Stencil-Assisted Electrospray Deposition of Silver Films on Insulators for EMI Shielding

Abstract The miniaturization of electronic devices places increasing demands on electromagnetic interference (EMI) protection, as shrinking volumes limit the use of conventional shielding approaches. Electrospray deposition (ESD) is an effective technique for creating thin, conformal films with controlled microstructure, making it attractive for EMI mitigation in compact packages. Silver is a particularly promising material for this purpose due to its high electrical conductivity and resistance to corrosion, which enables durable and effective shielding performance. However, the charge-driven nature of ESD favors conductive substrates, while insulating materials accumulate charge that inhibits continuous film formation and reduces deposition efficiency. Here, we present a stencil-assisted ESD method that overcomes this limitation. By passively manipulating the local electrostatic environment, material is concentrated through a stencil orifice onto the insulating target. Using this approach, we fabricate thin silver films directly on epoxy test structures. Modeling and experimental measurements support that charge accumulation on the stencil drives this focusing effect, passively directing material toward the target while reducing loss to surrounding grounded surfaces. This approach improves deposition and creates uniform, continuous silver coatings on insulating epoxy test structures. Film growth is further enhanced through multi-step ESD, yielding durable films with exceptional adhesion. The resulting test structures were evaluated for shielding effectiveness in the 3.5 ? 5 GHz frequency range (C-Band). The films achieved continuous coverage and provided effective EMI protection of up to 30 dB, highlighting the potential of stencil-assisted ESD to create compact, high-performance shielding for space constrained electronics.