Showing papers on "Copper plating published in 2022"

Research progress on the removal, recovery and direct high-value materialization of valuable metal elements in electroplating/electroless plating waste solution

Abstract: With the continuous development of the electroplating and electroless plating industries, a large amount of waste solution is generated every year, mainly including spent plating solution and plating pieces rinse wastewater. The discharge standard of waste solution is also continuously improved. If the electroplating/electroless plating waste solution is not treated timely and effectively, it will occupy the land resources of the factory increasing the operating cost, and pose a serious threat to the environment and human health. Additionally, the rich valuable metal resources in the waste solution will not be adequately reused. Therefore, there is an urgent need to develop more advanced electroplating/electroless plating waste solution treatment technologies. Herein, the electroplating/electroless Ni (Cu) plating waste solution (spent plating solution and plating pieces rinse wastewater) is taken to analyze the causes and component characteristics of the waste solution. The principle, advantages and disadvantages, and optimization progress of the treatment technology for electroplating/electroless plating waste solution are summarized from three aspects: simple and direct removal of valuable metal elements, separation and recovery of valuable metal elements, and direct preparation of high-value materials from waste solution. The technical advantages of multi-method combined treatment of waste solution have been analyzed. Further research direction such as direct high-value materialization utilization of waste solution is proposed.

Direct Electroless Plating of Conductive Thermoplastics for Selective Metallization of 3D Printed Parts

Abstract: Electroless plating is a promising approach for metallizing plastic 3D printed parts, but current approaches rely on surface activation with expensive precious metal catalysts such as palladium. In this work, we demonstrate conductive composite filaments loaded with metal or other conductive particulate can be electrolessly plated directly, without prior activation, with exposed particles serving as nucleation sites. Several commercially available filaments based on different particulate loading were plated, with both carbon black and copper particulate shown to nucleate in an electroless copper plating bath. Flash ablation metallization, the use of a flash of high energy white light to ablate the polymer on the surface and expose a higher density of metal particulate, was also shown to accelerate the plating process. Selective plating was then achieved through use of a dual extruder 3D printer to define conductive composite regions for plating on a non-conducting thermoplastic. Trace resistances were reduced by as much as five orders of magnitude after copper plating. A toroidal inductor was printed and shown to drop in resistance from 24 kΩ before to 2.3 Ω after plating, with post-plating inductance and quality factor 315 nH and 10.3 respectively. A 555 timer circuit demonstrator was also plated.

Laser-Assisted Selective Fabrication of Copper Traces on Polymers by Electroplating

Abstract: The selective deposition of metals on dielectric materials is widely used in the electronic industry, making electro-conductive connections between circuit elements. We report a new low-cost laser-assisted method for the selective deposition of copper tracks on polymer surfaces by electroplating. The technique uses a laser for the selective modification of the polymer surface. The electrical conductivity of some polymers could be increased due to laser irradiation. Polyimide samples were treated using nanosecond and picosecond lasers working at a 1064 nm wavelength. An electro-conductive graphene-like layer was formed on the polymer surface after the laser treatment with selected parameters, and the copper layer thickness of 5–20 µm was deposited on the modified surface by electroplating. The selective laser-assisted electroplating technology allows the fabrication of copper tracks on complex shape dielectric materials. The technology could be used in the manufacturing of molded interconnect devices (MID).

Routes towards manufacturing biodegradable electronics with polycaprolactone (PCL) via direct light writing and electroless plating

Abstract: The electronic industry has room for improvement in adopting cleaner strategies, both in production processes (often energy-intensive and polluting) and in waste management. Many small components like security tags are routinely disposed of via general waste, which could be reduced adopting biodegradable polymers. In this work, a method for selective deposition of metallic micro-tracks on polycaprolactone (PCL) for circuitry integration is presented. The polymer is biodegradable, flexible, suitable for 3D printing, and can be obtained from sustainable sources. Photoreduction of Ag ions was used to generate seeds for subsequent selective electroless copper (Cu) plating in a process that avoids common but undesirable compounds such as cyanides and palladium. Two different photopatterning methods were successfully used to achieve selective Cu plating: flood exposure with a 460 nm light-emitting diode (LED) and direct laser writing (DLW) using a 405 nm laser, achieving 47 ± 11 μm wide tracks. The deposition of uniform Cu layers on PCL substrates is demonstrated, with thicknesses of up to 14 μm and electrical conductivities of up to 2.06 × 107 S m−1, which is near the conductivity of bulk Cu (5.89 × 107 S m−1). Cu-plated interconnects were demonstrated to be fully functional for powering a 5 SMD LEDs circuit. Furthermore, DLW enabled the interconnect manufacturing on an uneven substrate. This method is flexible, selective, low-cost, vacuum-free and of minimized environmental impact, and it provides a new route towards the manufacturing of biodegradable electronics.

Controllable Simultaneous Bifacial Cu‐Plating for High‐Efficiency Crystalline Silicon Solar Cells

Abstract: Bifacial (BF) copper‐plated crystalline silicon solar cell is an attractive topic to concurrently reduce silver consumption and maintain good device performance. However, it is still challenging to realize a high aspect ratio (AR) of the metal fingers. Herein, a new type of hybrid‐shaped Cu finger is electromagnetically fabricated in a BF plating process. Cyclic voltammetry is employed to disclose the electrochemical behaviors of cupric ions in monofacial and simultaneous BF Cu‐plating processes, such that the controllability of the plating process could be assessed. The optimal hybrid Cu finger is composed of a rectangular bottom part and a round top part, such that an utmost effective AR value of 1.73 is reached. In BF Cu‐plating, two sub‐three‐electrode electrochemical cells are employed to realize equal metal finger heights on both sides of the wafer. Compared to our low thermal‐budget screen‐printing metallization, the Cu‐plated silicon heterojunction devices show both optical and electrical advantages (based on lab‐scale tests). The champion BF Cu‐plated device shows a front‐side efficiency of 22.1% and a bifaciality factor of 0.99.

Design Optimization of Pyramidal Horn Antennas for 3D Printing in the mm-Wave Range

Abstract: In this work, additively manufactured pyramidal horn antennas are presented which are fabricated from UV-curable polymer resin by a DLP 3D printing system and subsequently coated by copper electroplating. In order to improve printing and metal plating quality, the models are adapted following the slotted waveguide approach and build orientation is discussed to cope with support of overhanging structures. The manufactured specimens reveal almost identical performance compared to a commercially available equivalent. This way, successful application of the slotted waveguide approach is demonstrated with horn antennas for mm-Wave frequency range.

Efficient and Simple Fabrication of High-Strength and High-Conductivity Metallization Patterns on Flexible Polymer Films

Abstract: Conductive metal circuits, as a cornerstone of flexible electronics, are increasingly becoming an important integral part of modern industry. Herein, the metallized patterns and circuits with high strength and high conductivity were fabricated using efficient and simple laser technology. The laser activated polyimide film by a 1064 nm near-infrared (NIR) laser was metallized by the electroless copper plating (ECP) process. Moreover, on the basis of the ECP process, the electroless nickel plating (ENP) reaction and electroless gold plating (EGP) reaction are further carried out. The adhesion performance of the obtained copper layer on the PI film could reach the ASTM D3359-17 4B-5B level. In addition, the thickness of the prepared copper circuits on the PI film was around 4.8 μm, and the corresponding resistivity was calculated as 3.6 ± 0.2 μΩ·cm. Based on this laser-induced selective metallization (LISM) technology, the flexible electronics of electric heaters, ultraviolet light-responsive devices, wireless charging, and integration of microsupercapacitors (MSCs) were also explored. Therefore, this LISM technology exhibits great potential in the large-scale manufacturing of flexible electronics.

Grafted-to Polymeric Layers Enabling Highly Adhesive Copper Films Deposited by Electroless Plating on Ultra-Smooth Three-Dimensional-Printed Surfaces

Abstract: A process has been developed to produce highly adhesive metallic layers onto polymeric surfaces. It is specifically aimed at ultra-smooth polymeric substrates produced by stereolithography (SLA) with applications in the field of radiofrequency components. By combining the wet deposition of an azide-based primer and high molecular weight polyacrylic acid (PAA), a dense polyelectrolyte layer can be grafted to various plastic surfaces. Conformal metallization is achieved by electroless plating. Adhesion of the metal layer to the plastic substrate is promoted by specific affinity and chelating binding of the grafted layer to the catalyst, its robust anchoring to the plastic substrate by covalent bonds via nitrene insertion, and deep interpenetration with the metal layer. This process is highly versatile since it is effective on various polymeric substrates, environmentally friendly and chromium-free, and adaptable to three-dimensional (3D) geometries. It has been shown to provide high adhesion onto surfaces with nanometric roughness without using surface roughening techniques. This method has been extended to produce micrometric metallic patterns by selective electroless metallization. Patterns of grafted-to PAA were printed by aerosol jet printing, and the electroless copper bath was adapted to achieve selectivity of the electroless copper on the chosen patterns. The printing and plating process also aims to be compatible with the surfaces of 3D-printed plastics and composites.

Selective Electroless Copper Plating of Ink-Jet Printed Textiles Using a Copper-Silver Nanoparticle Catalyst

Abstract: The electroless copper plating of textiles, which have been previously printed with a catalyst, is a promising method to selectively metallise them to produce high-reliability e-textiles, sensors and wearable electronics with wide-ranging applications in high-value sectors such as healthcare, sport, and the military. In this study, polyester textiles were ink-jet printed using differing numbers of printing cycles and printing directions with a functionalised copper-silver nanoparticle catalyst, followed by electroless copper plating. The catalyst was characterised using Transmission Electron Microscopy (TEM) and Ultraviolet/Visible (UV/Vis) spectroscopy. The electroless copper coatings were characterised by copper mass gain, visual appearance and electrical resistance in addition to their morphology and the plating coverage of the fibres using Scanning Electron Microscopy (SEM). Stiffness, laundering durability and colour fastness of the textiles were also analysed using a stiffness tester and Launder Ometer, respectively. The results indicated that in order to provide a metallised pattern with the desired conductivity, stiffness and laundering durability for e-textiles, the printing design, printing direction and the number of printing cycles of the catalyst should be carefully optimised considering the textile's structure. Achieving a highly conductive complete copper coating, together with an almost identical and sufficiently low stiffness on both sides of the textile can be considered as useful indicators to judge the suitability of the process.

Novel, Simple, and Green Citrate-Based Copper Electronic Electroplating Bath in Microvia Void-Free Filling for Printed Circuit Board Application

Abstract: In this work, a novel, simple, and green citrate-based copper electronic electroplating bath with the characteristics of weak corrosion, low copper ion concentration, and simple composition is developed in microvia void-free filling for printed circuit board application. Succinimide (SM), regarded as a leveler, is the core component of the bath. The action mechanisms of SM on microvia void-free copper filling are carefully expounded. UV–vis spectroscopy and theoretical calculations demonstrate that only the [Cu2(Cit)2]2– coordination ion exists in the bath containing SM at pH 9.0. Linear sweep voltammetry and in situ Fourier transform infrared spectroscopy combined with X-ray photoelectron spectroscopy experiments illustrate that SM can inhibit the electroreduction of the [Cu2(Cit)2]2– coordination ion and promote the electroreduction of intermediate Cu(I) to Cu(0), resulting in the improvement of coating quality. Galvanostatic measurements reveal that the reduction of the [Cu2(Cit)2]2– coordination ion is electrochemically controlled, and SM is diffusion-controlled. The leveler properties of SM (diffusion control and inhibition of [Cu2(Cit)2]2– coordination ion electroreduction) promote copper in bottom-up growing and void-free filling of microvias.

Realization of high A/R and fine pitch Cu pillars incorporating high speed electroplating with novel strip process

Abstract: Fan-out wafer level packaging (FOWLP) enables high density heterogeneous integration of distinguished functions into single chip by 3D stacking logic and memory chips. High density 3D FOWLP requires Cu pillars to deliver power and signal between stacked chips. However, realization of reliable Cu pillars is a challenge due to its distinguished features including extreme height with high aspect ratio (A/R) and its exceptionally long process time for electroplating. Herein, this study reports realization of high A/R and fine pitch Cu pillars incorporating high speed electroplating with novel strip process. Process conditions including electroplating current, ion concentration, process temperature, and mechanical agitation were studied and experimentally evaluated to accelerate electroplating rate. Gradual modulation of applied current in electroplating process helps to resolve non-uniform ion distribution. Elevation of process temperature enhances diffusion and flow of Cu ions. Surface modification for photoresist leads the superior tolerance in high temperature electroplating bath through preventing leaching and deformation of the photoresist. High A/R structure of Cu pillar requires novel strip process, and identification and modeling of the process relating nozzle and spray position leads drastic improvement of its performance than conventional process. The derived knobs demonstrates mass-productive and reliable Cu pillar for 3D heterogeneous packaging.

Hybrid Membrane Technology for Acid Recovery from Wastewater in Coated Steel Wire Production: A Pilot Scale Study

Abstract: In the present study, the problem of sulfuric acid recycling from spent copper plating solution was solved using a hybrid membrane technology, including diffusion dialysis and electrodialysis. A real solution from the production of copper-coated steel wire, containing 1.45 mol/L of sulfuric acid, 0.67 mol/L of ferrous sulfate and 0.176 mol/L of copper sulfate, was processed. Diffusion dialysis with anion-exchange membranes was used to separate sulfuric acid and salts of heavy metals. Then, purified dilute sulfuric acid was concentrated by electrodialysis. The energy consumption for sulfuric acid electrodialysis concentration at a current density of 400 A/m2 was 162 W·h/mol, with a current efficiency of 16%. After processing according to the hybrid membrane scheme, the solution contained 1.13 mol/L sulfuric acid, 0.077 mol/L ferrous sulfate and 0.022 mol/L copper sulfate. According to established requirements, the solution of a copper plating bath had to contain from 0.75 to 1.25 M sulfuric acid, 0.16–0.18 M of copper sulfate and ferrous sulfate not more than 0.15 M. The resulting acid solution with a small amount of ferrous sulfate and copper sulfate could be used to prepare a copper plating bath solution.

Hybrid Membrane Technology for Acids Recovery from Wastewater of the Coated Steel Wire Production: A Pilot Scale Study

Abstract: In the present study, the problem of the sulfuric acid recycling from spent copper plating solution was solved using a hybrid membrane technology, including diffusion dialysis and electrodialysis. A real solution from the production of copper-coated steel wire, containing 1.45 mol/L of sulfuric acid, 0.67 mol/L of ferrous sulfate and 0.176 mol/L of copper sulfate was processed. Diffusion dialysis with anion-exchange membranes was used to separate sulfuric acid and salts of heavy metals. Then purified dilute sulfuric acid was concentrated by electrodialysis. Energy consumption for sulfuric acid electrodialysis concentration at a current density of 400 A/m2 was 162 W·h/mol with current efficiency 16 %. After processing according to the hybrid membrane scheme, the solution contained 1.13 mol/L sulfuric acid, 0.077 mol/L ferrous sulfate and 0.022 mol/L copper sulfate. The resulting acid solution with a small amount of ferrous sulfate and copper sulfate met the established requirements for a copper plating bath solution and can be reused in production.

8-inch wafer-level electroplating of nanotwinned copper redistribution layer for advanced packaging

Abstract: Wafer-level copper electroplating is an indispensable process in advanced packaging for manufacturing redistribution layers (RDL), micro-bumps, through silicon vias (TSV), etc., where coplanarity is a significant indicator to evaluates whether the plating thickness is uniform among different sized patterns and at different positions. Achieved through precise control of the electric field distribution, a good coplanarity can lower the reliability risks, for example, interfacial voiding or interlayer mismatch, to improve the product yield. However, with developments of greater wafer size and finer interconnect structure, higher demands are set on the material properties. Nanotwinned copper (nt-Cu) is of high-density and highly (111)-oriented coherent twin boundaries and exhibiting enhanced mechanical and electrical performances. In the present study, nt-Cu based electroplating for 8-inch RDL patterned wafer in wafer level packaging (WLP) is conducted with a proprietary plating bath on a horizontal electroplating system. Equipment setting/parameter effects such as shielding plates, circulating flow rate, and wafer spin rate are analyzed on coplanarity performance of nt-Cu. The results indicate nt-Cu microstructure can be formed throughout the wafer and the coplanarity indexed by within-die (WID) nonuniformity is manipulated below the technical threshold < 8%, which is repeatable in an 8 out of 30 random checks. This engineering research offers a pioneer practice for industrial application of nt-Cu electroplating technique.

TSV fabrication technology using direct electroplating of Cu on the electroless plated barrier metal

Abstract: We propose a new TSV fabrication process using electroless plating of a barrier metal layer in TSV, and succeeding direct electroplating of Cu on the barrier without Cu seed layer. The conformal and thick ( > 50 nm) CoWB barrier layer deposition inside a high aspect ratio TSV enables direct electro-plating of Cu from top to bottom of TSV entirely. Uniformity of CoWB thickness is within 10 % in 8-inch wafer. Furthermore, we successfully fabricated a daisy chain of TSVs of 1200 steps and evaluated electrical properties. Excellent endurance property of the TSV daisy chain was obtained without any change of the resistance. This technology is promising for the 3D LSIs that uses high aspect ratio TSVs.

Preliminary investigation into the use of silver seed layers in copper electroplating of waveguide parts

Abstract: We present a preliminary investigation into the copper plating of printed SLA plastics using a silver seed layer. The silver seed layer is deposited using the Tollens reaction, a chemical process used to test for aldehydes. The device under test is a split-block WR42 waveguide cut along the E-plane, manufactured with SLA printing. Initial results showed that the waveguide achieved a loss of better than 5.6 dB/m over the operating band. Repeatability was an issue with multiple waveguides exhibiting corrosion and high insertion loss.

A New Type of Coating Brush Plating Solution and Its Application Performance

Abstract: A new type of coating brush plating solutioncontaining stannous sulfate and potassium pyrophosphate was prepared by solution mixing method.Its structures, physicochemical properties, and the application effect in power equipment contact were also investigated by electrochemical workstation, X-ray photoelectron spectroscopy (XPS), scanning electron microsco (SEM), Mapping, and infrared thermometer. The results showed that the tin coating has good adaptability to the ambient temperature and good adhesion with the copper substrate. Cerium nitrate was evenly distributed over the tin plating layer, reduced the crystal refinement of tin and lead to a uniform distribution of microdefects. When the cerium nitrate content, the amount of additives, the amount of complex agent, and the number of brush plating operations are 0.1%, 10.0%, 8.0%, and 5 times, respectively, the tin plating layer has the best electrochemical performance. For application, the damaged contacts of power equipment can fully meet the demand of power use after being treated by the new brush plating solution.