EMI Shielding for System in Package using Nozzle-Less Ultrasonic Spray Coating and Silver Particle Free Ink

Abstract

There is a constant drive to pack electronics into smaller spaces. Recently, smart watches have been major drivers of further miniaturization and spurred System in Package “SIP” innovations. SIP enables several integrated circuits (ICs) along with larger capacitors/inductors to be housed in one package. Many of these ICs operate at radio frequencies and the proximity increases electromagnetic interference (EMI). The traditional solution of soldering a “metal can” is not feasible. Compartmental shielding of the package is necessary and sputtered metal has typically been utilized to provide the shield. The traditional sputtering method is a Physical Vapor Deposition process (PVD) that involves vaporizing a metal and depositing it onto the surfaces of the components. PVD is currently the most commonly used method to apply the EMI shield and it requires a complex, multi -step process. New materials and application methods are required to increase performance and reduce costs associated with producing an effective EMI shield. The EMI shield layer must be applied in a uniform layer on the package surfaces and into the trenches between compartments. This paper demonstrates the capability of a revolutionary particle- free silver ink in conjunction with a novel coating application technology in the form of a nozzle-less ultrasonic spray technology and digital dispensing technology. Performance parameters including coating thickness uniformity, EMI shielding effectiveness, adhesion, process cost will be compared and analyzed between this approach and other silver inks and application methods. Results of these analyses will be presented along with performance improvement and cost reduction potential of this technique for high-volume manufacturing.