Electroless Copper Plating Research Articles

Research on Surface Metallization of Polyimide Film

In order to make the Polyimide (PI) film material have good surface conductivity and meet its application in aerospace fields, for example, radar antenna, in this paper, the highly chemically inert PI material on the surface was modified by alkaline etching, and the metal layer on the surface of PI film was then deposited by electroless copper plating technology, to give PI good surface conductivity and meet its application in aerospace fields, for example, radar antenna. The microstructure and properties of surface metal layer of PI film before and after surface modification were characterized by SEM, contact angle tester and resistance tester. After alkaline etching at room temperature, there is a staggered and evenly distributed protrusion structure with dendritic and rivet structures on the surface of PI. However, the PI film surface etched at 60 °C presents pits with different sizes and depths of etching holes, and the hydrophilicity of the PI film surface is enhanced after etching. The coating on the PI is uniform and dense, and has good conductivity. This research realizes the preparation of high conductivity and high bonding force metal layer on the surface of PI film under alkaline etching, which provides technical support for the application of polyimide in aerospace fields.

Electroless copper plating mechanism of mesophase pitch-based carbon fibers by the grafting modification of silane couple agents

Electroless copper plating mechanism of mesophase pitch-based carbon fibers (CFs) by the novel silane couple agents (SCAs) sensitization method was investigated based on the three different functional groups of SCAs (KH550, KH570, KH792). The results showed that relatively stable oligomer films could be formed on the surface of CFs after the sensitization treatment with three kinds of SCAs, which promoted adhesion of CFs with copper plating. Besides, a larger crystalline size, lower resistivity, more uniform and continuous coated copper layers were observed in the copper-plated CFs with KH550 grafting modification (Cu@CF-KH550), in comparison with the copper-coated CFs prepared with KH570 or KH 792 grafting modification (Cu@CF-KH570, Cu@CF-KH792). Moreover, Cu@CF-KH550 had the higher thermal stability than Cu@CF-KH570 and Cu@CF-KH792.

Direct electroless plating of conductive thermoplastics for selective metallization of 3D printed parts

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.

Autocatalytic Laser Activator for Both UV and NIR Lasers: Preparation of Circuits on Polymer Substrates by Selective Metallization.

In laser-induced selective metallization (LISM), conventional laser activators only work at a single laser wavelength. This study reported a new laser activator (MoO3) very suitable for both 355 nm UV and 1064 nm near-infrared (NIR) lasers for the first time. When applying MoO3 to polymers, the prepared Cu layer on laser-activated polymers showed a good conductivity (2.63 × 106 Ω-1·m-1) and excellent adhesion. Scanning electron microscopy, optical microscopy, and resistance analysis revealed the excellent LISM performance of the polymer/MoO3 composites, and the quality of the Cu layer prepared using the UV laser is much better than that using the NIR laser. The limit width of the copper wire prepared by the UV laser is as narrow as 30.1 μm. We also confirmed the mechanism of MoO3 initiating electroless copper plating after laser activation to be the autocatalytic mechanism, which is very different from the conventional reduction mechanism. The effect of laser activation was only to expose the MoO3 active species to the polymer surface. X-ray diffraction and tube experiments revealed that the activity of α·h-MoO3 was higher than that of α-MoO3. X-ray photoelectron spectroscopy indicated that a part of Mo6+ was reduced to Mo5+ during laser activations, leading to the increase of the oxygen vacancies in MoO3 and possibly further enhancing the activity of MoO3. Besides, the micro-rough structures caused by the laser on the polymer surface provided riveting points for successfully depositing the copper layer. The Ni-Cu, Ag-Cu, and Au-Ni-Cu layers were obtained via the continued deposit of other metals on the Cu layer. The resistances of these metal layers had much better stability than that of the neat Cu layer. Furthermore, the Au layer further enhanced the conductivity of the circuit. The proposed strategy is easy for large-scale industrial applications, which will greatly expand the application scenarios of the LISM field.

Electroless plating of a 5G copper antenna on polyimide patterned with laser-induced selective activation and curing of metal–organic catalyst

An improved electroless copper plating method for fabricating 5G/Sub-6 GHz antennas is reported. A catalyst, palladium ion/4-vinylpyridine (Pd2+/4VP) complex, which not only initiated electroless copper plating but also promoted the adhesion of the copper layer, was dip-coated onto a polyimide (PI) substrate. Selective curing and activation of the Pd2+/4VP complex catalyst were induced by a pulsed UV laser. Wherever the laser scanned on the PI substrate, the palladium ions were reduced to palladium atoms, and the free radicals created from the decomposition of tert-butyl peroxybenzoate (TBPB) initiated the copolymerization of 4VP and PI, which enhanced the adhesion of the catalyst on the substrate. The unreacted Pd2+/4VP was removed by ethanol and collected for reuse, hence a much-reduced material cost. By adjusting the laser power, scanning speed, defocusing distance, and electroless plating time, the optimized process condition for Cu circuit fabrication without damaging the PI substrate was found. A high-quality copper circuit pattern was achieved with a laser power of 100 mW, a scanning speed of 330 mm/s, a defocusing distance of 2.0 mm, and an electroless plating time of 40 min. The copper patterns exhibited excellent adhesion and maintained good conductance after the bending fatigue tests. This laser treatment approach is simple, cost-effective, and applicable to non-planar 3D substrates, and the usefulness of this method was demonstrated by fabricating a 5G/Sub-6 GHz antenna with good device performances.

Rapid and Scalable Fabrication of Low Impedance, 3D Dry Electrodes for Physiological Sensing

AbstractMedical electrophysiological sensors that can study the body and diagnose diseases depend on consistently low impedance electrode–skin interfaces. Clinical‐standard wet electrodes use hydrogels and skin abrasion to improve the interface and thus the recorded signal quality. These electrodes are challenging to self‐administer and impede in‐home care. Wearable dry electrodes are more practical; however, they show higher impedances than wet electrodes and are costly to customize. This work presents a fabrication method for rapidly producing low impedance, anatomically fit dry electrodes that do not require hydrogels. By using electroless copper and gold plating with 3D printing, biocompatible electrodes can be optimized for individuals at a fraction of the cost of existing vacuum deposition‐based techniques. Example 3D dry electrodes made with this process are evaluated alongside clinical‐standard devices in typical scenarios to compare electrical performance and comfort. The resulting dry electrodes exhibit an average electrode‐skin impedance of 66.7 kΩ at 50 Hz and DC offset of −20 mV without any hydrogel, which, when area normalized, is within the range achieved by wet electrodes without skin abrasion.

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

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.

Effect of electroless plating time and temperature on the formation and antibacterial ability of Cu-plated cement-based material

Microbial induced corrosion (MIC) is an increasing challenge in concrete wastewater conveyance systems. Preventing MIC usually requires a corrosion-resistant chemical/antibacterial coating on cement-based materials. This study investigated the effects of electroless plating time and temperature on the preparation of the Cu-plated hardened cement paste (HCP) and successfully applied electroless copper plating to modify the HCP surface for antibacterial properties. The results indicated that the main components of the coating were metallic copper nanoparticles and phosphate sediment. The HCP plated for 4 h resulted in a relatively higher mass gain (0.76%) and Vickers hardness (163.6 HV). 65 °C was more favorable for reaction kinetics, displaying better mass gain and Vickers hardness. Besides, the antibacterial assays and accelerated bio-corrosion experiments indicated that the Cu-plated HCP had a significant improvement in the antibacterial performance and MIC resistance. Therefore, the proposed electroless plating process is a viable method for cement-based material to meet the MIC challenge.

Electrical wear performance of copper matrix composites reinforced with hybrid CNTs and TiB2 particles

PurposeCopper matrix composites are widely used in high-voltage switches, electrified railways and other electric friction fields. The purpose of this study is to improve its wear resistance and investigate the effect of hybrid carbon nanotubes (CNTs) and titanium diboride (TiB2) particles reinforced copper matrix composites on electrical wear performance.Design/methodology/approachCNTs and TiB2 particles were introduced into copper matrix simultaneously by powder metallurgy combined with electroless copper plating. Electrical wear performance of the composites was studied on self-made pin on disk electrical wear tester.FindingsThe results show that the friction coefficient and wear rate of (1CNTs–4TiB2)/Cu composite are respectively reduced by 40% and 25.3%, compared with single TiB2/Cu composites. The micron-sized TiB2 particles can hinder the plastic deformation of composites, and bear part of the load to weaken the wear rate of composites. CNTs with the self-lubricating property can form lubricating layer to reduce the friction coefficient of composites.Originality/valueThis work can provide a design method for further improving the wear properties of TiB2/Cu composites.

Direct additive copper plating on polyimide surface with silver ammonia via plasma modification

In this paper, a facile method of fully additive process to manufacture copper lines on flexible polyimide (PI) substrates was developed. The selective modification on film, involving silver ammonia solution and plasma treatment, was performed to produce Ag particles that catalyze electroless copper plating. It was found that reductive aldehyde groups (R-CHO) were generated at the treated PI surface to reduce silver ammonia ion to Ag particles, which is supported by the of chemical and morphological characterizations. The obtained solid copper deposition demonstrates highly reliable features including limited oxidation, lower roughness and compact crystalline grain with low resistivity of 3.83 × 10-6 Ω·cm. The practical fabricated flexible circuits with designed pattern have passed the mechanical and electrical property tests, confirming the compatibility of the developed additive method with the flexible PI substrate.

Fabrication and mechanical property of three-dimensional carbon fiber reinforced Mg-based bulk metallic glass matrix composite

Carbon fiber (CF) reinforced bulk metallic glass matrix composites (BMGMCs) have received widespread attention due to their light weight, but subsequent development is facing urgent challenges of uncontrollable interface reaction and poor plasticity. Here, we report a three-dimensional CF-reinforced Mg-based BMGMC, which significantly improves the microstructure and compressive plasticity by adjusting the pressure infiltration parameters. It has been found that the electroless copper plating improves the wettability of the CF and the melt without inducing the crystallization of the matrix, in spite of the partially dissolving and diffusing of the coating to the matrix. Under a similar infiltration pressure difference, high vacuum conditions are beneficial to reduce the capillary resistance of the porous CF preform, thereby improving the formability of BMGMC. Compression test results prove that the introduction of three-dimensional CF effectively improves the plasticity of the composite material and reduces its brittleness tendency. It can be attributed to the fact that the carbon fibers distributed in different directions effectively bridge the multi-directional cracks and prevent the early rapid shear band propagation. The present work provides meaningful enlightenment for the development of CF-reinforced BMGMC materials.

Functional building devices using laser-induced selective metallization on magnesium oxychloride cement composites

Magnesium oxychloride (MOC) cement as viable substrate candidate has unique applications in a range of functional and novel sensing applications due to their low thermal conductivity, high toughness, durability and excellent fire resistance. Here, we developed a facile strategy to fabricate metallized patterns on MOC cement composites through laser-induced selective metallization. The laser sensitiser of copper hydroxyl phosphate [Cu2(OH)PO4] was incorporated into MOC cement to prepare MOC cement composites. Then, the metallized copper patterns were obtained on MOC cement composites after 1064 nm pulsed laser activation and electroless copper plating (ECP). The obtained copper layer on MOC cement composites exhibited high electrical conductivity and excellent mechanical adhesion to the substrate. Furthermore, the rough copper patterns exhibited self-cleaning ability after superhydrophobic modification, which could prevent the surface from being contaminated. The metallized copper pattern could rapidly heat up when energised due to the Joule heating effect, and it can be applied for electric heating and automatic deicing in winter. In addition, a UV photodetector was fabricated by designing an interdigital metallized pattern combined with the UV light response characteristics of nano-ZnO, which has potential application on intelligent functional devices.

Advances in Pretreatments for Electroless Copper Plating on Polymer Materials

Advances in Pretreatments for Electroless Copper Plating on Polymer Materials

INVESTIGATION OF ENHANCING THE PERFORMANCE AND DEPOSITION CHARACTERISTICS OF COPPER (II) METHANE SULPHONATE SALT COMPLEXED WITH DMANNITOL BATH

The performance of the eco-friendly D-Mannitol electroless copper plating bath with additives has been investigated. D-Mannitol produces a lower plating rate which has been improved using exaltants viz., polyethylene glycol 600, oxalic acid and malonic acid. The performance of the bath shows improvement gravimetrically and by polarization studies. The surface morphology studies are also interpreted.

High-Accuracy Triboresistive Touch Sensing: Fabrication of Polydimethylsiloxane-Encapsulated Electroless Copper Plating Cotton with Multiple Electricity Generation Mechanism Towards Material Identification

High-Accuracy Triboresistive Touch Sensing: Fabrication of Polydimethylsiloxane-Encapsulated Electroless Copper Plating Cotton with Multiple Electricity Generation Mechanism Towards Material Identification

Selective metallization of piezoelectric ceramics by laser-induced surface modification combined with electroless copper plating

Conventionally, the surface of piezoelectric ceramics has been selectively metallized by screen-printing of Ag pastes. However, the use of expensive Ag materials and high-temperature annealing increases the manufacturing costs and complicates the process. In this study, simple and economical method for the selective metallization of piezoelectric ceramics has been developed. Using this method, high-adhesion copper patterns were successfully formed on piezoelectric ceramics by combining laser-induced surface modification and electroless copper plating (ECP). Although a copper layer was uniformly deposited onto the piezoelectric ceramic surface at various laser parameters, the scanning speed of 200 mm/s ensured sufficiently high adhesion strength and minimum laser damage of the piezoelectric surfaces. The d33 and kp values of the piezoelectric ceramics with the attached ECP-processed copper and screen-printed silver electrodes were very close. These results demonstrate the possibility of fabricating low-cost copper electrodes on piezoelectric ceramics without high-temperature heat treatment or surface activation with expensive catalysts.

Platinum Nanoparticles Modified Copper/Titanium Electrodes as Electrocatalysts for Borohydride Oxidation.

In this study, sodium borohydride oxidation has been investigated on the platinum nanoparticles modified copper/titanium catalysts (PtNPsCu/Ti), which were fabricated by employing the electroless copper plating and galvanic displacement technique. ICP-OES, XRD, FESEM, and EDX have been used to characterize PtNPsCu/Ti catalysts’ composition, structure, and surface morphology. The oxidation of sodium borohydride was examined on the PtNPsCu/Ti catalysts using cyclic voltammetry and chrono-techniques.

Low-Temperature Metallization and Laser Trimming Process for Microwave Dielectric Ceramic Filters.

This paper describes a low-temperature metallization and laser trimming process for microwave dielectric ceramic filters. The ceramic was metalized by electroless copper plating at a temperature lower than those of conventional low-temperature co-fired ceramic (LTCC) and direct bond copper (DBC) methods. Compared with filters made via traditional silver paste sintering, the metal in the holes of the microwave dielectric filters is uniform, smooth, and does not cause clogging nor become detached. Further, the batches of fabricated filters do not require individual inspection, reducing energy, labor, cost, and time requirements. A microwave dielectric filter was then manufactured from the prepared ceramic using a laser trimming machine with a line width and position error within ±50 μm; this demonstrates a more accurately controlled line width than that offered by screen printing. After using HFSS software simulations for preliminary experiments, the microwave dielectric filter was tuned to a target Wi-Fi band of 5.15–5.33 GHz; the return loss was <−10 dB, and the insertion loss was >−3 dB. To implement the real-world process, the laser parameters were optimized. Laser trimming has a higher success rate than traditional manual trimming, and the microwave dielectric filter manufactured here verified the feasibility of this process.

A facile process combined with roll-to-roll flexographic printing and electroless deposition to fabricate RFID tag antenna on paper substrates

A reliable and low-cost solution-processing procedure to synthesize low-resistivity metal antenna for radio frequency identification (RFID) tags on paper substrates via roll-to-roll printing combined with electroless deposition (ELD) is demonstrated in this paper. The silver precursor ink has good printability and can maintain stable performance for more than 60 days via adding hydroxyethyl cellulose (HEC) and adjusting the ratio of ink components. Through a series of characterizations proved that a copper layer with good crystallinity, uniformity and high purity had been formed on the substrate when the electroless copper plating time was 25 min. In addition, the narrow copper wire of 89 μm can be obtained, while the electrical resistivity was as low as 2.22 μΩ cm. It is proved that the RFID copper layer antenna prepared by flexographic roll-to-roll printing has qualified mechanical properties and excellent impedance matching with the IC chip, and even after 800 bends, the reading distance of the RFID tag can still maintain 96%. It can be concluded that the improved technology can be used to fabricate metal antenna for RFID tags on a paper substrate. Furthermore, these results suggest the great potential of this particle-free precursor ink in the field of large-scale flexible printed electronics.

Utilizing a pH-responsive palladium nanocomposite to fabricate adhesion-enhanced and highly reliable copper coating on nylon 6 fabrics

Conductive fibers are an important part of wearable electronic devices or smart textiles while several grand challenges have to be still overcome. In this study, we describe a simple and efficient method to prepare a copper layer on nylon 6 fabrics by using a pH-responsive styrene (St)-co-N, N-dimethyl-dimethylaminoethyl methacrylate (DMAEMA)/Pd nanocomposite. The St-co-DMAEMA/Pd can effectively enhance the adhesion between the copper layer and the substrate. Nylon 6 fabric is treated with an optimal acid concentration of 2.0 M before electroless deposition. The pretreatment will promote the affinity between the nanocomposite catalyst and the modified nylon 6 fabric and form a more favorable environment for copper deposition. Furthermore, the process yields excellent copper deposition (1.59 μm) onto nylon 6 fabric after electroless plating for 20 min. The copper layer formed by the method has a low resistance of about 2.51 Ω and the variation of resistance before and after bending test is small. In addition, the characteristic of pH responsive copolymers (St-co-DMAEMA) that displays high hydrophilicity at low pH values and high hydrophobicity at high pH values is crucial for electroless copper plating. This facile method is successfully applied in the metallization of nylon 6 fabric.