Metallization Process Research Articles

Advanced Fine Line Printing With Glass Stencils: Achieving Metal Contact Fingers Below 10 μm

ABSTRACTFor high‐efficiency solar cells, such as Si‐III‐V tandem solar cells, implementing narrow contact fingers is essential for achieving optimal conversion efficiencies. By achieving narrower contact fingers without compromising electrical performance, more sunlight reaches the active areas of the cell, thus reducing front‐side shading and enhancing overall energy conversion efficiency. In this work, we demonstrate a proof of principle for a novel low‐temperature metallization process using glass stencils to print ultra‐fine line contacts. The narrowest contacts achieved have a width of = 8.4 ± 1.3 with an aspect ratio of = 0.19 ± 0.05. Through optimization described in this work, contact fingers with = 9.7 ± 0.6 μm and a substantially greater aspect ratio of = 0.45 ± 0.1 could be achieved. To realize these ultra‐fine line fingers, glass stencils with tailored aperture channels were realized using a two‐step laser induced deep etching (LIDE) process that enables complex three‐dimensional aperture channel geometries.

Pushing Heterojunction Technology Further: Novel Metallization Processes and Architectures

This work provides an overview on the different approaches to make Silicon Hetero-Junction cell (SHJ) production more scalable by investigating alternative metallization processes which can potentially be competitive with the standard Ag-based processes (Ag micro-size). With this purpose, this research aims at introducing the idea of widely using Ag-coated Cu formulations and/or low-Ag deposit solutions involving Ag nanoparticles-based formulations and reactive Ag (also referred as particle free) inks for both rear and front cell depositions on a single (finger and busbars) screen-printing process.

A Simple Solid-State Direct Bonding Process for Fabrication of Ohmic Contacts on n-type Mg3Sb2-xBix-based Thermoelectric Materials

N-type Mg3Sb2-xBix materials are expected to replace n-type bismuth telluride because they are more abundant in the Earth's crust and lower in cost. However, the metallization process of this material, which is essential to develop modules, has been relatively under-researched. According to the literature, one-step sintering process based on powder metallurgy is mostly used to form an ohmic bonding layer on n-type Mg3Sb2-xBix materials. However, this method is not reproducible nor practical, and is unsuitable for industrial mass production. This paper presents a new, simple method for metallization, the solid-state direct bonding of Mg and Cu foils on sintered n-type Mg3Sb2-xBix. It employs interdiffusion between the thermoelectric material and the metal layer at elevated temperatures to form a tight and robust bond. Mgwas chosen as the contact metal so that the interdiffusion of Mg would not cause a Mg deficiency in the Mg3Sb2-xBix near the interface. Then, a Cu layer was selected as the second metal to wrap around the Mg layer so that the subsequent soldering process could be the same as that of bismuth telluride. Solid-state bonding with the Mg/Cu double layer formed a structurally perfect joint at 723 K. When the temperature of the solid-state bonding exceeded 750 K, the eutectic point of Mg and Cu, the Mg layer was lost due to liquid phase formation. Solid-phase bonding at 723 K produced no noticeable change in the Seebeck coefficient near the interface, which would be caused by the outdiffusion of Mg from the n-Mg3Sb2-xBix. The specific contact resistance was about 53.8 μΩ cm2. This is superior to the values reported for n-type Bi2Te3-based materials. In this study, we also fabricated a Mg3Sb2-xBix (n)-Bi2Te3 (p) hybrid thermoelectric module and evaluated the output characteristics, which confirmed the high applicability of our solid-state bonding process.

Damage mitigation as a strategy to achieve high ferroelectricity and reliability in hafnia for random-access-memory

This study presents a low-damage metallization process for ultra-thin hafnia-based ferroelectric films, achieving high polarization, low leakage currents, and reduced wake-up effect, paving the way for scalable and reliable FeRAM applications.

Study of the Effects of Different Dielectric Environments on the Characteristics of Electro-Explosive Discharge of Metal Wires and Shock Waves

The electrical explosive fragmentation technique has attracted widespread attention due to its environmental friendliness and high efficiency. However, the mechanism by which dielectrics influence rock fragmentation remains unclear. This study innovatively selected seven types of environmentally friendly dielectrics to systematically investigate their roles in the metallic wire electrical explosive rock fragmentation process. By precisely characterizing the crack morphology of concrete blocks, shock wave–strain responses, and discharge signal characteristics, the diverse mechanisms by which different dielectrics modulate rock fragmentation were revealed. The results indicate that oxide dielectrics release energy continuously through thermochemical reactions, highly conductive solutions accelerate energy deposition, and reductant suspensions generate strong secondary shock waves—all significantly outperforming tap water in terms of rock fragmentation performance. Notably, the energy deposition efficiency shows a nonlinear relationship with fragmentation effectiveness, influenced by factors such as energy release modes, dielectric composition, and bubble dynamics. The energy conversion mechanism of the electrical explosive rock fragmentation process studied in this paper provides a theoretical foundation for the fine-tuning, customization, and greening of electrical explosive rock fragmentation strategies in engineering practice.

Miniaturization Potential of Additive-Manufactured 3D Mechatronic Integrated Device Components Produced by Stereolithography

Three-dimensional Mechatronic Integrated Devices (3D-MIDs) combine mechanical and electrical functions, enabling significant component miniaturization and enhanced functionality. However, their application in high-temperature environments remains limited due to material challenges. Existing research highlights the thermal stability of ceramic substrates; yet, their reliability under high-stress and complex mechanical loading conditions remains a challenge. In this study, 3D-MID components were fabricated using stereolithography (SLA) 3D-printing technology, and the feasibility of circuit miniaturization on high-temperature-resistant resin substrates was explored. Additionally, the influence of laser parameters on resistance values was analyzed using the Response Surface Methodology (RSM). The results demonstrate that SLA 3D-printing achieves substrates with low surface roughness, enabling the precise formation of fine features. Electric circuits are successfully formed on substrates printed with resin mixed with Laser Direct Structuring (LDS) additives, following laser structuring and metallization processes, with a minimum conductor spacing of 150 µm. Furthermore, through the integration of through-holes (vias) and the use of smaller package chips, such as Ball Grid Array (BGA) and Quad Flat No-lead (QFN), the circuits achieve further miniaturization and establish reliable electrical connections via soldering. Taken together, our results demonstrate that thermoset plastics serve as substrates for 3D-MID components, broadening the application scope of 3D-MID technology and providing a framework for circuit miniaturization on SLA-printed substrates.

A Study on Electroless Copper Deposition for Desktop Stereolithography 3D Printing Materials

Electroless deposition is a method of metallizing parts without needing for an electrical source that can be performed on electrically conductive and non-conductive materials. Adhesion quality is an essential aspect of the electroless deposition process that determines the metal deposition conditions. The properties of stereolithography (SLA) 3D printed parts can be improved through the metallization process for various applications. In this study, optimization through the orthogonal design method was used to obtain the optimal processing parameters of electroless copper deposition on desktop SLA material with respect to adhesion quality. Experimental work was carried out according to the L9 (34) orthogonal array, followed by an evaluation of the signal-to-noise (S/N) ratio and analysis of variance (ANOVA). Based on the S/N ratio results, the optimal processing parameters for adhesion quality were potassium hydroxide concentration (400 g/L), etching time (30 min), formaldehyde concentration (3.75 mL/L) and deposition time (30 min). The results of the study are useful for industries such as rapid tooling, rapid prototyping, and semiconductors.

Nano-size Joule-Heating to Achieve Low-Ohmic Ag-Si Contact on Boron Emitters of n-TOPCon Solar Cells.

Over the past decade, Tunnel Oxide Passivated Contact (TOPCon) solar cells have emerged as a leading technology for high-efficiency silicon solar cells. Conventional metallization processes using silver/aluminum (Ag/Al) pastes encounter significant hurdles due to reliability risks and insufficient contact quality. Recent advancements in laser-induced metallization technologies, particularly laser-enhanced contact optimization (LECO), offer promising solutions. However, the mechanism of silver-silicon (Ag-Si) contact formation on the P+ emitter of TOPCon cells via LECO processing remains incompletely understood. This study designs and prepares two types of glass frits (GF-A and GF-B) for TOPCon cells and investigates the electrical properties of corresponding devices. Advanced techniques are employed to examine the Ag-Siinterfaces. The results demonstrate that GF-A-based TOPCon cells (Cell-A) outperformed GF-B-based cells (Cell-B) due to the construction of a current-confined Ag-Si interface. A composite conductive model for the Ag-Si interfaces by LECO treatment is introduced, revealing the nano-size Joule-heating to achieve the Ag-Si eutectic structure as the underlying formation mechanism. This work contributes to the understanding of metal-silicon contact optimization in solar cells and introduces novel methodologies for laser-induced synthesis and micro-nano interface engineering.

Visualizing Lithium Deposition and Identifying Two Types of Dendrites in Extreme-Fast-Charging Full Cells across the Entire Lifespan by Operando EPR and EPR Imaging.

Metallic lithium deposition processes in NCM811∥graphite full cells during extreme-fast charging of 4 C (fully charged within 15 min) are detected via operando electron paramagnetic resonance (EPR) and EPR imaging over hundreds of cycles to quantify lithium deposits and visualize their spatial distribution. EPR imaging shows that constant-voltage charge generates loose Li dendrites with divergent growth whereas overcharge leads to long dendrites with vertical growth, and these Li deposits accumulate at the anode edges, which could deplete the Li resource at the cathode edges. Moreover, quantitative EPR indicates that the stripping current correlates to the deposit surface areas, while the reintercalation current depends on the contact areas between plated Li and graphite. Overall, the results of EPR and EPR imaging suggest that the introduction of a relaxation period after extreme-fast charge for Li reintercalation into graphite is important to mitigate the accumulation of dead Li.

Titanium Additive Manufacturing with Powder Bed Fusion: A Bibliometric Perspective

Titanium additive manufacturing using powder bed fusion technologies has seen notable growth since 2015, particularly in high-performance sectors such as aerospace, biomedical, and automotive industries. This study focuses on key areas like metallic powder manipulation, laser optimization, and process control, with selective laser melting emerging as the dominant technique over electron beam melting. Advancements in powder materials and laser systems have been crucial to improving the efficiency and quality of the process, particularly in enhancing microstructure and porosity control. The bibliometric analysis reveals significant global interest, driven mainly by collaborations among institutions in Germany, the United States, and China, where further international cooperation is required to scale titanium additive manufacturing. However, additional research is essential to address challenges in scalability, sustainability, and post-processing, thus expanding the applications of PBF technology across industries. In conclusion, titanium processing via powder bed fusion is poised to make substantial contributions to the future of manufacturing, provided current challenges are addressed through innovation and enhanced global collaboration.

Laser Direct Structuring of Millable BN‐AlN Ceramic for Three‐Dimensional (3D) Components

This research introduces a novel process for the direct metallization of the composite ceramic BN‐AlN, a millable, high‐temperature resistant material, using laser direct structuring (LDS). LDS is, for example, used for molded interconnect devices (MIDs), to integrate mechanical and electronic functions into a single 3D structure. Traditionally, MIDs have relied on polymers, but increasing thermal demands in electronics are shifting focus toward ceramic substrates like BN‐AlN, which offer superior thermal stability and mechanical strength. Herein, electronic infrastructures are applied onto milled BN‐AlN 3D components through a parameter study on laser activation and electroless copper deposition, followed by the development of a sequential copper–nickel–gold (CuNiAu) deposition process. The laser structuring reveals small grains of elemental aluminum on the surface, which directly catalyzes metal reduction in the electroless copper deposition. The duration and temperature of the copper electroplating process are found to influence the nuclei size and layer thickness. A palladium chloride treatment, as well as additional etching steps during the CuNiAu layer deposition, shows promising results. The metallized BN‐AlN substrates are characterized for adhesion, contact reliability, resistivity, and thermal stability. The findings demonstrate the process's suitability for high‐temperature applications, highlighting its potential for advancing electronic system integration.

Metallization process optimization of HIT solar cell for high current density and silver reduction

The Silicon heterojunction (SHJ) solar cell belongs to the most viable cell structure that enables low cost as well as high efficiency. For SHJ cells, silver (Ag) paste has been used through screen-printed process that is hardenable at low temperature. The procedure of screen printing is essential for improving the electrical properties because it allows electrodes to make good contact with the top layer of solar cells. This paper describes the experimental procedure to optimize the process condition for achieving comparatively high efficiency with minimum usage of Ag consumption. It was noticed that adequate contact among electrodes and uppermost transparent conductive oxide layer in SHJ solar cell depending considerably on squeeze speed, squeegee pressure, scraper speed, curing time and temperature. By controlling the snap-off distance of 1.4 mm, squeegee pressure at 0.3 MPa, scraper speed of 10 mm/sec, squeegee speed of 170 mm/sec, curing time of 20 min and curing temperature of 190 °C respectively, we achieved comparatively high efficiency of 22.46 %.

Resource-efficient add-on structures for the mechanical postprocessing of laser powder bed fusion parts using five-axis machining

The combination of the laser powder bed fusion of metals process (PBF-LB/M) with mechanical finishing using state-of-the-art machining centers enables the production of high-performance structural components with both internal and external complexity and precision. However, the sequential machining of additive manufactured parts can be challenging due to the need for multiple clamping setups and part-specific clamping devices. Postprocessing typically accounts for 20%–40% of manufacturing costs and can even double the cost of the final part. To reduce component costs, mechanical postprocessing should be considered. This study presents a novel concept for the development of resource-efficient add-on structures that can simplify mechanical postprocessing. These structures can either be applied to the part design prior to additive manufacturing or integrated into the part’s support structures. The developed structures allow the direct mounting of near-net-shape components on automatable, state-of-the-art parallel clamping systems. The structures are designed to clamp the parts with increased accessibility for five-sided simultaneous machining. The additional material costs are calculated within the work. The procedure for generating the add-on structures for additive manufacturing, using bounding box, topology, and shape optimization is presented. The mechanical behavior of the add-on structures is verified by clamping and measurement tests. The developments were validated by the manufacturing of three different components from the aerospace and laser technology sectors, using PBF-LB/M and aluminum alloy AlSi10Mg. The overall functionality of the add-on structures was validated by finishing the functional surfaces of the components and mechanically removing the support structures, using five-axis vertical milling centers.

A Study of the Possibility of Producing Annealed and Metallized Pellets from Titanomagnetite Concentrate.

The current intensive development of steelmaking is being impeded by a scarcity of pure scrap. The potential to replace pure scrap with metallized raw materials that are naturally alloyed with vanadium and titanium, such as annealed unfluxed titanomagnetite pellets, could facilitate the achievement of key objectives in metallurgical development, particularly in the smelting of electric steel. The objective of this research was to produce annealed and metallized pellets from titanomagnetite concentrate under laboratory conditions, with the intention of further processing them as a commercial product in a blast furnace or as an intermediate product for the production of hot briquetted iron (HBI). The results demonstrate that pellets derived from titanomagnetite concentrate exhibit sufficient compressive strength (up to 300 kg/pellet) and a degree of metallization exceeding 90%, which aligns with the requirements for electric steelmaking. The suitability of pellets derived from titanomagnetite concentrate for use in both blast furnaces and metallization processes has been corroborated.

Models for the Design and Optimization of the Multi-Stage Wiredrawing Process of ZnAl15% Wires for Spray Metallization.

Metallization, a process for applying anti-corrosion coatings, has advantages over hot-dip galvanizing, such as reduced thermal stress and the ability to work "in situ". This process consists of the projection of a protective metal as coating from a wire as application material, and this wire is obtained by multi-stage wiredrawing. For the metallization process, a zinc-aluminum alloy wire obtained by this process is used. This industrial process requires multiple stages/dies of diameter reduction, and determining the optimal sequence is complex. Thus, this work focuses on developing models with the aim of designing and optimizing the wiredrawing process of zinc-aluminum (ZnAl) alloys, specifically ZnAl15%, used for anti-corrosion applications. Both analytical models and numerical models based on the finite element method (FEM) and implemented by computer-aided engineering (CAE) software Deform 2D/3D v.12, enabled the prediction of the drawing stress and drawing force in each drawing stage, producing values consistent with experimental measurements. Key findings include the modeling of the material behavior when ZnAl15% wires were subjected to the tensile test at different speeds, with strain rate sensitivity coefficient m = 0.0128, demonstrating that this type of alloy is especially sensitive to the strain rate. In addition, the optimal friction coefficient (µ) for the drawing process of this material was experimentally identified as µ = 0.28, the ideal drawing die angle was determined to be 2α = 10°, and the alloy's deformability limit has been established by a reduction ratio r ≤ 22.5%, which indicates good plastic deformation capacity. The experimental results confirmed that the development of the proposed models can be feasible to facilitate the design and optimization of industrial processes, improving the efficiency and quality of ZnAl15% alloy wire production.

Passivation with sputtered silicon nitride and modified heat treatment for lifetime improvement

It is widely inferred that Light and Elevated Temperature Induced Degradation (LeTID) is attributed to the diffusion of hydrogen into bulk silicon from the rear PECVD SiNx:H layer of PERC during the high-temperature firing process. We propose not only a simplified heat treatment flow for the typical PERC structure but also a new degradation-reduced structure with sputtered SiNx. The common N2 annealing after Al2O3 formation can be skipped to reduce process complexity and cost because we found that the lifetime can be even improved by omitting the moderate-temperature annealing while retaining the unavoidable high-temperature firing process for metallization. In the light soaking measurement of lifetime, the sputtered-SiNx passivated wafer displayed a higher lifetime than the PECVD-SiNx:H passivated wafer. The absence of excess hydrogen in the sputtered-SiNx film contributes to the suppression of LeTID. We further demonstrate that the sputtered-SiNx cells own higher VOC compared to PECVD-SiNx:H cells under light soaking.

Exploring low temperature-sputtered indium tin oxide (ITO) as an anti-reflection layer for silicon solar cells

Abstract This paper tackles challenges in silicon (Si) solar cells, specifically the use of hazardous Phosphorus Oxychloride (POCl3) for emitter formation and silane/ammonia for the Anti-Reflective Coating (ARC) layer, accompanied by high-temperature metallization. The study proposes an eco-friendly ARC layer process, replacing toxic materials. Indium Tin Oxide (ITO) with a refractive index of ∼2.0 is suggested as a non-toxic substitute for SiN x in the ARC layer. ITO enables fine-tuning of optical parameters and, with its electrical properties, supports low-resistivity contacts through efficient, low-temperature metallization processes. ITO-passivated solar cells with Ag polymer paste as a front contact exhibit promising characteristics: a commendable photocurrent density (J sc) of 20 mA cm−2 at 850 °C, low series resistance (R s) of 1.9 Ω, and high shunt resistance (R shunt) of 28.9 Ω, as demonstrated by illuminated I–V measurements. Implementing ITO as the ARC on a less toxic emitter junction enhances Si solar cells’ current density gain, minimizing current leakage during high-temperature processing. In conclusion, adopting less toxic materials and employing low-temperature processing in passive silicon solar cell fabrication presents an attractive alternative for cost reduction and contributes to environmentally sustainable practices in green manufacturing.

Electroless Deposition for Robust and Uniform Copper Nanoparticles on Electrospun Polyacrylonitrile (PAN) Microfiltration Membranes.

Filtration membranes coated in metals such as copper have dramatically improved biofouling resistance and pathogen destruction. However, existing coating methods on polymer membranes impair membrane performance, lack uniformity, and may detach from their substrate, thus contaminating the permeate. To solve these challenges, we developed the first electroless deposition protocol to immobilize copper nanoparticles on electrospun polyacrylonitrile (PAN) fibers for the design of antimicrobial membranes. The deposition was facilitated by prior silver seeding. Distinct mats with average fiber diameters of 232 ± 36 nm, 727 ± 148 nm and 1017 ± 80 nm were evaluated for filtration performance. Well-dispersed copper nanoparticles were conformal to the fibers, preserving the open-cell architecture of the membranes. The copper particle sizes ranged from 20 to 140 nm. Infrared spectroscopy revealed the PAN fiber mats' relative chemical stability/resistance to the copper metallization process. In addition, the classical cyclization of the cyano functional group in PAN was observed. For model polystyrene beads with average sizes of 3 μm, Cu NP-PAN fiber mats had high water flux and separation efficiency with negligible loss of Cu NP from the fibers during flow testing. Fiber size increased flux and somewhat decreased separation efficiency, though the efficiency values were still high.

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

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

Experimental recurrence of an unreported fire risk of power cable: Discharge of bracket cable metallic grounding under coupled vibration conditions

In environments like bridges and tunnels, power cables are laid on metal brackets (hereinafter referred to as bracket cables). If the aluminum sheath and metal bracket form a metallic grounding fault, the air gap near the contact point may bear an intermittent discharge under the cable vibration, which is a potential source of cable fires. However, current research on cable grounding systems does not focus on analyzing the physical metallic grounding process. Discharge from coupled vibrations has been overlooked. This study accomplished the experimental recurrence of discharge at the metallic grounding point of cables under coupled vibration. According to the experimental observations, intermittent electric sparks and AC arc occur with the contact and separation of the aluminum sheath and the metal bracket due to vibrations. Under coupled vibration conditions, metallic grounding faults in cables pose a risk of causing cable fires.