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

Abstract

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. direct metallization [4] of modified photoresists, [5] which has the advantage that it can be directly patterned by UV photolithography [6] without vacuum process steps for the metal deposition. DOIThe metallization of polyimides has received particular attention, due to their mechanical strength, biocompatibility, chemical resistance, and ability to withstand high temperatures. Different approaches have been followed to achieve this metallization, such as embedding silver nanowires, [7] decomposing metalorganic compounds [8] or the activation of a palladium seed layer for future plating. [9] One proposed methodology for the fabrication of metallic tracks on polyimides is surface modification by ion exchange and subsequent plating. [10] This method has the advantage of avoiding any vacuum processing steps. Moreover, the organometallic bonds can be selectively broken by irradiation, enabling direct light patterning. Finally, the use of a photoresist acting as a mold for electroplating can be removed from the manufacturing process. The nanoparticles (NPs) resulting from the photoreduction of the free metallic ions can then be used as seeds for subsequent plating. This also permits patterning by direct laser writing, [11] which could accommodate the selective plating of contoured, 3D surfaces.This manufacturing process has a plethora of advantages, but its industrial implementation has been held back as the photopatterning stage has been too slow to be implemented for mass production. Moreover, the exposure energy must be limited in order to avoid damage to the polymeric substrate. [12] These limitations have triggered a search for new processes in order to obtain faster nanoparticle formation.One approach has been to use assisted photoreduction of the metallic ions with a mild reducing agent [...

Liquid Metal–Based Soft Microfluidics

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PEI/Ag as an Optical Gas Nano-Sensor for Intelligent Food Packaging

“…We suggest that the thiol-silver interaction has led to the reduction of Ag + to Ag NPs, which corresponds to the change of the absorbance intensity. The absorbance that occurs at lower than 400 nm is due to PEI polymer [6]. For both 2-ME concentrations, the absorbance intensity increases with longer exposure times at the tested wavelengths.…”

“…Silver-treated PEI substrates were prepared according to an earlier method reported in [6]. PEI sheets were cleaned with isopropanol prior to use and treated with 15 M KOH for 20 minutes with stirring at 50°C.…”

“…During the immersion of PEI into alkaline solution, O=C-N-C=O imide ring opens up allowing the adsorption of potassium ions. The following immersion of modified PEI to a silver nitrite solution results in the exchange of the potassium ions to silver ions [6]. When the PEI substrate with adsorbed silver ions is exposed to 2-ME, the organothiols can reduce silver ions to Ag NPs [9].…”

Laser induced selective electroless copper plating on polyurethane using EDTA-Cu as active material

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