Improving electromagnetic compatibility performance of packages and SiP modules using a conformal shielding solution

High-speed digital and wireless devices radiate unintentional electromagnetic noise, which can affect the normal operation of other devices within the same system, causing intra-system electromagnetic interference (EMI) problems, or contribute to the total radiated EMI from the system, resulting in potential system-level EMI issues. PCB and system level shielding may alleviate the system-level EMI between wireless PCB board and the outside environment, but seldom prevent the intra-system EMI within the shielding enclosure. Package and System in Package (SiP) level shielding is desirable to shield the unintended radiation and protect the other circuits on board. Traditionally an external metal lid is employed to isolate the radiation from an IC, but the package cost and the size penalty due to the solder pads for shield attachment make the solution unattractive. In this paper, a new shielding technology for IC packages based on metal spray coating (conformal shielding) is presented. By spraying a conductive material on the sides of the package, a very thin metal layer is constructed around the top and four sides of a package. This very thin sprayed metal layer adds zero penalty to the package size and works similar to a solid metal shielding with very good shielding effectiveness; hence, it is suitable for wireless infrastructure, tele-communications, and high-speed digital applications.