrolytic manganese metal process, the energy consumption closely related to the electrolysis of cathode and anode. The effect of Cl- concentration on electrochemical oscillation at the anode of the electrolytic manganese metal cell was investigated. The results showed that the electrochemical oscillation at the anode was inhibited by Cl-, and the amplitude and frequency of the electrochemical oscillation decreased as the increase of Cl- concentration. When the concentration of Cl- was 2.68 g/L, the cathode and anode electrodes could be effectively activated, and the manganese current efficiency reached its minimum, correspondingly, the power consumption reached its maximum. In addition, the presence of the chloride reduced the production of MnO2 at the anode surface. ClO4- and free ions formed insoluble amorphous structures on the surface of the anode with the increase in reaction time and chloride ion concentration, and the insoluble amorphous structures prevented further generation of MnO2. Thus, electrolytic manganese metal energy consumption decreased.

A low cost of phosphate-based binder for Mn2+ and NH4+-N simultaneous stabilization in electrolytic manganese residue.

Electrolytic manganese residue (EMR) is a solid waste remained in filters after using sulfuric acid to leaching manganese carbonate ore. EMR contains high concentration of soluble manganese (Mn2+) and ammonia nitrogen (NH4+-N), which seriously pollutes the environment. In this study, a low cost of phosphate based binder for Mn2+ and NH4+-N stabilization in EMR by low grade-MgO (LG-MgO) and superphosphate was studied. The effects of different types of stabilizing agent on the concentrations of NH4+-N and Mn2+, the pH of the EMR leaching solution, stabilizing mechanisms of NH4+-N and Mn2+, leaching test and economic analysis were investigated. The results shown that the pH of the EMR leaching solution was 8.07, and the concentration of Mn2+ was 1.58 mg/L, both of which met the integrated wastewater discharge standard (GB8978-1996), as well as the concentration of NH4+-N decreased from 523.46 mg/L to 32 mg/L, when 4.5 wt.% LG-MgO and 8 wt.% superphosphate dosage were simultaneously used for the stabilization of EMR for 50 d Mn2+ and NH4+-N were mainly stabilized by Mn3(PO4)2·2H2O, MnOOH, Mn3O4, Mn(H2PO4)2·2H2O and NH4MgPO4·6H2O. Economic evaluation revealed that the treatment cost of EMR was $ 11.89/t. This study provides a low-cost materials for NH4+-N and Mn2+ stabilization in EMR.