Direct metallisation of polyetherimide substrates by activation with different metals

This article reports the performance of different metallic ions and nanoparticles (Ag, Cu, Ni, Pd, Cr, Co, Au and Fe) used as seed layers, formed by chemical or optical reduction, for the electroless Cu plating of metal tracks onto polyetherimide (PEI). Plated Cu performance was tested by adhesion, electrical conductivity, plating rate, XPS, SEM, XRD and EDX analysis. The application of Cu and Ag seeds resulted in high quality electroless Cu deposits presenting strong adhesion properties and high conductivity ((2.0 ± 0.5) × 107 S/m and (3.6 ± 0.2) × 107 S/m, respectively) compared with bulk copper (5.96 × 107 S/m). Performance is attributed to the high surface density and uniformity of seed layers. Of the metals, only Ag ions were photoreduced under the conditions applied and were subsequently used to electroless Cu plate high quality track features of 150 μm width. The application of sulphuric acid pre-treatment to PEI prior to Ag ion exchange, improved the photoinitiated track formation process, as demonstrated by a threefold increase to both photoinduced Ag nanoparticle density on the surface and electroless Cu plating rate, as well as improved electroless Cu adhesion to PEI

A rapid technique for the direct metallization of PDMS substrates for flexible and stretchable electronics applications

Metallization of a polydimethylsiloxane (PDMS)-based substrate is a challenge due to the difficulties in forming crack-free polymer and metal features using standard deposition techniques. Frequently, additional adhesion layers, rigid substrates, multiple processing steps (lift-off and etching) and expensive metal sputtering techniques are required, to achieve such metal patterns. This work presents a novel and rapid technique for the direct metallization of PDMS substrates using photolithography and electroless copper plating. The method has the advantage of not requiring expensive vacuum processing or multiple metallization steps. Electroless copper layer is demonstrated to have a strong adhesion to PDMS substrate with a high conductivity of (3.6 ± 0.7) × 107 S/m, which is close to the bulk copper (5.9 × 107 S/m). The copper-plated PDMS substrate displays mechanical and electrical stability whilst undergoing stretching deformations up to 10% due to applied strain. A functional electronic circuit was fabricated as a demonstration of the mechanical integrity of the copper-plated PDMS after bending

A Rapid Photopatterning Method for Selective Plating of 2D and 3D Microcircuitry on Polyetherimide

In this work, a method for the rapid synthesis of metallic microtracks on polyetherimide is presented. The method relies on the photosynthesis of silver nanoparticles on the surface of the polymer substrates from photosensitive silver chloride (AgCl), which is synthesized directly on the polyetherimide surface. The study reveals that the use of AgCl as a photosensitive intermediate accelerates the reactions leading to the formation of silver nanoparticles by up to two orders of magnitude faster than other photodecomposition schemes. The patterning can be conducted under blue light, with notable advantages over UV exposure. Polymers of significant interest to the microelectronics and 3D printing industries can be directly patterned by light using this photography‐inspired technique at throughputs high enough to be commercially advantageous. Light exposures as short as a few seconds are sufficient to allow the direct metallization of the illuminated polyetherimide surface. The results show that the silver required for the seed layer is minimal, and the later copper electroless plating results in the selective growth of conductive tracks for circuitry on the light‐patterned areas, both on flexible films and 3D printed surfaces

Selective Electroless Copper Deposition by Using Photolithographic Polymer/Ag Nanocomposite

This paper presents a novel, direct, selective, vacuum-free, and low-cost method of electroless copper deposition, allowing additive patterning of nonconductive surfaces. Ag nanoparticles (NPs) synthesized inside a photosensitive polymer are acting as seeds for electroless copper deposition. The resulting copper film surface morphology was studied with scanning electron microscopy. Copper films were shown to display a rough grain like structure, covering substrate uniformly with good metal-substrate adhesion. Copper thickness was studied as a function of the plating time, temperature, and Ag NPs seed concentration. A maximal copper thickness of 0.44 ± 0.05 μm was achieved when plated at 30 °C with 0.4 M Ag(I). The minimum feature resolution of copper patterns, grown with 0.025- and 0.1-M silver salt, is attained down to 10 μm. The maximum electrical conductivity of the copper film prepared with 0.025-, 0.1-, and 0.4-M Ag(I) approaches (0.8 ± 0.1) × 10⁷ S/m, (1.1 ± 0.1) ×10⁷ S/m and (1.6 ± 0.4)×10⁷ S/m, respectively. Electroless copper interconnections and LED circuit on glass substrate were fabricated as a proof of concept demonstrators

Hybrid Additive Manufacture of Conformal Antennas

This paper presents a new digitally driven manufacturing process chain for the production of high performance, three-dimensional RF devices. This is achieved by combining Fused Filament Fabrication of polyetherimide based polymer with selective light-based synthesis of silver nanoparticles and electrochemical deposition of copper. The resultant manufacturing method produces devices with excellent DC electrical resistivity (6.68 μΩ cm) and dielectric properties (relative permittivity of 2.67 and loss tangent of 0.001). Chemically modifying and patterning the substrate to produce the metallization overcomes many of the limitations of direct write deposition methods resulting in improved performance, adhesion and resolution of the antenna pattern. The fabricated demonstrators cover a broadband range of 0.1 GHz - 10 GHz and the measured results show a direct agreement with the simulated design over a wide frequency band. Overall the materials used as a substrate have a low relative permittivity and lower dielectric loss than FR-4, thereby making them well suited for antenna applications

Rainfall intensity and catchment size control storm runoff in a gullied blanket peatland

Upland blanket peat is widespread in the headwaters of UK catchments, but much of it has been degraded through atmospheric pollution, vegetation change and erosion. Runoff generation in these headwaters is an important element of downstream flood risk and these areas are increasingly the focus of interventions to restore the peat ecosystem and to potentially mitigate downstream flooding. Here we use a series of multivariate analysis techniques to examine controls on storm runoff behavior within and between ten blanket peat catchments all within 5 km of one another and ranging in size from 0.2 to 3.9 ha. We find that: 1) for all 10 catchments, rainfall intensity is the dominant driver for both magnitude and timing of peak discharge, and that total and antecedent rainfall is important for peak discharge only in small storms; 2) there is considerable inter-catchment variability in: runoff coefficient, lag time, peak runoff, and their predictability from rainfall; however, 3) a significant fraction of the inter-catchment variability can be explained by catchment characteristics, particularly catchment area; and 4) catchment controls on peak discharge and runoff coefficient for small storms highlight the importance of storage and connectivity while those for large events suggest that surface flow attenuation dominates. Together these results suggest a switching rainfall-runoff behavior where catchment storage, connectivity and antecedent conditions control small discharge peaks but become increasingly irrelevant for larger storms. Our results suggest that, in the context of Natural Flood Management potential, expanding depression storage (e.g. distributed shallow water pools) in addition to existing restoration methods could increase the range of storms within which connectivity and storage remain important and that for larger storms measures which target surface runoff velocities are likely to be important

Familie und Schule: zwei Orte der Erziehung.

B

A New Digitally Driven Process for the Fabrication of Integrated Flex-Rigid Electronics

Conventionally, flexible and rigid electronics are produced separately using mask-based lithography techniques thus requiring connectors to join circuits together introducing potential failure modes and additional assembly. This work demonstrates a new manufacturing approach which overcomes this limitation by allowing the co-fabrication of both flex and rigid electronic circuitry within the same part. This is achieved by hybridizing polyetherimide fused filament fabrication with selective photosynthesis of silver nanoparticles and copper electroless plating. The performance and reliability of this approach has been experimentally validated via manufacturing and testing positional sensors. By printing thin layers (< 50 µm), polyetherimide exhibits a high flexibility with minimal degradation from fatigue. Where part thicknesses exceed 180 µm, components start to exhibit rigid properties. A combination of various layer thicknesses allows rigid-flex substrates to be produced, with secondary processing to deposit the circuitry. Positional sensors with metalized feature sizes down to 300 µm have been fabricated that when deflected demonstrate a repeatable 1.4 Ω resistance change for 43,500 cycles

Spinach-based photo-catalyst for selective plating on polyimide-based substrates for micro-patterning circuitry

This work demonstrates the suitability of spinach extract as a bio-catalyser for the photo-catalysed synthesis of silver nanoparticles on polyimide and polyetherimide, and their suitability as a seed-layer for the formation of conductive micro-track after plating. The study reveals that the extract can accelerate the reaction rates of the photo-patterning process by an order of magnitude, when applied on materials for flexible electronics and 3D printing. The two main components of the extract that can act as photo-catalysers - chlorophylls and plasmatic salts - have been individually studied by energy-dispersive X-rays, UV/Vis spectroscopy and X-ray Diffraction. A simple and well-defined method for extraction of chlorophyll-A (Ch-A) from fresh spinach at 120 ± 20 mg/L, has been developed. The study reveals that the main component enhancing photoreduction rates is due to the ionic salts present in the extract. The spinach extract has been demonstrated to be a valid catalyser to achieve highly conductive, selective electroless copper plating of track features, of thickness 0.5 ± 0.2 μm and conductivity (0.7 ± 0.2) × 107 S/m. 10 μm wide tracks are obtained, and the copper plating withstands the adhesion test. Demonstration of selective, ionic-liquid immersion plating of silver onto electroless copper, highlights a high quality metal protective layer finishing process desirable for reduced waste and toxicity