Selective Electroless Plating Research Articles

Low-Cost, Compact Quadrupole Mass Filters with Unity Mass Resolution via Ceramic Resin Vat Photopolymerization.

This study reports novel, compact, and additively manufactured quadrupole mass filters (QMFs) with adequate filtering performance for practical mass spectrometry applications. The QMFs are monolithically fabricated via vat photopolymerization of glass-ceramic resin using 57µm×57µm×100µm voxels, and selective electroless plating of nickel-boron. Experimental characterization of QMF prototypes at 1.74MHz using FC-43 yields 131Da peaks with 0.50Da full width at half maximum (260 resolution), surpassing the resolution of reported miniaturized counterparts under similar conditions, and being on par with commercial, non-miniaturized, heavier devices. The sensitivity of the 3D-printed devices is estimated at 0.13mATorr-1 (comparable to that of optimized, commercial counterparts), while the devices attained up to 250Da of mass range (limited by the driving electronics). The work is of interest to low-cost, capable mass spectrometry, 3D-printed instruments, and in-space manufacturing of complex instrumentation.

Laser‐Activated Selective Electroless Plating on 3D Structures via Additive Manufacturing for Customized Electronics

AbstractThis work proposes a facile and economical hybrid additive manufacturing (HAM)technology combining fused deposition modeling (FDM) 3D printing and laser‐activated selective electroless plating (ELP) for fabricating full functional end‐use 3D customized electronics. A functional acrylonitrile butadiene styrene (ABS) filament doped with dicopper hydroxide phosphate (Cu2(OH)PO4) catalysts is developed for FDM 3D printing. The 3D printed structure is selectively laser‐activated to generate CuI plating seeds on the ABS surface and then electrolessly plated. The poor surface finish, especially the layer lines, is an intrinsic defect of extrusion 3D printing, which not only affected the fabrication quality of the 3D substrates but also the electrical performance of the attached circuitry. Herein, a chemical polishing process based on acetone vapor is explored and characterized to significantly improve the surface quality and thereby the electrical performance of the attached copper layer. In this way, highly conductive metallic circuitry can be freeformly deposited and patterned on the 3D structure which is extremely attractive for customized 3D electronics. To show the application potential of this technology, a 3D conformal 555 timer astable oscillator circuit board and a hot‐wire flowmeter are developed as demonstrators.

Laser Direct Activation of Polyimide for Selective Electroless Plating of Flexible Conductive Patterns

Flexible conductive patterns on polyimide substrates are attracting increasing research interest in the areas of wearables, biomedicals, automotives, and energy harvesters. This paper reports a laser-induced selective activation (LISA) process for electroless metallization and, therefore, the creation of complex conductive patterns on polyimide substrates. In this process, a Q-switched pulsed laser is utilized for scanning the surface and forming the catalytic layer consisting of microporous structures, which enhances the stability of electroless plated metallic structures on the polyimide surface and exhibits superior mechanical stability under repeated bending and harsh environments. The high resolution of the metallic patterning enables the demonstration of a copper microgrid pattern with a line width down to 50 μm. Moreover, flexible light-emitting diode displays and electromagnetic interference shielding films are successfully manufactured to indicate the promising capability of our LISA process.

High rate fabrication of copper and copper-gold electrodes by laser-induced selective electroless plating for enzyme-free glucose sensing.

In the current study, the method of Selective Surface Activation Induced by Laser (SSAIL) was used for the fabrication of metallic and bimetallic structures based on copper and gold on the surface of glass and glass-ceramics. It was shown that the fabricated electrodes are suitable for non-enzymatic detection of biologically essential analytes such as glucose. The implemented approach allows performing high-rate metallization of various dielectrics. Voltammetric methods were applied to evaluate the electrocatalytic activity of the obtained structures, which were used as working electrodes. The most promising results were revealed by copper–gold electrode structures manufactured on glass-ceramics. For these structures, sensitivity towards glucose sensing was 3060 μA mM−1 cm−2. The linear range of glucose detection varied between 0.3 and 1000 μM. Besides, the manufactured electrodes exhibited high selectivity and long-term stability.

Laser-Induced Selective Electroless Plating on PC/ABS Polymer: Minimisation of Thermal Effects for Supreme Processing Speed.

The selective surface activation induced by laser (SSAIL) for electroless copper deposition on Polycarbonate/Acrylonitrile Butadiene Styrene (PC/ABS) blend is one of the promising techniques of electric circuit formation on free-shape dielectric surfaces, which broadens capabilities of 3D microscopic integrated devices (3D-MIDs). The process consists of laser excitation, chemical activation of laser-excited areas by dipping in a liquid and electroless copper deposition of the laser-treated areas. The limiting factor in increasing throughput of the technology is a laser activation step. Laser writing is performed by modern galvanometric scanners which reach the scanning speed of several meters per second. However, adverse thermal effects on PC/ABS polymer surface abridge the high-speed laser writing. In this work, an investigation was conducted on how these thermal effects limit surface activation for selective metal deposition from the view of physics and chemistry. An advanced laser beam scanning technique of interlacing with precise accuracy and the pulse-on-demand technique was applied to overcome mentioned problems for fast laser writing. Initially, the modelling of transient heat conduction was performed. The results revealed a significant reduction in heat accumulation. Applied methods of laser writing allowed the overall processing rate to increase by up to 2.4 times. Surface morphology was investigated by a scanning electron microscope. Energy-dispersive X-ray spectroscopy was used to investigate the modification of atomic concentration on the surface after laser treatment. Experiments did not show a correlation between surface morphology and electroless plating on laser-treated areas. However, significant variation in the composition of the material was revealed depending on the surface activity for electroless plating.

Fabrication of Parts with Integrated Circuits by Selective Electroless Plating of Additively Manufactured Plastic Substrates

The use of printed circuit boards (PCBs) has become essential in manufacturing parts with electronic functions. However, the placement of PCBs inside a product requires special plates or fixtures that need to be separately designed, fabricated, and assembled. In addition, PCB manufacturing generally utilizes various toxic metals and etchants. Thus, there is a need to address the issues of space, cost, and environmental toxicity inherent in PCBs. This paper proposes a novel method of fabricating PCB-free part with electronic circuits in a set using the casing or exterior of a product. This process enables the manufacturing of a type of molded interconnect device without conventional molding technologies by directly forming conductive circuits on the side or back of 3D-printed substrates using selective electroless plating. For 3D printing of the product structure, this study uses substrates made of polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS), which are commonly used in the popular material-extrusion 3D printing technology. As ABS and PLA have different chemical properties, the region to be plated with the electrical circuit is fabricated using ABS, whereas the remaining substrate is fabricated using PLA. ABS was chemically treated to allow electroless plating. A process for forming 3D circuits was developed and evaluated by selective electroless plating of the areas of the substrate requiring circuitry. To verify the applicability of the proposed process, circuits and integrated parts used in the industry were redesigned into a single component and fabricated by applying the proposed process. The results demonstrate that the proposed process has good practical applicability. Furthermore, it has low environmental toxicity with low requirements for material consumption and processing energy.

Additive Preparation of Conductive Circuit Based on Template Transfer Process Using a Reusable Photoresist.

To solve the problems of a conventional subtractive process for preparing conductive circuits, numerous alternative additive processes have been investigated, such as screen or inkjet printing, selective electroless plating, laser-induced forward transfer, etc. They all lead to a simpler procedure, less pollution, and finer line width but are still faced with difficulties like low conductivity and thickness, poor adhesion, and high cost. PDMS is a kind of material with low surface energy, leading to low adhesion with adhesive. Under these circumstances, a simple template transfer process for additively preparing conductive circuits is reported. The process to form the template includes the preparation of a photolithographic mask on the carrier copper foil and adsorption of PDMS anti-adhesion coating. Followed by metal deposition through electroplating on the template, the conductive circuits are transferred to the target substrate. Thus, the designed conductive circuits on various substrates including paper and cloth are formed. The template can be used again after being reimmersed into PDMS anti-adhesion coating. The components and the concentration of the coating are carefully discussed, and the mechanism of anti-adhesion is also researched by EIS and XPS. The copper circuits show a line width of 10 μm, a peeling strength of 7.11 N/cm, and a resistivity of 1.93 μΩ·cm, which is similar to that of bulk copper. With low pollution and cost, high versatility, and good electrical and adhesion performance, the template transfer process shows a good application prospect in the large-scale production of flexible electronics like sensors, RFID tags, etc.

Reconfigurable directional coupler in lithium niobate crystal fabricated by three-dimensional femtosecond laser focal field engineering

For crystals, depressed cladding waveguides have advantages such as preservation of the spectroscopic as well as non-linear properties and the capability to guide both horizontal and vertical polarization modes, but fabrication is always quite time consuming. In addition, it is usually difficult to couple modes propagating in different depressed cladding waveguides through evanescent field overlap, so it is often required to dynamically reconfigure photonic waveguide devices using external fields for classical or quantum applications. Here, we experimentally demonstrate the single-scan femtosecond laser transverse writing of depressed cladding waveguides to form a 2×2 directional coupler inside lithium niobate crystal, which is integrated with two deeply embedded microelectrodes on both sides of the interaction region to reconfigure the coupling. By focal field engineering of the femtosecond laser, we specially generate a three-dimensional longitudinally oriented ring-shaped focal intensity profile composed of 16 discrete spots to simultaneously write the entire cladding region. The fabricated waveguides exhibit good single guided modes in two orthogonal polarizations at 1550 nm. By applying voltage to the deeply embedded microelectrodes fabricated with the femtosecond laser ablation followed by selective electroless plating, we successfully facilitate the light coupling from the input arm to the cross arm and thus actively tune the splitting ratio. These results open new important perspectives in the efficient fabrication of reconfigurable complex three-dimensional devices in crystals based on depressed cladding waveguides.

Selective Metallization of 3D Printable Thermoplastic Polyurethanes

This paper presents a selective metallization method for the newly developed 3D printable thermoplastic polyurethane elastomers (TPU): FilaFlex ® , SemiFlex TM , PolyFlex TM , and NinjaFlex ® . Silver nanoparticles were fabricated in-situ by photo-reduction on the surface of TPUs and acted as catalysts for copper ion adsorption. This method demonstrates the successful fabrication of copper patterns on flexible TPU filaments. Furthermore, Polyflex TM and acrylonitrile butadiene styrene (ABS) filaments printed in the same part have been used to enable selective electroless plating directly on PolyflexTMmaterial. Electroless copper deposited onto PolyflexTMhas a sheet resistance of (139.4 ± 7.2) m Ω /□ and a copper conductivity of (1.1 ± 0.1) × 10 7 S/m that is comparable with bulk copper. Copper-plated PolyflexTMinterconnects were fabricated as a proof of concept demonstrators.

Hybrid Additive Manufacturing Method for Selective Plating of Freeform Circuitry on 3D Printed Plastic Structure

AbstractThis work proposes a hybrid additive manufacturing method coupling the advantages of dual‐material fused deposition modeling (FDM) 3D printing and selective electroless plating. The method relies on the selective sensitization/activation and metallization of dual‐material FDM 3D printed structure. High‐conductive nickel alloy can only be deposited on the platable plastic surface leaving the nonplatable plastic bare. The study reveals that a combination of acrylonitrile‐butadiene‐styrene and polyethylene terephthalate glycol‐modified materials provides the best metallization selectivity and film adhesion strength. The effects of electroless plating parameters such as temperature, pH value, and duration on the electrical conductivity of metallic film are systematically investigated. Through four‐point probe measurement, energy‐dispersive X‐ray spectroscopy inspection, and scanning electron microscopy cross‐section analysis, it is found that the metal deposition rate majorly depends on the plating temperature, while the composition of plated film is mainly determined by the pH value. Thus, the conductivity of metallic film can be customized according to the detailed requirements of practical applications. A minimal resistivity of 6.7 × 10−5 Ω cm is obtained when electrolessly plated at 50 °C and pH 9. A light‐emitting diode (LED) blinking circuitry is fabricated in both 2D and 3D manners as demonstrators to prove the feasibility and potential of this technology in industry applications.

3D porous polysiloxane ion-adsorption films for additive fabrication of conductive patterns with high adhesion

Fabrication of conductive patterns by selective electroless plating is a widely studied process in recent years for its advantages of lower waste, simpler process, less pollution and lower cost compared to the traditional subtractive process. But the poor adhesion of the as-fabricated patterns is the prior problem of this process, which limits the thickness of the conductive patterns in sub micrometer range and thus degrades the electrical properties of the patterns. Many chemical and physical modifications have been used to increase the chemical bonding or physical interaction between substrates and deposited metal, but the effects are limited, especially after thick metal is deposited. However, increasing the interfacial mechanical anchor is an effective alternative to enhance the adhesion but has often been neglected. In our previous work, we have developed a novel patterning-adsorption-plating (PAP) process to additively fabricate copper patterns on flexible polymer substrates. In this paper, polystyrene (PS) microspheres are added into the ion-adsorption ink as templates to fabricate three-dimensional (3D) porous polysiloxane films. Thereafter, the as-fabricated copper patterns show excellent conductivity competitive to that of bulk copper and good adhesion with a distinct increase of mechanical anchor.

Formation of Micrometer Scale Metal Structures on Glass by Selective Electroless Plating on Photopatterned Titanium and Copper Containing Films.

A procedure for formation of catalytic SiO2 substrate adhesive layer patterns and selective electrochemical metal deposition on the catalyst images was investigated. A photoreactive solution containing a diazonaphthoquinone sulfonate ester and Ti and Cu complexes was developed to deposit Cu catalyst-TiO2 adhesive layer latent images on glass. Sub-micrometer/micrometer scale positive tone photoactive TiCu complex film patterns were formed using a conventional photolithography technique. The Cu ions in 40-50 nm thick Ti and Cu oxide layers formed by pyrolysis of the TiCu complex films were reduced, residual Cu displaced with Pd then the porous Ti oxide structure filled and plated with Cu by selective electroless then electrolytic plating. Annealing the Cu plating filled TiO2 layers on glass resulted in formation of a smooth Ti3+/Cu1+ oxide interface that enabled formation of 20 μm thick Cu deposits on glass substrate with up to 1 kN/m adhesion strength. The adhesion strength was attributed to chemical bonding of Ti3+ and Cu1+ oxides to the glass and Ti4+ oxide to the Cu plating that was formed upon annealing the Cu filled TiO2 interlayer. Furthermore, a dip coating procedure was adapted that allowed copper film deposition on the entire surface of a 300 μm thick glass substrate with 50 μm in diameter holes enabling formation of electrically conductive through glass substrate interconnects.

Selective electroless plating of 3D-printed plastic structures for three-dimensional microwave metamaterials

A technique of selective electroless plating onto PLA-ABS (Polylactic Acid-Acrylonitrile Butadiene Styrene) composite structures fabricated by three-dimensional (3D) printing is demonstrated to construct 3D microwave metamaterials. The reducing activity of the PLA surface is selectively enhanced by the chemical modification involving Sn2+ in a simple wet process, thereby forming a highly conductive Ag-plated membrane only onto the PLA surface. The fabricated metamaterial composed of Ag-plated PLA and non-plated ABS parts is characterized experimentally and numerically to demonstrate the important bi-anisotropic microwave responses arising from the 3D nature of metallodielectric structures. Our approach based on a simple wet chemical process allows for the creation of highly complex 3D metal-insulator structures, thus paving the way toward the sophisticated microwave applications of the 3D printing technology.

Ultra-fine Cu Wiring Surrounded by Electroless-Plated Ni: Effective Structure for High Insulation Reliable Wiring Applicable to Panel Level Fabrication

Abstract Panel level packages such as 2.1D organic interposer and fan-out packages have been attracting the attention as a low cost substrate technology with high density fine wiring layers which interconnect multiple die set side by side. The Cu trench wirings for these packages are usually fabricated by fine and almost rectangular shaped pattern formation of insulation film followed by Ti/Cu sputtering as a seed layer formation, Cu electroplating and CMP. However, sputtering tends to be difficult to deposit on the side wall of almost rectangular shaped pattern. Another challenge is insulation reliability between ultra-fine wirings because electrochemical migration of Cu ion is one of the most serious problems for ultra-fine wirings. Here, instead of seed sputtering, we applied a Ni electroless plating because electroless plating is appropriate to panel process and Ni has high corrosion resistance. Ni seed was uniformly formed on both side wall and bottom of these rectangular patterns. After Cu electroplating, CMP and Ni selective electroless plating on Cu, Cu trench wiring fully surrounded by Ni in 1.5/1.5 μm of line and space was fabricated which has passed biased HAST over 200 h by suppressing corrosion of wiring.

Magnetically Driven Micromachines Created by Two-Photon Microfabrication and Selective Electroless Magnetite Plating for Lab-on-a-Chip Applications

We propose a novel method to fabricate three-dimensional magnetic microparts, which can be integrated in functional microfluidic networks and lab-on-a-chip devices, by the combination of two-photon microfabrication and selective electroless plating. In our experiments, magnetic microparts could be successfully fabricated by optimizing various experimental conditions of electroless plating. In addition, energy dispersive X-ray spectrometry (EDS) clarified that iron oxide nanoparticles were deposited onto the polymeric microstructure site-selectively. We also fabricated magnetic microrotors which could smoothly rotate using common laboratory equipment. Since such magnetic microparts can be remotely driven with an external magnetic field, our fabrication process can be applied to functional lab-on-a-chip devices for analytical and biological applications.

Formation of Fine Metal Patterns by Selective Electroless Plating on Cyclic Olefin Polymer using Vacuum Ultra Violet Light Surface Modification

Formation of Fine Metal Patterns by Selective Electroless Plating on Cyclic Olefin Polymer using Vacuum Ultra Violet Light Surface Modification

Copper circuit patterning on polymer using selective surface modification and electroless plating

We have examined a potential new and simple method for patterning a copper circuit on PET substrate by copper electroless plating, without the pretreatment steps (i.e., sensitization and activation) for electroless plating as well as the etching processes of conventional circuit patterning. A patterned mask coated with a catalyst material, Ag, for the reduction of Cu ions, is placed on a PET substrate. Subsequent oxygen plasma treatment of the PET substrate covered with the mask promotes the selective generation of anisotropic pillar- or hair-like nanostructures coated with co-deposited nanoparticles of the catalyst material on PET. After oxygen plasma treatment, a Cu circuit is well formed just by dipping the plasma-treated PET into a Cu electroless plating solution. By increasing the oxygen gas pressure in the chamber, the height of the nanostructures increases and the Ag catalyst particles are coated on not only the top but also the side surfaces of the nanostructures. Strong mechanical interlocking between the Cu circuit and PET substrate is produced by the large surface area of the nanostructures, and enhances peel strength. Results indicate this new simple two step (plasma surface modification and pretreatment-free electroless plating) method can be used to produce a flexible Cu circuit with good adhesion.

Characterization of Nickel Silicide Formation by a Selective Electroless Plating Process for Crystalline Silicon Solar Cells

The nickel (Ni) electroless plating process is an encouraging method for selectively depositing Ni onto silicon (Si) wafers to form front electrodes of Si solar cells. Ni has the ability to block diffusion in copper (Cu), which is used for further thickening of the Ni contacts. The contact between Ni and Si can be optimized by an additional sintering step to form nickel-silicide (NiSix). This paper presents the characterization of NiSix according to bath conditions, deposition time, and sintering process. The selective electroless deposition of Ni was achieved by plating from an alkaline nickel chloride (NiCl2) bath with ammonia as the pH control and sodium hypophosphite as the reducing agent. Thin clusters of Ni were deposited on top of Si, which ensured the formation of uniform Ni seed layers with better surface coverage on both textured and non-textured Si surfaces. The dominant phase of NiSi that offered the lowest series resistance was confirmed by X-ray diffraction (XRD) analysis at sintering temperatures of 350 oC and 400 oC. Selective deposition of Cu over the Ni seed layer was achieved by light induced plating arrangements, and thin finger lines with widths up to 28.4 μm were realized. (Received July 1, 2015)

Selective Electroless Plating on UV-modified Polymer Film Surface Patterns to Form Copper Mesh as a Transparent Electrode

Selective Electroless Plating on UV-modified Polymer Film Surface Patterns to Form Copper Mesh as a Transparent Electrode

2A2-C07 2光子造形と選択的無電解めっきによる磁性体・ポリマー・ハイブリッド・マイクロ構造体の作製

We proposed and developed a novel three-dimensional (3D) microfabrication process to produce magnetitepolymer hybrid microstructures by the combination of two-photon microfabrication and selective electroless plating. In this method, 3D polymeric microstructures composed of two kinds of photopolymers were precisely created by twophoton microfabrication. The polymeric microstructures were additively and selectively magnetized by electroless plating. This selective magnetization process was based on the difference in reactivity between acrylate photopolymer and methacrylate photopolymer. In experiments, we demonstrated that alphabetical letter model composed of acrylate was only coated with magnetite by the selective electroless plating. In addition, we also fabricated a prototype of a magnetically driven microfluidic device, in which a magnetic microrotor was embedded in a microchannel. The 3D microfabrication process based on two-photon microfabrication and selective magnetization is expected to be applied in a wide range of area such as functional lab-on-a-chip devices and biological applications.