Session 8: Direct Write & 3D Printing I

Electromagnetic Shielding of Flexible Devices
Wednesday, February 14, 2018
11:30 AM - 11:50 AM

Electronic circuits often require electromagnetic shielding to suppress radiated emissions from the circuit and to protect the circuit against interference from external, and internal, electromagnetic sources. This is particularly true when devices contain both transmitting and receiving functions. The rigid, sheet-metal shells traditionally used for electromagnetic shielding cannot be used with flexible circuits. The bottom side of a die mounted contacts-up can be shielded either by the presence of a conducting plane on the flex circuit film, or by a conductive film deposited on the backside of the die. The top surface can likewise be substantially covered by a printed or deposited conductive layer, while leaving openings for contacts to the device. The small separation around the perimeter of the die between the bottom and top shields, however, interrupts the eddy current flow and significantly reduces the effectiveness of the shielding. It is necessary to provide a continuous conductive path from the bottom to the top surface around the entire perimeter of the die. In some cases, it will even be necessary to shield the contacts and connections to the flex circuit. Aerosol Jet® technology is able to spray-deposit a film of conductive material around the perimeter of the die connecting the top and bottom shields. If necessary, a dielectric layer can be deposited before the conductive layer to isolate the device sidewalls or interconnects. This paper will describe the formation of printed electromagnetic shielding barriers on both thin, flexible devices and thicker, rigid devices.